Search Documents

By Alexander Blatt, Franz-Werner Gerressen

Diaphragm walls are known as underground structural elements commonly used as retention systems for excavation pits and shafts and permanent foundation walls or elements. One can anticipate that global urbanization and increasing demands on environmental considerations will need to be accommodated in underground space in the future. These trends show an increasing requirement for diaphragm walling in even more complex conditions, especially in inner-city applications with limited space. 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 logistics 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. Therefore, the paper will describe the construction method and the sequence of activities required for the construction of diaphragm wall systems. It will describe also the main equipment that will be needed to execute these works under various conditions. In addition to the general description of the system and the required equipment, the paper will show some site examples for infrastructure projects with their specific solutions when working under space restrictions.

Nov 1, 2022

By Antti J. Perala, Teemu J. Yli-Kovero

"Efficient use of land is constantly requiring more underground construction. Minimized execution time and disturbance to surroundings and nearby structures are essential benefits for all construction techniques. To meet the demands of a modern construction project, suppliers have to be able to provide high-quality and tailor-made products just on time. RD pile wall is a retaining wall based on drilled steel pipe piles which are connected to each other with special interlocking profiles. RD pile wall is a solution which enables penetration of overburden soil, dense fill layers including stones and boulders, and embedding into the bedrock in one single operation. Several test installations and laboratory tests have been made to develop the system and to test and improve the water tightness of the wall. Beside these tests, RD pile wall has also proven its reliability in almost 70 projects. Largest project so far has been Pasila Tripla project in Helsinki, Finland. A permanent retaining wall with surface area of 18,000 m2 (193,750 ft2), excavation depth of 21 m (68 ft) and over 17 m (56 ft) of water pressure was made with 711 mm (28”) and 406.4 mm (16”) pile sizes. Piles were delivered to site in one piece with lengths up to 33.5 m (110 ft).INTRODUCTIONExcavations in cramped city centers and in between of existing buildings and other structures are facing more and more challenges. Installation of sheet pile walls is often problematic or even impossible due to obstacles in ground from old structures and due to demand to extend the excavations to even deeper and harder soil layers. Also installations of secant pile walls are facing difficulties due to cramped construction sites and constantly tightening execution times.On the other hand, an efficient and reliable piling technique suitable for the demanding soil conditions described above, percussion drilling, has been developed since the 1960’s, and especially from the mid- 1990’s, when the concentric drilling method with the ring bit and pilot was introduced. A new retaining wall application, the RD pile wall, was developed by combining that drilling method with the widely used retaining wall solution based on steel pipe piles and welded interlocks (a pipe pile wall normally installed with vibratory or impact hammers).PRINCIPLE AND MAIN BENEFITS OF THE METHODRD pile walls can be used in all soil conditions. Most beneficial the system is in extremely demanding soil conditions where the installation of traditional retaining walls is challenging or even impossible. The RD pile wall is a combination of drilled steel pipe piles and interlocking sections as shown in Fig. 1.Individual RD piles are connected to each other with interlocks welded to the piles on the automated welding line at the workshop. The matching dimensions of the drilling system and interlocking sections allow the installation of RD piles through stones and boulders and even into the bedrock, if necessary, in a single operation. Installation is done by a down-the-hole (DTH) hammer using the centric drilling system and oversized ring bits or a drilling system consisting of a pilot bit and reamer wings shown in Fig. 2."

Jan 1, 2017

By Bryan Bet

Retaining wall systems of soldier pile ground anchors (SPGAs) have been used for many decades to stabilize landslide activity. Due to successful use of these walls to address slope instability on the California state highway system, their use has expanded to include larger, more complex landslide mitigations. The increase in size and scope of SPGA wall applications, combined with more stringent seismic design standards, have created new and unique challenges for design and construction. Constructability issues are revealing themselves in real time in Northern California, where the California Department of Transportation (Caltrans) recently completed two large SPGA wall projects on state highways: the Peregrine Slide Project in inland Mendocino County, and the Westport Slide Complex located along coastal Highway 1. Each presented unique construction challenges that needed to be overcome quickly to make the projects successful. This article highlights some construction difficulties encountered on these projects, in greater depth, than what I covered last summer at DFI's S3: Slopes, Slides and Stabiliza- tion conference in San Francisco. Also covered are what steps were taken to overcome these difficulties, and mitigation advice for future wall designs. Specifically, ground anchor installation interference, ground anchor elongation variance, and difficulties with large diameter ground anchor drilled holes will be discussed.

Jul 1, 2022

By Ian Vaz, Takefumi Takuma

"The New Orleans area has been repeatedly flooded by major storms and hurricanes since its French colonial era. After severe flooding in May 1995, the U.S. Congress authorized a massive flood protection project called the Southeast Louisiana Urban Flood Control Program (SELA) in 1996 to improve interior drainage in Orleans, Jefferson, and St. Tammany parishes. However, the project was not fully funded before the landing of Hurricane Katrina in 2005 and Hurricane Rita, which breached many of the area’s levees and flooded 80 percent of the city. Finally, the project was fully funded in 2008 and has been worked on towards its 2017 completion. Another large project simultaneously worked on in the area is the Hurricane and Storm Damage Risk Reduction System (HSDRRS). This system was designed for a 100-year level of flood risk reduction. One particular project within the HSDRRS rendered successful due to an unconventional method of pile driving that was utilized to install sheet piles to reinforce an existing concrete I-wall. This paper will discuss how and why this non-vibratory method of sheet pile installation allowed the project to be successfully completed ahead of schedule.INTRODUCTIONSteel sheet piles were utilized on many of the SELA and HSDRRS projects for permanent cutoff walls under concrete I-walls or T-walls or for temporary earth retaining walls of drainage structures. Although the SELA Project was established in 1996 after severe flooding the year before, hardly any work was done on it until the two catastrophic storms Hurricanes known as Katrina and Rita triggered its revival. These two hurricanes also triggered the HSDRRS soon after the storms’ devastation. The SELA project authorized to improve interior drainage systems while the HSDRRS project was authorized to raise or restore levees and floodwalls mainly along Lake Pontchartrain, the Mississippi River, and Lake Borgne in addition to other areas. Figure 1 shows the SELA Projects that have been completed, are still under construction, or approved for construction. The projects fully highlighted in yellow within the map specified the press-in piling method. These improvements included drainage systems, pump stations, surge walls, and outfall canals as enhanced protection for future storms similar to Hurricane Katrina that caused so much damage by inundating the New Orleans area in August and September 2005 respectively (Facts and Figures, 2012). The completion of these projects were the responsibility of the U.S. Army Corps of Engineers, New Orleans District.Due to the fact that many of the projects were in densely populated areas, the Army Corps of Engineers specified a non-impact, non-vibratory press-in piling method for driving and extracting sheet piles for many of the projects to mitigate noise and vibration impacts. The soft soil conditions in the New Orleans area was also a contributing factor in the Army Corps of Engineers’ decision to specify this piling method due to the risk of settlement for existing historical as well as modern structures. In addition, there were other projects that elected to use the press-in method without any contractual requirements. One of these projects was the Inner Harbor Navigational Canal Reach II Emergency Interim Repair which was part of the HSDRRS project that has been under construction since its authorization in 2005 (Facts and Figures, 2012)."

Jan 1, 2017

By Ke Yang

Drilled shafts are widely adopted as the foundation for sound walls. However, there has been a lack of uniformity in design and analysis methods and design criteria, in terms of factor of safety against ultimate capacity failure as well as the allowable deflection. In order to establish a uniform design methodology for the drilled shafts supporting sound walls in cohesive and cohesionless soils, respectively, a database of full-scale lateral load tests on fully instrumented drilled shafts was collected. Based on the compiled database, existing design methods and design criteria of laterally loaded drilled shafts were evaluated. Broms method and COM624P (or LPILE) are suggested as the design methods for drilled shafts supporting sound walls in both cohesive and cohesionless soils. Additionally, the corresponding design criteria, including factor of safety and permissible deflection, for both design methods are recommended. Two full-scale lateral load tests on fully instrumented drilled shafts were subsequently conducted in Colorado to further verify the design recommendation. A comprehensive geotechnical investigation program was also carried out at the two new lateral load test sites that included pressuremeter test, SPT, as well as laboratory triaxial consolidated undrained tests and direct shear tests on the soil samples taken from the lateral load test sites. The test results obtained at these two load test sites were employed to validate the recommended geotechnical design and geotechnical testing methods for the drilled shafts supporting sound walls.

Jan 1, 2007

By Karsten Beckhaus

"Abstract Tremie concrete for special geotechnical works needs special properties, especially during the casting process. Today’s execution standards for bored piles and diaphragm walls, EN 1536 and EN 1538, as well as the draft version of concrete standard EN 206, all comprise regulations for deep foundation concrete which have not been changed for decades. Considering the recent development in concrete technology at the same time and its actual state-of-the-art, it is essential to develop new normative specifications and specification requirements.GeneralTo allow the required integrity and quality after placing and hardening, concrete for structural elements like bored piles or diaphragm walls, used as foundations of high-rise buildings or as retaining structures for large and deep building pits, must have adequate workability and stability.In addition to requirements on mechanical properties and on durability, both of which have increased within the last decades, concrete must be suitable for being cast in deep or extremely deep excavations, see figure 1. Today’s specialist foundation engineering machinery makes it possible to drill or cut down to in excess of100 m depth. Concrete technology has developed and allows the use of high performance concrete for deep foundations. But is this capability represented by actual regulations?It has become very common for the industry to supply or use concrete with low water cement ratios, nevertheless highly flowable and set-retarded for several hours if needed. Very low water cement ratios allow design strength of 60 MPa or higher (Larisch, 2011), and a very low porosity which is required for a long service life in aggressive conditions, e.g. by chlorides.To achieve best performance, it is obvious that the concrete must completely fill the excavation and fully embed the reinforcement. As vibration of deep foundation concrete is (usually) not allowed and was anyway inefficient, deep foundation concrete must be designed to self-compact under hydrostatic pressure. Generally, it must be considered that after placement the concrete’s quality cannot be influenced anymore. Therefore, both the pouring procedure and the concrete quality must be adequate."

Jan 1, 2014

By Stephan A. Jefferis, Adrian H. Bath

"This paper draws together some themes on the durability of barrier systems, and particularly cementitious systems. For contaminated land and water retaining structures, durability can be poorly addressed at all stages of a project, from specification, to barrier material selection, barrier design including toe-in and through to performance assessment in operation. Permeability (hydraulic conductivity) is a dynamic property which will vary over time as reaction processes propagate through a barrier. However, laboratory testing, when undertaken, tends to be focused on short term tests with aggressive chemicals so that the effects of longer-term processes such as carbonation and leaching by permeating water are missed. For water retaining structures, carbonation and leaching actually may be the most significant processes affecting barrier performance as the groundwater adjacent to many water bodies can be otherwise rather benign (as regards bentonite and cementitious systems). These and other reaction processes have been modelled in the arena of nuclear waste repositories and procedures are well recognised. However, such procedures have yet to be widely adopted for the assessment of other barrier systems.INTRODUCTIONOver the last few decades there has been an enormous amount of laboratory research on the durability of barrier materials or more specifically papers reporting the results of permeability tests. Unfortunately there is a much smaller literature on scaling test results to barrier dimensions in the field or to required design lives. Although in the geotechnical industry durability research has been largely laboratory based, in the nuclear industry where relevant timescales are multi-millennia rather than decades, research has been heavily underpinned by geochemical modelling. A significant purpose of this paper is to examine the tools that may be used to analyse the results of tests on barrier materials used in geotechnical engineering, for example, for water retaining structures and contaminated land and draw the attention of the construction industry to the potential of the modelling procedures developed for nuclear repository assessments. Modelling can help to identify underlying processes and so augment information from laboratory testing focused on changes of physical properties such as permeability and strength."

Jan 1, 2016

By Ganesh Deepak K., Anjana R. K., Dr. Kumar Pitchumani N., Rajasekharam R. M. V. M. S. S.

The Phase 2 of Chennai Metro is being introduced in the city to ease the dependence on the existing transportation systems. Phase 2 is a combination of underground and elevated metro stretches comprising of three corridors. The current study focusses on the underground stretch of Corridor 3 which has a total of 29 underground stations. Construction of the underground cut and cover stations results in ground movements, which in turn impact the structures adjacent to the excavations. The greenfield ground settlement can be evaluated with the help of empirical approach or an approach requiring finite element modelling (FEM). The paper compares empirical and FEM approaches with regards to ground conditions in Chennai. Further, with the predicted ground settlements, building damage assessment is performed. The damage category of a building is defined based on the estimated tensile strains. This paper also compares the building damage assessment with empirical method and finite element modelling.

Nov 1, 2022

By Michael J. Garlich

Steel sheet piling has a long history of use in a variety of permanent and temporary structures. Current engineering practice uses numerous publications and standards for design guidance. U.S. design guidance is fragmented, with numerous inconsistencies between design guides. To improve current U.S. design practice, the North American Steel Sheet Piling Association has initiated a project to produce a design standard that will unify design procedures and provide specification guidance for engineers and users of steel sheet piling. The wide range of uses for sheet pile structures presents a challenge in developing such a standard. Load factors or allowable stresses acceptable for a temporary retaining wall in soil may reasonably vary from those for a river cofferdam or a dockwall located in sea water. However, it is still possible to provide consistent and rational guidance for such varying uses. The standard also can address sheet pile design aspects often neglected in U.S. publications, such as vertical load capacity and resistance to loads applied parallel to the sheeting.

Jan 1, 2008

By George Aristorenas, Carlos Englert, Jesús Gómez

"Laboratory test data of strain softening soils exhibit the development of a maximum (peak) shear strength followed by a decrease in the strength with continued straining. The rate of strength loss decreases such that an asymptotic minimum value, known as the residual strength, is approached. This paper presents an investigation of the evolution of strength degradation in excavation supported soils that exhibit strain softening behavior. The paper presents a numerical investigation of excavation support of slicken-sided clay, and results of shear testing on materials with similar strain softening behavior. A strain softening constitutive law is presented that can be used with the finite element computer software Plaxis for analysis of excavation support. A typical design section of a deep excavation support in stiff, fissured clay is presented that illustrates the limitations and conservatism of the residual strength approach for excavation support design. Finally, a discussion is presented on the impact of stiffer walls such as diaphragm walls, compared to less stiff systems such as sheet piles, on the design parameters.INTRODUCTIONIn the Washington, D.C. metropolitan area, the Potomac Formation is generally composed of stiff, fissured clays. Geotechnical engineers often associate the presence of slicken-sided planes within the formation as evidence that the soil cannot develop its peak strength. Although it is unclear how old and continuous these slicken-sided planes are, their occurrence, persistence and orientation appear to be somewhat random. Due to this uncertainty, the design of open cut slopes in these materials is often conservatively performed assuming residual shear strength values. This design approach may be justified for long-term open cuts when there is limited amount of geotechnical information and in view of back stability analyses of past slope failures. Furthermore, the lack of confinement in open cuts allows relatively high shear strains near the surface and toe throughout their existence, which promote mobilization of post-peak strength values and the ensuing progressive failure. Indeed, such behavior has been discussed in the past (Skempton, 1970; Schnabel et. al., 1982; Derrenbacher, 1998). A thorough study by Mesri et. al. (2003) of numerous slope failures concludes that the lower bound strength for stability analysis of non-failed slopes is the fully softened strength, which is intermediate between the peak and residual strengths, but that part of the slip surface may be in a residual condition prior to failure."

Jan 1, 2015

By J. A. Yeats

This paper describes the loading to 25MN of a 1.2m diameter bored cast-in-situ test pile founded in the Thanet Sand which was base grouted. The pile was sleeved over the major portion of its length to test primarily the base response of the pile. The results are presented and compared with similar pile load tests in Thanet Sand.

Jan 1, 1989

By Louay Owaidat, Daniel Jabbour, Allan Frappier, Jose Gomez, Mark Stanley, Tino Maestas

The U.S. Army Corps of Engineers (USACE) is implementing a levee strengthening program along the Sacramento River East Levee (SREL) designed to correct 11 miles of deficient levees as identified by recent hydraulic and geotechnical investigations. The first project, the subject of this paper, completed in 2020 resulted in approximately 3.0 miles of improvements to the California Central Valley Flood Protection system. The project area lies along the east bank of the Sacramento River in Sacramento. The program consists of constructing cutoff walls through existing levee embankments to remediate levee through seepage and under-seepage. Key challenges included designing and constructing measures to remediate a 100-year-old legacy levee system, the presence of both industrial and residential properties immediately adjacent to the landside of the levee creating severe space and access limitations, and performing this work during the 2020 statewide mandate to shelter-in-place due to the COVID-19 pandemic. The project team of contractors, USACE, state and local agencies, and engineering firms partnered to bring this project to successful completion within budget and on schedule expending more than 60,000 man-hours with no lost time accidents. With the issuance of future planned contracts, the program will significantly reduce flood risk to the City of Sacramento.

Sep 8, 2021

By Andrew R. Klaetsch, Peter W. Deming

"The Washington Avenue tunnel in Kingston, NY was completed in 1912 to convey combined storm water and sanitary sewage. Over a mile in length, the tunnel was driven almost entirely in bedrock, with the exception of an approximately 170 foot long brick arch segment constructed in soil. About 90 years after the tunnel was put into service, persistent subsidence problems and sinkholes were observed in Washington Avenue above the shield-driven soil tunnel segment, eventually causing the important traffic thoroughfare to be closed. Subsequent tunnel inspections revealed a breach in the brick arch and a significant volume of fine soil within the tunnel. A two-phase remediation program was implemented to control seepage, reduce soil migration, and remedy sinkhole problems. The first phase included in-situ soil densification by vibratory pile probe driving to improve density in shallow sandy soil loosened by ground loss. The second phase included installation of a continuous soilcrete arch structure over and alongside the tunnel, extending to rock or compact glacial till and spanning the length of the soil tunnel segment. Overlapping vertical soilcrete columns were installed through interlayered sandy and clayey silt by jet grouting to form a continuous arch structure, using grout parameters verified by full scale field testing.PROJECT BACKGROUNDThe Washington Avenue tunnel in Kingston, NY (Figure 1) was completed in 1912 to convey combined storm water and sanitary sewage to Rondout Creek by the Board of Water Supply of the City of New York. The tunnel is over a mile in length and constructed primarily in rock. Contract documents indicate the tunnel was designed with a horseshoe shape at least 3 ft wide and 5.5 ft high."

Jan 1, 2016

By A. F. van Weele

In general cast-in place piles will have an irregular pile shape. However, it is possible that these irregularities are so large that they may lead to pile deficiencies. It is very rarely possible to examine the pile foundations visually. Also the performance of a static or dynamic load test on each individual pile is not practical and much too expensive. This is the reason why pile integrity tests have been developed: to reduce the risk of inadequate pile foundations by performing a simple test. Pile integrity tests are non destructive tests which are carried out after a pile has been installed. Over the years a number of techniques have been developed of which the most important techniques are briefly described in this paper. Of all pile integrity testing methods, Sonic Integrity Testing is the most widely used method in western Europe. This method has been developed by TNO some 15 years ago. Since then the method has been improved, largely due to advances in micro-processing. A major improvement was made by the introduction of digital signal processing techniques. This made the Sonic Integrity Testing method more accurate (smaller defects can be detected), faster (more than 200 piles can be tested on a single working-day) and more reliable (the results are easier to interprete). A few cases will be presented which will show the usefulness of the Sonic Integrity Testing method. In one of these cases, a helpful tool for interpretation of the results is explained: the Sonic Integrity Testing Simulation program TNOWAVE. Notwithstanding the fact that Sonic Integrity Testing is a powerful method, it has also some strict limitations. These will be discussed at the end of the paper.

Jan 1, 1987

By Paul J. Axtell

The results of in-situ geophysical cross-hole tests on improved soil by soil mixing (SM) and jet grouting (JG) are described. This testing was conducted on soil improved by SM and JG columns constructed in the downstream free-field of Tuttle Creek Dam near Manhattan, Kansas as part of the seismic retrofit. Results of similar geophysical testing performed on untreated soil in the vicinity of the Downstream Test Program (DTP) area, as well as beneath the embankment at several locations, are also described and used for comparison purposes. In-situ shear moduli are also compared with those determined in laboratory resonant column tests. The increase in stress wave velocities and associated shear moduli by SM and JG treatment are presented for use in liquefaction potential and seismic deformation analyses of SM or JG treated soil. This data is required to determine the decrease in liquefaction potential and earthquake-induced permanent deformations due to SM or JG with respect to that of untreated soil.

Jan 1, 2008

By Ed Kase

Cross-hole sonic logging (CSL) has become the universal standard, nondestructive testing (NDT) method used in evaluating the integrity of foundation structures to maintain quality assurance and quality control (QA/QC) of transportation facilities and infrastructures. Tomography, based on three-dimensional cross-hole sonic logging data processing technology, offers an improvement over the techniques currently used to characterize the interior structure of drilled shafts. The underlying concept for seismic tomography is based on the principle that acoustic waves propagate at different velocities through different types of material or the same material with different physical properties. Three-dimensional velocity tomographic images provide greater detail of the interior structure, making defects easier to classify with respect to size and location within the foundation structure. By accurately classifying these defects, an engineer has the information necessary to accurately assess whether these structures meet the applicable design requirements, allowing them to repair or replace inadequate foundation structures. The end result is that the foundation structures will meet the safety and service life requirements for their project. This paper will present applications of seismic tomography, illustrating how seismic imaging can provide accurate information regarding the integrity of foundation structures.

Jan 1, 2003

By Maurice Bottiau

"Abstract When addressing the performance of deep foundations, many parameters play a role, from adequate soil investigation to performance monitoring and testing. The correct understanding of pile construction, though, remains crucial. After a long period of empirical design and regulations, the last decades have been the ones of theoretical considerations and extensive codes writing. The interaction between technology and design, however, still plays a determinant role. The introduction of hydraulics and the exponential increase in available power on one hand, the miniaturization and the introduction of electronics in control and monitoring systems on the other hand have exerted a major influence on new foundation systems or the evolution and control of existing systems. It appears important to try to take execution related parameters and their control during execution more deeply into account when assessing the final result of the deep foundations and the achieved level of safety and reliability. In this contribution, we will try to analyze how systems, equipment and pile production monitoring and testing can influence the pile performance, and if/how this influence could/should be translated in adapted safety or installation factors. This analysis will run through different categories of piles: driven, augercast and displacement auger piles and bored piles. INTRODUCTIONThe global performance of a deep foundation depends on different aspects (Poulos, 2003):1. Ground investigation2. Design and analysis3. Construction4. Testing5. Performance monitoring6. Remediation and performance enhancementThis paper intends to address the importance of pile construction and the control of it on the final performance of the pile-group of piles. There has been an increasing interest for theoretical analysis over the last 20 years, followed by an increasing impact of regulation and codes. Without denying the importance of the latter, the author wants to point out how installation procedure and project specific parameters can largely influence the reliability of the deep foundation. In this context, detailed and prescriptive standards can miss their objective of intended improvement of accuracy and reliability, but even worse they can adversely impact engineering judgment. In today’s construction world, it is possible to gather installation information which can be of outmost importance for the final deep foundations performance. Therefore, the increase or decrease of installation reliability through adequate pile testing and performance monitoring should be emphasized and should be taken into account in the codes. This is the case already in most advanced codes, but in a limited and insufficiently refined way. After reviewing how codes deal with this issue today, we will show some recent examples of unexpected results due to pile installation. We will try to put these examples into a broader perspective by highlighting some reference and/or recent literature considerations. Finally we will try to summarize how pile testing and installation documentation can increase reliability and attempt to open the debate on how codes could/should allow for more engineering judgment."

Jan 1, 2014

By Bernardo J. Jiménez Vega, Edy L. T. Montalvan PhD

The experience gained during more than 900 Crosshole Sonic Logging (CSL) tests on drilled shafts shows the importance of establishing proper project acceptance and repair protocols. Drilled shaft evaluation is a multidisciplinary task that should not be left solely to the outcome of the CSL test. This test allows to characterize and delimit areas of different qualities of concrete, and it is important that all the interested parties understand the difference between flaws and defects. The information presented here is intended to give a guideline to contractors, inspectors, engineers, owners and clients on how to deal with acceptance and remediation of defective drilled shafts, detected using CSL tests. A database of flaws is presented depending on their location, intensity and remediation method. Procedures that allow the flaws to be analyzed are presented in order to dismiss or classify them as defects. In many cases, the CSL test may indicate an anomaly, but by coring the concrete and analyzing the structural demands and conditions, the flaw can be classified as non-severe. When flaws are classified as defects, their repair will depend on the area where they are located in the drilled shaft pile. In this document two procedures are described for repairing defects depending on their location. For defects in the drilled shaft head area, the procedure takes into account the interaction between the new and old concrete. For repairing the middle zone of the drilled shaft by grouting, the major concerns are the difficulty of accessing through the drilled shaft at deep depths and the communication between boreholes. For defects at the drilled shaft tip, two proposed remediation methods are presented. Finally, tomography tests are presented to compare the effectiveness of remediation by grouting.

Oct 1, 2022

By Nikolaus Schneider

"Abstract: The combination of failure in joints of diaphragm walls and their exposure to water pressure may have far reaching effects ranging from water leakage to the risk of catastrophic loss of stability for the retaining wall and civil structures behind it. Investigations of imperfect joints in diaphragm walls have led to the development and testing of a quality tool to monitor the joint integrity of diaphragm walls during construction. By applying independent mechanical sensors (“joint inspector”) to the steel frame of hydraulic or mechanical grabs, it is now possible to record the surface conditions of exposed primary joints during the construction of secondary panels. This allows for the implementation of corrective action during the construction process should joint quality not indicate a watertight connection to the adjacent panel. The joint inspector, used for different types of stop ends, was tested on a full scale test field at several construction sites. The implementation of this new quality tool drives a new quality standard for deep excavations in inner city areas.General introduction to diaphragm wallsDiaphragm walls are reinforced concrete elements constructed using bentonite slurry to temporarily support an open trench in the ground. They are used in two main fields of application in civil construction, as foundation elements for vertical and horizontal loads (barrettes) and as retaining walls for excavation pits.Particularly for deep excavation pits in inner city areas, diaphragm walls are used as temporary or permanent walls of retaining walls. Alternative retaining wall systems would be secant pile walls, sheet piles or soldier piles, but these have disadvantages in structural strength when compared to diaphragm walls. If the vertical load of existing buildings next to the excavation pit has to be accommodated, the most practical solution can be found using diaphragm walls supported by prestressed anchors, steel struts or slabs."

Jan 1, 2014

By Daryl W. Wurster

The Liberty Bridge in Greenville, South Carolina is a curved, cable-stayed, pedestrian bridge with primary support provided by two towers. The bridge is part of the Falls Park redevelopment. The bridge was originally designed to be supported on drilled piers. Alternately, the bridge was supported on a combination of micropiles and anchor piles because of difficult access and subsurface conditions. The use of micropiles and anchor piles led to improved construction scheduling and reduced costs. Micropiles were used to resist compressive loads. Anchor piles were used to resist tensile forces and to eliminate excessive settlement of pile caps into underlying fill during pre-stressing. This paper describes the site history, bridge construction, site and subsurface conditions encountered, and the decisions that led to support of the bridge using micropiles and anchor piles and foundation construction.

Jan 1, 2006