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By Prodyot Kumar Ray, Sudip Kumar Koley, Aminul Islam, Somnath Banerjee

One of the most important topics in the construction industry is the building of railway embankments. Being such a delicate and significant structure, it is crucial to properly design the embankment and build it while adhering to all statutory criteria and design guidelines. A railway embankment's subsoil condition and fill material, groundwater table, dynamic and static loads during operation, and embankment geometry are some of its most crucial design considerations. This paper discusses the likely causes of the collapse of a railway embankment in eastern India as well as the suggested rehabilitation scheme. It was observed that an embankment collapsed in the aforementioned area during a inccesent rain. Along with the side shifting of a cantilever retaining wall that was positioned at the bottom of the embankment, the embankment next to the railroad track settled vertically. According to the available geotechnical report, the sub soil strata in half of the area adjacent to the embankment profile, where the embankment height gradually decreases from maximum height, is stiff to hard clay with an undrained cohesion value of around 50 kpa followed by dense sand, and the sub soil strata in the other half is soft clay with an undrained strength of 15 kpa. As a result, in the rainy season due to the sudden increase in the water table, the self-weight of the embankment increased and further caused the under-laying soft clay to get squeezed away and settle. Due to this squeeze/settlement effect of the soft clay layer, the retaining wall got disturbed along with the generation of an undulated embankment top profile. As a remedial measure, it is proposed to construct a contiguous bored pile wall at the toe of the embankment to stabilize the slope, and additionally, compaction grouting is recommended beneath the embankment to improve the soft clay. In order to carry out the analysis, certain commercial geotechnical software like Slide, Wallap, and Plaxis 2D are used. The factor of safety of the embankment slope considering the above restoration scheme is adequate under static and seismic conditions.

Sep 1, 2022

By Matthew E. Meyer

Renovation, rehabilitation, restoration and expansion of existing residential, retail, commercial, hospital facilities and historic structures requires assessment and evaluation of foundation systems of various ages. The concept of demolition and reconstruction in urban areas is often more challenging, costly, and even prohibitive in some cases due to historic regulations. The authors have been involved with numerous projects related to existing foundation assessment and retrofit, including: hotel and hospital expansions, historic Art-Deco hotel renovations and expansions, garage structure expansions, additions to prominent auction houses, casinos, printing facilities; high-rise structure foundation retrofitting; and forensic evaluations of existing building and highway structure foundation systems, and marine bulkhead sheeting systems. The use of non-destructive testing techniques, high-strain dynamic load testing, full scale pile cap load testing and 3-D laser scanning technology has proved to be vital in the assessment and evaluation process, as well as design of foundation retrofit alternatives. This paper presents various methods and techniques to facilitate a phased approach for re-use of foundation systems. These methods and techniques are illustrated through the author?s experience and selected case histories from projects with varied foundation and geologic conditions.

Jan 1, 2009

By Franz-Werner Gerressen, Manfred Schoepf

"Diaphragm walls are known as underground structural elements commonly used as retention systems for excavation pits and shafts and permanent foundation walls or elements. It can be anticipated that, with the increasing trend of utilizing more and more underground space to accommodate environmental considerations and urban/suburban development, there will be an increasing requirement for diaphragm walling in even more complex conditions. Complex and/or challenging conditions in terms of ground conditions have a major impact in regards of choosing the right tools for excavation purpose. Complex conditions in terms of space limitations, especially for inner city job sites, require specifically adapted solutions for slurry, spoil, reinforcement and concrete handling and the related logistic to ensure smooth production. Furthermore, one focus will be given to the QA/QC topics of the production process. Real time installation control, data transfer and reporting systems become more and more important ensuring the five dimensions of a jobsite. Therefore, the paper will describe the construction method and the sequence of activities required for the construction of diaphragm wall systems with the focus on the cutter technology. It will describe also the main equipment which will be needed to execute these works under the various conditions INTRODUCTION Diaphragm walls are known as underground structural elements commonly used as retention systems for excavation pits and shafts and permanent foundation walls or elements. It can be anticipated that, with the increasing trend of utilizing more and more underground space to accommodate environmental considerations and urban/suburban development, there will be an increasing requirement for diaphragm wall usage in even more difficult conditions. Of course diaphragm wall can also be used as deep groundwater barriers (Cut-Off-Walls). This market has shown that the demand for these types of walls is reaching more and more difficult soil conditions or required depths which are surpassing the current standard. The trench cutter is the most important tool for performing this work. The trench cutter itself is a reverse circulation excavation tool. It consists of a heavy steel frame with two drive gears attached to its bottom end, which rotates in opposite direction around horizontal axis. Cutter wheels are mounted onto the drive gears. As they rotate, the soil beneath the cutter is continuously being broken up, removed, mixed with the bentonite slurry in the trench and moved towards the opening of the pump suction box. The slurry loaded with soil and rock particles is pumped by a centrifugal pump which is located right above the cutter wheels, up through a hose system up to a desanding plant where the slurry is cleaned and returned into the trench."

Jan 1, 2015

By Tae Hwan Lee, Jun-Shin Lee, Daejin Kwag, Sangchul Bang, Gerard T. Houlahan, Moo Sung Ryu

"Geotechnical engineers have been installing innovative, permanent underwater foundation systems utilizing suction buckets for the offshore industry since the early 1980s (Senpere and Auvergne, 1982). This foundation system has been successfully used on numerous and various types of offshore structures in a wide range of environments. Suction buckets have numerous advantages compared to conventional underwater foundation systems. The more notable advantages include easy installation, large loading capacity, low noise and retrievability. The application of reduced water pressure inside the bucket facilitates the installation of the suction buckets, where a suction pump attached at the top of the bucket can accomplish the entire driving operation. Because of this efficient operation, very large suction buckets can be driven into the seafloor, which eliminates the use of a large number of small piles.In Korea, one of the most economical and reliable renewable energy sources is wind power; however, onshore wind power generation has encountered many problems, such as the lack of favorable sites and public concerns about noise and environmental damage. Consequently, offshore wind power generation has attracted increasing attention due to its abundant potential, high efficiency of grid connection, and availability of easy expansion.In November 2011, the government of Korea announced a national offshore wind power development roadmap, which targeted its offshore wind power generation with the goal of becoming one of the top three nations in the world for offshore wind power generation. Korea Electric Power Corporation Research Institute (KEPRI) is the main research arm of the Korea Electric Power Corporation (KEPCO) and conducts research and development on electricity, power generation, renewable energy and other energy-related matters. KEPRI ultimately provides forefront knowledge and leadership to KEPCO with respect to energy and related areas for its near- and long-term needs. Financial support for the overall project, of which the suction bucket foundation system installed for the pilot phase wind turbine is described below, was provided from the New and Renewable Energy Program of the Korea Institute of Energy Technology Evaluation and Planning funded by the Korean Government Ministry of Trade, Industry and Energy"

Jan 1, 2017

By Tae Hwan Lee, Jun-Shin Lee, Daejin Kwag, Sangchul Bang, Gerard T. Houlahan, Moo Sung Ryu

"Geotechnical engineers have been installing innovative, permanent underwater foundation systems utilizing suction buckets for the offshore industry since the early 1980s (Senpere and Auvergne, 1982). This foundation system has been successfully used on numerous and various types of offshore structures in a wide range of environments. Suction buckets have numerous advantages compared to conventional underwater foundation systems. The more notable advantages include easy installation, large loading capacity, low noise and retrievability. The application of reduced water pressure inside the bucket facilitates the installation of the suction buckets, where a suction pump attached at the top of the bucket can accomplish the entire driving operation. Because of this efficient operation, very large suction buckets can be driven into the seafloor, which eliminates the use of a large number of small piles.In Korea, one of the most economical and reliable renewable energy sources is wind power; however, onshore wind power generation has encountered many problems, such as the lack of favorable sites and public concerns about noise and environmental damage. Consequently, offshore wind power generation has attracted increasing attention due to its abundant potential, high efficiency of grid connection, and availability of easy expansion.In November 2011, the government of Korea announced a national offshore wind power development roadmap, which targeted its offshore wind power generation with the goal of becoming one of the top three nations in the world for offshore wind power generation. Korea Electric Power Corporation Research Institute (KEPRI) is the main research arm of the Korea Electric Power Corporation (KEPCO) and conducts research and development on electricity, power generation, renewable energy and other energy-related matters. KEPRI ultimately provides forefront knowledge and leadership to KEPCO with respect to energy and related areas for its near- and long-term needs. Financial support for the overall project, of which the suction bucket foundation system installed for the pilot phase wind turbine is described below, was provided from the New and Renewable Energy Program of the Korea Institute of Energy Technology Evaluation and Planning funded by the Korean Government Ministry of Trade, Industry and Energy."

Jan 1, 2017

By Artak D. Mirzoyan

Pile foundations near the edge of a slope are often required to resist lateral loads. This is particularly important for piles at abutments of bridges. However, very few full-scale tests are available that compare the effect on lateral resistance of piles installed in sloping ground to piles installed in horizontal ground. To investigate the effect of a slope on lateral pile resistance, three full-scale lateral load tests were performed on an instrumented steel pipe pile. For the first test, the pile was laterally loaded in horizontal ground; in the second test, the pile was at the crest of a 30º downward slope; and for the third test, the pile was located three pile diameters from the crest of a 30º slope. The soil around the pile consisted of well-graded clean sand (concrete sand) and was compacted to 95% of the modified Proctor maximum unit weight in all three tests. Lab and in-situ direct shear tests indicated that the friction angle of the sand was approximately 39 degrees. The pile was instrumented with strain gauges so that the bending moment versus depth profile could be determined. Pile head load, deflection and rotation were also measured. Based on the load versus deflection curves, the presence of the slope resulted in a decrease in lateral resistance of about 20% for the pile at the crest of the slope and 8% for the pile at 3D from the crest of the slope relative to the pile in horizontal ground. The presence of the slope also resulted in an increase in the maximum moment of 29% and 20% for the piles at the slope crest and at 3 pile diameters from slope crest, respectively. Analyses using LPILE with the measured friction angle significantly underestimated the lateral resistance for the horizontal soil profile. After calibrating the model with the response of the pile in horizontal sand, analyses including the slope still underestimated lateral resistance by about 20%.

Jan 1, 2007

By Paul Pedini

The challenge of Contract C19E1 of Boston's Central Artery Project called for the construction of two roadways under the commuter rail yard at North Station. Two options were offered for the method of their construction: Slurry Wall Roof-First or Soft Ground Tunneling. The instability of the indigenous soils seemed to rule out the use of tunneling, so the slurry wall method was chosen. However, these soils were incapable of holding up during slurry trench excavation. After many episodes of ground loss on early panel excavations, Modem Continental Construction suggested a method of trench wall stabilization. The Contractor (MCC) both suggested wall stabilization method and requested that the owner participate in the funding for the effort. The Project and the Contractor were able to agree on a solution which resulted in collapse-free excavation...and found an innovative way to fund the solution.

Jan 1, 2002

By Michael Perlow

Helical screw piles in use since 1838 are routinely used for energy, transportation, municipal, industrial, marine and coastal infrastructure as well as for excavation support, environmental remediation, and foundation repair. They are especially well suited for work in constrained areas, renovations and structure retrofits. Helical pile design procedures over the past 10 years have gone through a remarkable evolution with the establishment of the 2007 AC358 Helical Pile Acceptance Criteria and inclusion of helical screw piles in the 2009 International Building Code (IBC). New 2009 IBC building code requirements and AC358 Acceptance Criteria are presented along with advances in helical pile design procedures, installation, QA/QC, and recommended load test verification criteria. Use of helical smart piles to validate helical pile design and verification of ultimate pile capacity is highlighted.

Jan 1, 2011

By David Peterson, Terry Tucker, Rafael Serrano

"The Alameda Corridor-East (ACE) Construction Authority awarded a $172.6 million contract to Walsh Construction Company (Walsh) for the construction of a 2.2 mi (3.5 km) long grade separation including a 1.4 mi (2.3 km) long trench that will allow Union Pacific Railroad (UPRR) and Amtrak passenger trains to operate below ground through the city of San Gabriel, Calif. The project is necessary as the ACE trade corridor accommodates approximately 60% of the shipping containers that move from San Pedro Bay, the busiest port facility in the western hemisphere, to the rest of the country via an extensive rail network. Rail traffic is expected to increase by as much as 160% by 2020, and the resultant delays to vehicular traffic is projected to increase by an estimated 300%. The San Gabriel Trench Project is designed to mitigate the effects of this increased train and vehicle traffic throughout the San Gabriel Valley. Malcolm Drilling Company (Malcolm) was selected by Walsh to perform the specialty foundation and ground improvement work for the San Gabriel Trench.This project is part of ACE’s program to create 22 grade separations and safety improvements at 39 grade crossings throughout the San Gabriel Valley. In addition to safety improvements that will eliminate crossing collisions and delays to emergency responders, the project will reduce vehicle congestion and emissions from passenger cars and trucks having to wait for passing trains, and the project will also reduce locomotive horn and crossing bell noise to local residents.Construction of this portion of the project began in late 2012, and it is scheduled to be completed by the end of 2017, having created approximately 9,000 jobs during this period. The project is being funded from Proposition 1B transportation bonds approved by California in 2006, the Metropolitan Transportation Authority (MTA) Measure “R,” and other local and federal funds. The overall project cost is estimated to be $313 million."

Jan 1, 2017

By Mikael Calando, Thomas Joussellin

"San Francisco's rapid growth has caused the city to plan for the Transbay Transit Center Project, a visionary transportation and housing project, that will transform downtown San Francisco and the San Francisco Bay Area’s regional transportation system by creating a “Grand Central Station of the West” in the heart of a new transit-friendly neighborhood that will be home to more than 20 new towers rising a high a 1,070 ft. This paper describes the specificities of using advanced diaphragm wall technology, tooling, equipment and installation practices for deep foundation and permanent underground structures. In particular, this paper will emphasize on the urban constraints, geotechnical conditions, and the novel approaches adopted for the construction challenges of the Transbay Transit Center’s Load Bearing Elements, or Barrette PilesPaperThe Transbay Transit Center Project consists of the construction of a new multimodal, five-story Transit Center located in the South of Market neighborhood near the Financial District in San Francisco. The future Transit Center will incorporate nearly 83,000 square feet of retail, a 5.4-acre rooftop park, an extensive public arts program and bus ramps that will connect the Transit Center to a new off-site bus storage facility and the San Francisco–Oakland Bay Bridge. The new facility will accommodate more than 100,000 passengers each weekday and up to 45 million per year. Additionally, the new Transbay Transit Center will replace the since-demolished San Francisco Transbay Terminal, and nearly 20 towers, such as Salesforce Tower, will take advantage of the height increases allowed through the Transit Center District Plan.The approximately $4.5 billion project features a new five-story structure (including two underground stories) and new bus ramps which include a cable-stay bridge. The deep foundations for the pylon of the bridge (Pylon 9) consist of two each 21 ft x 5 ft barrettes (also called Load Bearing Elements in the US) extending more than 180 feet below grade and 10 feet into the bedrock. The barrettes were chosen because of the combination of high loads, significant depth and small footprint. The barrettes are installed using the Diaphragm Wall technology. Nicholson Construction was contracted by Shimmick Construction to install the cable-stay bridge’s foundation elements."

Jan 1, 2016

By Tomio Tsuchiya

A construction method of bored steel H piles enclosed in soil-cement columns was developed by modifying steel H piles from the driven pile method and soil-cement walls from the earth retaining wall method, the latter of which produces cut-off walls and reduces noise and vibration during construction. In this method, as shown in Figure 1, rich mix cement paste is injected into the bottom of a borehole which is pre-excavated by a casing auger, then a steel H beam is inserted before it hardens. Since the high vertical resistance of piles created with this method has already been confirmed by loading tests, we have been investigating the applicability of this method for piles used to temporarily support building loads for top-down construction on raft foundations until the raft foundation is completed. However, in the loading tests, the bearing capacity at the lower end of the pile was measured by loading from ground surface on test piles which had friction cut to eliminate the shaft friction resistance. In other words, the loading tests neglected the effect of overburden pressure of soil above the lower end of the pile. To investigate the effect of the overburden pressure on the bearing capacity at the lower end of the pile, loading tests were carried out on a bored steel H pile of lm diameter (test pile) bored in a compacted sandy soil layer with N-value of 100 to 250 at each stage of a three-step excavation. The results show no significant change in the bearing capacity at the lower end of the pile when the depth ratio of the pile is in the range of 5.7 to 22.7.

Jan 1, 1996

By Chaz Weaver, James Sheahan, Michael Mo

"The Virginia Department of Transportation (VDOT) undertook a program to replace four bridges along approximately 4 mi (6.4 km) of US 340 in Northwest Virginia. Two of these bridges, which span Compton Creek and the Norfolk Southern Railroad respectively, are the subject of this article. HDR provided roadway and structural design as well as geotechnical engineering services for the Norfolk Southern Railroad Bridge while their subconsultant, Saeed Associates, provided structural engineering services in support of the HDR roadway and geotechnical team for the Compton Creek Bridge.The project is located in the Valley and Ridge Geologic Province of Virginia, on an alignment that is adjacent to the Shenandoah River. The project lies within the Beekmantown Group consisting of limestone and dolostone that are prevalent and prone to karstic activity in a band that passes through the project area and north into Central and Eastern Pennsylvania. This area has been impacted by karst limestone conditions where caves and sinkhole activity is common. Caves at Luray and Front Royal, located to the south and north of the project, respectively, are popular public attractions.Since the potential for variability of subsurface conditions can be, and often is, greater in karst terrain, the need to develop a design that provides as much flexibility as possible during construction, and then to be prepared to efficiently review and respond to construction questions is heightened. Coordination and communication among the design staff, VDOT’s design and construction staff, and the contractor was a key factor in completion of this project.Compton Creek BridgeThe alignment for the new Compton Creek Bridge is located about 125 ft (38 m) west of the existing bridge, placing it between that bridge and the existing Norfolk Southern Railroad Bridge. No information about the foundations was available for the existing bridges. Borings in the Compton Creek valley encountered extensive voids (some clay filled and some open) with numerous boulders, rock ledges and pinnacles, particularly on the north side of the creek. Geophysical and geotechnical investigations indicated that below a poor and variable upper zone of rock was a layer of more competent and consistent limestone, which appeared to contain little or no voids."

Jan 1, 2017

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

By Joel L. Volterra

Since 1910, Mueser Rutledge Consulting Engineers (MRCE) has regularly provided professional engineering services including inspection of pile load tests. Historically, such services included on-site inspection of the driving of test piles and subsequent static load tests by qualified Geotechnical Engineers. Load testing procedures are specified by local or State Building Codes, locally the 1968 Building Code of the City of New York (1968 BCCNY). Between 1968 and 2008, the 1968 BCCNY required a minimum 48-hour hold period for standard loads per pile type, an extended 96-hour hold period for higher capacity piles, and a settlement criterion that the pile maintain a test load equal to two times the design load with less than 0.012 inches of settlement over the last 48 hours of the hold period. Effective July 2008, the new 2008 BCCNY shortened the hold period and relaxed the settlement criteria to that which is more similar to other governing codes and standards such as the International Building Code (IBC 2006) and the American Society for Testing and Materials (ASTM). MRCE implemented an automated load test monitoring system to reduce costs and to alleviate or minimize overnight and off-hour staffing for load test readings. Initially, a series of linear variable differential transformers (LVDTs) and data loggers were included in the Contractor?s load test setup to electronically record pile head settlement and where applicable, settlement of telltales installed to varying depths in the pile. A pressure gage was subsequently added in the hydraulic line, then a load cell, strain gages, and remote access using modems. The ease of the setup and modular adaptive nature of this system have proven it to be a useful tool and improved our ability to better serve our clients and manage our pile load testing services.

Jan 1, 2008

By Paolo Cavalcoli, Federico Pagliacci

"As opposed to the static functional recovery of existing structures, the construction of infrastructures in an urban environment, when combined with complex geological situations, often involves building foundation structures, whether circular or rectangular in section, through rock formations or chaotic strata (sand and gravel with cobbles). Until a few years ago, these formations or strata were sometimes an insurmountable constraint on traditional foundation installation techniques. The difficulty in overcoming these geological situations is sometimes added to the increasingly frequent need to reach depths that were unimaginable just a decade ago. These are real challenges for those carrying out these works and for those manufacturing the necessary equipment. There are two main methodological approaches to these problems, that can be summed up in the rhetorical figure of ""David and Goliath"": cunning versus force. In reference to the case studies in this article: the permanent retaining walls for the Copenhagen Metro, and the structural repairs to the Arapuni Dam in New Zealand and the Wolf Creek Dam in the U.S., we will describe the foundations constructed in presence of rock using combined small-diameter direction drilling solutions, associated with their enlargement up to the project’s size, at depths exceeding 300 feet. Finally, a case study will be presented on the implementation of a large cross-section of an excavation in the rock, at depths greater than 800 feet.IntroductionAs opposed to the functional recovery of existing structures, the construction of infrastructures in an urban environment, when combined with complex geological situations, often involves building foundation structures, whether circular or rectangular in section, through rock formations or chaotic strata (sand and gravel with cobbles).Until a few years ago, these formations or strata were sometimes an insurmountable constraint on traditional foundation installation techniques. The difficulty in overcoming these geological situations is sometimes added to the increasingly frequent need to reach depths that were unimaginable just a decade ago.These are real challenges for those building these works and for those manufacturing the necessary equipment. There are two main methodological approaches to these problems, that can be summed up in the biblical figures of ""David and Goliath"": cunning versus force. In the engineering field, the force is summarized in the use of ever-larger drilling equipment in terms of installed power, weight in working conditions, winch and rotary capacity."

Jan 1, 2015

By Tracy Brettmann, Melis Sutman, C. Guney Olgen

"The use of energy piles for geothermal heat exchange has been steadily increasing during the last decade, yet there are still pending questions on their behavior during temperature changes. This paper focuses on the thermo-mechanical response of three full-scale energy piles installed in Richmond, TX. The behavior of test piles subjected to thermo-mechanical loadings was studied in situ with the aim of quantifying the thermal influence on the performance and capacity of energy piles. An extensive field test program, including conventional pile loading tests and application of heating-cooling cycles was conducted on the test piles during a period of six weeks. For thermal load applications, the heat exchanger fluid with maximum temperature of 113°F (45°C) and minimum of 47°F (8°C) was circulated in the geothermal loops placed at the center of the test piles. Optical fiber sensors, vibrating wire strain gages, thermistors and thermal integrity profile wires were installed to monitor the strain and temperature variations along the energy piles throughout the field tests. The strain and temperature profiles during heating-cooling cycles on the test piles under static loads and without a maintained load were monitored to investigate the effect of thermo-mechanical and pure thermal loads on the energy piles, respectively. Conventional pile load tests were applied before and after the application of thermal cycles. The results of the pile load tests are compared to evaluate the effect of temperature cycles on pile capacity.IntroductionEnergy piles are deep foundation elements designed to access and exploit the relatively constant temperature of the ground and its heat storage capacity for efficient heating and cooling of buildings. The deep foundation elements that are already in place for structural support are integrated with adsorber pipes to perform as heat exchangers connected to ground source heat pump (GSHP) systems. With the use of energy piles, the heat energy is fed into and withdrawn from the ground for cooling in the summer and heating in the winter, respectively.Energy piles present an innovative way to harvest near-surface geothermal energy and to provide lower carbon emissions, however, there are still pending question on their performance. During heating-cooling cycles, energy piles experience temperature changes, which result in expansion or contraction of the piles."

Jan 1, 2017

By Gary T. Brill

In the presentation, the development and new applications of the jet grouting technique in the North America are briefly introduced at first and followed by the outline and advantages of Jet Grouting. Several recent projects for jet grouting are presented in which the applications to underpinning and excavation support, foundation, groundwater barrier and seismic stabilization are briefly discussed.

Feb 10, 2003

By Andrew Baxter

The Crystal Bridges Museum of American Art in Bentonville, Arkansas is a beautiful glass and concrete structure cut into a valley that mingles with water ponds spanned by multiple bridges with suspended roofs. Or, at least it will be when completed in 2009. At Crystal Bridges, most of the proposed buildings involve cuts up to 50 ft high to be retained by the building structures. This requires the construction of retaining walls adequately founded to support lateral loads of up to 70 kip/ft. To add to this difficulty, the site is within a karst region with all the variability and irregularities associated with solutioning and erosion of the parent rock in this environment. The irregular rock profile made it virtually impossible to conceive a predictable arrangement of shallow footings and shear keys for the retaining walls. The existence of layers of soft soils within a hard rock formation made a caisson foundation impractical. The authors developed an innovative solution based on micropiles, which proved to be invaluable from a cost and schedule point of view. In areas where rock was shallow, micropiles were used as ?shear pins? to transfer the horizontal loads to the rock. In areas with significant overburden, a system of vertical and battered micropiles was devised to carry vertical and horizontal loads from the retaining walls. This paper presents a detailed description of the design and installation of the micropiles used as shear pins, and includes the results of lateral load tests performed on full-scale models of the grade beams on shear pins. The work performed shows that micropiles in rock can be effectively utilized for support of significant lateral loads provided that an adequate arrangement of suitably sized micropiles is provided, and that micropiles used as shear pins may develop significant tensile stresses when loaded laterally.

Jan 1, 2008

By Kiyotaka Ohno, Nobushige Yasuoka, Yosuke Hioki

"The diameter of improved columns adopted by the original DJM Method had been 1000 mm, however, in order to comply with the social need for construction cost reduction, the Expanded Dry Jet Mixing (EX-DJM) Method with maximum column diameter expanded to 1300 mm was developed between 1998 and 2001 and has been widely applied since then. From the first application of EX-DJM in January 2002 for a first construction project, the total volume of improved soil has reached 325,000 m3 in 17 projects up to September 2014. Because of the advantages of the EX-DJM such as reduction of construction costs and periods leading to reduction in the number of improved columns, adoption of this method is expected to increase in the future. This paper describes the advantages of the EX-DJM, its construction results and case examples including those applied to restoration projects after the Great East Japan Earthquake, 2011.1. BACKGROUND OF DEVELOPMENTThe Dry Jet Mixing (DJM) Method is a soil stabilization method in which a powdery or granular binder is pneumatically fed into and mixed with soft soil to induce chemical reactions that stabilize and strengthen the soil. It was developed by government - private collaboration in Japan between 1977 and 1979. Up to March 2014, the total volume of soil improved by DJM method reached 33,500,000 m3. The initial diameter of improved columns of the original DJM Method was 1000 mm. In order to comply with the social need for construction cost reduction, the Expanded Dry Jet Mixing (EX-DJM) Method with maximum column diameter 1300 mm was developed between 1998 and 2001.2. ADVANTAGES OF EX-DJMThe construction equipment for the EX-DJM consists of two major parts, which are DJM machine and binder plant are shown in Fig. 1.The construction machine is of double mixing-shaft type with its column diameter expanded to 1200mm or 1300mm. In association with the increase in the column diameter, the binder feeder has also increased its discharge rate by approximately 1.69 times. Same as the increase rate of the area of original diameter 1000mm to diameter 1300mm are shown in Fig. 4."

Jan 1, 2015

By Gilbert R. Tallard

"Pouring deep foundations by the tremie pipe method is nowadays such a common process that it has becomes an unspecified practice. Means and methods are almost entirely at the contactor’s discretion. A variety of practices are permitted and seldom associated with the discovery of abnormalities and areas of random defects in concrete. This writer wishes to call the attention of stakeholders to the initiation details of the tremie pour operation.KEYWORDSINTRODUCTIONThe advent of slurry as a means of shoring an excavation of relatively small cross section but of possibly great depth has become part of state of the art in foundations construction, with the substitution of said slurry by concrete to provide the structural end product element through the use of tremie pipes. In appearance, there is nothing more simple than pouring concrete into a tremie pipe through a hopper after the basic work has been done i.e. the excavation or drilling, the cleaning of the slurry, the placement of the reinforcing cage, then the tremie concrete pour is almost a reward for a successful achievement. Force of habit has removed the awareness on the process fundamentals for initiating the pour; a variety of practices used call for a review and a reassessment as a means of reducing construction defects that may result from flawed practices, and and especially we are pouring deeper holes. This writer intends to address this issue focusing both on the drilled shaft and the diaphragm wall industries.TREMIE PIPES AND HOPPERSA tremie pipe diameter needs to be sufficiently large to allow the rapid descent of concrete with a minimum of friction loss and avoiding possible bridging in relation to aggregate size. Impervious joints between pipe sections are essential to prevent slurry “raining” over the concrete which can cause concrete segregation pockets and possibly plug the pipe with damaging consequences. That tremie pipes be long enough to reach the bottom may be self-evident but poorly written specifications can be erratic on that subject and seldom specific in terms of inches. A standard pipe of 10 inches is well accepted throughout the foundations industry; double O rings and spline joints are common and function well if properly maintained. However the practice to cover the joint with the ineffable duct tape indicates that all is not always well with this detail. Also, spline cables may shear in case of very long tremie pipes causing the separation of the tremie pipe requiring a restart in midstream with another probable source of inter mixing of concrete and slurry with subsequent defects."

Jan 1, 2017