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By Richard E. Sylwester

Evaluating surface and subsurface conditions for marine foundations (bridges, causeways, terminals, etc.) is often done with a limited amount of data. Subsurface information for these projects is primarily acquired using traditional methods, such as boreholes, test pits or divers, which tend to be expensive and limited in the area of coverage. A number of geophysical methods, including precision bathymetry, sidescan sonar, and seismic reflection or subbottom profiling are extremely cost-effective and obtain significantly more data than can be acquired using traditional intrusive methods. These geophysical methods provide detailed surface images and continuous profiles of the subsurface stratigraphy. This information can be invaluable for selecting the best location for geotechnical boreholes and to map potential geohazards such as submarine slides and filled or open scour holes. Offshore investigations conducted for a proposed highway bridge (Knik Arm Bridge, Cook Inlet, AK), the retrofit of two existing bridge (Antioch and Dumbarton Bridges, CA) and a proposed cruise ship terminal (Ketchikan, AK) used a combination of geophysical methods to map water depth, detect and map debris on the seabed, map the thickness of unconsolidated sediment, determine the depth to bedrock and identify potential geohazards such as scour holes. The results of the geophysical investigations will be used to select locations for obtaining geotechnical borings, to extrapolate geologic information between existing or proposed boreholes, evaluate the potential depth of scour and design a pile support pier. Geotechnical engineers, offshore contractors and bridge designers are realizing the importance of the early use of offshore geophysics for (i) site characterization, (ii) to reduce the uncertainty of geotechnical conditions thus avoiding designs that may be overly conservative and thus more expensive and (iii) to assist in selecting locations for geotechnical borings.

May 11, 2007

By Filippo Leoni, Wesley Schmutzler

"The LPV-111 East Back Levee Improvement Project lies along the Gulf Intracoastal Waterway (GIWW) in Orleans Parish of New Orleans, La., and is an essential component of the New Orleans Hurricane Protection System. The Hurricane Protection Office of the U.S. Army Corps of Engineers (USACE) attributed failure of the New Orleans East levees system to overtopping, erosion and subsequent breaching of LPV-111 along the GIWW, as well as other sections of flood protection during Hurricane Katrina in 2005. The existing levee suffered extensive damages from Hurricane Katrina, such that the USACE elected to provide earth stabilization and to rebuild the levee sections. Due to the adverse geotechnical properties of the foundation soils, the Corps deemed ground improvement necessary to stabilize the new levee and to limit its footprint. Wet Deep Mixing Method (DMM) was selected as the most suitable technology for this task.ChallengesDesign: This reach specifically protects East New Orleans and the Bayou Savage National Wildlife Refuge, the largest urban wildlife refuge in the U.S. and home to several threatened or endangered species of birds as well as many reptiles, amphibians and small mammals. The Corps chose DMM due to the sensitivity of the protected marshlands and because the method limits the footprint of the raised levees. The increase in the load bearing capacity of the treated soil significantly decreases the footprint necessary to attain the required height increase. This limitation required the new levee to have steep slopes, drastically increasing the surcharge on foundation soils characterized by overall poor geotechnical properties (soft clays and peats). The design also considered the increased horizontal stresses on the levees due to the extreme storm surges during a hurricane.The design of the 1.6 m diameter (5.25 ft) DMM elements called for overlapping them to form a double auger element that formed buttresses perpendicular to the levee alignment. The contractor installed the buttresses at a maximum on center spacing of 4.7 m (15.5 ft). One additional double auger DMM element was midway between consecutive buttresses at the centerline of the levee to further help prevent settlement (Figure 1)."

Jan 1, 2013

By Vijaya Bhushan Rao, Jason Redgers

The typical Vibrocompaction projects undertaken in the UAE are on reclaimed Sands. These Sands which are predominantly the crushable, calcareous, carbonate sands found locally as opposed to the more common quartz or silica sands that are featured in most design literature. The famous reclamations such as the iconic Palm Jumeirah in Dubai, often have specification for mitigation of liquefaction induced settlements, bearing capacity increases and total and differential settlement requirements. Often these performance targets are achieved by the means of achieving a particular relative density that are generally measured by a defined Cone Penetration Test, CPT targeting values of cone resistance (Qc), MPa at respective depth zones. In this paper some case studies are presented, where soil suitability for deep compaction by vibratory methods was firstly assessed for suitability using the Massarsch, 1991 compactability chart prior to the application of vibrocompaction and its subsequent evaluation. One such project named the Island Development required 17 to 23m depth of penetration only to treat the lower 5 to 6m of sand above rockhead as eventually the top 15m of sand will be further excavated to allow for the construction of basement. The paper will present pre and post CPT results, the results of initial site calibration trials and evaluation of the completed works.

Oct 1, 2022

By William B. Conway

This paper will describe the large caisson pier foundations for four of the bridges crossing the Mississippi River in the New Orleans area; and will discuss some of the unusual problems encountered during their sinking. Certain settlement phenomena experienced during their service life will also be related: The four bridges in order of their construction: The Huey P. Long Bridge, River Mile 106.1, completed in 1935 The Greater New Orleans Bridge No.1, River Mile 96.0, completed in 1958 The Hale Boggs Bridge, River Mile 121.6, completed in 1983 The Greater New Orleans Bridge No.2, River Mile 96.1, completed in 1988 Each of these bridges employed large open-dredged concrete caissons as foundations for one or more of the river piers, with the smallest being the 65ft by 102ft caissons for Piers I and II of the Huey P. Long Bridge and the largest being the 99ft by 214ft caisson for Pier II of the Greater New Orleans Bridge No.2. The Huey P. Long caissons are founded in a dense fine sand at -170 while all of the other bridge caissons are founded in hard preconsolidated clay at elevations varying from -150 to -185. The Huey P. Long Bridge is currently being widened without increasing the caisson foundations under any of the river piers; and the design reasoning that led to this decision is presented.

May 11, 2007

By Ronnie X. Gu, Xing Zheng, Gem-Yeu Ma

Due to implementation of the rotator construction method from which a smooth shaft was anticipated, a full-scale pile load test (Osterberg Method) was performed at Pier 14 Pile 9 of the main span of the New Benicia-Martinez Bridge to confirm the design parameters of the rock sockets. Two levels of load cells were fabricated in the reinforced cage of the rock socket. Each level consisted of three 670-mm Osterberg load cells with a total testing capacity of more than 50 MN in both directions. In an attempt to separate side friction and end beari ng, a 75 mm thick compressible Styrofoam material was placed at the bottom of the cage. The pile load test was carried out in four stages. The multi-level multi stage pile load test data was interpreted for casing friction, side friction for two rock strata, end bearing, and residual side shear values under repeated loading in opposite directions. The side friction from the casing in soils at Stage 2 is approximately 9 MN. The end bearing at the tip of the rock socket at Stage 3 was calculated to be approximately 17 MN at a displacement of about 75 mm. The residual side shear resistance for the 10 m 50% RQD rock strata was calculated to be 9 MN or approximately 50% of initial values, after being pushed 0.3 mm upward in Stage 1, 71 mm downward in Stage 2, then 55.5 mm upward again in Stage 3, and finally 105.3 mm downward in Stage 4. The test results surprising ly indicate that the side shear resistances from both low RQD intensely weathered rock and higher RQD slightly weathered competent rock are about the same at approximately 19 MN. This pile load test provides very critical information for confirming deep shaft design and analyses.

Jan 1, 2005

By Ke Yang

"Drilled shafts are typically used to support structures subjected to large moments at the shaft head. The large moment can produce push and pull forces on the two sides of a drilled shaft. Consequently, the applied moment is partially resisted by the push-pull moment resistance induced from the vertical side shears. This type of push-pull resistance has not been fully recognized in most design and analysis methods. In this paper, a 30 finite element model for a drilled shaft subjected to lateral load and moment is presented and is validated against two field lateral load tests. Based on the 30 finite element model, a parametric study is carried out. It shows that the push-pull moment can resist 18-35% of the applied moment. The parametric study also shows that the push-pull resistance varies linearly with loading eccentricity when the eccentricity is less than the shaft embedment length. A method to estimate the push-pull resistance is proposed based on the results of the parametric study. Then, a new method for lateral capacity prediction is proposed to account for the push-pull resistance. The base shear resistance is significant for short drilled shafts; therefore it is also included in the proposed method. A case study on four lateral load field tests illustrates that the new method could improve the accuracy of lateral capacity prediction when compared with the traditional Broms method.INTRODUCTIONDrilled shafts are typically used to support a variety of structures subjected to large moments. Sound walls, highway signs, traffic signals, high-rise buildings, electrical transmission towers, and bridge piers are examples of cases where lateral loads with large eccentricity would result in high overturning moments on foundations.Current analysis methods for capacity predictions (Broms, 1964a and 1964b; Brinch Hansen, 1961) or deflection predictions (Reese, et al. 197 4) of laterally loaded drilled shafts are based on the lateral resistance of soils and rocks. However, O'Neill pointed out that moments can be partially resisted through the push-pull resistance provided by the vertical side shears due to the rotation of the pile (Reese, 1997)."

Jan 1, 2005

By Evangelia Ieronymaki

Civil engineering education relies on traditional methods of teaching, comprising mostly of deductive instruction by presenting the theory, followed by applications. This paper presents an alternative way for teaching foundation design to senior students, introducing a more inductive approach. The students are presented with a project/game adapted to a real-world problem at the beginning of the course. They are asked to identify the correct steps and methods throughout the lectures, for reaching an appropriate solution that they document and present at the end of the course. To make the project more enjoyable, the project has the format of a game where the students compete with each other on completing the task faster and more efficiently. The goal of this teaching approach is to enhance the ability of the students for problem solving and the engineering way of thinking, while playing a game. In the end, the students were requested to respond to a survey regarding the efficiency of this project/game on their learning. The results showed that students prefer more inductive methods for a design course, feeling that this project made them think more like engineers, while the ‘game’ twist of it made the whole course more fun. INTRODUCTION Most civil engineering courses are taught in 2019 the same way they used to be taught 40 years ago in the 80s. Classic methods are mostly deductive, where the instructor presents the theory first and then applications of that theory follow. Little or no attention is given initially to why the theory was developed or what are the problems it solves. The applications of the theory, and thus the purpose it serves, come only in the end and after methodologies have been presented, leading the students to show low interest in the material. As Albanese and Mitchell (1993) have reported, people are mostly motivated to learn things when they clearly see the need to know them. This explains the students’ little motivation that, if any, comes mainly from the fact that the material may be useful either in other courses or in their future careers. On the other hand, there are alternative inductive methods of teaching, where the role of the students is more active. A lot of researchers have highlighted the benefits of inductive methods in teaching engineering courses. Based on Prince and Fedler (2006), inductive methods include; a) inquiry-learning, b) discovery learning, c) problem and project-based learning (PBL), d) case-based teaching, and e) just-in-time learning. Inquiry-learning is maybe the most traditional method of inductive teaching/learning methods, where the instructor asks questions or poses problems and the students need to apply the theory they have learnt in order to find the solution (Bateman 1990; Prince 2004; Lee 2012). Similar to inquire-learning is the discovery learning, where students have to find the solution to a problem or answer to a question, while the instructor simply provides feedback to the students without guiding their efforts (Leonard 1988; Westbrook and Rogers 1994).

Jan 1, 2019

By Lois G. Schwarz

I did a project (Sungai Piah) as a consultant to your firm in Malaysia, where we were faced with a similar situation as sketched out in your question. The following is what we did for the grouting of the primary holes, which were both located upstream of the plug as well as downstream: We used a hydrophobic MDI based semi-rigid polyurethane prepolymer in the first phase of the grouting operation when grouting under water flow conditions. Then in the second phase and also for the contact grouting we used a two component water compatible polyurethane elastomer. And then for deeper formation grouting, when all the water flow had been stemmed in the vicinity of the plug, we used a regular (balanced stable) cement based grout. So it may not exactly answer your question, but we first used hydrophobic grout because it is very efficient to grout a formation through which water flows. We didn't stop all the leaks day-lighting downstream of the plug or all water running through the formation near the plug, but the flow of water through the rock formation adjacent to the plug was reduced by 99.9%, after completing the urethane grouting. This facilitated the placement of cement based suspension grouts without wash-out.

Feb 10, 2003

By John P. Turner, Steven S. Dapp, Dan A. Brown

"The Goethals Bridge Replacement (GBR) spanning the Arthur Kill Waterway between Elizabeth, NJ and Staten Island, NY is supported on over 200 drilled shaft foundations ranging in diameter from 4.5 ft to 10 ft and socketed into Passaic Formation siltstone. Four drilled shafts, two on each side of the bridge (NJ and NY), were load tested using the bi-directional axial load method. Axial test results demonstrate that RQD, taken by itself, is not necessarily a reliable indicator of side or base resistance. High recovery with low RQD can be a function of horizontally bedded siltstone and shale where the individual pieces of core do not exceed four inches, but may still provide very high side and base resistance. Axial testing was followed by a lateral rapid-load test (Statnamic) on each of the same four shafts. In addition, one of the shafts was subjected to a static lateral load test to validate the rapid-load method as being representative of static loading conditions. Results of the axial load tests provide the basis of unit side and unit base resistances used in the LRFD design of the rock sockets for axial loading, while results of the static and Statnamic lateral load tests were used to calibrate p-y curve parameters used for design under lateral and moment loading. This paper describes implementation of the load testing program and its role in the design process.INTRODUCTIONDesign of drilled shaft foundations for the Goethals Bridge Replacement (GBR) required load testing in order to validate the parameters used for calculating geotechnical axial and lateral resistances. The bridge, including foundations, was designed in accordance with the AASHTO LRFD design specifications, 6th Edition (2012). The bridge owner is the Port Authority of New York and New Jersey (PANYNJ). One of the PANYNJ project requirements was stated as follows:“Perform a minimum of two (2) separate axial compression load tests (one [1] in New York and one [1] in New Jersey) for each demonstration shaft of different size and construction methodology to verify the design assumptions and construction procedures. At a minimum, one (1) demonstration shaft is required to be representative of production shafts with a diameter within one (1) foot above or below the demonstration shaft diameter.Conduct a minimum of two (2) lateral load tests (one [1] in New York and one [1] in New Jersey) for each demonstration shaft of different size and construction methodology. At a minimum, one (1) demonstration shaft is required to be representative of production shafts with a diameter within one (1) foot above or below the demonstration shaft diameter.”"

Jan 1, 2016

By Federico Pagliacci

"Many existing dams are subject to underwater seepage due to subsoil conditions, like deep alluvial deposits or pervious rocks or karst. Remedial works are necessary in order to install new cut-off walls to stop the water flow. In some cases the cut-off walls have to be executed at depths never reached so far, and difficult to reach with traditional foundation techniques. In many cases the Hydromill technology proved to be the best system to overpass rocky layers and ensure the required verticality. The maximum depth reached by the industry was in the range of 120-150 meters. This article describes the test performed to excavate and cast in place a 3.2x1.5 m panel to a depth of 250 m. The article will also describe the stratigraphy of the site down to 250 meters, as well as the technique adopted to achieve the said depth with deviations from verticality of 30 cm along the longitudinal axis (0.12%) and 20 cm along the transverse axis (0.10%), measured at the bottom of the excavation. The concreting of the panel, for about 1,100 m³, with plastic concrete in the lower portion and conventional concrete in the upper portion will be illustrated. Finally, the tests performed during the excavation and after concrete casting will be also described, with special attention to the continuous directional core drilling that was performed along the whole length of the panel to verify the results of the deviation from verticality, through the onboard instruments, and to control the quality of concrete at a depth never reached before. IntroductionMany existing dams are subject to underwater seepage due to subsoil conditions, like deep alluvial deposits or caves and cavities or acid solutions in the bedrock formations.Conventional remedial works generally consist in the construction of an additional cut-off wall throughout the dam body and the subsoil, in most cases being deeper than the original one. Today, many examples of successful remedial cut-off walls allow the engineers to design the most suitable solution according to the dam and subsoil characteristics and nature.The real difficulty stems from the depth at which the new cut-off wall has to be socketed in competent rock or soil, so as to eliminate underwater seepage. The maximum depth ever achieved with a cut-off wall is 122.5 m for the remedial work of Mud Mountain Dam, Washington, USA, in 1988-1990. This 0.85-1.0 m thick cut-off wall was realized by means of a Hydromill, by excavating single 2.8 m-wide secant panels."

Jan 1, 2017

By Seiji Mizutani, Hirofumi Taguchi, Makoto Yoshida, Hidenori Takahashi, Naotoshi Shinkawa, Kazuo Konishi, Yoshiyuki Morikawa, Masaya Kawata

"The lattice-shaped cement treatment method has been used to improve the seismic performance of liquefied sandy soil in Japan. The efficacy of the method has been confirmed by the huge earthquake in Japan. In the present study, a new method to improve sandy ground by using the lattice-shaped cement treatment method is proposed as a liquefaction countermeasure. It is the floating-type and lattice-shaped cement treatment method, where cement treated soil is not fixed to an un-liquefiable stratum. In this method, a fixed-type structure such as treated soil should be formed at the side of the floating-type treated soil to reduce its lateral displacement. In the study, one-dimensional dynamic response analyses were firstly conducted to confirm the mechanism of the new method. Secondly, a series of centrifuge model tests were performed to demonstrate the effect in a proto-type scale's stress condition. The analyses and model tests confirmed the effect of liquefaction countermeasure of the new method.INTRODUCTIONLiquefaction induced by an earthquake generates sand boiling and ground settlement. Other problems have also been reported, including a decrease in bearing capacity and an increase in the horizontal earth pressure against retaining walls. To prevent these problems caused by liquefaction of the ground, various countermeasures have been proposed, such as cement deep mixing and high-pressure jet mixing methods. These methods have the big advantage of being applicable to ground that contains soil with a fine-grain fraction. Furthermore, the unnecessary displacement caused by the construction can be reduced. In Japan, a lattice-shaped cement-treatment method has frequently been used at many construction sites to prevent liquefaction, where cement-treated piles are intersected to form a lattice, as shown in Fig. 1. The lattice-shaped walls can reduce the shear stress generated by an earthquake, restricting the liquefaction at that location. However, the construction cost of the cement treatment is relatively high compared to other methods such as the sand compaction pile (SCP) method, and needs to be reduced. Therefore, decreasing the total volume of the cement treatment is necessary to reduce the construction cost."

Jan 1, 2015

By Yu Chuang, Zai Jinmin, Liu Songyu

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

Jan 1, 2005

By Abu B. Siddique, Anthony S. Crincoli

"The New Jersey Turnpike Section 2 widening program consisted of widening between Interchange 6 in Mansfield Township, Burlington County and Interchange 9 in East Brunswick Township, Middlesex County. To accommodate large volume of traffic the roadway was widened from 6 to 12 lanes with major modifications performed at four interchanges. The Section 2, NJTA Interchange 6 to 9 Widening Program is a 4.2-mile section of Turnpike roadway which included a total of 12 new or modified structures. In order to facilitate the construction process Section 2 was divided into three construction contract packages. This paper will cover the last and final Contract T869.120.203 which is 1.7 miles in length. The work generally consisted of eight new ramps connection to and from the toll plaza to the new inner and outer roadways. New mainline bridges were constructed over several ramps. A new bridge was constructed to take northbound outer lanes traffic over two ramps along with new mainline bridges over Black’s Creek, Georgetown Road, and Laurel Run. In addition, a new bridge was constructed to take a ramp over Laurel Run and the existing U-turn Bridge was replaced with a new one.For Contract T869.120.203 a total of 74 five-foot diameter drilled shafts has been constructed to support all pier foundations for bridges. Three drilled shafts were tested using Osterberg Load Cells to verify the estimated shaft resistance during design phase. One Osterberg Load Cell test was performed on a demonstration (sacrificial) shaft and the other two Osterberg Load Cell tests were performed on production shafts. This paper compares the estimated total, side and tip resistances with corresponding measured total, side and tip resistances and provided recommendations for future design purpose.INTRODUCTIONTo accommodate large volume of traffic the New Jersey Turnpike Authority (NJTA) decided to widen Section 2, which included Interchange 6 through Interchange 9. The Section 2, a 4.2-mile section of Turnpike roadway that was widened from 6 to 12 lanes with major modifications performed at four interchanges.The New Jersey Turnpike Authority (NJTA) procured AECOM to perform engineering services for the final design of Section 2, NJTA Interchange 6 to 9 Widening Program. Section 2 is a 4.2-mile section of Turnpike roadway that will widen from 6 to 12 lanes and will include a total of 12 new or modified structures. It encompasses modifications of the existing and the design of four new ramps at Interchange 7. The project also includes the modification of two local roads over the mainline, two local roads under the mainline, two maintenance U-turns, and retaining walls. In addition, the project consists of the design of noise walls, sign structures, storm water management basins and the more typical drainage, utilities, lighting, roadway, ROW, and signing and striping design."

Jan 1, 2015

By H. Yoshida

Jet grouting was first introduced in Japan in the second half of the 1960s, approaching 50 years ago. By the end of the first 40 years, jet grouting from single to triple fluid systems had become a global technology. In the last ten years, progress in the jetting has been remarkable, and operational efficiency has improved. The quantity of carbon dioxide emitted in unit soil improvement has become one-third that of the initial technology. Meanwhile, technologies in waste recycling and horizontal jet grouting are also emerging. This paper discusses developments in the most recent ten years.

Jan 1, 2010

By Mohammed Faizal, Abdelmalek Bouazza

"The operation of ground source heat pumps combined with foundation piles can have an effect on the thermal behaviour of the pile and the surrounding soil. This paper presents the effects of continuous heating, continuous cooling, and alternate heating and cooling operations on ground and pile temperatures as well as the thermo-mechanical behaviour of a field scale energy pile. The effect of pile operation on the ground temperatures is highest near the pile and reduces with increasing radial distance. The results of the present studies generally showed that the thermal elasticity of the pile is not affected.INTRODUCTIONGeothermal energy piles are foundation piles used as underground heat exchangers to maintain thermal comfort in buildings, via the use of ground source heat pumps (GSHPs). Ground source heat pumps are more economical and environmental friendly compared to conventional heat pumps. Energy piles can be combined with supplemental surface heaters or coolers, known as hybrid systems, for forcefully recharging the ground during non-operational times of the GSHP. Alternative heating and cooling of the GSHP improves geothermal energy usage and alleviates heat build-up in the ground and provides a balance of ground temperatures around the heat exchanger (Jalaluddin and Miyara, 2012).The temperatures induced in the piles during GSHP operation can lead to a complex response of thermal strains and stresses in the pile concrete. An assessment of the thermo-mechanical response of energy piles for various thermal loads may assist engineers in the design process. Furthermore, an assessment of ground temperatures will also highlight any potential thermal interactions with other energy piles in actual building operations.At present, the thermal strain and stress distribution in field scale energy piles has mostly been studied for continuous operation (Laloui et al., 2006; Bourne-Webb et al., 2009; McCartney and Murphy, 2012; Akrouch et al., 2014; Mimouni, 2014; Murphy and McCartney, 2014; Murphy et al., 2014; Wang et al., 2015). These studies have contributed considerably to the understanding of the axial thermal strain and stress distributions in the piles and have shown that pile thermal behaviour is mostly thermo-elastic without inducing major structural concerns.The present paper adds to the current knowledge by assessing the pile thermo-mechanical and ground thermal response for continuous and alternating thermal loads of a field scale energy pile. The operation modes studied are 24 hours continuous cooling (Faizal et al., 2015), 24 hours continuous heating, (Wang et al., 2015) and alternate heating and cooling operation (Faizal and Bouazza, 2016). The forced ground thermal recharging is done during the non-operating times of the cooling unit, simulating a solar hybrid GSHP system for a scheduled intermittent mode of operation."

Jan 1, 1900

By Stefan Larsson, Jan Ekström, Jennie Kock-Larsen, Håkan Garin

"This paper describes the testing procedure (or protocols) for quality control of dry deep mixing columns in a major ground improvement project carried out in Sweden. Quality control was mainly based on column penetration tests performed at different stages in the project and on two occasions after installation. In the paper, the results from the tests are compared with tests on the unimproved clay. As expected, the results show that the correlation between undrained shear strength in the columns and in the unimproved soft soil depends mainly on the in-situ stress. However, the correlation probably depends on when the tests were performed after mixing. When the influence of the in-situ stress was excluded from the analysis, no significant correlation could be identified. This means that the undrained shear strength in the columns and in the unimproved soft can be considered to be uncorrelated when the strengths and the corresponding variability are evaluated with depth from groups of tests.INTRODUCTIONQuality control and quality assessment of deep mixing (QC/QA) constitute a key component in verification of the limit state design. Due to the complex mixing process and varying geological conditions, it is normally not possible to sufficiently assess the strength and deformation properties in advance. In Sweden, the most commonly used QC/QA method for verification of the limit state is the column penetration test (Axelsson and Larsson 2003; Bergman et al. 2013). The method works well but is time-consuming and requires many tests since property variability is normally high. The column penetration test can be used to assess the undrained shear strength Cu,col. However, it is not clear how the strength correlates to the undrained shear strength of the unimproved soil Cu,soil. There are common factors such as the in-situ stress state and the natural water content, which makes a positive correlation probable, i.e. as Cu,soil decreases, Cu,col also decreases and vice versa. The unimproved soil has a natural spatial variability, but it is not known if the improved soil follows the same variation. The mixing process has a substantial influence on the strength variability and may supersede the influence of other factors. However, if a sufficiently good correlation exists between Cu,col and Cu,soil, information from the geotechnical ground investigations can be used in the design and planning of QC/QA of deep mixing in a more stringent manner. Information about the correlation is also essential in reliability based design, where a strong positive correlation may have a negative influence on reliability. However, as discussed by Al-Naqshabandy and Larsson (2013), this correlation may be weak or insignificant for a representative failure domain where the mixing process may have a dominant influence on the strength variability. It is thus of interest to assess the correlation."

Jan 1, 2015

By Joel Moskowitz, George J. Tamaro

"A new office complex is being constructed within 25m of the Hudson River in New Jersey. The project, about 140m by 100m, will include 4 basements under the entire footprint. The perimeter was to be secured by a 0.8m thick diaphragm wall, laterally supported by high capacity tieback anchors to rock. Columns were to be supported on footings or piers to rock at a nominal bearing pressure of 3.8MPa at depths up to 17m. Although some variation in rock quality was observed in borings, a substantial vertical seam of weathered and/or decomposed rock, 1 to 2 meters wide by as much as 8 meters deep, was encountered during construction necessitating field redesign. In some locations, the seam dipped below rock that is more competent. Footings were redesigned for support on drilled caissons, or soft rock was excavated and replaced with concrete necessitating a reduction in bearing pressure of the footings by one half. The tower covering the south half of the site was topped out in 2002 and the garage levels in the north half of the site were completed in 2003.PROJECT DESCRIPTIONIn September 1999, a major investment company began the due diligence process to evaluate a property on the shore of the Hudson River in Jersey City, New Jersey for a new multi-use complex. The site offers a spectacular view of lower Manhattan directly across the river from the site of the former World Trade Center. The site, covering two city blocks, was previously occupied by manufacturing and office facilities of Colgate-Palmolive.The building footprint is approximately 140m by 100m, the southern half of which is occupied by a 260m tall office tower, shown in Fig. 1. As of this writing, design of the structure for the northern half of the site has not been finalized, but it is expected to comprise an 11-story office building. A glass-covered atrium will occupy the street that formerly separated the two blocks. As part of the due diligence process and preliminary design evaluation, alternatives were considered to accommodate various numbers of parking places, both above and below existing grade. A major consideration for below grade parking is the proximity of the Hudson River some 25m east of the east building line."

Jan 1, 2004

By Lori A. Simpson, Linda H. Liang

A high-rise building, consisting of two tower structures occupying the entire site, is in construction in San Francisco. The North Tower will consist of 12 and 35 stories above a one-level basement. The South Tower will consist of 9 and 22 stories over one partially below-grade level of common space; a portion of the South Tower will have a three-level basement. The towers will be supported on mat foundations bearing on native very dense sand in the footprint of the threelevel basement and on ground improved with soil-cement mixed (SCM) panels that extend through loose sand and marsh deposits into very dense sand. Shoring systems for the basement excavations include cantilevered and tiedback soldier-beam-and-lagging systems and SCM cutoff walls. Subsurface conditions include loose fill and Dune Sand and loose and soft marsh deposits overlying very dense sand of the Colma formation. Groundwater is approximately 15 to 22 feet deep; the three-level basement extends below groundwater. The site is on Market Street in San Francisco, with SF Municipal Railway (MUNI) and Bay Area Rapid Transit (BART) tunnels running below Market Street approximately 45 and 36 feet north of the site, respectively. Both tunnels are 16.5 feet in diameter. The top of MUNI and BART tunnels are 25 feet and 63.5 feet below street grade, respectively. BART has stringent requirements regarding construction adjacent to their facilities, including disallowing adding pressure to their tunnel, lowering groundwater by more than two feet, and vibrations from construction activities. Design of the shoring and the foundations within the BART zone of influence were subject to their design requirements. The project was also subject to a peer review, as required by the San Francisco Department of Building Inspection. We used FLAC to evaluate stresses at the BART and MUNI tunnels and on the SCM panels. This paper will present the mitigations needed to address seismic hazards and BART restrictions and to provide adequate foundation support for a tall building with high seismic loads.

Jan 1, 2017

By Lori A. Simpson

A high-rise building, consisting of two tower structures occupying the entire site, is in construction in San Francisco. The North Tower will consist of 12 and 35 stories above a one-level basement. The South Tower will consist of 9 and 22 stories over one partially below-grade level of common space; a portion of the South Tower will have a three-level basement. The towers will be supported on mat foundations bearing on native very dense sand in the footprint of the three-level basement and on ground improved with soil-cement mixed (SCM) panels that extend through loose sand and marsh deposits into very dense sand. Shoring systems for the basement excavations include cantilevered and tied-back soldier-beam-and-lagging systems and SCM cutoff walls. Subsurface conditions include loose fill and Dune Sand and loose and soft marsh deposits overlying very dense sand of the Colma formation. Groundwater is approximately 15 to 22 feet deep; the three-level basement extends below groundwater. The site is on Market Street in San Francisco, with SF Municipal Railway (MUNI) and Bay Area Rapid Transit (BART) tunnels running below Market Street approximately 45 and 36 feet north of the site, respectively. Both tunnels are 16.5 feet in diameter. The top of MUNI and BART tunnels are 25 feet and 63.5 feet below street grade, respectively. BART has stringent requirements regarding construction adjacent to their facilities, including disallowing adding pressure to their tunnel, lowering groundwater by more than two feet, and vibrations from construction activities. Design of the shoring and the foundations within the BART zone of influence were subject to their design requirements. The project was also subject to a peer review, as required by the San Francisco Department of Building Inspection. We used FLAC to evaluate stresses at the BART and MUNI tunnels and on the SCM panels. This paper will present the mitigations needed to address seismic hazards and BART restrictions and to provide adequate foundation support for a tall building with high seismic loads.

By Vijaya Bhushan Rao, Jason Redgers

A substantial lifestyle destination in the United Arab Emirates, in the Emirate of Abu Dhabi comprising of 1315 villas, town houses and non-residential leisure facilities is built over an area of 280 hectares of former mangrove areas, natural sands and reclaimed lands. Large-scale subsoil investigations including field and laboratory testing carried out dividing the entire site in to 7 clusters. This investigation revealed alternating layers of loose sands and silty clays within the load influence zone of planned foundations, showing susceptibility to excessive settlements. Therefore, ground improvement works were undertaken using a combination of stone columns, Rapid Impact Compaction (RIC) and excavation and replacement of soils plus a 0.4m thick load transfer platform. This was necessary to limit the settlements, increase-bearing capacity and prevent long-term settlements. 30 no’s of full-scale Zone Load Tests, ZLT were carried out each for a duration of 30 days in order to ascertain the anticipated long-term settlements in the clay layers. In addition, further testing of electrical cone penetration tests, CPT, and Plate Load Tests, PLT. The use of Priebe and Asaoka’s observational procedure were applied to predict the final settlements and the use of back-analysis from the 30 days Zone Load Tests, ZLT results to establish the site-specific consolidation parameters in clay layers to optimize the design and ground improvement works.

Sep 8, 2021