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By M. Hesham El Naggar, Tony Sangiuliano, Alper Turan

"Bridge abutments supported on pile foundations are often constructed over weak and compressible soils. The consolidation settlements induced by the embankment loads are known to result in downdrag and lateral forces on the piles supporting the bridge abutments. The performance of a pile group including inclined piles embedded in consolidating soils was investigated numerically considering surcharge loads from approach embankment construction. A two-dimensional numerical model was constructed using commercial finite element software PLAXIS and calibrated against field measurements of the abutment movements observed on Brookdale Avenue Underpass Structure located on the Macdonald-Cartier Freeway in Ontario between Cornwall and the Quebec border. The soft soil model (SSM) was used to simulate the constitutive behavior of the compressible soil deposit. The SSM model parameters were determined based on the laboratory tests. Subsequently, time dependant development of downdrag effects was comparatively evaluated for vertical and inclined single piles as well as a pile group that included both vertical and inclined piles.Results showed that drag loads increased with the consolidation time. However, majority of accumulation of drag loads took place within first 120 days after installation of piles. The results also indicated that the shear forces and bending moments are controlled by the lateral spreading of foundation soil and their accumulation is proportional to consolidation time. The large axial strains caused by large downdrag forces are considered to have yielded the piles and this is a possible reason for unusual abutment movements. The results presented in this study are considered to be of interest to researchers and practitioners.1. IntroductionDeep foundation units are widely used for supporting bridge piers and abutments, where weaker surficial soils preclude shallow foundations. Particularly in Ontario, semi-integral and integral abutment bridges are typically supported on end-bearing steel driven piles. The construction of approach embankments over weaker, compressible soils results in significant vertical and lateral soil movements, which induce additional loads on piles supporting the abutments. In order to minimize such effects, preloading and surcharging are commonly employed approaches to avoid unanticipated settlements prior to the installation of piles. Other alternatives such as aggregate pier supported approach embankment are also being studied as the schedule restrictions imposed by preloading and surcharging becomes cost prohibitive (Turan et al. 2012)."

Jan 1, 2015

By Deepak Pappusetty, Miguel A. Pando

This study is motivated from the increased interest in recent years to explore use of Ocean Energy Converters (OEC’s).OEC’s can be tidal or generate electricity from wave or current action. Design of foundation systems for these OEC’s is a key consideration as it can represent about 35% of the initial installation cost. The primary focus of this paper is related to foundation systems involving monopiles where a key design consideration includes gradual accumulation of pile head deformations beyond serviceability limits of the OEC. This design consideration is important since these foundation systems are often subjected to more than 108 low amplitude repetitive dynamic load cycles during a normal 30 year design life. Research on single model piles installed in sand and subjected to over 104 low amplitude lateral load cycles have shown that pile head displacements and rotations tend to increase gradually with increasing load cycles. This gradual development of pile head deformation is related to plastic strain accumulation in the soil in the vicinity of the monopile. Analytical methodologies based on conventional p-y curves typically cannot predict these accumulated pile head rotations and displacements. Even 3D dynamic Finite Element Analyses may not capture this response for several conventionally used soil constitutive models. This manuscript presents predictions using p-y based methods as well as 3D dynamic finite element analyses. The different numerical predictions are compared to available experimental data. Results from this study show that conventional p-y methods do not predict the gradual pile head displacements observed experimentally. Modified p-y curves, developed for cyclic loading, do a better job than conventional p-y curves but tend to greatly under predict deformation. This is believed to be related to the cyclic load test data used to develop these cyclic p-y curves which involved at most up to 500 cycles and did not include high frequency contents or partial unloading cycles. The 3D FEA captured reasonably well the general observed trends of gradual accumulation of pile head rotation and lateral deformation with increasing constant amplitude lateral load cycles.

Jan 1, 2015

By Ramdane Bahar

The new Algiers airport building is a reinforced concrete building of more than 80 thousand square meters of floor slabs. It is located at Dar-EI-Beida, near the old passenger terminal, about 20 km east of Algiers. The project is designed to receive about six millions passengers annually and leaves the possibility of future extension. Due to the presence of a top layer of compressible soil and great concentrated loads transmitted to the foundations, the building is to be founded on 1730 bored piles of 1.2 meter diameter varying in length between 14 and 28 m. Construction work started in 1986 and was interrupted in 1996 due to financial difficulties when the structure was almost complete. The structure was left unattended for more than three years without any weatherproofing and in 1999 a new firm was appointed to complete the work and hence an evaluation of the existing structure was necessary. This paper describes and discusses the foundation design, construction supervision, site quality control and assessment by the parallel seismic method of the deep foundations built in cohesive soils. The variation in soil conditions and identified geotechnical and hydrogeological problems associated with the development of the area, required a thorough knowledge of the soil conditions. A variety of tests, involving more than 200 locations, were carried out. The ground investigation, pile tests as well as different problems encountered during piles construction, are presented.

Jan 1, 2002

By Fredrik Sarvell, Harald. Ihler, Veli-Matti Uotinen, Jukka Rantala

"Many of the valid international building codes state that the lateral support provided by the soil is sufficient to prevent buckling of fully embedded piles. However, the development of small diameter micropiles and especially the use of high strength steel have evolved to applications including high capacity elements. The ultimate structural load bearing capacity of a pile in a cohesive soil is decided by examining which gives the lowest value, the peak buckling load and the resisting moment provided by the surrounding soil medium or the structural capacity of the pile cross section. In both cases, the initial deflection of the pile is a significant factor when the axial load bearing capacity of the pile is determined. Steel micropiles are joined commonly with mechanical splices. A less rigid mechanical splice is often a weaker hinge that allows the pile to bend and deflect more during installation increasing the initial deflection of a pile. In addition the less rigid splice element decreases the bending capacity of a jointed pile section and the ultimate axial load capacity of the entire pile. A series of FE analysis performed for various pile sizes suggest that the steel pipe piles including separate pile sections and mechanical splicing elements should have the combined bending stiffness of EIshaft = 0,75 × EIpile. This requirement yields to the buckling resistance of at least 96 % of the solid reference pile with the sameinitial eccentricity in similar soil conditions.IntroductionMany of the valid international building codes state that the lateral support provided by the soil is sufficient to prevent buckling of fully embedded piles. However, the development of small diameter micropiles and especially the use of high strength steel have evolved to applications including high capacity elements. The potential buckling of these very slender high capacity piles in soft soils may in many cases be the controlling design factor of the pile, especially with end bearing micropiles.A typical sequence of soil strata in Nordic countries, such as Norway, Finland and Sweden, constitutes of friction soil or dry crust clay on top of soft clay followed by till. This soil stratum often rests on solid bedrock of granite or gneiss. Conditions like these are suitable for slender end bearing piles subjected to buckling and especially steel pipe piles where most of the material is located at the edge of the cross section. Other reasons for using slender steel pipe piles are for example fast installation with minimal waste, efficient manufacturing and relatively well established design and execution procedures. Minimum quality criteria’s regarding splices for steel pipe piles are recommended to be set as national provisions to ensure quality and comparable procurements in foundation business."

Jan 1, 2014

By Josef K. Alter

Long-term performance and behavior of post-tensioned ground anchors subjected to axial cyclic loading constitutes an important aspect of the stability, reliability and overall performance of wind turbine deep foundations. Axial cyclic loading of post-tensioned (PT) ground anchors in soils has not been thoroughly investigated as evidenced by the research conducted for this topic. This paper evaluates research test data, available literature, and industry expert opinion on the current status and problems of deep foundation post-tensioned ground anchor (PTGA) technology, as applicable to the wind energy industry. It also introduces a proposed design solution that addresses the problems of construction cost and long-term performance of wind turbine deep foundations in soils subjected to dynamic cyclic axial loading. Deep foundations using ground anchors for wind turbines have only recently gained attention as a possible viable alternative to the mass spread footings currently in use. One of the primary problems with general acceptance of current PTGA designs is the need for long-term anchor maintenance. The research that was conducted for this study indicates that current literature only partially addresses the many factors influencing load capacity and pullout performance of ground anchors. The lack of information indicates the deep foundation industry has fallen behind in designing and implementing new technology to improve safety and performance, ensure sustainability, reduce costs, and address environmental responsibility. This paper describes the significance of this problem as it applies to the wind energy market, and proposes a new technology solution. The research, expert opinion, and analysis presented by the author is used to support the premise that ground anchor construction cost and long-term maintenance can be reduced with PTGA systems using the Con-Tech Systems (CTS) patent-pending Groutable Void Form (GVF) technology.

Jan 1, 2010

By Richard Hanke, Franz-Werner Gerressen

"The twin decked Alaskan Way Viaduct is a passage to Seattle’s downtown waterfront and of great economic importance to the city. In 2001, the Nisqually earthquake damaged the viaduct and led to the redevelopment of this corridor. The project includes two miles of 57.5 ft diameter bored tunnel beneath downtown Seattle and a stretch of new highway and overpass bridges at the southern tunnel entrance. State-of-the-Art special foundation equipment was mobilized for the project to perform a broad range of geotechnical construction. Applications included soil mixing and jet grouting for confinement cells around new bridge foundations, large diameter secant pile walls for the Tunnel Boring Machine launch portal along with an extensive jet grouting regime for ground improvements within the tunnel alignment. This paper will study the evolution and use of advanced special geotechnical construction equipment and describe its application at the Alaskan Way Viaduct Replacement Project.INTRODUCTIONThe evolution of geotechnical construction equipment continues through innovative applications and continued modification or enhancement of machinery. Similarly and in parallel, market expectations continually demand more in terms of construction speed and performance. Together, market demands and contractor innovation have led way to the development of specialty geotechnical construction equipment with capabilities previously not seen feasible or possible. Several examples of this scenario have recently developed during design and construction of the Alaskan Way Viaduct Replacement Project.The Alaskan Way Viaduct Replacement Project is a joint project between the Federal Highway Administration (FHWA), the Washington State Department of Transportation (WSDOT), and the City of Seattle. Three build alternatives were under consideration for replacing the Alaskan Way Viaduct: the Bored Tunnel Alternative, the Cut-and-Cover Tunnel Alternative, and the Elevated Structure Alternative. Ultimately, the bored tunnel option was selected as the best value approach. The project includes two miles of 57.5 ft diameter bored tunnel beneath downtown Seattle and a stretch of new highway and overpass bridges at the southern tunnel entrance. Several other associated improvements tie into this project that will ultimately lead to the complete demolition of the viaduct and redevelopment of Seattle’s waterfront."

Jan 1, 2015

By Yahia M. Al-Smadi

Effect of lateral loading against existing sheet pile wall and distribution of gravity loading due to various number of construction loading scenarios were studied. The objective of this effort was to determine the loading case that permits the contractor to utilize a 400 ton crane at the specified location with the existing limitation imposed on site. Staged analysis was determined as the methodology that will more accurately predict the exiting and additional stress due to the impose crane loading. A reliable and robust analysis (ANSYS) software was used to complete both 2D and 3D finite element model and analysis. Analysis model parameters such as material properties, non-linear behavior of the soil, and meshing are presented and discussed. At the conclusion specific range of crane operation and pick weights operating on existing concrete mat supported on top of an existing tunnel was reviewed and deemed acceptable.

Jan 1, 2010

By Rasin Duzceer

In this paper, the results of pile load test on 24 piles from twelve sites are presented. The pile load tests were performed on 14 driven and 10 bored piles of varying diameters and lengths installed in different ground conditions in Turkey, Saudi Arabia and Kazakhstan. The purpose of this study is to evaluate and compare the axial capacity of the piles obtained using pile load test interpretation methods. Davisson, Brinch Hansen %80, Chin-Kondner, Shen-Niu, De-Beer, Housel, Mazurkiewicz, Fuller-Hoy, Brinch- Hansen (90%), Corps of Engineers, Butler Hoy and Tangent Intersection methods were used to determine the axial capacity of the piles. Static analysis using FHWA method was performed to predict the axial capacity of the piles. A statistical analysis was performed to compare and quantify the load test interpretation methods. The ratio of interpreted (Qi) to predicted (Qp) pile capacity was compared for each method. For each pile load test and for each interpretation method, the mean and coefficient of variation of (Qi)/ (Qp) were calculated. Among twelve methods investigated, the highest Qi/Qp value was obtained as 1.37 for Chin-Kondner method whereas the lowest Qi/Qp ratio of 0.70 was obtained from De Beer method.

Jan 1, 2002

By Alice Y. Tseng, Dan MacLean

"Corrosion protection of all deep foundation systems made of steel is THE issue when considering durability of the element in the long term. Protecting steel from corrosion and maintaining the steel tendon cross sectional area ensures a competent and durable system. The foundation of a building is usually difficult to repair and therefore high risk is taken when unknowingly choosing a non-adequate solution.Requirements according to EN 1990 (Eurocode 0 or EC 0) on construction durability requires a service life over 100 years. How can a service life over 100 years be achieved? How shall bare steel be protected in soil, which sometimes could be an aggressive environment to the steel? Which corrosion protection methods are commonly used in Europe and in North America?This paper will focus on hollow bars used as Micropiles, Anchor piles and Soil Nails. It gives an overview about the state of the practice in regards to corrosion protection (including head construction) and evaluates different options following the European Standards focusing on type of material and method of installation. Further the different corrosion protective methods such as thickness of grout body, coating types and sacrificial loss are listed with the pros and cons evaluated.Based not only on North American standards like FHWA “Micropile Design and Construction Guidelines”, FHWA Geotechnical Engineering Circular No. 7 for “Soil Nail Walls“ and Post-Tensioning Institute “Recommendations for Prestressed Rock and Soil Anchors”, but also European standards like EN 14199 “Execution of special geotechnical works – Micropiles”, EN 14490 “Execution of special geotechnical works - Soil nailing”, EN 1537 “Execution of special geotechnical work – Ground anchors“, and other relevant standards, all possibilities of protecting the hollow bars and the steel quality will be introduced, discussed and compared ."

Jan 1, 2017

By Clifford J. Wren

A geotechnical foundation solution was required to halt and prevent further structural distress suffered by a residential four storey apartment building in Hamilton, Scotland. Residents of the ten year old building started to notice cracking and signs of distress approximately one year after moving into the property. A detailed intrusive inspection of the structure revealed that the building was moving and had suffered significant settlement and structural distress at the shared party wall between it and an adjoining building. Roger Bullivant Limited (RBL) was appointed Principal Contractor to carry out an agreed remedial works contract which included a complete structural ?strip-out? of the ground floor, underpinning, contiguous bored pile retaining wall and reinstatement. The paper describes how a proprietary pile and needle beam underpinning system was used to prevent further differential movement and provide a new secure foundation for the residential building. The case study illustrates how a flexible problem solving approach can be applied to a difficult and sensitive geotechnical project.

Jan 1, 2008

By Jon E. Bischoff

Construction of a secondary clarifier on the banks of Rainy River, Northern Minnesota, required the driving of H-piles 14HP102 to a sloping, very strong bedrock through thick deposits of soft and medium stiff soils. Pile toe protection, APF Hardbite HP 77750, was specified to prevent damage to the pile toe and to enable the pile toe to bite into the bedrock surface. The toe protection worked well for bedrock sloping less than 2H:1V. However, where the bedrock was steeper, the piles experienced damage and failed to reach bearing. In most cases, the also the replacement pile failed. Pile Driving Analyzer measurements showed that on encountering the bedrock, the pile toe reflection, which at first was sound, deteriorated indicating pile toe damage. Extraction for visual inspection showed that the failed piles were bent and had deformed pile shoes. In areas of steeply sloping bedrock and for replacement piles, an alternative shoe, the Scanpile Herkules rock shoe, was employed. This pile shoe proved to be able to secure the pile toe into the rock and to eliminate the problem. The costs of the Herkules rock shoe considering price, shipping, and attaching, were about equal with the Hardbite shoe.

Jan 1, 1993

By Nathan A. Ingraffea

The use of steel sheet pile walls and drilled shaft foundation elements to enable up-down construction methods has been used successfully on recent high-rise structures with multi-story below grade parking. The John Ross Tower and The 3720 Tower in Portland, Oregon each make use of this system and are discussed in-depth. Up-Down construction involves the simultaneous construction of the building levels above and below grade instead of the standard construction technique of excavating and shoring the below grade construction before being able to build upward from the base of the excavation. Advantages of the up-down system include a shortened overall construction schedule, permanent basement walls that double as the temporary shoring walls, elimination of the typical continuous wall footing or grade beam at the building perimeter, increased use of recycled material (steel) while maintaining an overall decrease in total materials, elimination of wall forming costs, decreases in forming costs for slabs, decreases in waterproofing costs for walls and elimination of pile caps and/or footings for the building columns. Lessons learned during the construction of both buildings include the need for more extensive geotechnical boring information, descriptive sheet pile and drilled shaft specifications, a clear understanding from the design team on finished appearance of sheet pile and shafts, and careful consideration of the connection between both slabs and the sheet pile wall and slabs and drilled shafts.

Jan 1, 2008

By Vladimir M. Korolev

The field studies conducted at the experimental-production sites allowed to develop the technology of arranging drilling piles in loess subsiding grounds over 25 m deep and over 250 mm in diameter, to select optimal compositions of flush fluids, to assess the carrying capacity and field of use of the piles under test and to produce a special equipment. The dependence of the ultimate axial pressing-in load on pile driving into the non-subsiding section, its diameter and method of fulfillment, as well as the ground moisture dependence of the specific ground resistance along the piles' side surface within the limits of the subsiding section were determined. The study results allowed to reduce the length of the work piles and the number of bars in the reinforcement frames. The obtained experimental data enable to give a preliminary assessment of the piles' carrying capacity under complicated engineering-geological conditions of subsiding grounds.

Jan 1, 2002

4.5.1 General The provisions of the article shall apply to the design of axially and laterally loaded driven piles in soil or extending through soil to rock. 4.5.1.1 APPLICATION (Revised Article 4.3.1.1) Piling may be considered when footings cannot be founded on rock, or on granular or stiff cohesive soils within a reasonable depth. At loca-tions where soil conditions would normally permit the use of spread footings but the potential for scour exists, piles may be used as a protection against scour. Piles may also be used where an unacceptable amount of settlement of spread footings may occur. 4.5.1.2 MATERIALS Piles may be structural steel sections, steel pipe, precast concrete, cast-in-place concrete, prestressed concrete, timber, or a combination of materials. In every case, materials shall be supplied in accordance with the provisions of this Article.

Jan 1, 1989

By Emad Farouz

This paper compares the predicted axial capacity of driven Pre-cast Pre-stressed Concrete (PPC) piles for the Lake Gaston Water Treatment Plant (LGWTP) using several design methodologies versus the axial capacity measured from dynamic and static load testing. The LGWTP site is located in Chesapeake, Virginia and is part of the Great Dismal Swamp. The subsurface investigation included soil borings, in-situ dilatometer (DMT) tests, and in-situ piezocone (CPTu) tests. The axial capacity predictions of the PPC piles were performed using the computer programs DRIVEN and FB-DEEP which are based on SPT N-values. Additionally, an empirical method proposed by Martin, et al. (1987) based on local experience with PPC pile design in the Yorktown formation in the Tidewater area of Virginia was also evaluated. Finally, the ?Laboratoire Central des Ponts et Chausées (LCPC)? method developed by Bustamante and Gianeselli (1982) based on CPT measurements was also used to develop the axial pile capacity of the piles. This paper shows that the FB-DEEP computer program and the LCPC method provided a reasonably good prediction of the pile axial capacity measured from PDA, CAPWAP, and Static Load Tests in comparison with the other design methods used. The soils in this area develop significant setup over time and it was found that FB-DEEP and the LCPC method are capable of incorporating this setup in the prediction of the long-term axial capacity of driven piles in this area.

Jan 1, 2007

By Jorj O. Osterberg

The practice of using side shear resistance in the design of drilled shafts socketed in rock is discussed. In the absence of field test data for the particular rock involved, the designer often neglects the side shear altogether or uses an extremely conservative value. The uncertainty of using strength data from compression tests on rock cores is discussed. Examples of full scale load tests are given which illustrate that even in the weakest of rocks, considerable side shear resistances are obtained, enabeling reductions in the depths of the sockets and consequent savings. Existing Practice. The existing design practice in using side friction/bond between a drilled shaft in rock or hard soil varies very considerably in different areas of the U.S., in different areas of the world, among different Geotechnical Engineers, and in the requirements of different building codes. In fact, the variation is so great that it is inconsistent and contradictory. For example, in Florida where fairly weak coral limestone and sandstone is prevalent, the general practice is to use side friction only and to allow no end bearing. In Chicago, Detroit, Boston and other areas where soft clay overlies stiffer clays, hardpan and limestone or other hard rock, the common practice is to allow for no friction and to use end bearing only, even though the lower portion of a shaft frequently penetrates stiff to hard clays and hardpan (glacial till) before bearing on hardpan or rock. In Hong Kong, if the hole is stabilized with drilling mud, no end bearing is allowed. In Boston (Thompson, Erikson, and Smith, 1989), two tests at two sites on 18 inch pipe piles penetrating 100 feet of soft clay and driven only inches into an argillite, tested 140 and 210 tons in ultimate side shear resistance. Certainly, with long drilled shafts, no matter how soft or weak the soil or rock is, some if not considerable side friction occurs, and where drilling mud is used, there must be considerable end bearing.

Jan 1, 1991

By Salim Mezazigh

Usually different methods for designing a single pile submitted to a lateral loading are available. They are based on theory of elasticity with the parameters E,v or subgrade reaction method using the p-y curves. The subgrade reaction methods are commonly used. They allow determining the efforts exerted along the piles and their corresponding displacements. Before any design the reaction curves P-y must be well defined for each foundation soil layer. These curves link the pile horizontal displacement y to the subgrade reaction of soil P. Different in situ tests such as the static penetrometer or the pressuremeter give a possibility to get the P-y curves in the case of a single pile installed in sand with an horizontal surface and statically laterally loaded. These ideal conditions are not always respected on the site around the pile if appear slopes, embankments, or buildings... The behaviour of such configurations of piles is more sophisticated due to the proximity ( slope, embankment, earthworks, buildings,..). A research program has been conducted to determine the influence of a slope on the P-y curves by centrifuge modelling. The centrifuge tests constitutes an experimental approach allowing parametric studies in respect with similitude laws in geotechnique. Before all, repeatable tests have demonstrated that the test conditions, the instrumentation equipment and the installation method for piles are well controlled. By this way, the obtained results from centrifuge tests can be transferred to the prototype i.e. the in situ piles. Many tests have been performed on piles in sand to determine the influence of a pile on the p-y curves. The main objective is to give for practice some coefficients to apply to p-y single pile curve to take into account the proximity slope effect. Here the experimental set up is described and in particular the proximity slope effect is discussed. Deduced subgrade reaction reduction factors are proposed for piles in sand under lateral loading.

Jan 1, 2002

By Ross Cutts

As a public servant geotechnical engineer, I observed how costly and valuable geotechnical field explorations are to the success of every project. Often however, the field exploration is a long and complex process that is made less efficient by the difficulty of retrieving and utilizing nearby internal or external historic geotechnical datasets. As an employee of a public agency, we would often start our investigations for every project from scratch, given the difficulty of locating and utilizing historic geotechnical data. This is an ethical and technical failing of our profession. When we start subsurface explorations from scratch, not only do we often duplicate investigations, we are also likely defaulting to reapplying tradi- tional test methods that yield con- servative geotechnical parameters, resulting in overly conservative and potentially costly construction. To address this issue while working as a public servant, I started a research program with Yunfeng Zhang, Ph.D., of the University of Maryland, to build a tool that could compile internal historic geotechnical data and extract additional value from it, using machine learning. This tool was able to provide, upon request, nearby historic geotechnical data, estimated soil parameters and recommendations for geotechnical test methods best suited for a given project site. This prevented common field ex- ploration problems such as, requesting duplicate data, requesting test methods that were not applicable for the project geology, not realizing presence of karsts, missing permits for wetlands, private property and others. This tool allowed for more efficient field investigations with regards to time and money saved. There was one problem with this tool: it could only be used by internal employees of a single state's depart- ment of transportation (DOT) for which this data was compiled. I realized at that point that it would be of tremendous value to make this concept universally accessible to the geotechnical engi- neering profession. I left public service to devote time to building a platform that would host historic geotechnical data from publicly funded sources throughout the country. The tool I helped build as a public servant was the foundation of Geosetta, a nonprofit company dedicated to serving the geotechnical profession. The nonprofit structure was adopted to prevent acquisition by a for-profit company and to ensure that Geosetta remains an independent steward of our profession's valuable data. Geosetta provides a GIS (geographic information system) platform that enables users to view historic geo- technical data and extract value from it with machine learning-based predictions and visualization tools. This data is provided in an open and interchangeable format called DIGGS, which stands for Data Interchange for Geotechnical and Geoenvironmental Specialists, making it easy for users to integrate it into their workflows. Geosetta is collaborating with the American Society of Civil Engineers' Geo-Institute and other sponsors to extract public data at no cost to the agency and provide the profession with free access to the existing data and access to advanced tools through a subscription to support the nonprofit mission.

Nov 1, 2023

By Wei Tu

A grade separation was required to allow uninterrupted traffic crossing for a busy rail spur and a county road. The grade separation was achieved by creating a 30-foot (9-meter) high embankment that incorporates two multiplate tunnels and allows the passage of a rail spur and an existing county road. The site is located in an abandoned meander channel in the floodplain of the Mississippi River, near Osceola, Arkansas, and is underlain by more than 40 feet (12 meters) of soft clay and interlayered clays, sands and silts. Without soil improvement, the post-construction settlement would exceed 3 feet, slowly crushing the proposed tunnel structure and cutting off the railroad. Preloading, combined with vertical drains, was used to accelerate the consolidation of the underlying soil layers and to reduce the post-construction settlement under working loads. Six settlement plates were installed to monitor the progress of consolidation under surcharge load. The Asaoka observational method and the hyperbolic fitting method were used to analyze the measured settlement data to predict the end of primary settlement. The in-situ consolidation coefficient, ch, was back calculated from the measured settlement data. The stress release caused by the removal of the preloading surcharge load and the tunnel installation was determined using a Plaxis 3-D finite element model. The measured and predicted settlement using Hansbo's analytical solution demonstrated reasonable agreement. Early removal of the surcharge and construction of the tunnel prior to reaching the end of primary settlement was accomplished by analyzing the post-excavation stress reduction achieved via tunnel construction.

Jan 1, 2009

By James Warner

Although use of low mobility grout is just now beginning in some parts of the world, its advantage for many applications has been well established through more than 50 years of positive experience. The single largest area of application continues to be densification of soil by way of compaction grouting. Because it is often the safest and least costly method for soil improvement in general, and virtually always that in connection with soil improvement under, or adjacent to structures or in developed areas, use will undoubtedly increase both geographically and in diversity of application.

Feb 10, 2003