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By Katerina Ziotopoulou, Martin Yossifov, Jim Gingery, Katherine Cheng

Soil mixing is an in-situ soil treatment method that consists of mixing cementitious binders with in-situ soil to create soilcrete. The success of this treatment often relies on the value of the Unconfined Compressive Strength (UCS) of the soilcrete after a given curing time. Estimating the UCS can be challenging because numerous factors influence the results, including soil type, soil moisture content, binder content, soil chemistry, soil heterogeneity, and mixing means and methods. In current North American design-build practice, pre-construction design UCS values are typically estimated qualitatively based on a contractor’s experience. Existing correlations may not be suitable for current applications because of recent advances in deep mixing equipment and methodologies. There is a need for more rational and quantitative estimates of UCS for use in pre-construction design analyses.  This paper will explore the intersection of Machine Learning (ML) with geotechnical engineering and soilcrete applications. A database of soilcrete UCS and site/soil/means/methods metadata is compiled from recent Keller projects and leveraged to explore UCS prediction with advanced ML regression techniques. From this ML exploration, a blueprint of how to scaffold, feature engineer, and prepare soilcrete data for various ML techniques will be created. However, many ML models sacrifice explainability for higher accuracies. To achieve insights from ML models, Explainable ML will be applied to the ML models to explain variable importances. Explainable ML can reveal complex patterns and interactions in the model variables, along with the relative importance of each variable’s contributions to the final UCS value. The insights received from the Explainable ML model can then be further pursued in traditional geotechnical research approaches to expand soil mixing knowledge.

Oct 7, 2024

By Yu Chuang, Zai Jinmin, Liu Songyu

"The piled raft foundation is a geotechnical composite construction method, consisting of three elements, piles, raft and soils, which is applied for the foundation in an increasing number. Differential settlements have numerous negative effects on a superstructure in piled raft foundations. Through the analysis of the production mechanism of differential settlements and differential settlements control measures, a method of adjusting pile configurations is presented to control differential settlements. By comparing the measured data and finite element method analysis of one oil storage piled raft foundation, the new method is verified that the differential settlements can be reduced effectively and the inner forces of foundations are more reasonable with varying length pile configurations. The differential settlements can be minimized or even reduced to zero with right pile length.INTRODUCTIONPiled raft foundations are widely adopted for the prominent advantage of limited settlements and adequate bearing capacities. However, there always exits differential settlements in conventional piled raft foundations. The differential settlement is the main cause that produces additional stresses in the structure. Differential settlements have numerous negative effects on a superstructure as well as on a foundation, and should be restricted to allowable limits. How to control the differential settlement is the key interest.An increasing number of structures are founded on piled rafts. For this reason, design strategies that enable an optimized design have a major importance for safety and economy. An optimized design may be defined as a design achieving maximum economy of the solution, that is minimum cost for the installation of the foundation."

Jan 1, 2005

By Douglas L. Scaggs

Over the past several years, pile foundations have grown to meet the demands of larger and heavier structures. As the foundations have grown, so has the need for larger and more robust piles to carry the increased loads. Seismic considerations have also required larger and tougher piles to withstand the added component of supporting structures during earthquakes. While H-piles, precast concrete piles, timber piles and small pipe piles have been the product of choice, many applications are now calling for much larger piling requiring larger equipment and presenting the contractor with new challenges. This paper is not intended to be a ?how to? guide as much as a discussion on the potential pitfalls a contractor should watch out for when considering a project where mega piles are required.

Jan 1, 2013

By Bernhard Bruggaier

Outside the oil and gas industry there is an increasing demand to install big piles for the foundation of ports, bridges, and wind-energy plants. This article introduces the design and techniques in using large MENCK pile driving hammers to install big foundation piles. Piles with a length up to 120 m, an outside diameter of 1.0 m to 3.15 m and weighing between 25t and 400t are being driven for these types of foundations. The required energy lies between 200 and 1700 kNm. Pile driving hammers that bring this amount of energy weigh from 38 to 300t and have a length between 10 and 20 m. Handling these big pile driving hammers requires a crawler crane on land or cranes on floating pontoons or jack-ups when working in water. Possible are either vertical or inclined piles, using a leader for inclinations up to 1:1.7 or up to 1:3 in a free riding version. Project descriptions demonstrate the versatility and practical use of the equipment under diverse operating conditions.

Jan 1, 2002

By Paul J. Lewis

Estimation of the axial side shear resistance of drilled shaft rock sockets is directly related to the unconfined compressive strength of the bedrock. Commonly, the mean unconfined compressive strength value is calculated from a range of laboratory test results and is used to estimate the side shear of the bedrock. This paper presents the results from a full scale axial load test performed on an 8.5-feet-diameter drilled shaft rock socket, and compares measured side shear values to estimated values for two different rock strata. Measured side shear values correlated well with the design value calculated for the ?strong? rock stratum, but did not correlate well with the design value calculated for the ?weak? rock stratum. The mean unconfined compressive strength was used to calculate the side shear in both strata, but review of the laboratory data indicates that this value may not have been appropriate for the weak stratum due to a large variation in the laboratory test results. Also included in this paper is a discussion of the subsurface conditions, the laboratory test results, and the methodology used to design the drilled shaft rock sockets for axial and lateral resistance.

Jan 1, 2013

By Peter J. Nicholson

Recognition of the liquefaction susceptibility of dam embankments has been heightened since the San Fernando Dam near failure incident in 1971. Both the downstream and upstream slopes of dams can be at risk for slope failure that can lead to breaching of the dam during or after a seismic event. Many dams have been remediated by various means such as the installation of stone columns or by excavation and replacement of the liquefaction susceptible material. Recent engineering and technology advances in equipment and materials has shown that construction of shear walls to the appropriate depths and at the right center to center spacing may be an economical alternative to the more traditional methods. Recently, the downstream embankments of at least 4 dams, from South Carolina to California, have been, or in the process of being remediated by the use of shear walls. The method of installation has been either multi-axis Cement Deep Soil Mixing walls or walls constructed by the use of trench excavation under self-hardening slurry. Four case histories of dam remediation are discussed, three by multi-axis paddle auger CDSM equipment one with the use of self hardening slurry trenches.

Jan 1, 2008

By Jr. D'Angelo, Michael M. Blendy, Shawn Downey

"A grouted helical pile was used to support new buildings in the reconstruction of a large residential development. Foundation options were complicated by urban fill underlain with variable alluvial soil. A driven timber pile and grade beam system was recommended to support the new buildings. Other foundation options are also discussed. The grouted helical pile was quoted as an alternate and ultimately won the bid based on the economics and performance of the system. Data from 8 load tests was used to develop an empirical site specific relationship for determining pile capacity based on both installing torque and installation depth. Design to incorporate tolerance on installed pile location is presented. With the three phases completed, 554 residential dwelling units supported by 3645 grouted helical piles had been constructed covering 18 city blocks on the 44 acre site. IntroductionThe Philadelphia Housing Authority reconstructed the Tasker Homes housing complex located in southern Philadelphia, Pennsylvania, adjacent to the Schuylkill Expressway in the Grays Ferry area. Keating Building Corp. and Pennoni Associates were the general contractor and the structural engineer respectively. The original Tasker Homes development was constructed from 1940 to 1941 and consisted of 44 acres of primarily two and three-story residential brick buildings. These buildings were supported by a timber pile foundation system. The structural condition of the buildings supported on the timber piles was generally good in comparison to areas outside the buildings. These areas had settled possibly up to 2-feet in places due to the heterogeneous nature of the urban fill."

Jan 1, 2005

By Gokhan Inci

Stability problems with dam spillways on existing landslides and appropriate mitigation measures to remedy them are ongoing concerns for geotechnical engineers. The first successful application of drilled piers as stabilizing structures under the spillway was at the Trinity Dam in Sicily, Italy. ?Underpinning? was considered as an alternative to spillway relocation during the Alpaslan 2 embankment dam design in eastern Turkey. Based on the available literature the first application of drilled piers to stabilize a spillway chute in the U.S. was at the Ralston Dam in Colorado. Ralston Dam, which is a 175-foot-high zoned fill dam located 15 miles northwest of downtown Denver, was built in the late 1930s. The concrete spillway for the dam was built on the Pierre Shale Formation in the left abutment. Since reservoir operations began, mass movements have occurred downstream of the chute area. These movements have required periodic spillway maintenance. After the occurrence of recent movements and because of high piezometeric levels, URS was contracted by Denver Water to develop a more permanent solution by the installation and monitoring of additional instrumentation, analysis of slope stabilizing measures, design, repair, and reconstruction of the distressed section of the spillway chute. With state of the art modifications that include: 1) a stabilizing berm with a toe trench that improves the global stability; 2) seepage prevention and control measures that prevent the infiltration of water; and 3) the structural support of the replaced chute section with drilled piers and reinforced concrete the probability of future displacements or other problems have been reduced for the Ralston Dam Spillway.

Jan 1, 2007

By Robert B. Bittner

The new gated dam on the Monongahela River at Braddock, Pennsylvania, was built for the US Army Corps of Engineers using an innovative ?In-the-Wet? technology. A key feature of this technology involves construction of the foundations through the water and later mating the completed structure or a shell of the structure to the pre-installed foundation. This paper presents a description of the structure, its foundation, construction sequence and design details required to successfully implement this technology.

Jan 1, 2013

By Takeshi Maki, Kh. Adeel Tariq

"The lateral resistance of the structure plays an important role during seismic event and it can be increased by using ground improvement. In this study an attempt has been made to investigate the effect of cement-treated sand on the lateral capacity of the pile. The behavior of piles surrounded by sand only and cement-treated sand confined in a steel box (30 x 30 x 50 cm) which is subjected to lateral cyclic load has been investigated. Piles having a diameter of 2.5 cm and embedded to a depth of 45 cm were used. Steel and aluminum piles were used to investigate the effect of flexural stiffness on the lateral capacity of the pile. Bottom supports of piles were also changed from pinned to fix. Well graded sand compacted to 70% of relative density (RD) was used. Cement-treated sand having a compressive strength of 3.7 MPa was used. Displacement controled lateral load tests were performed and cyclic loads were applied until pile displacement was 4%, 10%, 20%, 35%, 50%, 75% and 100% of pile diameter. Results evaluated are compared with common method of analysis like Brinch hansen (1961), Brom (1964), Poluos (1980) etc. Results have indicated that the stiffness of a pile affects its lateral capacity. The introduction of central cement-treated sand part increased 5 times the lateral capacity of piles as compared with a sand only condition.IntroductionPiles are used extensively around the world to support loads of structures. Piles are commonly used to carry axial load, but in some structures, the lateral capacity of the pile is more important than the axial capacity: for example piles supporting earth retaining structures, electric tower foundation, etc. Structures can be subjected to both axial and lateral forces, like structures constructed at harbor that are subjected to lateral force due to waves action; and structures built in earthquake prone areas like Japan."

Jan 1, 2017

By Kessi E. Zicko, Eric A. Hackenberg, Paul J. Lewis

"Following snow melt and spring rains in 2011, a landslide measuring approximately 600 feet long and 300 feet in slope length occurred within the southbound roadway embankment of a heavily travelled 2-lane divided highway in North Central Pennsylvania. Driven steel piles were designed to stabilize the embankment slope. Factors affecting the selected stabilization technique included an adjacent reservoir, wetlands, the length and depth of the failure plane, extent of glacial lake deposits, excess pore pressures in the foundation soils, and an area of archaeological interest. Field reconnaissance and subsurface explorations including borings, instrumentation, geophysics, and laboratory testing indicated that glacial lake deposits were present in the toe region of the embankment. Instrumentation proved key in measuring excess pore pressures and in locating the failure plane, and geophysics was utilized to estimate the extent of the soft glacial lake deposits and to estimate pile lengths. The existing condition of the embankment was modeled in computer slope stability analyses, which were also used to help assign soil parameters. Significant costs were associated with constructing a berm due to the impacts on adjacent site features. Therefore, multiple rows of driven steel H-piles were designed for installation along the toe of the embankment. The design lateral load in the piles was based on slope stability analyses, and the pile size and number of piles were based on lateral pile computations with modified p-y curves to account for installing piles in an active landslide. The relationship between the factors of safety from slope stability and the LRFD pile design was significant in determining pile loads for lateral analyses.INTRODUCTIONA landslide developed along the lower portion of the southbound embankment of State Route 15 in Tioga County, Pennsylvania. The road passes through a steep valley and is located along the southern extent of the Tioga Reservoir. Although no damage to S.R. 15 was attributed to this landslide, the close proximity of the slide to the road posed a concern for the long-term stability of this section of roadway.This paper presents a summary of the site history; the subsurface conditions based on borings, instrumentation, a geophysical survey, and laboratory testing; slope stability analyses including alternatives assessment; and the pile design.SITE HISTORYS.R. 15 was originally located in the valley along the Tioga River and traversed through the towns of Tioga and Mansfield. Although the reason is unknown, it is interesting to note that Old S.R. 15 curved away from the river in the area of the landslide. In the mid 1970’s, S.R. 15 was relocated to the eastern hillside prior to construction of the Tioga-Hammond Reservoir by the U.S. Army Corps of Engineers. The relocated highway was constructed in stages. Two lanes of relocated S.R. 15 were initially constructed to carry one lane of northbound and one lane of southbound traffic. At this same time, the majority of the fill was placed for two future lanes immediately to the west, which would eventually allow for two lanes in each direction. The two eastern lanes would then carry northbound traffic after completion of the two southbound lanes to the west."

Jan 1, 2015

By Ruth McKeown, Gilson de F. N. Gitirana, Murray Fredlund, HaiHua Lu

The current design standards for the use of anchors in slopes is based on two-dimensional (2D) limit equilibrium analyses. Anchors are considered as discrete loads and the 2D anchor, factored based on the spacing distance, corresponds to extending anchors indefinitely in the third dimension. A three-dimensional (3D) analysis offers a more realistic representation of the problem, including the true discrete nature of the anchor point loads. This paper explores the typical differences between analyzing anchors in 2D and 3D, using four typical conceptual models. Slopes with constant cross sections were shown to be adequately represented by the traditional 2D approach. The maximum difference between 2D and 3D models was 21% and becomes negligible for lower anchor spacing values, as expected. A slope with an external load was analyzed to evaluate critical slip surfaces with lower aspect ratios. Slip surfaces with lower aspect ratios presented higher edge effects that contributed to the stability of the slope. The results indicate that optimum design requires the 3D evaluation of field conditions inducing low aspect ratios, such as concave and convex surfaces, weak layers, and external loads. INTRODUCTION Slopes may be stabilized using a variety of solutions, including anchors. When performing an analysis, geotechnical engineers often follow the traditional two-dimensional (2D), Limit Equilibrium Method (LEM). It is important to understand the consequences and limitations of the assumptions on which the 2D LEM is based. There are numerous studies on anchors that show the importance of considering the actual three-dimensional field conditions. Desai et al. (1986) proposed a three-dimensional procedure based on the Finite Element Method and considering elastoplastic behavior and interface elements, to account for stress and displacement distributions, the relative motion between the anchors and the soil mass, and nonlinear soil behavior. Several important stabilization mechanisms were explained. The role of grout injection was evaluated in terms of the produced normal stresses along the anchor-soil bounding surface. The approach was shown to reproduce adequately experimental tests on a sand, proving realistic stress distributions around the anchor. Nonlinear soil behavior influenced to a large extend relative interface motions. Michalowski (1989) applied an upper-bound limit analysis in 3D to slope stability analyses. Anchors were not specifically considered in this study, but the consideration of locally loaded conditions shed light on important modeling aspects. The manner how the slide mechanism becomes three- dimensional as the slope is locally loaded was demonstrated. This emphasizes the fact that anchors should produce field conditions that require 3D analysis approaches.

Jan 1, 2019

By A. V. Rose

A redevelopment in the City of London has been constructed with a piled foundation system that is believed to be the first of its kind. The purpose of the research is to explore this novel foundation method, which involves the installation of closely spaced piles in a perimeter arrangement with a body of soil enclosed in the centre. Both centrifuge modelling and numerical modelling techniques are used.

Jan 1, 2011

By Rajni Saggu

This study presents the cyclic load-displacement response of thermal piles in a pile group consisting of thermal and mechanical piles. To investigate the effect of different (i) layouts of thermal piles and mechanical piles, (ii) pile spacing, and (iii) soil type on the pile displacements and axial stresses, numerical analyses were performed over 50 cycles of thermal loading and unloading of the thermal piles. The analysis outcomes show that the thermal changes in the load-displacement characteristics of the piles become complex during cyclic thermal loading and unloading of the thermal piles. The mechanical piles also exhibit uplift after thermal loading of the thermal piles, and significant differential displacements occur at the pile cap, head and base for all the piles. Higher pile spacing imposes a positive effect in terms of lower thermo-mechanical stresses in the piles compared to the case of closely spaced piles. Axial stresses in each pile are notably non-uniform after the thermal loading cycles applied on the thermal piles. Cyclic alterations in the load-displacement of thermal piles also impose alterations in load-displacement of the mechanical piles. Further, the layout of thermal piles, pile spacing, and soil type control the long-term cyclic thermo-mechanical response of the pile group.

Oct 7, 2024

By Sam X. Yao

In construction of drilled shafts under water, placing concrete in the shafts is technically demanding and involves complex construction logistics. Past construction experience has demonstrated that high quality concrete can be placed in drilled shafts under water with a proper concrete mix and proper placement techniques. However, a significant number of failures have occurred which have resulted in excessive cost overruns and delays. These problems may have occurred because proper underwater concrete construction techniques have not been widely disseminated within the industry. This is a technical area where competent design and sound construction planning can achieve a significant reduction in both risk and cost. This paper will discuss some key technical issues in the concrete mix design, concrete production and placement for the drilled shaft construction. The paper also describes two lesson-learned case histories from drilled shaft construction projects.

Jan 1, 2013

By Richard T. Stain

"In 2001, a pile trial site was established at Limelette in Belgium consisting of 25 displacement screw piles and 5 driven pre-cast piles. Interested parties were invited to participate in a pile prediction event, whereby they would submit predicted static load test behaviour in the form of load settlement plots. These predictions could be based on soil investigation results supplied by the organizers, or dynamic load test measurements.Following the submission deadline, the organisers released the results of static load tests for comparison.Of all the six participants, including Statnamic, the SIMBAT method was independently accredited with achieving the best predictions.This paper examines at the differences between SIMBAT and other systems, and presents the correlations from the Limelette trial.INTRODUCTIONThe Belgian Building Research Institute (BBRI) initiated an ambitious research programme involving the construction and testing of some 60 trial piles spread between two sites, a clay site at Sint Kateline Waver and a sandy site at the BBRI headquarters at Limelette. The project was financed largely by the Belgian Ministry of Economic affairs. (ref 1.) This paper refers only to the second site.At Limelette, six different types of displacement pile were installed: one driven pre-cast and five cast in place screw piles - Atlas, DeWaal, Fundex, Olivier and Omega. A detailed site investigation was carried out including in-situ and laboratory tests.An international pile capacity prediction event was publicised, participants being invited to predict static pile behaviour. Predictions could be based on:"

Jan 1, 2005

By Mu Chen, Ye-Shuang Xu, Dong-Wei Hou, Shui-Long Shen, Huai-Na Wu

"This paper presents a laboratory investigation on the mechanical behaviors of the cement-clay admixture improved by polypropylene fiber. Cement can significantly improve the clay admixture. The fiber additive also improves the strength and ductility of the improved clay. The Unconfined Compression Strength (UCS) of the polypropylene fiber-reinforced cement-clay presents an overall trend to grow with the increase of fiber length. The improved clay reached its peak strength at the fiber content of 0.5%. Then the UCS of the improved clay will slowly reverse if the fiber content continues to rise. For study of curing time, improved clay behaves better in its early strength, but an inhibition will be brought about if fibers are excessive.INTRODUCTIONGround improvement technology is essential for construction of structures in soft ground. Some traditional techniques often cost much but result in little. For instance, along the coastal region of China, soft ground is often improved by backfill with high quality sandy soil transported far away, leading to high additional haulage costs and long construction period. Reutilizing the excavated soil as backfill or subgrade after treatment, by contrast, will be more economical and effective (Hufenus et al., 2006). Many researches have been conducted to improve the compression strength of soft soil, among which, the method of mixing the soft soil with cement and fly ash is one of the most common ways (Kolias et al., 2005; Horpibulsuk et al., 2009; Porcino et al., 2012). It is known that soil resists well against compression and shear force but behaves poorly in resistance to tension. Therefore, utilizing tensile elements such as fibers and strips to improve the tensile strength will be effective because of its strength isotropy, better durability and cost effective (Haeri et al., 2000; Kaniraj and Havanagi, 2001; Consoli et al., 2010)."

Jan 1, 2015

By Kyle Kershaw

Micropiles are routinely used in the United States for foundation support and stabilization of slopes. In recent years, several retaining walls have been constructed using micropiles in an A-frame type configuration to support temporary and permanent excavations at sites with limited access and limited right-of-way. Typical A-frame micropile walls consist of a row of vertical micropiles at the face of the wall and a row of battered micropiles extending into the soil or rock to be retained. The two rows are then tied together with a pile cap such that the front pile acts primarily in bending and the back pile acts primarily in tension. Because of tight right-of-way constraints at a residential site in Aspen, Colorado, it was not possible to construct the wall using conventional shoring systems or micropiles in the typical A-frame configuration. Rather, the wall was designed such that the row of battered piles was installed at the wall face and the row of vertical piles was installed adjacent to the property line behind the wall. As a result of the reverse configuration of the A-frame wall, FLAC, a two-dimensional, finite difference software program, was used to model the soil-structure interaction. The final wall design consisted of both temporary and permanent retaining wall sections with maximum heights of 26 feet. Inclinometers were installed in several piles to monitor the behavior of the retaining walls during and after excavation. This paper presents an overview of the design method, a discussion of construction techniques, and a comparison between the FLAC model and the measured behavior of the wall in the field.

Jan 1, 2007

By Richard Stone, Rouzbeh Afsharhasani, Moses Karakouzian

"Caliche, a hardened sedimentary deposit of calcium carbonate that occurs worldwide, generally in arid or semiarid regions, is frequently encountered in Las Vegas, Nevada. The presence of a caliche layer in a soil profile affects the response of deep foundations to axial load. This paper studies the stiffening effect of caliche layers on the elastic settlement of a pile foundation. In order to evaluate the response in a layered soil-caliche profile, finite element analyses were performed on a typical-sized single pile and a pile group, both having constant diameter and length of the pile. The results indicate that the stiffening effect from the caliche is noteworthy, and a layer with a relative thickness of at least one pile width, regardless of its location, reduces the pile settlement for both single piles and group of piles systems by at least 50%.IntroductionThe presence of cemented materials in the soil profile influences the settlement response of foundations. One type of cemented material that can be found in arid places around the world is a sedimentary deposit of calcium carbonate called caliche. Caliche, a hardened sedimentary deposit of calcium carbonate, is common in arid and semi-arid urban areas, such as Las Vegas, Nevada (Wyman, et al. 1993).Caliche is mostly observed in lacustrine, river, and alluvial fan deposits (Jr.C.C 1970). It is also found in Central and Western Australia, the Kalahari Desert, the High Plains of the Western U.S., and the Sonoran Desert of the U.S. and Mexico.Some conditions required for the formation of caliche are that country or basement rocks must be a carbonate type, carbonate must be present in the soil zone of the area, climate regime is semi-arid to arid, there exists widespread capillary activity, and carbon dioxide (CO2) is present in the environment. As a result, caliche occurs as a product of the carbonization process (Atabey, Atabey and Kara 1998). In such areas where foundations are constructed on thin rock layers (caliche), special geotechnical design conditions should be considered, particularly if the supporting rock layer is underlain by a weaker material."

Jan 1, 2015

By J. P. Burland

The paper describes a number of recent case histories in the United Kingdom where field instrumentation and measurements have played a major role in the design and construction of excavations, piles and foundations. It is shown that the design and construction procedures for deep excavations in London Clay are based almost entirely on the results of field measurements. Examples are given of successful application of such measurements. The present understanding of the behaviour of bored piles in stiff clays and their design is based on a number of instrumented pile loading tests. The results of these tests have led to a radically new concept of pile design in which the piles operate at their full shaft capacity under working loads thereby resulting in considerable savings in design and construction. Some examples of the successful application of this concept are given. Finally it is shown that the present knowledge of the stiffness properties of chalk is based entirely on field observations. An example is given of how direct field measurements were used to solve a foundation problem at the base of a coffer-dam in chalk.

Jan 1, 2010