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By David C. Kraft

Atlas Systems, Inc. (ASI) resistance type piers were used to underpin a 100 year old historic structure at Fort Monroe, Virginia. This 3-story structure with basement was underpinned with 155 steel tubular push piers (4" OD) that were hydraulically installed to depths ranging between 90 and 110 ft. and to installing forces in excess of 60,000 lb. Project requirements included lowering the basement floor by 1-1/2 ft. and constructing new footings and adding stem walls to connect to the existing masonry walls. Additionally, the underpinning piers were temporary which required the development of a decoupling system to permit the transfer of the building loads from the underpinning piers to the new footings. The structural loads at the foundation level required a c. to c. pier spacing of 3.75 ft. in order to meet project requirements of a minimum Factor of Safety of 3.0 on the pier load capacity. Project requirements included a load test on the selected underpinning pier (ASI - AP2 4000.219) in order to establish installation depths for seating the piers to 60,000 lb. The project was successful in supporting the full load of the structure during the construction phase. Considerable savings in time and cost were achieved as well as avoiding any vibrations or noise during installation of the piers.

Jan 1, 2002

By Mohammad Ali Rowshanzamir, Mehdi Aghayarzadeh

"This article is an effort to improve our understanding of the performance of geogrid retaining structures (GRS) through numerical analyses. The numerical modeling utilized a commercially available finite difference program, FLAC3D. In this context an extensive parametric study has been carried out on two different GRS walls (vertical reinforced block and inclined reinforced block) to investigate the influence of internal design factors such as soil strength properties and reinforcement stiffness on the performance of these walls. The main purposes of the parametric study were to (1) investigate the sensitivity of the modeling results to the input material properties, (2) examine the influence of the internal design factors on the performance of GRS retaining structures, and (3) improve the internal design of GRS walls on the basis of the working stress information obtained from the parametric study. Based on the analyses results, it was revealed that GRS walls with oblique reinforcement and reinforced block (rotated against natural backfill) have much better performance in terms of reduction in the stresses and strains of reinforcing elements as well as decrease in the wall lateral and vertical displacements in comparison with vertical reinforced block (conventional wall). For example, with 12° inclination of the wall reinforced block there was 50% reduction in the backfill settlement. Also increasing the reinforcement stiffness amount from 10MPa to 50MPa decreases the wall face displacement more than 50% in both GRS walls.INTRODUCTIONOver the past few decades, Geosynthetic- Reinforced Soil (GRS), a soil mass reinforced by geosynthetic layers to restrain the soil lateral deformations, has been employed in the construction of many types of earth structures, including retaining walls, embankments, slopes and bridge abutments. In fact GRS structures are typically more flexible (hence more tolerant to differential settlement), more adaptable to low quality backfill, easier to construct, require less over-excavation, and more economical. Nevertheless, there is a need for an accurate design tool that can predict the performance of GRS structures under working stress conditions and can predict their failure loads as well.Many studies have been published on the performance of the soil reinforced walls such as Isabel et al., 1996; Bathurst et al., 2000; Kazimierowicz-Frankowska, 2005; Nernheim and Bathurst, 2008; Chen and Chiu, 2008 Correia et al., 2012; Erlich et al. 2012. Several numerical studies have also been made throgh finite elements and finite difference techniques on reinforced soil retaining walls to analyze the wall deformations (e.g. Hatami et al. 2001& 2006, Liu and Won 2009, and Abdelouhab et al. 2011). A limited laboratory research has been reported indicating of improving effect of tilting face on GRW performance (Chen and Chiu, 2008). However no major numerical study was found on the effects of face or reinforcement tilting."

Jan 1, 2017

By Yoshio Mitarai, Takeshi Nagatome, Yosuke Tanaka

"This paper describes an application of lightweight soil in a deep water area to stabilize an existing quay wall at the Port of Tokyo. Super Geo Material, abbreviated SGM, is a type of lightweight soil, which consists of dredged cohesive soil, cement and air foam, and is applied in coastal development work, such as port and airport construction. This paper reports a SGM construction project at the Port of Tokyo by using a SGM special plant vessel, which was deployed for the Tokyo International Airport (TIA) Expansion Project in order to achieve large-scale and rapid construction. The key issue in SGM construction is quality control. One key quality issue is control of the mix proportion of SGM in consideration of volumetric changes due to air foam-breaking during pumping and air foam shrinkage due to water pressure when SGM is placed in deep water. A smart technique for placing SGM is also necessary to prevent quality deterioration when SGM is placed in deep water, for example, increased bulk density and decreased shear strength due to water absorption. This paper introduces an actual case of SGM construction with a particular focus on quality control of SGM during construction.INTRODUCTIONSuper Geo Material, abbreviated SGM, is a lightweight stabilized soil which is used in coastal development work in Japan (CDIT 2008). SGM is applied as a backfilling material behind existing quaywalls or above underground structures in order to reduce earth pressure on the existing structure and improve seismic resistance. SGM has been applied in many coastal development projects. In particular, SGM was used at the Tokyo International Airport (TIA) Expansion Project (Haneda Airport) as the backfilling material at a quay wall at the joint between the reclaimed area and pier part in a new runway (Nagatome et al. 2010a & 2010b, Yamatoya et al. 2010, Mitarai et al. 2011). In this project, large-scale and rapid SGM construction was implemented by the special SGM plant vessels within 6 months under the condition of limited construction period.This paper introduces a new SGM construction project at the Port of Tokyo in 2011. This project employed the special SGM plant vessel, “Ryujin Mark II”, to achieve large-scale and rapid construction within a limited period. SGM was also placed in a deep water zone at the maximum water depth of approximately 15 m. Thus, quality control of SGM was a key issue for meeting project requirements. This paper describes the actual SGM construction in the Tokyo Bay area and quality control techniques for SGM, considering volume changes due to pumping and placement below water."

Jan 1, 2015

By Stefan Larsson, Jan Ekström, Jennie Kock-Larsen, Håkan Garin

"This paper describes the testing procedure (or protocols) for quality control of dry deep mixing columns in a major ground improvement project carried out in Sweden. Quality control was mainly based on column penetration tests performed at different stages in the project and on two occasions after installation. In the paper, the results from the tests are compared with tests on the unimproved clay. As expected, the results show that the correlation between undrained shear strength in the columns and in the unimproved soft soil depends mainly on the in-situ stress. However, the correlation probably depends on when the tests were performed after mixing. When the influence of the in-situ stress was excluded from the analysis, no significant correlation could be identified. This means that the undrained shear strength in the columns and in the unimproved soft can be considered to be uncorrelated when the strengths and the corresponding variability are evaluated with depth from groups of tests.INTRODUCTIONQuality control and quality assessment of deep mixing (QC/QA) constitute a key component in verification of the limit state design. Due to the complex mixing process and varying geological conditions, it is normally not possible to sufficiently assess the strength and deformation properties in advance. In Sweden, the most commonly used QC/QA method for verification of the limit state is the column penetration test (Axelsson and Larsson 2003; Bergman et al. 2013). The method works well but is time-consuming and requires many tests since property variability is normally high. The column penetration test can be used to assess the undrained shear strength Cu,col. However, it is not clear how the strength correlates to the undrained shear strength of the unimproved soil Cu,soil. There are common factors such as the in-situ stress state and the natural water content, which makes a positive correlation probable, i.e. as Cu,soil decreases, Cu,col also decreases and vice versa. The unimproved soil has a natural spatial variability, but it is not known if the improved soil follows the same variation. The mixing process has a substantial influence on the strength variability and may supersede the influence of other factors. However, if a sufficiently good correlation exists between Cu,col and Cu,soil, information from the geotechnical ground investigations can be used in the design and planning of QC/QA of deep mixing in a more stringent manner. Information about the correlation is also essential in reliability based design, where a strong positive correlation may have a negative influence on reliability. However, as discussed by Al-Naqshabandy and Larsson (2013), this correlation may be weak or insignificant for a representative failure domain where the mixing process may have a dominant influence on the strength variability. It is thus of interest to assess the correlation."

Jan 1, 2015

By Clinton O. Rex, Adam S. Hurley, W. Morgan NeSmith

"Hartsfield-Jackson Atlanta International Airport underwent a $1.2 billion dollar expansion project centered on the construction of the new Maynard H. Jackson International Terminal. Passenger access between the new International Terminal and the domestic airport facilities is primarily via underground Automated People Mover (APM) trains. Prior to this expansion, the APM tunnel terminated beneath Concourse E, which previously served all international flights. The new International Terminal is located approximately ½-mile from the previous terminus of the APM tunnel.A paper describing the general approach to excavation support for construction of the entire APM tunnel extension from under Concourse E to the new International Terminal was published by two of the authors (Hurley and NeSmith, 2014). One of the features of note of the approach involved the intersection of the proposed new alignment of the APM tunnel extension under Concourse E with the old terminus. Specifically, the new tunnel extension conflicted with the location of the existing Auger Pressure Grouted (APG) piles supporting four columns in Concourse E. This paper presents design and installation details of the micropile underpinning approach used to support the existing columns to allow for the proposed excavation including the cutting and removal of the existing APG piles, while allowing Concourse E to remain in service during construction.PROJECT DETAILSGeneralThe construction of the APM extension required an excavation support system for a 450-ft long, 55-ft deep excavation across Taxiway Dixie and a 900-ft long, 30-ft deep excavation beneath the basement of existing Concourse E. The excavation under Concourse E required both excavation support and support of the existing columns over the proposed excavation zone. A general overview of the work area is shown on Figure 1."

Jan 1, 2017

By Gihan E. Abdelraham, Youssef G. Youssef, Mohamed M. Kamel

"Previous studies defined Narrow Mechanically Stabilized Earth, NMSE, walls as a retaining wall with aspect ratio (wall width to its height, L/H) less than 0.70 as in traditional walls. Some studies investigated its behavior and its failure planes compared to those of traditional walls. In this paper, parametric study using finite element analysis PLAXIS, 8.2 has been introduced to discuss global factor of safety, FS, maximum horizontal displacement, Ds, maximum tension force of reinforcement element, Tmax, and active earth pressure coefficient, ka, as a function of different aspect ratio of NMSE wall, L/H, reinforcing elements spacing, S, elastic axial stiffness of reinforcement element, EA, wall batter, 1/m, soil friction angle, f, and wall height, H. The results indicated that increasing aspect ratio increases the factor of safety, maximum horizontal displacement, maximum tensile force and active earth pressure. Increasing elastic axial stiffness increases factor of safety, maximum tension force of reinforcement element while decreasing the maximum horizontal displacement.IntroductionReinforced earth is a composite geoconstruction material, which embodies two basic components; namely engineering fill and reinforcing elements. The latter one is responsible for improving the tensile and shear resistance of the soil. The soil-reinforcement technique has been in use for many geotechnical applications especially MSE walls.A narrow wall system is referred to as a MSE wall with an aspect ratio, L/H, below 0.70 that is placed in front of a stabilized wall. An example of a narrow wall system with its dimensions is illustrated in Fig. 1."

Jan 1, 2017

By Anthony T. C. Goh

"For deep excavations in soft clay, it is common to use jet grouting piles (JGP) prior to excavation to minimize wall deflections and ground settlement, and to prevent basal heave instability. In this paper, finite element analyses were carried out to assess the basal heave factor of safety for excavations in soft clay supported by JGP. Comparison of the factor of safety from the finite element analyses with limit equilibrium methods was then performed. Subsequently, to account for the uncertainties in the soil and JGP properties, a simplified reliability analysis procedure is proposed to estimate the probability of basal heave failure for deep excavations supported by JGP.INTRODUCTIONJet grout piles (JGP) are often used to prevent basal heave instability and to minimize excessive wall and ground movements associated with deep excavations in soft clay deposits (Shirlaw 2003; Wen 2005; Ou 2006). The jet grouting process which is carried out prior to any excavation works produces a series of short overlapping grout columns resulting in a “continuous” base slab (commonly termed as jet grout pile or JGP) below the final excavation level that spans across the entire excavation (Gaba 1990; Hsieh et al. 2003; Ho and Hu 2006). Typically, the JGP thickness ranges from 2 m to 4 m.The focus of this paper is on the assessment of basal heave instability for deep excavations in clay stabilized with JGP. Finite element analyses were first conducted to determine the basal heave factor of safety for deep excavations in clay with JGP. Comparisons were then carried out with factors of safety based on conventional limit equilibrium methods. Since the conventional factor of safety approach does not explicitly reflect the uncertainties of the soil and JGP properties, it is demonstrated in this paper that a simple reliability based approach (Hasofer and Lind 1974) can be used to assess the probability of basal heave failure.LIMIT EQUILIBRIUM METHODFor excavations is clay, the Terzaghi (1943), Bjerrum and Eide (1956) and Eide et al. (1972) methods which are based on bearing capacity theory, are commonly used to determine the basal heave factor of safety. Another commonly adopted method in Japan and Taiwan is the slip circle method which involves taking moments about the lowest strut level (JSA 1988; Hsieh et al. 2008; Luo et al. 2012). The slip circle method has also been applied for excavations with a JGP at the base by incorporating the undrained shear strength of the JGP. In the slip circle method, the basal heave factor of safety FSslip is assessed by taking moments about the lowest strut level (Fig. 1)"

Jan 1, 1900

By K. Viking

It's well known that conventional impact hammers, usually are the method to use in order to drive precast prestressed concrete piles. However sometimes the vibratory technique might be considered as a suitable alternative due to favourable soil conditions. It is also well known that piles driven into granular soils can be installed more efficiently by the use of a vibratory driver compared with impact hammers. However, the use of the vibratory technique is seldom regarded as the first choice, since the technique is constrained by several uncertainties related to the pile capacity, and concrete piles to cope with tensile stresses. With the opportunities of having suitable subsurface conditions and a fair amount of piles to be installed, it was anticipated that the use of the vibratory method could result in a significant reduction of the installation costs. Part of the uncertainties of using a vibrator was intended to be eliminated by restriking the vibratory driven pile with an impact hammer and use a Pile Driving Analyzer? (PDA) to correlate recordings of soil resistance to driving with measured rate of penetration, and to evaluate the static capacity and load/settlement characteristics of the vibratory driven pile by conducting static load test. The conducted test study of using a vibrator to drive the precast prestressed test pile (14-in. square by 30-ft-long) did not turn out to the author's complete satisfaction. The present paper focuses mainly on a numerous practical engineering issues in relation to the use of the vibro-technique to drive precast prestressed concrete piles in granular soils. The obtained experiences of using a PDA to monitor vibro-driven piles, with its potential and limitations, is presented and discussed. Furthermore, a simple method of how to subjectively pre-estimate the soil resistance due to vibratory driving is presented and discussed. The reasons for the partly unsuccessful test study are discussed in great detail based on the obtained experiences. Suggestions of how to better approach a similar situation in the future are also provided in great detail

Jan 1, 2004

By Min Sunn Ye, Wei Wang, Huawen Xiao, Kai Yao, Fook Hou Lee, Siang Huat Goh

"Previous research have shown that introducing fibers to cement soil mixture is effective in improving the ductility as well as maintaining the strength of cement-treated soil. A good knowledge of stiffness of the improved soil at small strain is essential for realistic predictions of ground movements that may affect adjacent buildings or underlying infrastructure. This paper presents a triaxial system with local strain measurement developed for studying shear modulus degradation of cement treated clay with fibers. Cylinder specimens (70mm diameter by 140mm height) with 50% cement, 100% water, 0% to 1% polypropylene fibers by mass, and 7 days of curing period were used. A local strain measurement system with floating type miniature submersible LVDT is introduced in this paper. Configuration of the mounts including the pin size, length and distance are presented and discussed. Based on the experimental results, a reasonable configuration of the mounts is recommended for fiber reinforced cement treated clay. Results showed that the proposed local strain measurement system is effective for testing the shear modulus degradation of cement treated clay with fibers under both unconfined and confined condition. Comparisons with results from resonant column and bender element tests served to verify the reliability of the local strain measurements using the proposed method.INTRODUCTIONIn many geotechnical engineering problems, the operational strain domain ranges from 10-3% to 10- 1%. A good knowledge of stiffness at small strains is essential for realistic predictions of the ground movements that may affect adjacent buildings or underlying infrastructure. As such, during the last 3 to 4 decades, the importance of using the small strain stiffness of soils for the design of foundation and underground structures has widely been accepted. Triaxial testing has been widely used to study the stress-strain behavior of soil in the laboratory. However, the stiffness obtained from the conventional triaxial apparatus is usually far smaller than those back-calculated from field measurements. This is mainly attributed to the overestimation of axial strains from the external strain measurements, which usually includes compliance effects of the loading and load measuring system as well as sitting, bedding and alignment errors between sample and system (Baldi et al., 1988). The poor resolution of the external strain measurements is another important contribution. Therefore, conventional procedures are inappropriate for small-strain stiffness evaluation due to low accuracy and resolution."

Jan 1, 1900

By James L. Christensen, Gregory Sanchez, Michael P. Walker

The Fogg Museum expansion project required excavation and construction in a congested urban area in Cambridge, Massachusetts. A soldier pile tremie concrete (SPTC) wall provided the support of excavation and now serves as the permanent basement wall of the new expansion of the museum. The existing Fogg museum had a single basement level. The new expansion has a two-level basement for new exhibit space and an amphitheater. The east side of the site is about 20 feet above the basement level of the existing Fogg structure which resulted in a significant unbalanced load that needed to be resolved without damaging the original Fogg structure. The SPTC wall was supported with a combination of tiebacks and internal bracing. The final depth of the excavation was about 40 feet below street level. Strict movement control was imposed because the existing museum contained an Italian Renaissance-style courtyard. The southeast corner of the SPTC wall had to accommodate underpinning of an historic concrete ramp which was ultimately incorporated into the expansion. Challenges during construction included excavating the SPTC wall panels up to 12 feet into argillite bedrock which had occasional diabase dikes and sills. The following topics are discussed in more detail after a general project.

Jan 1, 2015

By Shawna Munn, Carol Dounitch, Erika Acton

The EQ Bank Tower, a 24-storey office tower with 4 levels of underground parking, is currently under construction at 25 Ontario Street in the downtown core of Toronto, Canada. The tower geometry required an 18 m (60 ft) deep excavation inside an existing 3-storey 100-year-old façade, to be retained in place throughout construction. This presented a variety of design challenges that required several innovations and a customized monitoring program. In this paper, we will discuss two major challenges, and highlight the innovative and adaptable solutions carried out using performance-based design leveraging the observational method. The first was installation of a shoring system in a 500 mm (20 in) gap between the historical façade and a live gas main. The second involved excavating 10 m (33 ft) into expansive shale bedrock adjacent to a sensitive neighbouring building.

Oct 1, 2022

By Ashraf M. Eid

Most research dealing with the problem of laterally loaded piles has been the response of individual piles subjected to lateral loads and/or bending moments. However, piles are seldom used individually but are normally constructed in clusters or groups. Little information is available of the effect of pile-soil-pile interaction (PSPI) on the performance of the group. This may be attributed to the difficulty of carrying out full-scale tests. Such tests are prohibitively expensive and require special installations to provide the required large lateral loads. The problem of laterally loaded single piles or pile groups involves the complexity of extending the theoretical solutions to the limits where the actual soil behaves nonlinearly. As the load increases, the elastic soil behavior cannot be adopted for design. Nonlinear soil behavior or the elasto-plastic behavior is evident. This research consists of experimental and theoretical models. The experimental work was conducted on models of free head pile groups in different configurations. The piles were in a sand formation and compared to the behavior of a single pile. The possible factors that influence the group behavior could be visualized. The experimental data was also compared to the widely used theoretical approaches to determine their adequacy. The analytical model makes use of the finite difference approach to calculate the soil non-linearity. A new approach equates the measured ground deflection and maximum bending moments of each row at every load level with the analytical model of single pile. This is the Deflection-Moment Fitting (DMF). The most suitable non-linear soil modulus modes and row contributions could thus be determined. Design of pile groups can be based on data pertaining to soil characteristics of the single pile. Results of the analysis were consistent with other approaches and proved to be adequate for design.

Jan 1, 2005

By Jesús E. Gómez

A total of 260 micropiles were installed as part of a retrofit effort for two existing bridges. The micropiles consisted of hollow core bars installed under limited headroom conditions. Of the total number of micropiles, 180 were installed in submerged sand and 80 were installed in stiff, silty clay. The micropiles were drilled using a lean cement grout which was re-circulated for de-sanding and re-use. Final grout was injected upon completion of drilling to the design tip elevation. The micropiles were subject to a rigorous quality control that included grout quality testing and proof-testing of each production micropile. This paper presents a description of the procedure for installation and quality control of the micropiles. The successful proof-testing of all the production micropiles showed that hollow core bar micropiles can be used effectively in granular and fine-grained soils. Hollow core bar micropiles offer particular advantages when installed in submerged sand formations with respect to other traditional micropile types. The results of the proof load tests are presented in a companion paper.

Jan 1, 2007

By Chu E. Ho

This paper describes a case history involving the use of the Equivalent Driving Energy concept for evaluating timber piles that failed to achieve the termination criterion traditionally based on final driving resistance and minimum pile depth. It was assumed that a pile would be acceptable if the overall energy delivered during pile driving was at least equal to that of an ideal pile that achieved the design pile capacity established during an initial load test. The equivalent driving energy was determined by integrating the cumulative driving resistance profile over the embedded length of the pile within the founding soil strata. The required equivalent driving energy was calibrated using representative restrike PDA capacities of production piles as piling progressed. This approach enabled piles that failed to meet the original acceptance criterion to be re-evaluated, resulting in a significant reduction in the number of rejected piles that would otherwise have to be replaced.

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 Anthony T. C. Goh, Zhiye Zhao, Laddu B. Jayasinghe, Hongyuan Zhou, Yilin Gui

"Ground vibrations from blasting are undesirable and they are very short in duration with high principal frequencies and high amplitude. Structural response to that kind of excitations may differ significantly from that generated by lower-frequency earthquake vibrations. In practice, the damage to nearby structures to generated ground vibrations has been controlled by various codes and regulations available. However, the existing vibrations limits are not always applicable, as they depend on the geological conditions of the site and the dynamic characteristics of the structure. This paper investigated the influence of the rock-soil interface on the response of pile foundation to ground-borne vibration from rock blasting, through numerical simulations using finite element software LS-DYNA. It is found that the slope of the rock-soil interface greatly influences the location of damage and the extent of damage on the pile. The bottom of the pile is subjected to a larger blast pressure and stresses are highly concentrated at the pile bottom. Thus, the pile bottom can fail in shear before it reaches its plastic moment capacity.INTRODUCTIONDrilling and blasting is the widely accepted method to large-scale rock breaking activities in civil engineering constructions due to its cost effectiveness, higher efficiency and ability to break hard rock. However, ground vibrations from blasting are undesirable and it can cause damage to nearby structures. In practice, the damage to nearby structures to generated ground vibrations has been controlled by various codes and regulations available. The existing vibration limits are not always applicable, as they depend on the geological conditions of the site and dynamic characteristics of the structure.Pile foundations are commonly used as foundations of high-rise buildings and bridges to transfer the heavy loads from the superstructure above through weak compressible soil strata into deeper, competent soil layers which have adequate capacity to carry these loads. In engineering practice, many piles are normally designed to carry mainly vertical loads and very little lateral loads, as typically the vertical loads (the gravity) are significantly larger than the horizontal loads such as wind loading. However, in recent years, there have been a number of reported case studies of translational soil movements that have induced stresses and bending moments that have damaged pile foundations and in some cases resulted in collapse of the superstructure. Typical lateral load include nearby construction activities such as an excavation for a basement or slope, the construction of a road embankment or a tunnel, as well as earthquakes (Abdoun 1997; Goh et al. 1997; 2003; Chen et al. 1999; Dobry et al. 2003; Boulanger et al. 2007; Black et al. 2007)."

Jan 1, 1900

By Osamu Taki

The innovative Soil-Cement Mixed Wall Technique emerged in Japan and obtained recognition in the engineering and construction communities in the 1980's. This technique was introduced to the United States in 1986. It was accepted as the most credible construction technique by the U.S. Bureau of Reclamation for ground stabilization and cutoff wall work in the Jackson Lake Dam Project, Wyoming in 1987 and 1988. It was also accepted as a remediation technique by U.S. EPA for a Superfund Innovative Technology Evaluation (SITE) demonstration on in-situ solidification/ stabilization. The Soil-Cement Mixed Wall Technique consists of mixing in-place soils with cement grout or other reagent slurries using multiple axis augers and mixing paddles to construct overlapped soil-cement columns. The overlapped column panel is then extended to form an underground continuous soil-cement wall for use as a cutoff wall or a structural diaphragm wall for groundwater control and excavation support. By arranging the column panels in various configurations, the technique becomes a versatile tool for stabilization of soft or liquefiable soils.

Jan 1, 1990

By Chang-Yu Ou, Shao-Chi Chien, Hsuan-Hsiang Chang

"A field test was performed to investigate the applicability of electroosmosis with the injection of saline solution of Taipei silty clay. The calcium chloride solution and sodium silicate solution were used as the saline solution for the injection in this test. The results of this study indicate that injection using calcium chloride solution and sodium silicate solution during the electroosmosis to increase drained water from cathode and electro-chemical reaction can greatly improve the effect of electroosmosis and shorten the time of treatment. The results of field vane tests showed that the undrained shear strength after treatment increased an average of approximately 120% for a treatment period of 24 days.INTRODUCTIONThe first field application of electroosmosis in soil was demonstrated by Casagrande in 1939. Since then, more complete field applications of electroosmosis such as Bjerrum (1967), Fetzer (1967), and Lo et al. (1991b) have been made.The results of field electroosmotic work for a period of 120 days were presented by Bjerrum et al. ( 1967). The mean undrained shear strength, Su, increased from 18 to about 40 kPa, with a uniform surface settlement of about 0.5 m. Lo et al. (1991b), with a more sophisticated installation and a relatively larger spacing, also had positive results. For a 3 m electrode spacing during the treatment of a period of 33 days, the mean Su increased from 18 to about 25 kPa. Although the effect of the electroosmosis could be applied in the field based on the above examples, the response remained slow. For actual field work, the application of electroosmosis will be limited due to short project schedules and request of the effect of improvement."

Jan 1, 2005

By C. Guney Olgun, Mohammad Khosravi, Daniel W. Wilson, Deepak Rayamajhi, Scott A. Ashford, Shuji Tamura, Ross W. Boulanger

"Dynamic centrifuge tests were performed on unimproved and improved soil with soil-cement column models. The reinforcing effect of isolated soil-cement columns for reducing liquefaction potential and ground deformation in improved soil were investigated. This paper presents the observed acceleration, pore pressure, and settlement responses under an earthquake base motion for both unimproved and improved soil models. In addition, lateral reinforcing effects of soil-cement columns were also investigated in terms of site stiffening effects and the increasing natural frequency of improved soil. The test results show that the soil-cement columns were rather ineffective in preventing liquefaction triggering in improved soil and in significantly reducing the magnitude of the resulting soil settlement compared to the model with unimproved soil profile. Furthermore, the predicted natural frequency of the improved soil profile estimated using existing design equations is shown to be significantly higher than the observed natural frequency inferred from centrifuge tests results. These design equations assume shear strain compatibility between the columns and the surrounding soil. On the other hand, revised design equations that account for shear strain incompatibility between column and surrounding soil are shown to give reasonable estimates compared to the observed natural frequency of the improved soil model.INTRODUCTIONGround improvement using stiff columns (e.g., stone columns, deep-soil-mixing columns, and jet-grout columns), are often used in practice to reduce liquefaction potential (and associated deformations) in loose soil sites. Typically, saturated silty soils are difficult to densify or drain rapidly due to their lower hydraulic conductivity, so densification and drainage techniques of improvement are often found to be ineffective. Instead, the shear reinforcing mechanisms of stiff columns are considered effective for reducing the seismic stresses and strains, and thereby reducing liquefaction potential in the enclosed saturated silty soils (Baez 1995, Adalier and Elgamal 2004, Mitchell 2008)."

Jan 1, 2015

By Gerry Houlahan

The east span of the 3.5 km long SF-Oakland Bay Bridge is supported by different types of foundations along its span. Starting from the west, its first 460 m section comprising twin concrete box-girders is supported by sands and rock on Yerba Buena Island. A 620 m long steel suspension span then bridges a 25 m deep channel that is formed in sediments overlying rock. Twin concrete box girder structures, each 2.4 km long, complete the stretch over the remainder of San Francisco Bay to the engineered earth fill landing at its east end. For most of its length, the Skyway bridges water 3 to 10 m deep over soft surficial Young Bay Mud. The foundation types include spread footings with hold-downs, steel and concrete piles that are set in drilled rock sockets up to 3 m in diameter and 2.5 m diameter steel tubular piles driven to penetrations of up to 100 m. The design and construction-related considerations are presented. The different foundation types, influences of the site geology and earthquake demands on the substructures are discussed. The seismic motions of the bridge superstructures and substructures, as well as the depth-varying soil motions, influenced the foundation design. Together with performance-based design criteria, including post-earthquake footing displacement limits, these seismic demands influenced various aspects of the foundation design, including the use of battered and vertical piles.

Jan 1, 2013