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By Mary Ellen Bruce Large

"INTRODUCTIONIn partnership with California Department of Transportation (Caltrans), Federal Highway Administration (FHWA), and with support from International Association of Foundation Drilling (ADSC), Deep Foundations Institute (DFI) organized a workshop on quality assurance (QA) practices for acceptance of post-grouted drilled shafts in conjunction with DFI’s 40th Annual Conference on Deep Foundations. The 1½-day workshop was held on October 15-16, 2015 at the Oakland Marriott City Center in Oakland, CA.Post-grouting, in the context of this workshop and report, refers to the alternative design and construction of base-grouted drilled shafts wherein a grout distribution system is installed during construction and used to grout the base under pressure after the drilled shaft concrete has gained adequate strength, resulting in a stiffer axial-compression load-displacement relationship and additional possible ground improvement effects. The primary goals of the workshop were to•?Identify and summarize the state of the practice for design, construction, inspection, verification, acceptance criteria, reliability and performance of post-grouting.•?Identify gaps and needs in quality assurance that should be addressed for successful use of post-grouting.This report is structured to follow the workshop program: workshop presentations outlined the state of practice and views from owners, engineers and contractors on acceptance of post grouting methods for drilled shafts; and subsequent workshop discussions attended by a small invited group of participants focused on identifying areas of agreement and disagreement on post-grouting best practices, acceptance criteria, design and verification procedures, and inspection requirements. A partial list of attendees of the open and closed sessions is provided as Appendix A, and copies of presentations are included as Appendix B.FHWA and Caltrans are the primary audiences for this report, and its content will be used to develop a roadmap for deploying the findings into policy and practice. The secondary audience is the broader industry group, and the report content will be disseminated in a variety of formats."

Jan 1, 2016

By Heman Manchanda, Sandeep Sharma

Several infrastructure projects are in various stages of construction and planning in India and almost all of them involves open ground excavation extending to varying depths. These structures are generally multipurpose and fulfil several needs of the society, their failure can be catastrophic. The design and construction of deep open excavations is generally associated with a high level of risks due to a whole series of uncertainties involved, and the success of such projects depends on various factors including appropriate evaluation of ground behavior and response to excavation stages, correct choice and analysis of construction supports, control of ground water flow during excavation, etc. One of the most critical amongst all these is ground water flow during construction and stability of underground excavation depends to a large extent on ground water control. This paper uses numerical studies for the assessment of the potential impact of ground water and ground water movement for the design of underground deep structures. The studies are being conducted using PLAXIS 2D finite element software and analysis all construction stages to which an open underground excavation shall be subjected. The paper discussed in detail the impact of water table fluctuations and comparative evaluation of different water flow conditions – a) Different Stages of excavation in line with the construction sequence (Phreatic), b) Coupled flow analysis (Transient- 1 year and 2-year duration) and c) Steady state flow conditions. The paper also covers seepage calculation and design of dewatering system.

Sep 1, 2022

By Ambarish Ghosh, Chitralekha Ghatak, Tanumaya Mitra, Tarun Sengupta, Sajib Das, Sankar Kumar Nath

"Currently construction of important structures like bridges, flyovers and high rise buildings in and around Kolkata are in full swing. These structures have mostly pile or well foundations. The design methodology and construction techniques are being employed keeping in view both the safety and economy of the project. The data presented in this investigation have been taken from Geotechnical Investigation report of Component B in connection with construction of Extradosed Cable Stayed Bridge over River Hooghly in Hooghly and Nadia district of West Bengal, India. The investigation site is located within close proximity of Eocene Hinge Zone which is being taken as the principal contributor of Earthquakes in and around Kolkata. Considering the importance of the project detailed and exhaustive geotechnical investigation has been carried out and site specific response spectra have been generated for analysis and design of the bridge. This paper presents site specific response spectra, liquefaction analysis and comparison of lateral load carrying capacity of pile using Winkler approach and IS 2911 guidelines.INTRODUCTIONPile foundations are used to transfer the load of the super structure through soft soil deposit to deeper bearing stratum by means of skin friction or end bearing or both. Pile foundations are regarded as a safe alternative for supporting structures in seismic areas and have been used for this purpose in non-liquefying as well as liquefying soils. But their design in case of potentially liquefiable soil is quite different from that of non liquefiable soil. In liquefiable soil the progressive buildup of excess pore water pressure will cause stiffness degradation and loss of strength which in turn will induce additional shear force and bending moment in the pile. The mechanism of pile behavior in liquefying soil has been investigated by several investigators in the recent years based on observations of pile performance during earthquakes and studies in the centrifuge and Shake Table tests. Exhaustive geotechnical investigation has been carried out along the proposed alignment of the Extradosed Cable Stayed Bridge i.e., along Baropara, Bansberia ROB, Ishwar Gupta Bridge, Saraswati River to collect disturbed as well as undisturbed soil sample, to develop average soil profile and to determine the design parameters. The proposed project site is very close to Eocene Hinge Zone, which is basically a strike slip fault, capable of generating an earthquake of Mw 6.7. Thus it is evident that the proposed Bridge needs to be designed considering the adverse geo-hydrological condition as well as the earthquake aspects needing special attention following the state-of-the-art technology as guided by relevant codes and published literatures. Considering the soil profile of these locations ground response analysis has been carried out using equivalent linear method to determine the site amplification. Site specific response spectra have been developed for the four zones and zone factors have been determined. The computed zone factors are 0.198g, 0.195g, 0.195g and 0.20g for the four zones respectively, much higher than the zone factor 0.16g, which is for zone III, as stipulated in IS 1893:2002."

Jan 1, 2015

By Dario Libano

"The Line 5 Extension, in Sao Paulo, Brazil, is currently the most important investment in public transportation by Sao Paulo’s state government. It will connect the south part of the city to the city center, crossing through four other major Metro lines and stations; all currently in operation. The total extension of the line is 11 km (6.8 mi), and includes a new parking yard for the trains and 11 new stations. The Brooklin Station, one of the new stations due to be open and operating in 2016, has a unique geometry of five secant shafts.The original design included constructing five secant shafts stabilized by two plastic slurry walls using conventional grab technology. One slurry wall, along the Santo Amaro Avenue, was to contain the contamination plumes, and another was for temporary support to enable the excavation of the shafts. The final retaining wall design was changed to a concrete structural diaphragm wall that reduced the construction time of the shafts by half, allowing the contractor to meet the construction schedule. This solution also avoided dewatering effects in a geological region characterized by Quaternary sediments and environmental contamination plumes. It was the first time that a hydromill was used in such a situation in Brazil. The hydromill, by overcutting the panels, increased the quality of the joints, and decreased the probability of having seepage into the shafts. The hydromill also created a seepage barrier and avoided movement of the contaminated plumes.The GeologyLocal geology is composed of a superficial Quaternary soil, basically soft organic clays and sands and gravels. From the depth of 8 m (26 ft) until 18 m (59 ft), geology is composed by tertiary medium compact sand with thin silt-clay layers. From 18 m (59 ft) down, there are alternations between compact silt-sands layers with very hard clays layers. Each is approximately 5 to 10 m (16.4 ft to 33 ft) thick.The Initial Basic DesignThe original basic design of the Brooklin Station was to be constructed from five 40 m (131 ft) diameter intersecting circular shafts, all in a line along the axis of the Metro tunnel, in 555 days. In the excavation sequence, the odd shafts were first excavated, waterproofed and had part of their inside cast-in-place structure built before the even shafts were excavated. During the excavation of the even shafts, part of the odd shaft’s support was demolished and connected with the even support. A 0.8 m (2.6 ft) thick plastic slurry wall, acting together with the wire mesh reinforced shotcrete support, ensured the excavation stability around the five shafts."

Jan 1, 2014

By Srijit Bandyopadhyay, Aniruddha Sengupta, G. R. Reddy, Raj Banerjee

The objective of the present endeavor is to compare the performance of a pile raft system in foundation sand subjected to lateral loads. To study the behavior of pile raft system in sand a laboratory test was conducted on small scale model foundation system. The raft and pile was modeled by square concrete foundation of 250 mm x 250 mm x 15 mm in length, breadth and thickness and 25mm diameter and 250mm long circular pile located at the center of the raft. The system was tested under static lateral loads of 6.25N, 12.5N, 18.75N and 25 N respectively resting on dry Kasai River sand. A vertical surcharge pressure of 1.5kPa (10 kg) was applied on top of the model raft for each case. The results of the model tests have been simulated by a general purpose 3-D finite element software and the model has been validated with experimental results. The moments of the pile obtained from the model tests and those predicted by the numerical analyses for all the lateral loads matches reasonably well. For matching the trend of bending moments obtained from experiments, validation with theoretical results have been done with the help of Matlock and Reese (1960) approach for a single value of lateral loading. Moreover, a parametric study has been conducted with 5mX5mX0.3m raft size with 0.5m diameter and 5 meter long pile with increasing number of piles namely 2, 5 and 9 respectively to study the response in terms of moment and lateral deformation under available earthquake loadings, like Loma Prieta (1989) and Darfield Christchurch (2010). Bending moments of piles and load deformation curves for lateral loading have been studied for each case in which it is observed that the bending moments of pile significantly reduces (around 4 times) as the number of pile is increased to two, but it decreases to a nearly constant value (it saturates) as the number of pile is increased to five and nine. Moreover, the lateral deformation of piled raft system drastically reduces (around 2.4 times) for two pile system, and it saturates to a constant value with five and nine pile system. All these results indicate the constancy of stiffness irrespective of the number of piles in the piled raft.

Jan 1, 2015

By Susan Rafalko, Mike Walker, John Sankey, Sherif Aziz, Alex Potter-Weight, Mary Nodine, Frederic Masse

"After several successful projects on the Garden State Parkway and New Jersey Turnpike for support of single-stage MSE (Mechanically Stabilized Earth) walls using rigid inclusions (Controlled Modulus Columns) as an alternate to two-stage MSE walls and surcharge, the Bass River Bridge Widening project presented additional challenges in terms of soil conditions and height of embankment that created opportunities for the design-build ground improvement contractor and its MSE wall-designing partner to enhance their design and construction methods. The specialist contractor decided, in association with the wall system supplier, to perform an independent large scale instrumented test area on the project to demonstrate the ability of the design techniques to model the behavior of the system, as well as the capacity of the rigid inclusions to provide the necessary bearing capacity and settlement control to allow the construction of the highway without any consolidation period. This paper presents a detailed description of the design of the ground improvement system and MSE wall system, as well as the results and conclusions of the monitoring data gathered on the large scale test program. The combination of rigid inclusion ground improvement technologies, such as the CMC system, together with an MSE wall system allows for the rapid and economical construction of high embankment without waiting for a surcharge and consolidation period or the necessity to use a two-stage wall system. In-depth understanding of the design techniques and advantages of this combination will be provided and should be beneficial for any geotechnical engineer or owner looking for innovative solutions to save both time and cost on their projects.1. IntroductionAs development continues on sites with poor ground conditions throughout the world, conventional MSE walls remain a flexible design solution; however, construction of MSE walls in combination with ground improvement is becoming more frequent where extreme differential and/or total settlement prevail due to soft ground conditions. Various techniques have been used in the past in such conditions (e.g. conventional surcharge, staged construction, or two-stage MSE walls), even though these design solutions have typically involved longer waiting times for settlement to occur. As a result, conventional MSE wall design has been combined with a variety of ground improvement techniques consisting of rigid inclusions for an economical and efficient solution with the potential to accelerate construction and limit long term settlement. For the particular subject of this paper, the specialist contractor (Menard) proposed to use CMCs (Controlled Modulus Columns) to support the highest part of the MSE wall. CMCs are grouted displacement rigid inclusions installed in a grid-like pattern using a displacement auger. Before the CMCs are installed, a working platform may first need to be placed to allow equipment to move around the site depending on the ground conditions. Following the CMC ground improvement, an LTP (Load Transfer Platform) is installed prior to the construction of the MSE wall."

Jan 1, 2015

By H G. Poulos

"This paper sets out a simplified approach by which the practical foundation designer can undertake the relevant calculations to satisfy the requirements for deep foundation design in seismic areas. The following matters are dealt with:a. Design issues that should be addressed;b. Pile design for axial loading, including the possible effects of liquefaction;c. Pile design for lateral loading where liquefaction does not occur;d. Pile design for lateral loading where liquefaction does occur;e. Measures to mitigate against liquefaction effects.The paper is a modified version of a paper presented in 2013 to the 19th NZGS GeotechnicalSymposium, Queenstown, New Zealand.1. INTRODUCTIONConsideration of the effects of earthquakes and seismic loadings is an increasingly important aspect of modern foundation design, and most contemporary standards have a mandatory requirement for such consideration. For example, the Australian Piling Code, AS 2159-2009, states that “a pile shall be designed for adequate strength, stiffness and ductility under load combinations including earthquake design actions”. However, the methods by which such considerations can be undertaken are generally not set out in the standards, and many approaches have been utilized, ranging from very simplistic methods to extremely complex computer analyses. Accordingly, there appears to be scope for an approach that is soundly based but which is neither too simplistic nor too complex.Poulos (1989) has suggested that there are three categories of analysis and design, as follows:1. Category 1: empirical methods.2. Category 2: simplified but soundly-based methods.3. Category 3: more comprehensive methods that are soundly-based, and site-specific.The objective of this paper is to set out a systematic but simplified approach which falls into Category 2 above, and by which the foundation designer can undertake the relevant analyses to satisfy the foundation design requirements for seismic regions. Emphasis is placed on methods that do not require “black box” software or which employ complex soil models in which the physical meaning of the parameters is unclear."

Jan 1, 1900

By David Gatto, Nicolas A. Willig-Friedrich, Jeff A. Segar

"With the increasing demand for electricity, and requirements to generate this power cleanly, more producers are turning towards hydroelectric power. A project in Iowa currently under construction will retrofit an existing Army Corps of Engineers Dam with a hydroelectric generating facility. The design of the intake structure requires the construction of a diaphragm retaining wall. The T-shaped diaphragm wall elements retain an unbalanced fill height up to 21.3 meters (70 feet). The design required a single production element be constructed, tested, and instrumented prior to beginning construction of the rest of the elements. The testing included extensive concrete mix design development, coring, and Cross Hole Sonic Logging. Installed in the other production elements are 10 inclinometers, 4 pressure cells, 4 piezometers, and multiple survey monuments. Some of these instruments require manual readings while most are monitored by an automatic data acquisition system and instantly transferred to a website providing real-time graphical display of the data. This paper will discuss the construction of the diaphragm wall from the contractor’s perspective when working on a site only large enough for two service cranes and a Hydromill excavation unit, without any storage area on the construction pad, describe the testing performed and the quality control procedures employed, and investigate the information gained from the automated instruments providing real time measurement readings.INTRODUCTIONIn 1964 the US Army Corps of Engineers (USACE) constructed a dam by raising the surface grade approximately 34.7 meters (114 feet) above the natural ground line using a combination of fill types. This earthen dam stretched slightly longer than a mile intersecting the flow of the existing Des Moines River. The center of the dam is a concrete spillway consisting of 12 monolith sections. On each end, three of the sections extend 42.6 meters (140 feet) from the spillway to transition from the concrete dam sections to the earthen dam section. Adjacent to these three sections on the East end is where the contractor is actively working, for a private developer under a lease agreement with USACE, on this site to convert it to a Hydroelectric facility licensed for an output of 36.4 megawatts, enough power to meet the needs of about 18,000 homes. To create this, a powerhouse structure, housing two vertical Kaplan turbines is being added to the downstream side of the existing dam. From the power house, two penstock pipes will be cored through the existing concrete monolith sections and connect to the Intake structure on the upstream side of the dam. Protecting and reinforcing the dam adjacent to the intake structure is a new diaphragm wall. This wall is constructed using T-shaped diaphragm elements, acting as a cantilever retaining wall for the intake platform. Figure 1 shows a diagram of the upstream features of the construction."

Jan 1, 2016

Jan 1, 1984

By Adnan A. Malik, Tadashi Maejima, Jiro Kuwano

"Previous studies revealed that the helix deflection reduced the end bearing capacity of screw pile in dense ground even if the installation process is completed with minimal soil disturbance. The ultimate end bearing capacity in dense ground is difficult to achieve during the full-scale pile load test due to the limitation of the loading system. Therefore, in the present study, model scale of testing is selected to investigate the effect of helix deflection on load settlement behavior of single helix screw pile under increasing stress level. It is observed from the test results that the applied surcharge pressure, which is used to simulate the effect of stress level, is decreased with increase in model ground thickness. This decrease in the stress level is due to the frictional resistance between the container wall and sand. It is also observed that the end bearing capacity of screw pile increases with the increase in stress level but at gradually decreasing rate. The test results indicated that the helix deflection during the pile load test should not be more than critical deflection (0.72 mm average) of the helix to avoid any reduction in the end bearing capacity of screw pile. The helix deflection, which is measured after the pile load tests are also compared with the equations of flat circular plate having uniformly distributed load over the plate with simply supported and fixed inner edges.INTRODUCTIONThe screw pile consists of a central steel shaft with one or more helices attached at different location on the central shaft. The installation mechanism of screw pile consists of torque and pushing force. The screw pile installation mechanism can affect the unit weight of the ground during its installation. This effect is small in cohesive soils but it is quite noticeable in loose to medium dense sands (Adams 2011; Santos et al. 2013). The pushing force should be controlled in such a manner that pile penetration should be at least 80% of the pitch of the helix, during each revolution (Perko, 2009)."

Jan 1, 2017

By K. Madhusudan Reddy

Pile response under combined uplift and lateral load is very important and it is imperative to evaluate the effect of combined loading and only few studies were reported on pile behavior under combined uplift and lateral loads. Model pile made-up of aluminum having an outer and inner diameter of 25.4 mm and 19.4 mm respectively is used. Dimensions of the model steel tank are fixed as 1.0 m x1.0 m x 1.2 m (depth) to avoid the boundary effects under combined lateral and uplift loads. Experiments were carried out on single piles at isolated uplift, isolated lateral loading and combined lateral and uplift loading, embedded in sandy soil. Results indicate that load?deflection behavior is nonlinear for isolated uplift and lateral load tests as well as in case of combined loadings. It is also observed that the behavior of piles under isolated loadings is substantially different when compared to combined loading.

Jan 1, 2002

The intent of this manual is to provide guidelines for inspectors of drilled shaft construction otherwise referred to as drilled piers, caissons or bored piles. It should also be helpful to train beginning geotechnical engineers with limited first hand experience or for geotechnical engineers who are training inspectors. It is expected that the general guidelines and procedures described here will be supplemented by local geotechnical engineers working in a particular region based on local practice and experience. Since drilled shaft construction procedures vary widely based on local geology and size of project, an all-inclusive manual is not considered practical. This manual focuses on traditional topside inspection for routine drilled shaft construction. Other inspection and evaluation methods that rely on electronic equipment are available, but these methods require extensive training and experience in the interpretation of results. These more sophisticated methods of drilled shaft inspection and evaluation are common in construction, but they are usually provided by specialty subconsultants. The subconsultant will typically submit a report for each shaft, which will be reviewed by the geotechnical engineer. Other manuals are available to describe the electronic methods of drilled shaft inspection.

Jan 1, 2004

By Peter Cali, David Yang, Rakshya Shrestha, Ralph Griffin, Sushil Kafle, Motoji Watanabe

"As a part of the ‘US Army Corps of Engineers - New Orleans to Venice, Louisiana Hurricane Protection Project’, deep mixing ground improvement was designed to reinforce the soft ground for the emergency repair of a 7297-foot (2,224 m) long section of the Mississippi River West Bank levee in Buras Levee District under the contract ‘Emergency Levee Repairs – Contract P-17A, Plaquemines Parish, Louisiana’. The ground improvement utilizes a series of soil-cement panels oriented in the transverse direction of the levee. Each soil-cement panel consists of overlapped columns installed by the deep mixing method (DMM). DMM is performed from the existing top of levee and extended to competent stratum at depths varying from 26 feet (7.9 m) to 47 feet (14.3 m) below the working platform. The main purpose of the DMM panels is to provide shear resistance to the levee against lateral loads at high flood water condition. The DMM panels support the additional vertical load created by the increased height of the levee for hurricane protection and control the long-term settlement of the remediated levee, which might otherwise occur due to the compression of soft foundation soils. The total amount of DMM treatment is approximately 54,000 cubic yards (41,500 cubic meters). This paper reviews the project background, subsurface soil conditions and presents the design, construction and quality control of the deep mixing work for this levee repair project.INTRODUCTIONIn August 2005, Hurricane Katrina caused major damage to the federal and non-federal flood control projects in southeast Louisiana. In September 2005, Hurricane Rita caused further damage to this flood protection system. In an effort to minimize further damage and to enhance the protection level, certain non-federal levees located on the west bank of the Mississippi river in Plaquemines Parish, Louisiana were incorporated into the New Orleans to Venice Hurricane Protection project by the US Army Corps of Engineers (USACE). DMM techniques were then utilized by the USACE in several of these emergency projects and in many medium sized projects between 2006 and 2010 (Bruce et al. 2012). This project (called P-17A hereafter) which forms a part of this protection system is executed under the contract Emergency Levee Repairs, Contract P-17A. This is one of the largest projects of the USACE after LPV- 111. The huge LPV-111 project (5.5 miles (8.9 km) of levee) treated by DMM), the largest DMM project ever conducted outside Japan, began in 2010 and was completed in 2012 (Cali et al. 2012, Bruce et al. 2012).DMM is utilized at P-17A to construct a series of soil-cement panels oriented in the transverse direction of the existing levee to provide shear resistance to the levee against the lateral load during high flood water condition. The project extends 7297-foot (2,224 m) along the West Bank Levee of the Mississippi River in the Buras district of Louisiana, parallel to Louisiana Highway 23 (LA-23) as shown in Figure 1. It is located approximately 60 miles (96 km) south-east of downtown New Orleans."

Jan 1, 2015

By John C. Tosh, Peter M. Kandaris, Sheldon John

Geologic, geotechnical and hydrologic studies were performed for the design of 115 deep, large diameter drilled shaft reinforced concrete foundations (6 to 12 feet) to support tall steel monopoles for a new 13-mile long 230/69kV transmission line in southwestern Arizona. The subsurface conditions along the alignment posed a wide range of challenges for performing investigation and design studies. These conditions include saturated, loose granular flood plain deposits with generally low lateral capacity, potential ground loss up to 23 feet due to occasional river flow (scour and embankment loss), liquefaction impacts from nearby active fault seismicity that can generate magnitude 6.5-7.0 earthquakes, and unsaturated alluvial and eolian sand-dominated soils to full depth with low lateral capacity. All conditions will require significantly deeper than normal foundation embedment (depth ranging from 22 to 77 feet) and will present construction difficulty due to ground instability from groundwater and dry soil sloughing. A phased investigation was performed to accurately characterize the conditions for design and construction, and included performing a review of existing data, detailed field geologic reconnaissance, a limited number of standard exploratory borings (limited access), seismic cone penetrometer soundings (SCPT) in saturated soils to better understand liquefaction and strength loss potential, and hydrologic analyses to estimate scour/ground loss potential. This paper describes the site conditions, presents details on the investigation team’s approach, documents findings in relation to deep foundation analysis and design, and discusses recommendations for foundation construction to help in reducing risk.

Sep 8, 2021

By Bernardo J. Jiménez, Harlem Lora, Roberto Acosta Mora

Circunvalacion Norte project is currently the most important infrastructure project in Costa Rica. It is the last segment of the urban perimeter highway. Site investigation of local geotechnical conditions were studied by SPT, CPT, pressuremeter tests and boreholes. A static load test was executed as a proof test with an associated ultimate resistance of 12056 kN (2710 kips). Drilled shaft design was done using PMT tests and axial nominal resistance varied between 4000 kN (900 kips) and 6000 kN (1350 kips). A total of 416 drilled shafts were constructed in 15 months with drill performance of 32 m/day (105 ft/day). Drilled shaft lengths varied between 4,0 (13 ft) m and 40,0 m (130 ft). Selfconsolidating concrete was used to achieve an adequate workability even in high densities rebar cages. Several site conditions proved the importance for maintenance of the working platform, predrilling of rock sockets and having spare parts to avoid increase in project’s cost. New procedures were taken to prevent concrete segregation on excavations near underground water flow. Monitoring the quality of the shafts from CSL test showed less than 3% of the shafts presented a considerable anomaly, which proved that the adopted construction method and materials were adequate. For the concrete anomalies, successful remediation was performed by means of grout at the base of the shaft with two different types of drilling methodology depending on the concrete anomaly.

By George Moses K, Mahendran K

Grouting is performed in rock masses in order to increase its strength properties and also to reduce the seepage. In the design of underground structures such as tunnels or caverns located in weak rock masses, grouting plays an essential role. Grouting is a complex process demanding high degree of skill and knowledge in understanding of grout flow and requirements for certain geological conditions. This paper discusses the design process for grouting in rock masses adopted for a cavern project and the practical difficulties faced during the execution at site. The design parameters of grouting includes the injection pressure, grout material properties and stopping criteria. The paper also discusses the various tests performed at site to evaluate the efficacy of the grouting process which was initially defined based on the design and previous experiences. The final grouting scheme suiting to the present geological condition is arrived based on the test results. The practical difficulties faced during the execution and the measures taken to overcome these are discussed in detail. This work shows the importance of state of art in the development of a grouting process based on geological and hydrogeological conditions prevailing at site and can be helpful in grouting design for weak rock masses.

Nov 1, 2022

By Sushant Upadhyaya, Deniz Karadeniz, Ahmed Mohamed

Soil setup analysis provides opportunities for efficiencies in pile foundation design and installation. Soil setup gain with time was evaluated as part of the foundation design and installation for twelve bridges along the Interstate 64 corridor between York County and Newport News in Virginia. The substructure elements of the bridges consist of driven precast prestressed concrete piles or H-piles. This case study describes lessons learned to understand the soil setup phenomenon during the installation of the piles in coastal plain. We were able to make expedited decisions during construction by analyzing previously performed pile dynamic analyzer (PDA) test results within the project alignment. Data evaluation included analyses of PDA data obtained from initial driving and restrike after a few hours to 5 weeks. The test data showed pile resistance increase up to twice in most cases and as high as four times in some cases. Foundation design and acceptance based on soil setup can provide opportunities for cost savings and advanced scheduling during construction.

By Brian Metcalfe, Kord Wissmann, Gianni Martinez

The Middle East consists of vast deserts that reach temperatures up to 50 degrees Celsius, with some areas characterized by endless sand dunes. When the project team selected the location for a large new transportation project, little did they know that the site would be characterized by soft, nearly normally consolidated silt and clay extending below a thin sand crust. Searching for solutions, the design team elected to reinforce the subsurface with Rammed Aggregate Pier® (RAP) ground improvement elements and desired verification that the novel method would stand the test of prolonged static loads. Because the concrete pavements would serve to spread the load, a “zone load test” was performed, consisting of applying a uniform bearing pressure of 150 kPa over a 7.5m square concrete footing. Unlike individual pier load tests, the zone test allowed the project engineers the opportunity to confirm design parameter values under large-loading area conditions, a situation not often available to most designers. This paper presents the results of the zone load test whose results may be interpreted to better understand design parameter values. This paper is of particular significance because it adds a value contribution to the relatively few numbers of “group load tests” available in the literature for ground improvement applications.

May 1, 2022

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