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By Chris L. Powell, Russell J. Denny

"The remotely located Cockatoo Island iron ore mine off the Kimberley coast in the northwest of Western Australia has been in operation since 1951. The mine was recently expanded up to about 50 m (165 ft) below sea level using staged construction to create a rockfill seawall around the open cut mining operation. Late in 2013, to allow expansion of subsea iron ore mining operations, Wagstaff Piling was engaged to install a seepage barrier through the rockfill seawall and into the underlying seabed sediments.Earlier stages of seawall construction had used a variety of different construction techniques with varied success, and the history of subsea mining on the island had been plagued with failures, including failures in the slope of the seawall itself, hanging wall failure underneath and inside the seawall, and footwall failures as the ore was mined leaving the rock face inclined at 55 degrees, parallel to the bedding. The current expansion, known as the Stage 4 expansion, was more tightly constrained by the pit geometry and available materials than previous seawall expansions that adopted clay core and sheet pile seepage barrier solutions. In Stage 4, an innovative seepage barrier solution using a grout curtain was selected to provide the necessary cutoff to allow access to highgrade ore, while protecting the mine from inundation by the sea.Seawall ConceptThe open cut subsea mining operation consisted of a 3 km (1.9 mi) long narrow pit along the south side of Cockatoo Island that extended to depths of about 50 m (165 ft) below sea level, and were exposed to the open sea on the south side of the pit. Massive tidal variations of more than 10.5 m (34.5 ft) required a seawall founded on the seabed, extending upwards to RL+13, to safely protect the pit from the high tide level rising to above RL+10."

Jan 1, 2017

By P. Kiruthika, A. Murali Krishna

Soil liquefaction is a dangerous phenomenon that involves huge damages during strong earthquake ground motion event. Stone columns (SCs) are widely used as liquefaction mitigation element which is expected to perform the improvements against liquefaction hazard by densifying, increasing the stiffness and rapid dissipation of excess pore water pressure in the surrounding soil. Although in the recent times few studies on the behaviour of stone columns in the seismic zone has evolved, the performance of SCs in the multi-layered soils is not extensively examined. This paper presents the numerical investigations on the performance of SCs installed in the multi-layered soils as a liquefaction mitigation measure against the seismic loading. The acceleration time histories, Excess Porewater Pressure (EPP), vertical displacement and stress ratio evaluated along different depths using PLAXIS 2D. With the installation of stone column there is a considerable reduction in the acceleration amplitude, which in turn reduces the EPP and vertical displacement at different locations and the amplitude of reduction depends on the soil stiffness levels at the depth.

Sep 1, 2022

By Gang Guo, Zhong Liu

"In response to an increasing demand of anchored structures for underground space and transportation infrastructure in China, an innovative underreamed ground anchorage system was created. The novel anchorage system has provided more efficient functions with higher capacity at lower cost, because of the enlarged cylindrical body (known as ECB) sealed in capsule at bottom of anchorage. This paper presents the detailed structure of innovative anchorage system and its special features. To investigate the bearing mechanism of new anchorage, we evaluate its performance and failure mode based on the experimental results, and also indicate its strain-hardening load-displacement relationship. Unlike the shaft anchorages, it is identified no overall failure to be found in soil surrounding the underreamed anchorage. More importantly, the anchorage capacity is governed by the base resistance, which takes more than 80% of total pullout capacity resulting from the contribution of ECB. Finally a case history of anti-floating project introduces the new combined construction approach and procedure, which has provided the contribution to the quality control and cost efficiency.INTRODUCTION AND BACKGROUNDThe construction boom over two decades in China has resulted in an increasing demand for underground space and slope stability. The infrastructures market requires the more efficient anchorage systems for retaining structures, resisting uplift forces and slope protection. The major concern focuses on gaining higher capacity and lower cost resulted from perfecting anchorage systems. There are three main anchorage systems designed to achieve the above objectives: ? single bore multiple anchorage system (Barley 1997), ? regroutable anchorage system (Smoltczyk 1991), ? underreamed anchorage systems (Xanthakos 1991). Generally, the concept ? comparing with the other two, can be more competitive due to its distinct advantages. To improve the performance and durability of ground anchorages under the complex geological conditions and diversified engineering requirements, a number of different underreamed anchorage technologies had been used, which included cone - shape anchorage described by Liao, Wu and Shu (1997) in Taiwan, Soilex anchorage developed in Sweden (Massarsch et al. 1997), Soletanche anchorage proposed in France, blasting anchorage used in Czechoslovakia (Hobst and Zajic 1986), jet-grouting anchorage innovated in Europe (Anon 1988), as well as deep mixing anchorage created in Japan (Cheng et al. 2000).The underreamed anchorage systems have the remarkable advantages compared to the shaft anchorage system. However, there are also some weaknesses inherent in the underreamed systems. For instance, the mechanical underreamed anchorage is unsuitable in sand or waterbearing ground, because the enlarged hole is easy to collapse, and it is hard to ensure the quality of anchorages. On the other hand, relying on the blasting in deep hole, the geometrical space and dimension of enlarged hole is uncontrollable, meanwhile, the continuous blasting operations may easily cause the serious ground deformation and the negative effects to the completed anchorages."

Jan 1, 1900

By Bernard Hertlein, Chia K. Tan

"The move to LRFD methods for structural design by AASHTO, ACI, AISC , ASCE, and the FHWA has been a major change for the American construction industry. The deep foundations industry has arguably been placed most at risk by this situation, because of the need for, and the difficulty of providing, reliable quality assurance.LRFD is attractive for both the owner and the engineer because it promises cost reductions, but the assumption underlying LRFD is often overlooked - that the acceptable margin of safety can be rationally reduced, thus saving costs, provided that all the factors involved are closely controlled. This means that both the quality of the materials and the quality of the construction work must be closely monitored, and held to an acceptable standard.This paper describes the type of comprehensive quality management program that is needed in deep foundation construction projects based on LRFD. Case histories are used to illustrate the importance of both adequate inspection and reliable testing to a comprehensive quality management program.IntroductionOver the last thirty years, the major organizations that set standards and practice policies for the American construction industry, such as the American Association of State Highway and Transportation officials (AASHTO), the American Concrete Institute (ACI) , The American Institute for Steel Construction (AISC), the American Society of Civil Engineers (ASCE), and the Federal Highway Administration (FHWA), have embraced Load and Resistance Factor Design (LRFD) as an alternative to, and in some cases, a complete replacement for, Allowable Stress Design (ASD). AASHTO first published a new set of LRFD-based design guidelines for bridges in 1996, with several revisions in 1997, 1998, and 1999 (AASHTO, 1996). The 1996 AASHTO Bridge Design Code was the first in the United States that required foundations to be designed using LRFD procedures. LRFD has a clear advantage over conventional ASD where variability in material strength, bias in design methodology, and degree of construction quality can be rationally accounted for to achieve an acceptable level of risk."

Jan 1, 2005

By M Muzammil, S. Mukerjee, S. Saran, M. Bharathi

"This paper presents the results of in-situ tests conducted on a set of under-reamed piles in a silty sand deposit. Three piles (i.e. vertical, vertical with one bulb and vertical with two bulbs) of diameter 0.2 m were cast upto a depth of 5 m. The pile cap had four foundation bolts cast into it so that a mechanical oscillatormotor assembly could be mounted centrally on it. The oscillator-motor assembly was used to generate purely sinusoidal dynamic forces, in either horizontal or vertical directions. For both horizontal and vertical vibration cases, it was observed that (i) the natural frequencies decreased with an increase in the excitation force level, (ii) for the same excitation level, the natural frequencies as well as the maximum amplitude of vibration are almost the same irrespective of the pile geometry i.e. number of bulbs in the pile, indicating that the full pile length is not being excited. For the vertical vibration case, the soil-pile stiffness at frequencies, before resonance, were observed to be higher than those at frequencies after resonance. In the horizontal vibration case, the stiffness of the soil-pile system was found to be decreasing with an increase in the excitation force level. The damping ratio was found to be increasing with an increase in the excitation force level.INTRODUCTIONUnder-reamed piles are piles, normally upto a depth of 6 m, with one or more bulbs along the pile stem. These have been used for structures like transmission towers, structures on expansive soils etc. for a very long time, however it is only in the last 30 years that dynamic response of a pile has been studied. Evaluation of dynamic soil-pile interaction is a very complex problem as the conditions and properties of soil are highly variable and unpredictable. Various models and approaches have been suggested by various investigators for evaluating the dynamic soil-pile interaction problem, but most of them are based on the assumptions that the behaviour of soil is linear and the soil surrounding the pile is strongly adhered to it. But in practice, it is not so. The soil surrounding the pile is always somewhat loosened and undergoes some deformation when a sinusoidal load is applied. This causes the soil-pile system to behave nonlinearly.In earlier studies by Novak, (1974), Novak and Aboul-Ella, (1978) etc. a linear elastic behaviour of soil was assumed. This approach was very useful in understanding the mechanism of soil-pile interaction to a large extent. Subsequently various models were suggested like the lumped mass models with nonlinear discrete springs, dashpots and friction elements Matlock et al. (1978), weak cylindrical zone around the pile model Novak and Sheta, (1980), ideal boundary zone model with non-reflective interface, Han and Sabin, (1995) etc. These approximate solutions give an idea about the mechanism of dynamic pile-soil interaction to a large extent. However, in reality both separation and slippage can occur due to the formation of a weak bond at the contact surface between the soil and the pile when a dynamic load is applied. In addition, the soil column adjacent to the pile experiences large deformations under dynamic loads and thus behaves nonlinearly.Some computer aided model studies on the dynamic response of under-reamed piles have been reported, however, very few insitu dynamic tests on under-reamed piles are reported. Dynamic tests on piles were carried out by Novak and Grigg (1976) on small scale single piles and pile groups in the field. Similar field tests on small scale piles were conducted to study the nonlinear behaviour of a single pile and a pile group under strong harmonic excitation by Han and Novak (1988), Han and Vaziri (1992), Burr et al. (1997), Manna and Baidya (2010) etc. The majority of these experimental studies were focussed on the response of the specific pile groups and compared with the results of a single pile. Hence there was a need to study the influence of pile g"

Jan 1, 2015

By Anburaj C., Srinivas A.

Deep excavation with support system is required to construct various part of underground structures like shafts, stations and entry structures etc. These structures have to be constructed using permanent or temporary embedded retaining walls with support system. The selection of a suitable type of retaining wall will depend upon the geological condition present in the particular location, time, cost and available equipment etc. In Bangalore Metro Rail Project, secant pile wall is adopted as the temporary earth retaining system and depth of excavation is about 20 m. It is designed initially based on bottom up construction methodology with 3 level of struts and 3 level of anchors but at later stage due to time and other construction related issues, it is decided to change the configuration to 6 levels of strut. Generally, in deep excavations, all the underground structures should be designed and checked for the critical forces from both permanent stage and construction stages. Since, secant piles are used as temporary retaining wall, only construction stage analysis is carried out to get the governing forces and deformation. In construction stage analysis, soil layers are defined with boundary conditions and the surcharge during construction and surcharge from actual building near the secant pile are considered. This paper discusses the effect of change in the support system from anchors to struts and how these changes in the support system affect the behavior of secant pile and subsequently adjacent buildings present in the influence zone of the excavation. As a result, in changing from anchors to struts, the wall displacement, strut forces and ground movement on the adjacent ground and buildings increases. The increase in deflection, ground movements and strut forces occurs during backfilling sequence of the underground station excavation. During backfilling, struts has to be removed and this imparts higher magnitude in deflection, strut forces and ground movements.

Nov 1, 2022

By Jesús E. Gómez

Verification and production testing of soil nails requires debonding the upper section of the soil nail to isolate the portion of the soil nail intended for testing within a specific ground type. In pre-drilled soil nails, debonding can be accomplished relatively easily because the bar can be fitted with a debonding sheath before its installation. However, debonding of hollow core bar soil nails requires special procedures to achieve the intended result. This paper is a summary of the Federal Highway Administration (FHWA) Hollow Bar Soil Nail (HBSN) Test Program, which is described in detail in FHWA-CFL/TD-10-001. The program was developed to establish a suitable debonding procedure to test hollow core bars in soil nailing applications, and to initiate a database on typical bond values of HBSNs. The investigation showed that it is possible to debond hollow core bars for testing. It was also found that hollow core bars installed in granular soils may present ultimate bond values that are significantly higher than those typically used for design of conventional pre-drilled soil nails.

Jan 1, 2011

By Eric P. Bregman

As part of an on-going effort to improve water quality and reduce discharge into Boston Harbor, the Massachusetts Water Resources Authority (MWRA) East Boston Branch Sewer Relief Project was designed under a Federal mandate from the United States Environmental Protection Agency (EPA) to upgrade the aging sewer system, increase system storage and greatly reduce the volume of combined sewer overflows into the Harbor. The project scope of work includes the installation of over 2 miles (11,800 linear feet) of 36-inch and 66-inch diameter sewer relief piping, twenty (20) temporary shafts and an approximate 100 foot open cut section, located within the densely populated neighborhood of East Boston, Massachusetts. This area is a former marshland backfilled in the early to mid 1800?s where busy commercial streets co-mingle with thickly settled residential houses. The subsurface conditions present within Boston?s complex geology include the presence of subsurface contamination as well as complex networks of underground utilities. Additional site limitations included low headroom, noise, and traffic restrictions. Together these limitations required the design of individual earth support systems, tailored for each shaft location. Moreover, challenging subsurface conditions identified during construction required design modifications to minimize cost and schedule impacts related to construction dewatering, treatment of contaminated groundwater, internal bracing, and utility relocations. This paper provides a case history of the Geo-structural design and performance of various earth support techniques utilized to construct jacking and receiving shafts designed to launch and receive two (2) micro-tunnel boring machines (MTBM) and to support the construction of new deep shaft structures in an urban coastal area.

By Eric P. Bregman, Franklin M. Grynkewicz, John E. Regan

"As part of an on-going effort to improve water quality and reduce discharge into Boston Harbor, the Massachusetts Water Resources Authority (MWRA) East Boston Branch Sewer Relief Project was designed under a Federal mandate from the United States Environmental Protection Agency (EPA) to upgrade the aging sewer system, increase system storage and greatly reduce the volume of combined sewer overflows into the Harbor. The project scope of work includes the installation of over 2 miles (11,800 linear feet) of 36-inch and 66-inch diameter sewer relief piping, twenty (20) temporary shafts and an approximate 100 foot open cut section, located within the densely populated neighborhood of East Boston, Massachusetts. This area is a former marshland backfilled in the early to mid 1800’s where busy commercial streets co-mingle with thickly settled residential houses.The subsurface conditions present within Boston’s complex geology include the presence of subsurface contamination as well as complex networks of underground utilities. Additional site limitations included low headroom, noise, and traffic restrictions. Together these limitations required the design of individual earth support systems, tailored for each shaft location. Moreover, challenging subsurface conditions identified during construction required design modifications to minimize cost and schedule impacts related to construction dewatering, treatment of contaminated groundwater, internal bracing, and utility relocations.This paper provides a case history of the Geo-structural design and performance of various earth support techniques utilized to construct jacking and receiving shafts designed to launch and receive two (2) micro-tunnel boring machines (MTBM) and to support the construction of new deep shaft structures in an urban coastal area."

Jan 1, 2017

"This model specification includes sample text shown in normal font with commentary in italics. The commentary is intended to highlight project-specific items the specification writer should consider during development of the specification. In some sections, typical values are presented to indicate common practice, and these values may be changed to reflect projectspecific requirements. The commentary should be removed before using the specification for a project.1. SCOPEThe work consists of designing, furnishing, installing, post-tensioning and testing helical anchors used to support tension loads, and any ancillary materials (e.g., load transfer devices, etc.) according to the project plans provided and these specifications. Unless otherwise noted, the installing contractor shall provide all labor, tools, equipment, and materials necessary to accomplish the work. The parties referred to in this specification are as follows:• The Owner is the property owner.• The Owner’s representative is the individual or firm hired by the Owner to execute project tasks required for the successful design and construction of the overall project. Tasks could include construction management, design, oversight, etc.• The anchor designer is the individual or firm generally hired by the installing contractor to design the helical anchors.• Installing contractor installs and tests (if necessary) the helical anchors, and possibly other tasks associated with the project.It is important to clearly define the roles and responsibilities of every party on each project to promote good communication and reduce potential for contractual misunderstandings. Different types of contractual vehicles (design-build, value engineering, etc.) require different roles and responsibilities for the various parties, which should be considered in specification development.The Owner will provide suitable access to the construction site for the installing contractor’s personnel and equipment. Unless specifically noted otherwise in the contract documents, the Owner will remove and replace any structures, utilities, pavements, landscaping or other surficial improvements in the work area as necessary to facilitate the work. The Owner will be responsible for overall construction oversight to minimize potential for developing unsafe conditions. The work may include post-construction monitoring of anchor performance if required by the Owner or the anchor designer to confirm performance of the anchors subsequent to their installation. The work may also include installation of additional anchors if the initial installation does not meet specified capacity or performance requirements. Responsibility for providing subsurface investigation shall be addressed in the bid documents. The Owner is responsible for providing to the installing contractor all available subsurface soils, rock and groundwater information and geotechnical testing data."

Jan 1, 2016

By Mario A. Terceros Herrera, Mario Terceros Arce, Antonio Marinucci

This paper describes the general principles of the expander body with post-grouting (EBI) system, and how it is similar in nature to a large-scale pressuremeter device. The results from the installation of an EBI can be used to provide information about the stress-strain characteristics of the soil adjacent to the device and to compute estimates of nominal axial resistance. As the EBI expands during grouting, pressure is applied to the in-situ soil surrounding the device thereby compacting/densifying the soil. The nominal axial resistance for small diameter piles/ground anchors can be increased due to the greater soil stiffness and shear strength around the device, larger surface and end area, and improved soil-to-EBI interaction in side resistance. The shape of the response curves depends on the geotechnical conditions of the soil (e.g., in-situ stress state, strength, and stiffness) and the installation method of the piling/ground anchor. This technique has been used successfully with different pile types and ground anchors in a wide range of conditions from very loose sands/silts to very dense sands and medium-dense gravels as well as in soft to stiff clays. This paper also describes a mini case history in which 80 piles were installed to support an office building, and the results of the static axial compression load tests performed on a production FDP+EBI pile is also included.

By Sanjay Gupta, Sorabh Gupta, Ravi Sundaram

A geotechnical forensic evaluation of piles for an industrial facility in Haryana was performed to assess the quality of the piles and to evaluate piles installed using two different types of rigs. Low strain pile integrity tests were performed on all piles to assess the pile length and possible presence of structural defects. Coring was done through questionable piles for the clinching evidence of concrete quality and pile length. Probe holes adjoining piles helped confirm the bulging of piles at shallow depth. The paper highlights the importance of implementing a well-planned quality assurance program to confirm that all piles installed are of the desired quality.

Sep 1, 2022

"This model specification includes sample text shown in normal font with commentary in italics. The commentary is intended to highlight project-specific items the specification writer should consider during development of the specification. In some sections, typical values are presented to indicate common practice, and these values may be changed to reflect project-specific requirements. The commentary should be removed before using the specification for a project. 1. SCOPE The work consists of designing, furnishing, installing, and testing helical piles used to support foundation loads (compression, tension and lateral), and any ancillary materials (e.g., load transfer devices, etc.) according to the project plans provided and these specifications. Unless otherwise noted, the installing contractor shall provide all labor, tools, equipment and materials necessary to install the required piles. The parties referred to in this specification are as follows: • The Owner is the property owner. • The Owner’s representative is the individual or firm hired by the Owner to design and oversee the overall project. • The pile designer is the individual or firm generally hired by the installing contractor to design the helical piles. • Installing contractor installs and tests (if necessary) the helical piles, and possibly tasks associated with the project. It is important to clearly define the roles and responsibilities of every party on each project to promote good communication and reduce potential for contractual misunderstandings. Different types of contractual vehicles (design-build, value engineering, etc.) require different roles and responsibilities for the various parties, which should be considered in specification development. The Owner will provide suitable access to the construction site for the installing contractor’s personnel and equipment. Unless specifically noted otherwise in the contract documents, the Owner will remove and replace any structures, utilities, pavements, landscaping or other surficial improvements in the work area as necessary to facilitate the work. The Owner will be responsible for overall construction oversight to minimize potential for developing unsafe conditions. The work may include post-construction monitoring of pile performance if required by the Owner or the pile designer to confirm performance of the piles subsequent to their installation. The work may also include installation of additional piles if the initial installation does not meet specified capacity or performance requirements. Responsibility for providing subsurface investigation shall be addressed in the bid documents. The Owner is responsible for providing to the installing contractor all available subsurface soils, rock and groundwater information and geotechnical testing data."

Jan 1, 2015

By Tim Chapman

This general report considers what promoters of deep basement projects want from their teams and whether they get it often enough. Most large projects are based on complex financial models where the funding is related to a future income stream. Project delays and cost over-runs can critically affect the financial model. Too often, delays and cost over-runs originate in the substructure and foundations. We must take positive steps to improve our industry's reputation for reliability.

Jan 1, 2006

By H. Shiri

Iran's largest natural gas field is South Pars, geologically an extension of Qatar's 900-Tcf North Field. South Pars was first identified in 1988 and originally appraised at 128 Tcf in the early 1990s. This Field contains 38.6 % of the gas resources of Iran and is regarded as the largest offshore gas field in the world. Offshore geotechnical site investigations are one of the key activities of upstream fields operators to supply the EPC contractors with the required results for designing approaches of offshore complexes. In the mean time a lot of marine site investigations have been carried into execution within the phases of South Pars development. The authors are currently trying to create the fundamentals of investigating the small- and large-scale spatial variability of the South Pars Gas Field in Persian Gulf/ IRAN. Part of this investigation is the providing of an extensive data base of the offshore geotechnical properties of South Pars. Such a data base, will enable a model to be developed of the large-scale variability of these properties. In addition, this data set will provide a data whereby general trends to be established, as well as, providing relationships between geotechnical parameters and spatial parameters utilizing probabilistic and data mining methods like ANN (Artificial Neural Network) in Geotechnical Engineering.

Jan 1, 2006

By Aditya Ayithi, William G. Ryan, Dean Herbst

"For rock socketed drilled shafts, it is a common practice not to include the frictional resistance of overburden soils into the nominal capacity estimation. The primary reason often being cited is “overburden soils resistance is negligible compared to that of rock socket resistance.” However, in certain geological conditions, where the rock layer is located at greater depths, friction resistance from overburden layers can be significant. In addition, at such great depths, shaft drilling becomes very complicated and expensive. In these situations, considering the resistance of the overburden layers can be an economic alternative.This paper presents a case study of an Osterberg cell (O-cell) load test conducted on a 161.8 feet long and 78-inch diameter instrumented test shaft. Based on initial designs, a 72-inch diameter rock socket of lengths 23 and 26 feet was required to provide a LRFD factored friction resistance of 3,200 kips. The load test results revealed that the material in the 72-inch diameter socket does not represent a true rock. However, the test results also proved that the factored friction resistance of overburden layers is greater than the required design resistance. Based on the load test results, it was decided to allow the overburden soils frictional resistance to be considered in the shaft design, resulting in significant economic savings.INTRODUCTIONRock socketed drill shaft design guidelines of various State Department of Transportation (DOTs) agencies allow friction and/or end bearing resistance of only the rock socket portion into the design capacity estimation. It is typical to neglect the frictional resistance of overburden soils. However, in certain geological conditions where the rock layer is at greater depths, friction resistance of the overburden soils can be significant. In this case the friction resistance of overburden soils was verified via the specified instrumented O-cell test program and then used as part of the design capacity.PROJECT DESCRIPTIONAs part of I-29 improvement project, Iowa Department of Transportation (Iowa DOT) planned to replace the dual four lane bridges that cross the Floyd River in Sioux City, Iowa with dual six lane bridges (Fig. 1). Expected benefits from this improvement include improved safety, traffic operations and roadway infrastructure conditions.BRIDGE SUBSTRUCTUREThe project consists of two individual bridges; a new south bound bridge and a new north bound bridge. The south bound bridge is 646-ft long and the north bound bridge is 644-ft long. Both are six-span, pretensioned and pre-stressed concrete beam bridges of varying width. Bridge foundations were designed such that the abutments of both bridges will be supported on driven steel piles and the bridge piers will be on drilled shaft foundations."

Jan 1, 2016

By Diane Reid, Antonio Marinucci, Robin Mao

Super Cells are an innovative, open-shaped bi-directional static load testing device used to promote concrete flow during placement while utilizing greater cross-sectional area of the pile to achieve large applied axial loads at relatively low hydraulic pressures (≤ 250 bar). This paper describes the results of multi-level load testing performed on a sacrificial drilled shaft that was 3.8 m (12.7 ft) in diameter and 110.6 m (363 ft) in length for the Jiaxing-Shaoxing River Crossing Bridge that spans Hangzhou Bay in Shaoxing, China. The test shaft was instrumented with embedded strain gauges and telltale rods along with displacement transducers at the top of the pile to measure the load-induced displacements along the length of the shaft. Load testing was performed twice using a Super Cell placed near the tip of the shaft, prior and subsequent to tip post-grouting, and then again using a Super Cell placed higher in the shaft. The axial resistance for the tested conventional drilled shaft was more than 5 times greater than the estimated axial resistance. In addition, the axial resistance after tip post-grouting (347,100 kN (39,033 ton)) was about 5.3% greater than the ungrouted axial resistance (329,600 kN (37,050 ton)). INTRODUCTION During the past few decades, the magnitude of axial, lateral, and flexural loading has considerably increased due to updated design codes, larger superstructures, and the manner in which extreme event loading (e.g. seismic and scour) is incorporated into design. The diameter and depths to which bored piles or drilled shafts are constructed have increased considerably during the last three decades due to the advancements in equipment technology and capabilities. In addition, monoshaft foundations have become increasingly used, as one large drilled shaft is able to replace a group of smaller diameter piles connected by a cap. Correspondingly, adequate strata, for both side and end resistance, must be discovered/determined as well as achievable to be able to construct the required foundations to support the greater design demands. As design demands have increased, the need to ensure integrity, quality, and performance of a constructed drilled shaft has become ever more crucial. Load tests are essential to validate design assumptions of side and end resistances, to assess the behavior and load transfer characteristics of the constructed drilled shafts, and to evaluate construction methods. Load tests utilizing a bi-directional static load testing (BDSLT) device can achieve considerably large applied axial loads and can be performed more economically, in less time, and in a much safer manner than conventional top-down static load testing methods.

Jan 1, 2019

By Damir Dedic, Wörle. Patrick

"Soil properties within a construction project area are analyzed during the planning phase. However, it is only possible to achieve selective soil exploration, even in the case of very extensive investigatory programs, which results in a certain soil risk and uncertainties for planning and execution.Therefore, the application of monitoring systems is becoming increasingly important in the field of geotechnics. The application of suitable monitoring systems for these particular purposes provides considerable knowledge relating to the load bearing behavior of the soil and the ground anchor. Applications that present major challenges to measuring anchor forces include back-anchorages of long-lasting and very deep construction pits, construction pits in urban areas, slope and embankment supports for track and vehicular routes, port and lock structures, and uplift control. Apart from overseeing individual construction stages, monitoring systems analyze the interaction between the soil and structure throughout the latter’s entire life cycle and safeguard the functional capability of the applied system components. Geotechnical construction projects can be adapted, optimized and carried out with enhanced safety from the information obtained.Conventional Monitoring SystemsThere are numerous approaches for determining anchor forces of bar or strand anchors. Lift-off tests and measurements with load cells are the most common methods.Lift-off Test: Lift-off tests provide a possibility to monitor the prevailing force in strand or bar anchors. The entire anchor head structure is lifted using the appropriate equipment. The steel tendon is prolonged, or in the case of strand anchors, a screw-on cap holds the wedge carrier so that a tensioning jack can be mounted above it. Then, the tendon is prestressed until the lower anchor nut (bar) or wedge carrier (strand) is lifted off from the anchor plate. The intersection of the two straight lines in the figure represents the force at which the anchor nut or the wedge carrier lifts off from the anchor plate. Thus, the intersection displays the actual load of the anchor. This form of anchor force control gives conclusive results, but at the same time requires extensive accessories and extra personnel to execute the test. For this test, a sufficient bar overhang must be available, the wedge plate must possess an external thread, or there must be a strand overhang of at least 24 in (60 cm). Furthermore, the anchor head must be freely accessible and in a position to be reached with the necessary equipment."

Jan 1, 2017

By Leena Korkiala-Tanttu, Noora Lindroos, Juha Forsman

"Construction works at the Helsinki city sea shoreline requires dredging and handling of contaminated sediments. Most of these soft dredged sediments are regarded as too poor quality material for earth construction purposes. Mass stabilization technology has been applied to improve the technical and environmental properties of the dredged sediment in order to utilize the material in construction. The treatment site presented in this article is placed in the West Harbor where the dredged sediments are disposed in basins, mixed with binders by mass stabilization and transported to utilization sites. The volume of these basins is about 90 000 m3. So far these basins have been used three times during the years 2011-2014. The most applied binder has been cement. Its high price and carbon footprint have encouraged use alternative binders. Other used binder materials include fly ash and end product of desulphurization from coal combustion, and fly ash from combustion of Estonian oil shale. The technical and environmental properties of stabilized sediments have been studies in the laboratory and in situ thoroughly. Some properties of the stabilized sediments which have been studied are: compression strength, modulus, hydraulic conductivity, leaching of contaminants, etc. The leaching test results show that heavy metal leaching is very low with all binder materials tested.1. INTRODUCTIONContaminated marine sedimentsMarine sediments in the coastal areas are often contaminated as a consequence of industrial and port activities, as well as the influence of cities located there. Construction activities and reclamation of shore line require dredging and handling of contaminated sediments since the level of contamination inhibit dumping of dredged sediments into the sea. Based on their technical properties, most of these dredged soft and watery sediments (clay, gyttja, etc.) are regarded as too poor quality material for earth construction purposes. Economic, sustainable and environmentally safe management of contaminated, dredged sediments is a key issue in many construction sites.In the City of Helsinki, mass stabilization technology has been applied to improve the technical properties of the dredged sediments in order to utilize the material in construction. Owing to stabilization / deep mixing / solidification, also the contamination is encapsulated in a monolithic solid of a high structural integrity. Thus, contaminants migration is restricted by the decreased surface area exposed to leaching.The treatment site presented in this article is placed in the West Harbor (a place of Helsinki called Jätkäsaari) where dredged sediments are disposed into stabilization basins, mixed with binders by mass stabilization and then transported to final utilization sites. The location and principle of these basins is presented in Figures 1-4. The overall volume of these four stabilization basins is about 90 000 m3."

Jan 1, 2015

By Joel Moskowitz, Jan Cermak

"New York City has unique geologic conditions which must be considered when designing pile foundations. Where shallow foundations are not feasible, the City's subsurface conditions require a variety of deep foundation systems, ranging from high capacity rock socketed piles, to piles end-bearing on bedrock, to friction piles bearing in alluvial or glacial deposits. Pile load testing is essential in confirming pile capacities as pile analyses include assumptions on soil and soil-pile response, and pile driving equipment. Load test results must be interpreted to estimate the long-term pile behavior. Except for lightly loaded driven piles, the New York City Building Code (the Code) requires that pile capacities be confirmed by static load testing. The Code provides the number of static load tests required, test procedures, and acceptance criteria. In the last few decades, methods other than static load testing have been developed including dynamic and rapid (pseudo-static) load tests. Recently, those methods have also been employed on several projects in New York City. The traditional approach to pile load testing in New York City is discussed herein including engineering involved in the analyses of test data with examples. In addition, several projects which included non-static load testing are discussed INTRODUCTIONPile load testing complements the subsurface information and pile design by providing further data on pile-soil interaction for the selected pile type and installation method. Traditional approaches to pile load testing in New York City involve static load tests to verify the design capacity of the piles for a given minimum factor of safety.In the late 1950's, Dr. Phillip C. Rutledge summarized his views on the philosophy of pile foundations in an unpublished, in-house document. He viewed pile foundations as good illustrations of pertinent and impertinent aspects of geotechnical engineering. In the analyses of piles he divided engineering into four general types:(a) Theoretical engineering in which decisions are made based on theoretical analyses. This represents ideal engineering, in which all factors affecting the pile design are well established or, at least, few simplifying assumptions with known effects on the analyses are made."

Jan 1, 2005