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By Brian Isherwood, Tara Brown, Paul Kreycir, Jenny Earle

"The Shangri-La hotel and luxury condominium tower, recently opened on University Avenue in downtown Toronto, required eight levels of underground structure, four extending into the shale bedrock.Isherwood Geostructural Engineers was retained in 2007 by Anchor Shoring Limited to provide an alternative design-build solution to better address serious foundation risks. The site, bounded on three sides by City streets, abuts an existing 1957 14-storey building with five underground levels to the north. Sitting on the rock surface along the east perimeter under University Avenue runs the existing Toronto Transit Commission’s University Subway Line built by cut-and-cover in the 1950’s and which was believed to lie very near the property boundary at the southeast corner of the site.The bedrock under Toronto is known to contain very high locked-in horizontal stresses, much higher than can be resisted by shoring techniques, which result in inevitable wall movement when excavating deep into the rock. The strategy adopted to control the risk to the Subway, adjacent building, and major utilities is described in the paper, along with the comprehensive monitoring of movements, and their comparison to predictions.The ProjectThe 66-storey Shangri-La hotel and luxury condominium tower, recently constructed on University Avenue in downtown Toronto, houses 222 hotel rooms in floors 1-17; 287 residences on floors 18-49; and private estates including two 2-storey penthouses on floors 50-66. These comprise 873,000 square feet of development. Eight levels of underground basement are required to provide parking and other amenities, the lower four extending into the shale bedrock."

Jan 1, 2015

By Mihir B. Roy

"Coal transported by rail for Thermal Power Plant in Haldia, West Bengal, India, was to be received and stored in Coal Complex comprising of Wagon Tippler, Track Hopper, Junction Houses and network of horizontal and inclined tunnels. The site was very soft with high ground water level. Deep excavation and dewatering posed great difficulty. Original plan was to drive about 1000 m of steel sheet pile and well sinking which had major impact on cost and time. High ground water was identified as the main problem. Controlling water level and maintaining it would allow open excavation over major areas. Scheme for lowering aquifer with one and two-stage well-point dewatering system was developed following basic principles of groundwater and seepage. Arrangements of wells, installation and pumping were worked out in detail. Water levels could be lowered below bottom levels of excavation. Design of sheet pile was modified under lowered ground water condition. Overall length and depth of sheet pile were reduced drastically. Open excavation was possible in segments over major areas. The scheme was highly successful in smooth and fast progress of underground works. The works were completed safely months ahead of schedule time and with significant saving in cost.INTRODUCTIONThe Coal Receiving Complex of thermal power plant comprised of 250 m long 8 m deep Track Hopper (TH), 12 m deep Wagon Tippler (WT) with provision for addition of another Wagon Tippler. Track center lines of TH and WT were very close. Coal unloading facilities were connected with a network of underground tunnels and Transfer Points (TP) upto Pent House (PH). The facilities were optimized in a compact layout within about 400 m x 120 m area. Initially excavation for TH was started adopting side slope of (1 V : 1.5 H) with 2 m wide berm and dewatering by in-pit sump and pump. When depth of excavation reached about 5-6 m, failure occurred over a long stretch as shown in Figs. 1a - 1b photos. Further work was stopped to develop scheme for carrying out deep excavation and civil works safely."

Jan 1, 2015

By Sumit Kumar Biswas, Moyukh De, Sibapriya Mukherjee

"The piles often are also subjected to lateral (horizontal) forces and moments. In fact, there are some structures where the primary function of piles is to transfer lateral loads to the ground. Proper analysis of laterally loaded piles is very important to the geotechnical and civil engineering profession.In the present investigation an experimental study has been carried out with free head short model cast iron hollow piles of outer diameter of 24 mm and L/d ratios of 8, 10, and 15. The experimental results have been supplemented by numerical techniques using PLAXIS-3D Foundation version 2.1 software. The results have been found to agree reasonably well with the experimental results. Further finite difference approach has been adoptedto reduce the computational time and to calculate the coefficient of modulus of subgrade reaction (?h) from the load- deflection data obtained from PLAXIS output at different pile depths. The parametric study has been extended for the non-dimensional form defined as flexibility ratio (F.R.),where ?h, L, Ep and Ip are the coefficient of modulus of sub-grade reaction, the embeddedlength of model pile, elastic modulus of pile material and the moment of inertia of model pile about the central axis respectively).The variation of coefficient of horizontal modulus of sub-grade reaction (?h) has been studied with respect to the following parameters for homogeneous soil system: relative density andL/d ratio. It has been found that the logarithm of flexibility ratio increases with increase inrelative density and increase inL/d Ratio. The values of ?h obtained by the proposed method have been, found to be close to the numerical results.As output of this research, graphs have been generated in respect of different parametric variations to gain an insight into behavior of piles under lateral load for short piles."

Jan 1, 2015

By Aniruddha Sengupta, Rana Chattaraj, G. R. Reddy, Raj Banerjee

"Earthquake induced liquefaction in saturated granular soils is an important phenomenon which causes severe damage to life and property. In the present study, dynamically induced liquefaction of saturated Kasai River sand is studied in 1-g shake table to assess its liquefaction potential. In the shake table, the soil was subjected to sinusoidal motions of amplitude 0.35g at a frequency of 2Hz. A numerical model using FLAC 2D (Itasca 2005) was performed to simulate the shaking table tests. Reasonably good agreement between the experimental and the numerical results has been observed. Moreover, wavelet analysis has been conducted to identify the occurrence of liquefaction in sand and to correlate the observations found from the experiments. The nonlinear curves used to represent shear strain dependency of stiffness of the Kasai River sand was obtained from cyclic tri axial tests.INTRODUCTIONThe term Liquefaction is used in conjunction with a variety of phenomena that involve soil deformations due to cyclic disturbance in saturated soil under undrained conditions. The generation of excess pore water pressure is the hallmark of all liquefaction related phenomena and the reduction in the volume or the tendency of cohesionless soil to densify during undrained loading condition as prevails during an earthquake is also well known. Use of shaking table tests to understand liquefaction of soils has been demonstrated by several researchers (Ye et al. 2013; Ha et al. 2011). Mohajeri and Towhata 2003 and Towhata et al. 2006 carried out 1-g shaking table tests on soil models prepared in laminar box to study the rate dependent behavior of liquefied soils. Ueng et al. 2010 used a biaxial laminar shear box mounted on shaking table to study the settlements in saturated clean deposits of sand and related the volumetric strain in liquefied sand to the relative density for various shaking durations and earthquake magnitudes. Maheshwari et al. 2012 reported increase in liquefaction resistance of reinforced sand through shaking table tests and concluded that the type and amount of reinforcement in the soil layer has influence on its liquefaction potential.The objective of the present study is to compare the behavior of dry and saturated Kasai River sand when subjected to seismic shaking. The Kasai River separates two growing cities, Medinipur and Kharagpur in the state of West Bengal in India. A number of road and railway bridges exist over the river connecting the two cities. The area being in Seismic Zone III, that is, a zone with moderate probability of earthquake, it is important to characterize the behavior of the Kasai River sand during a possible earthquake event especially when a number of bridges are existing over it. Small scale laboratory model tests and numerical analyses using a commercial finite difference algorithm called FLAC2D (Itasca 2005) have been utilized to study the difference in behavior of dry and liquefied Kasai River sand during dynamic loading conditions."

Jan 1, 2015

By Mark Spence, Tom Lardner, Matthew Janes

"IntroductionThe design-build method streamlines project delivery through a single contract between the Contract manager and the design-build team. The design-build method places emphasis on collaborative project management between design and construction disciplines to minimize project schedule, reduce costs, encourage balance risk amongst the design-build team. Since 1985, the percentage of nonresidential design and construction projects has increased from 5% to 45%.1A project carried out in Edmonton, Alberta, Canada will be used as an example to illustrate the challenges of the design-build project delivery method and the merits of establishing a GBR. The project involved a complex slope stabilization as part of an extensive freeway widening. At the project location the roadway was being widened within the base of a historic stream valley into a steep slope with a history of a previous slope failure. The slope was to be steepened through the installation of a series of 14 interlocking arc structures constructed half way up the slope. Access and schedule proved critical to the successful completion of the project.Geotechnique and Site HistoryThe geotechnical investigation undertaken for the site included six boreholes drilled at the crest of the slope to depths ranging from 14.5 m to 30.2 m. Laboratory testing of the soil samples included direct shear tests, Atterberg limits and grain size analysis. The geotechnical report also referenced a previous geotechnical investigation that was carried out in response to a failure of the slope in 1971."

Jan 1, 2015

By Sumantra Sengupta

"Northeast Frontier Railway (NF Railway) intends to connect Imphal, the capital of Manipur (bordering Myanmar) with Assam by railway link. They have planned a 125km long railway line that passes through steep rolling hills of Patkai region, eastern trail of Himalaya, and as a result large number of tunnels and bridges need to be designed. While the high mountains are penetrated by tunnel, the deep gorges between the mountain ridges are connected by tall bridges. The tallest of such bridges connects a gorge at about 140m above its bed level with an overall length about 700m at rail level. In all, five such bridges with tall piers are now under construction. With extensive study on possible alternate arrangement of the bridges considering the effect of high seismicity of the area, moderately to highly weathered siltstone/ sandstone as ground bed material, slope of the hills etc it was decided that bridge will be founded on 1.5m diameter bored cast in situ piles with length varying from 20m to 30m depending on the location. The substructures are RCC hollow pier and superstructures are steel open web through type girder of 103.5m span. Considering absence of any major construction work in the vicinity, it was decided that prior to design work, Site-specific spectrum study will be carried out and design will be carried out considering the varying stiffness of the tall piers, each of different height. Interesting results were obtained regarding behavior of piles under lateral loads generated by high seismic conditions. The paper discusses in detail the design of Pile foundations and the effect of bed material along the steep slope on which the piles are being constructed.INTRODUCTIONIndian Railway has undertaken the construction work of connecting the North-Eastern states of India through railway line. The major stretches of the area passes through hilly terrain and as a result the line passes through tunnels and bridges in succession. The tall mountains are being penetrated with tunnels and immediate after deep gorges are crossed with high level bridges. The entire area is under high seismically active zone. The bed material below the ground level of the sloped hill is 4 to 10 meter of mixed soil of sand, gravel, pebbles etc underlain by moderately to highly weathered sandstone, siltstone at the higher level and moderately weathered sandstone, siltstone at lower level. Considering all the aspects like constructability, maintainability, geological and geotechnical aspect, seismicity, stability, safety, functional aspect and cost it was finally decided that the bridges will be simply supported structure with open web through type steel superstructure of maximum span 103.5m and hollow cylindrical discretely varying RCC substructure with 1.5m diameter group of piles as foundation. The paper discusses on the design aspect of the pile foundation in the rocky strata in the hill slope. The codes and standards that have been followed for design are IRS (Indian Railway Standard), IS (Indian Standard), IRC (Indian Road Congress), AREMA (American Railway Engineering and Maintenance-of-way Association), UIC (International Union of Railway) provisions."

Jan 1, 2015

By Filippo Mira-Cattò, Andrea M. R. Pettinaroli, Elena Rovetto

"The construction of Powisle station of Metro Warsaw Line 2, in Poland, required the execution of two shafts next to an urban road tunnel adjacent to the Vistula River. The shafts were linked by three conventionally mined tunnels to be excavated 10 m below the water table level, into an upper sandy and sandy silty layer and a lower stiff clayey stratum. After a failed dig attempt under the protection of jet grouting and forepoling, it was decided to deal with the tunnels excavation problem by using the ground freezing technique as a temporary, non-polluting geotechnical treatment, keeping in service the upper road tunnel. The planning of the activities and the executive phases had a significant importance for the success of the work. For work scheduling reasons the mixed system was adopted, i.e. using both the liquid nitrogen system and the brine freezing method. The freezing process management, with a real time evaluation of the soil temperature measured by thermometric strings and an accurate monitoring of the overlying road tunnel structure, allowed the tunnel excavation and lining stages to be performed under difficult conditions, without water leaking from the frozen ground shell, within the expected times and saving extra costs.INTRODUCTIONThe new Underground Line 2 in Warsaw connects the eastern and western part of the town. One of the most critical interferences was the under passing of the Vistula river and of the Wislostrada motorway tunnel, a very congested motorway along the western bank of the river, with the construction of the new station Powisle. The construction of the station required the excavation of two shafts, using the top-down system with the creation of intermediate slabs while deepening the excavation.The shafts were used for the extraction of four Tunnel Boring Machines (TBMs), two approaching from the Vistula river side (east-side) and two approaching from downtown (west-side); in order to connect the two shafts was foreseen the realization of three tunnels, two for the underground lines and the central one for the exchanging passenger platform. These tunnels were underpassing the “Wislostrada Road Tunnel” and interfered with this tunnel foundation, which consisted of diaphragm walls (DW), the “barrettes” (Figure 1).Due to the variable geological conditions at the site, the first excavation stage, with a temporary underground support constructed of horizontal jet grouting columns and forepoling, caused the North tunnel face failure, that required an immediate filling of the empty cavities with lean mix concrete under the Wislostrada tunnel slabs. Thereafter, the recovering attempt with the grout injections could not be completed because of the development of heaves induced on the tunnel structures (Bringiotti et al. 2016). In those conditions the tunnel excavation with traditional technologies appeared to be very problematic, with high risk for the structural safety of the Wislostrada tunnel. This would have meant longer duration for the works and higher costs for the General Contractor as well as for the city Council."

Jan 1, 2015

By Jogeshwar P. Singh, Mohamed Ashour

The Soil-Foundation-Structure-Interaction (SFSI) problem involves Kinematic Soil- Foundation Interaction occurring during large (cyclic and permanent) ground deformations as well as Inertial Foundation-Structure Interaction occurring during shaking all of which take place while the soil and possibly structural properties degrade with time. The design of the deep foundations for liquefaction induced lateral spread loads include estimation of passive pressure applied by the liquefied material as well as the amount of anticipated displacement. Coupled analyses for SFSI problems that account for liquefaction induced lateral spread and their interaction with the deep foundation system can be performed using sophisticated numerical modeling techniques based on finite element and/or finite difference methods using computer programs such as FLAC or OPENSEES. Such complete SFSI analyses are very tedious and expensive and not feasible for most projects. In 2011, California Department of Transportation (Caltrans) released guidelines for foundation loading and deformation due to liquefaction induced lateral spreading. This simpler prescriptive approach combines empirical and analytical methods through decoupled analyses using computer programs such as LPILE and SLOPE-W together with liquefaction induced lateral spread estimates based on published empirical equations. Pile group effects and pile caps are accounted for using a concept of super-pile. In this paper, we discuss the solution of the same lateral spreading related SFSI problem using computer program CGI-DFSAP (CGI-Deep Foundation System Analysis Program) based on the strain wedge theory that can account for liquefaction, lateral spreading, pile groups, pile caps and nonlinear behavior of piles in a more coupled manner to analyze the foundation system under the lateral spread loadings. CGI-DFSAP can be used to analyze piles in sloping ground conditions as well as piles beneath the abutments near a free-face slope. We have included Strain Wedge Model (SWM) solutions using CGI-DFSAP of several field and laboratory case studies of lateral spreading related to pile foundations. Finally, we have also included the SWM solution of one of the Caltrans (2011) example problems.

Jan 1, 2015

By Rajarshi Pramanik, Nirjhar Dhang, Dilip K. Baidya

"This paper performs the reliability evaluation of pile foundation under vertical loading condition using the concept of fuzzy set theory. The uncertain parameters are expressed as fuzzy numbers. Monte Carlo simulation technique in conjunction with fuzzy set theory and fuzzy reliability index approach are implemented in evaluation of the probability of failure of pile foundations. The results are validated through some well established methods such as, First Order Reliability Method (FORM), Second Order Reliability Method (SORM), and direct Monte Carlo Simulation (MCS). Response surface method (RSM) is used to approximate the original limit state equation through second order polynomial. The effect of the position of the water table is also highlighted. Finally, the effect of the variation of applied load is examined and it is observed that the fuzzy reliability analysis gives more conservative estimate of failure probability than the other methods.INTRODUCTIONCivil engineering structures, such as high rise buildings, bridges, offshore platforms etc. are always subjected to vertical as well as horizontal loads. To support these structures, pile foundations are generally the solution in most of the situation. It transmits load from the superstructure to soil at a reasonably great depth. This transfer may be by vertical distribution of the load along the pile shaft or a direct application of load to a lower stratum through the pile tip. Different methods are available to estimate the capacity of piles embedded in different types of soil and under the application of vertical and horizontal loading. To consider the variability in soil and other unforeseen able situation, generally a reasonable value of factor of safety is used to estimate the designed capacity of the pile. Recent developments have shown a trend to place the treatment of uncertainty on a more formal basis, in particular by applying the results of reliability theory to geotechnical engineering. Keeping in mind the importance of pile foundation in the engineering structures it is essential to maintain a high structural safety which result in increase in reliability. The probability theory has been proved to be a powerful tool for representing variability in mathematical models. The variability associated with soil parameters and the modeling uncertainties are needed to be considered for the reliability assessment purpose.Recent development (Zhang et al. 2005; Misra and Roberts 2006; Haldar and Babu 2008; Basu and Salgado 2012; Teixeira et al. 2012; Pula and Rozanski 2012; and Chan and Low 2012) showed that the reliability analysis of pile foundations subjected to axial as well as lateral load has been one of the important current research topic in geotechnical field. Probabilistic based performance criteria were quantified for a single pile and pile groups in cohesionless soil by Eloseily et al. (2002). A p-multiplier approach was incorporated into the analysis to modify the p-y curve for a single pile to obtain the p-y curve for individual piles in a pile group. A statistical analysis of set up capacity of pile was carried out from the database of a large number of pile testing data in clay by Yang and Liang (2006). Load and resistance factor design (LRFD) using FORM was used for examining the different load and resistance factor for different target reliability index. Limit state analysis of drilled shaft was performed by Misra and Roberts (2006) in probabilistic framework. The fuzzy based reliability analysis (Dodagoudar and Venkatachalam 2000; and Park et al. 2012) of the earth slope was reported in the literature. Dodagoudar and Venkatachalam (2000) presented a new approach, called fuzzy point estimate method (FPEM) for reliability evaluation of earth slope. Park et al. (2012) reported a hybrid approach, fuzzy set theory in conjunction with Monte Carlo simulation technique, to determine the failure probability of earth slope. Second Order Reliability Method"

Jan 1, 2015

By K Ilamparuthi, R. K. Madhumathi

"This paper presents the results of 1g model tests conducted on model piles both single and two pile groups embedded in sand by physically inducing lateral soil movement. From the test results it was found that the pile with higher L/D ratio exhibits higher deflection in case of pile embedded in medium dense sand whereas in loose sand the response is vice versa with higher deflection for the pile of lesser L/D ratio. The induced bending moment in piles is more for longer piles than shorter piles irrespective of the density of sand bed. It is also found that the pile head deflection and the bending moment are found to decrease exponentially with increasing distance between the pile and the wall. For pile group arranged in a row parallel and perpendicular to retaining wall, the deflection of single pile is more than the deflection of two pile group irrespective of the depth of excavation for spacing of piles tested. The influence of soil movement on the lateral response of pile is also analyzed through 3-dimensional finite element analysis. The numerical results thus obtained are validated with the results of experiments. The Mohr-Coulomb material model adopted to represent the soil behaviour predicts the response of pile reasonably and compares well with the experimentally observed response.INTRODUCTIONPile foundations are adopted to support structures such as foundations of high rise buildings, transmission towers, offshore platforms, bridge abutments etc., when good bearing stratum is not present at shallow depth to bear the loads of these structures. In the recent past particularly in the urbanized areas structures are built close to one another and nearby excavation will cause a reduction of lateral earth pressure and soil movement behind the retaining wall (Ong, 2004). The reduction in support stress will induce additional movement to the pile and leading to distress in pile foundations located adjacent to supported excavation. In these situations understanding the response of piles next to supported excavations becomes essential.The behavior of piles subjected to soil movement was studied by Poulos and Chen (1996 and1997) through tests on 1g models and the findings concluded that the maximum bending moment was found to decrease with decreasing pile diameter and decreasing pile spacing . Leung et al. (2000 and 2003) studied the effects of excavation induced soil movement on pile foundations in sand through centrifuge tests and established that the restraints on the pile head would cause additional shear force and/or bending moment at the pile head, although the restraints help to reduce the pile head deflection/rotation. In the theoretical studies of Poulos & Chen (1997), boundary element method (PALLAS) was used for analysing the pile subjected to lateral soil movement and charts were proposed for designing the piles. Pan et al. (2002) and Miao et al. (2006) analysed the passive pile behavior through three dimensional finite element analyses. However research works reported on piles subjected to lateral soil movement are limited."

Jan 1, 2015

By S. P. Mukherjee, Smita Tung

"Piles are generally subjected to uplift in case of under ground and water front structures. Sometimes piles are also to resist uplift loads in transmission towers, dry rock, and so on. Experimental investigations of single piles and pile groups have been carried out using model hollow circular aluminum piles, having 25.4 mm outer diameter and lengths of 600 mm, 750 mm and 900 mm. Pile groups of 2?1 and 2?2 arrangements have been used in the experimental investigations. L/d ratio has been kept equal to 24, 30 and 36 in all the cases. All the single piles and pile groups have been tested under vertical uplift. Spacing between two piles in a group has been varied with respect to pile diameter such that spacing to diameter ratios of pile are 3, 4 and 5 in case of pile groups. An attempt has also been made to analyze those models of single piles and pile groups under vertical uplift by PLAXIS 3D software. Good analogy has been observed between the results of experimental and numerical studies. A parametric study has been carried out to observe the variation of ultimate uplift capacity of pile groups with spacing and depth of embedment. It is observed that for a particular embedment length of pile and a particular group arrangement the ultimate uplift capacity increases with increase of spacing. It is also investigated that for a particular spacing and particular group arrangement, the ultimate uplift capacity increases with increase of embedment depth. Those variations have also been presented with graphs which are generated considering non dimensional forms of parameters. The paper brings out change in pullout capacity of pile groups with spacing and embedment depth of piles.1. INTRODUCTIONPrediction of uplift capacity of single piles and especially of pile groups is one of the most interesting areas of research in geotechnical engineering. Pile foundations are frequently used to transmit the superstructure loads to deeper strata if the subsurface soil is of inadequate strength. The worst possible case may be considered to occur when all the piles in a group subjected to uplift. In cohesionless soils, the shaft resistance is an important source of pile capacity under axial loading, especially when the pile is subjected to uplift loading. Poulos and Davis (1980) recommended estimating the uplift capacity of piles as 2/3 of the downward shaft resistance. Later Ramasamy et al. (2004) indicated that the upward shaft resistance is significantly less than the downward shaft resistance. Some studies were conducted on the behavior of a single pile under uplift loads, such as those by Sowa (1970), Vesic (1970), Das and Seeley (1976), Levacher and Sieffert (1984), Rao and Venkatesh (1985), Chattopadhyay and Pise (1986), and Shanker et al. (2007). Das et al. (1976) conducted a model study to test the uplift capacity of single piles and pile groups buried in sand, and they also determined a relationship between the efficiency of a pile group and its spacing. Chattopadhyay and Pise (1986) proposed an analytical method for predicting the uplift capacity of piles embedded in sand and obtained reasonable agreement between experimental and theoretical results. Gaaver (2013) investigated experimentally that an upward displacement of about 1.4–2.5% of the pile diameter is required to attain the net uplift capacity for both single piles and pile groups. The uplift resistance of pile groups depends on the several variables like group size, shape, spacing to diameter ratio of piles, embedment depth to diameter ratio of piles, soil type and its density and soil-pile friction angle."

Jan 1, 2015

By José Carlos do Amaral, Marcelo Groszownik, Jorge Beim

"Initiated in 2008, the project of this 1800 km long Electrical Transmission Line is a job of extreme technical complexity, crossing regions of major forests and rivers. When ready, it will allow the large Brazilian states of Amazonas, Amapá and Pará to use the energy from hydroelectric plants, thus eliminating the need for the use of diesel fuel thermal plants, with their much larger environmental footprint. Due to its extraordinary characteristics, the Green Peace and the Discovery Channel constantly visited the job. The part between the Amazon and the Xingu rivers started in 2012, and encompassed about 100 transmission towers with up to 150 m height, through a region known as “Alagados”. This region exhibits a 1.5 m water level during the rainy season, and soaked ground the rest of the year. Navigation of regular vessels is impossible during the flood season, when a dense vegetation called “bulhado” fills the riverbed, and vehicle traffic is impossible during the dry season, due to the extremely low surface soil resistance. Great logistical and technical difficulties were encountered for driving and determining the capacity of the piles. New systems had to be developed for driving the piles, with the simultaneous use of 15 small piling rigs. The final penetration, total number of hammer blows during driving, plus Dynamic and Static Load Tests were used for determining the driving and acceptance criteria.The geographical challenge and initial conditionsThis paper describes the execution of foundations for a 500 kV Electrical Transmission Line in a region that becomes flooded during the rainy season and heavily muddy during the dry season. This is the monsoon climate, typical of the equatorial region of Brazil, where there is a rainy season lasting for about half the year, followed by a very dry season. The temperature varies very little throughout the year, due to the proximity to the equator. The locals call the rainy season “winter” and the dry season “summer”.The most important part of the so-called “Alagados” region is situated inside an Environmental Extractive Reserve (RESEX) called “Verde para Sempre” (Forever Green), created in 2003. This is one of the largest environmental reserves in Brazil. It is an area controlled by the Brazilian Environmental Control Department, the Chico Mendes Institute (ICMBio). The environment control parameters are very strict.No deep foundation had ever been executed before along the “Alagados” region. The main challenge faced on this job, however, was working in a place where self-propelling vessels or land vehicles and equipment cannot be used. During the rainy season there is a dense and intricate vegetation called “bulhado”, which prevents the movement of outboard motor boats with propellers going deeper than 50 cm. In the dry season, the heavy mud prevents the movement of foundation equipment, excavators, trucks and other machinery."

Jan 1, 2015

By Abolfazl Eslami, Sepide Lotfi, Mohammad M. Eslami

"Via direct CPT methods for pile capacity prediction, correlation coefficients smaller than unity are used to relate cone tip resistance (qc) and sleeve friction (fs) to pile toe capacity (rt) and shaft capacity (rs), respectively. For linking CPT data to pile capacity, factors such as diameter, penetration rate, partial embedment of pile toe into a hard layer, mechanism of plunging, failure zone, data processing, and stress-strain conditions must be considered. The aim of this paper is to investigate the role and significance of scale effects and establish direct relation between CPT data and pile shaft capacity. A database has been compiled including 40 full scale pile load tests and CPT sounding records for calibration and validation of the proposed approach. Analytical studies demonstrate that differences between pile and penetrometer penetration rate, geometry, and stress-strain conditions influence the relation between fs and rs. By considering the determinants, a procedure is proposed from which the pile shaft capacity can be predicted. This approach demonstrates better agreement with measured capacity by static loading test and less scatter than other current CPT methods.IntroductionAmong different approaches for pile capacity prediction, in-situ tests such as SPT and CPT have been used as supplementary of static analysis. Due to similarities between CPT and pile, the measured cone tip resistance and sleeve friction can be employed for prediction of unit toe and shaft capacities, respectively.Determination of pile capacity from CPT data includes two main approaches: direct and indirect methods. Direct CPT methods apply the measured values of cone tip resistance (qc) for pile toe capacity (rt), and sleeve friction (fs) for pile shaft capacity (rs) with some modifications regarding scale effects. Indirect CPT methods employ friction angle and undrained shear strength values that have been estimated from CPT data.When using direct CPT methods to relate qc and fs to rt and rs, correlation coefficients smaller than unity are used. Factors such as diameter, penetration rate, mechanism of plunging, failure zone, data processing, and stress-strain conditions must be considered for correlation between CPT and pile capacity. The work presented in this paper aims toward ameliorating the situation in the area of pile shaft capacity prediction, based on cone sleeve friction.Case histories from full-scale tests are compiled and analyzed by means of six methods including five direct CPT methods for shaft capacity prediction and the proposed method."

Jan 1, 2015

By Sanjay Gupta, Sorabh Gupta, Ravi Sundaram, Abraham Varghese

"Geotechnical investigation for the Kochi Metro revealed a critical section of the Viaduct near Ernakulam Junction Railway Station. Four piers, located over a 220 m stretch, were passing through an area with substantial thickness of soft clay. The scope of the geotechnical investigation included two boreholes and a static cone penetration test at each pier location. In the boreholes, field vane shear test was conducted at different depths in addition to the routine SPT. The design of heavily loaded piles in such strata is a challenge due to the liquefaction of the shallow sands and negative skin friction / down-drag in the soft under-consolidated clay. Bored cast-in-situ piles of 1500 mm diameter extending to 50-60 m depth were used to carry 500-600 tonnes load.INTRODUCTIONThe first phase of the rapid transit system at Kochi, Kerala (See Fig. 1) whose elevated route spans from Aluva to Thripunithura covers a total distance of about 25 kilometers. One of the more critical sections of the viaduct exists near the Ernakulam Junction Railway station where the alignment takes a sharp curve to move towards Vyttila, crossing the railway tracks and running partially over the approach of South over-bridge.In this section, four piers located on either side of the railway tracks near the Route Relay Cabin of Ernakulam Junction Railway Station pass through an area with substantial thickness of soft underconsolidated clay.The alignment is geotechincally challenging due to the presence of loose liquefiable sand and soft underconsolidated and sensitive clay.Initial investigations by the owner based on limited boreholes only yielded conservative and inconclusive pile capacities. For a thorough understanding of the soil behaviour, a detailed geotechnical investigation was carried out to assess the engineering behaviour of the soil strata.The scope of the geotechnical investigation included two boreholes and a static cone penetration test at each pier location. In the boreholes, field vane shear tests were conducted at different depths in addition to the routine SPT."

Jan 1, 2015

By Rick Piovesan, Pramod Rao, Nihal Bohra, Mark Wahler

"This paper discusses the approach followed for the geotechnical design of 355 mm and 457 mm diameter driven open-ended steel pipe piles used for a gas plant at a green field site in Pilbara region in Australia. The principal bearing layer at the site comprises of calcareous Red Bed soils and weak rock, which is the typical geology along a significant length of the northern Western Australian coastline with carbonate content up to 70%. The uncertainty associated with the mechanical behavior of the calcareous soils and cemented soils (weak rocks) presented design challenges in the selection of appropriate pile design method and design parameters for pile capacity estimation during Front End Engineering Design (FEED). The American Petroleum Institute (API)-based design methodology was adopted. The representative design parameters for the Red Bed weak rock were established by treating the weak rock as clay with undrained shear strength as one-half of the characteristic unconfined compressive strength (UCS) value. Both statically load tested and CAPWAP (Case Pile Analysis Wave Program) estimated ultimate axial pile capacities on 25 early pre-production indicator piles demonstrated that the API design methodology for siliceous soils provides reasonable prediction of axial pile capacity in the red bed soils/weak rock and no reduction to API computed axial capacity due to carbonate content is warranted. The results also demonstrated that penalizing axial pile capacity solely based on carbonate content is not appropriate.IntroductionA gas processing facility was proposed to commercialize the gas reserves located 130 km offshore from the north-west coast of Western Australia (WA). The project site is a green field site located in the Pilbara region along the northwest coast of WA. Specific information regarding the site has been withheld due to confidentiality reasons. The site layout is shown in Figure 1.The site comprises low-lying tidal flats, clay pans and sand dunes covered with low scrub. The onshore site levels vary from elevation 1 m to 10 m AHD (Australian Height Datum), with the largest proportion of the area (excluding sand dunes) between elevations of 1 m and 3 m.The onshore facilities are to comprise a liquefied natural gas (LNG) plant site, a construction camp, the land-based portion of the materials offloading facility (MOF), roadways, and borrow pit areas.The existing ground levels within the process train area, where pile load testing was performed, vary from over 7 m AHD where the summits and peaks of the central dune exist to typically 1 m to 2 m AHD towards the east and west edges of the dune. The proposed finished grade for the process train is set at 7 m AHD."

Jan 1, 2015

By João Veludo, Eduardo Júlio, Helen D. Robinson, Jesús E. Gómez

"Utilization of micropiles for structural retrofit requires connection of the micropiles to the footings of the existing structure. Almost ten years ago, an experimental research effort was carried out in the US to investigate the magnitude and mechanism of development of the bond strength between micropiles and existing concrete. The study resulted in important conclusions on the mechanism of connection capacity development and provided specific recommendations for practical design of micropile-to-footing connections. In the last five years, the original study was complemented by an intensive experimental effort in Portugal aimed at answering many of the questions still remaining on this topic. This paper is a summary of the knowledge that is presently available on the capacity of micropile-to-existing footing connections. It presents the results and observations of model tests performed in the US and Portugal, as well as some tests from actual construction sites. The paper presents clear evidence that friction may be the most important component of connection capacity. It also presents a clear correlation between confinement and connection capacity.IntroductionUtilization of micropiles for structural retrofit requires connection of the micropiles to the footings of the existing structure. This is often accomplished by drilling through the footing and developing the connection by direct bond between the micropile grout and the existing concrete. Almost ten years ago, an experimental research effort was carried out in the US to investigate the magnitude and mechanism of development of the bond strength between micropiles and existing concrete. Smooth and textured micropile inserts of varying lengths were tested to failure inside pre-drilled holes of varying diameters. That investigation led to several publications (Gomez et al. 2005, Wilder et al. 2005, Cadden 2009) on the mechanism of development of bond strength between micropiles and concrete, which included a chart for preliminary bond value selection depending on the diameter of the hole and texture of the micropile.An intensive testing program was carried out in Portugal in the last five years. The program focused on answering questions posed by the original investigation and on finding the relationship between connection capacity and level of confinement. Both investigations, and especially the testing performed in Portugal, provided an invaluable amount of information on the mechanisms of failure of micropile-to-footing connections. This information should be the basis for development of design procedures that, until now, were not available."

Jan 1, 2015

By Daniel W. Mageau, Larry W. Applegate, Aaron K. McCain

"An innovative method of ground freezing was successfully tested to create a “dry” excavation condition for a new building foundation at a site in downtown, Miami, Florida. The subsurface conditions in Miami generally consist of very porous, weak limestone and sand with groundwater near the surface. Water flow through these materials can be very high. Dewatering is extremely restricted in Miami so deep below-grade structures are rare and expensive. A new, innovative method to allow deep excavations in dry conditions without dewatering involves the creation of a thick, temporary, frozen soil plug below the planned excavation depth across the entire site to cut off vertical groundwater flow during construction. Frozen soil is impermeable and very strong and has long been used for temporary structural and water-tight shored walls. Using the same proven principals, frozen soil plugs are very effective at cutting off water from the bottom of the excavation as well as resisting upward buoyant forces. This new freezing method can be used for fairly deep excavations in new building construction supported on deep foundations. The building piles act as temporary anchors for the frozen plug to resist very high upward buoyant pressures until the permanent structural slab is completed.IntroductionUnlike other Cities, below grade basements are rare in Miami. The few basement foundations constructed have utilized a cumbersome and expensive method of excavation and shoring involving underwater excavation, tremie slabs, and commercial divers. The key issue for underground construction in this area of the country is the vertical flow of groundwater through the base of the excavation. To deal with this issue in the past, the contractor first installed all of the building piles and the perimeter shoring walls. Then, interior sheet pile walls are installed to create small manageable excavation pits. Each pit is then excavated through standing water “in-the-blind” and around the buildings support piles. The final excavation, interior struts, and inspection is performed by commercial divers. Finally a thick foundation tremie slab is poured under water. This method could be successful but proved to be time consuming and expensive. In addition, some building piles were occasionally damaged during the under-water construction process."

Jan 1, 2015

By Kenneth Gavin, Weichao Li, Paul Doherty

"The lateral load capacity is one of the most important issues to be considered in designing piles to resist berthing loads, ship impact forces and for monopiles used in the offshore wind sector. A number of semi-empirical design approaches are available to calculate the ultimate soil resistance and assumed soil reaction profile along the piles’ embedded depth. In order to investigate the response of monopiles to lateral loading, a series of field experiments were conducted on instrumented steel pipe piles. Two lateral loading tests were performed on model piles with a diameter, D, of 340 mm and embedded depth, Lem, of 2.2 m, giving a Lem/D ratio similar to those adopted in the offshore wind sector. The piles were driven into dense sand at the University College Dublin geotechnical test bed site in Ireland. 10 pairs of strain gauges were installed on each model pile along the embedded depth at 10 levels to capture the load transfer and bending moment within the piles. The deflection and rotation at the model pile head were measured by Linear Variable Differential Transformer (LVDT) and inclinometers. The tests results were used to perform a detailed evaluation of current design methods. In the final section, discussion on the determination of the ultimate lateral load capacity for monopile design was conducted. IntroductionA pile’s lateral load capacity is determined, for design purposes, by two conditions: 1) the ultimate lateral load, Fu, divided by an appropriate safety factor; and 2) the load according to the maximum lateral deflection that the support structures can sustain. In view of the first condition, design methods to calculate the ultimate load were developed for piles used in the offshore oil and gas sectors, which tend to be much more slender than monopiles used in the wind industry. The purpose of this study was to investigate whether these design methods provide reasonable estimates of ultimate capacity, for short rigid monopiles.The methods to determine the ultimate lateral load generally follow three steps: 1) determine the ultimate soil resistance, Pu, along the pile embedded depth; 2) adopt the most appropriate soil reaction profile, Pz, along the piles embedded depth when the pile subjected to the ultimate lateral load condition (four of the most popular ones are depicted in Figure. 1); and 3) ensure equilibrium of lateral forces (see Equation 1, symbols are listed at the end of the paper) acting on the pile and bending moments (see Equation 2) about a point in pile is employed to determine the ultimate lateral load."

Jan 1, 2015

By Anup Kumar Mandal, Sanjoy Chowdhury, Biswajit Das

"Tailing pond of an iron ore mine necessitated raising the height of its embankment to create additional storage capacity. The tailing pond is located in eastern India and raising the height of embankment was going on during the month of January, 2014. Upstream method of construction was adopted since there was no space available at the downstream side. During the construction, about 200 m stretch of the north east embankment of height about 5.5 m failed forming a classical slip circle on the upstream side involving about half the top width of the embankment. To find out the root cause of the slope failure, detail geotechnical investigation work was carried out within the embankment as well as in the adjacent areas within the pond. About 7.5m thick very soft tailings were detected below the constructed embankment. Shear strength of the soft tailing was very low and was inadequate to sustain imposed embankment load. This resulted in the failure of the embankment. Analysis of the tailing deposit revealed that even after failure, settlement was continuing due to imposed embankment load. Under normal onedimensional consolidation, the tailing deposit would have taken about 5.7 years for 90% of primary consolidation. However, in order to mitigate the scarcity of storage space, mining plan required raising the height of the embankment within next six to eight months. Therefore, despite the fact that there was a failure, it was necessary to continue the construction on the underlying weak stratum. The system was redesigned with installation of prefabricated vertical drains (PVDs) to accelerate the consolidation process thereby gaining the in-situ strength. Strength was additionally enhanced by installing geogrids in multiple layers. It stabilized the existing embankment and also ensured construction of additional height over and above the existing embankment.INTRODUCTIONBeneficiation plant in the Iron mines enhances the mineral content by separation of contaminants and fines. The residue (waste material) is called tailings/tailings depending upon the grain sizes. These tailings in a slurry form are generally disposed in a pond called as tailing pond/tailing pond. Height of embankment of such ponds is increased either by upstream or by downstream or by centrally raising methods in different phases as quantum of deposition in the pond increases with time."

Jan 1, 2015

By Brandon Buschmeier, Frederic Masse

"Inclusions are a type of ground improvement that provide an improvement of a soil mass by insertion of a material with better characteristics than the surrounding soils. There are primarily two types of inclusions: “Soft” inclusions which are constructed of granular material (Stone Columns, Rammed Aggregate Piers, VibroPiers...), and “rigid” inclusions which are constructed of grout inserted with or without pressure (VibroConcrete Columns, Controlled Modulus Columns, Soil Mixing Columns).While the central principle of the inclusions is similar (i.e., overall improvement of characteristics of the soil mass below the structure), the load transfer mechanism is radically different for each technique. Therefore, the applicable design methodology is specific to the type of inclusions and there exists no universal method of design which spans across all inclusions.This paper will present an in-depth comparison between the standard design methods used for “soft” granular-type inclusions (Priebe modified, Balaam & Booker, Goughnour & Bayuk...) and the methods used for “rigid” inclusions which mainly rely on finite element analysis. The paper will explain why the design for soft inclusion methods cannot be applied to rigid inclusions and vice-versa. Each design method will be reviewed in detail to better emphasize its limitations and advantages.Two case histories will also be presented; one for each type of inclusions in order to illustrate the concepts developed in the first part of the paper.1 INTRODUCTION1.1 GENERAL OVERVIEW OF GROUND IMPROVEMENT WITH INCLUSIONSThe use of ground improvement methods to provide the appropriate amount of foundation support is a growing and constantly evolving industry. Traditional structural foundation methods including ‘shallow’ and ‘deep’ foundations do not adequately address the wide range of settlement tolerances, soil conditions, and loading considerations inherent to each unique potential project. In some instances, ‘shallow’ foundation solutions are simply not feasible due to soil and loading constraints. Furthermore, ‘deep’ foundation solutions are used to ‘bridge’ the soft compressible soils, ensuring that the entirety of the load in the structure is transmitted through individual elements into competent layers below the ground surface (bedrock, dense residual soils). Highly concentrated structural loads are transferred into the individual elements by means of direct contact requiring the use of structurally rigid surficial components (structural slabs, grade beams, and pile caps).Ground improvement bridges the gap between these two traditional methods, offering adequate foundation support while using more costeffective techniques and design methodologies. Inclusions are a type of ground improvement used to provide a reinforcement of the soil mass through the vertical insertion of a material with better characteristics than the surrounding soils. Much like deep foundations, inclusions are installed through soil layers with high compressibility and/or low bearing capacity and terminated in a suitable bearing stratum. However, unlike deep foundations, ground improvement inclusions rely on a distribution of load between the soil and the inclusions. By doing so, some of the structural load is applied directly to the soil in a proportion equal to its bearing capacity and compressibility limits, while the rest of the load is shed into the vertical inclusions down to the bearing stratum. Load sharing is a critical aspect in the performance and design of the various ground improvement methods."

Jan 1, 2015