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By Muttharam M, Karthick Kumar V

Helical piles foundation systems have been extensively used in engineering application. It is commonly adopted to resist the compression, uplift force, overturning moment and lateral forces. Helical pile system is extensively used in many structures such as Transmission towers, Wind farms and other offshore structure because it is easy and quick to install. Realizing the importance of helical pile, an attempt is made in the present investigation to bring out the effect of spacing between the helix, blade thickness, and shaft thickness through numerical analysis. To validate the finite element model experimental investigation was carried out. In this investigation model steel piles with dual helical plate embedded in clay bed with the consistency of 0.4 was tested to study the effect of uplift loading on the behaviour of piles in tensions. Model helical pile with 12.5 mm diameter circular shaft and helix diameter of 25 mm. The model pile embedded in clay bed for a depth of 400 mm. Parametric analysis of helical pile by varying blade thickness, shaft thickness, and the spacing of helix was carried out by using Finite Element tool Plaxis 3D. From this analysis, an increase in thickness from 4 mm to 10mm increase the uplift load. Similarly, an increase in spacing of helices from 0.5 m to 1.5m increase the uplift capacity beyond that it decreases the uplift capacity. By keeping the contact area of the helix as constant as the number of a helix and helical spacing was varied, the critical number of the helix was found as 2 and the critical spacing of helix was found as 1.5 m for this study.

Nov 1, 2022

By Emre Biringen

"Results from a small-scale laboratory experimental program show the changes in the vertical stiffness and strength of a soft clayey soil adjacent to the shaft of an inserted pile (i.e. expansion of a cylindrical cavity). The experimental program provides a realistic axi-symmetric physical model of an element of a cylindrical pile and the surrounding soil. The study interprets the improvement and assesses its magnitude in vertical stress-strain-strength properties of a normally consolidated soft cohesive soil in response to preloading impact in the radial direction. The results verify that insertion of a cylindrical pile causes densification of surrounding soil in a radial direction due to change in stress state around the pile, and thus consolidating and stiffening of the soil.The test results indicate that most improvement in modulus and strength takes place within a distance of 4 times the radius of a pile, though significant improvement is realized to a distance of 8-10 times the radius, beyond where there is negligible effect. Settlement characteristics of the surrounding soil in a zone of 12 times the pile radius improve significantly after the formation of a cylindrical cavity. The miniature vane shear strength tests show a 1.5 times increase in a zone of 4 times the pile radius compared to the strength at 10 pile radii. The results also imply that the spacing of cylindrical piles should not be more than 4 to 10 times pile radius, so that the surrounding soil matrix may improve the vertical bearing capacity under any foundation or embankment loading.INTRODUCTIONThe engineering community is familiar with different techniques to improve the bearing capacity and settlement characteristics of weak cohesive and organic soils. Some of the in situ techniques to improve the properties of soft ground (e.g. soft clays) prior to placement of foundations are vertical preloading, deep cemenUlime mixing, stone columns, and grouting (Henn 1996; Moseley 1993). In addition to these methods, researchers have recently showed interest in achieving soft ground improvement by means of applying radial compression method for which different names exist including expanding pile (Kelleher et al. 2001 ), Preload™ Pier (Biringen and Edil 2003), and sand compaction pile (Lee et al. 2004). Handy (2001) has described how preloading can also be achieved by imposition of radial loading in soft ground with an expected improvement in stiffness. The idea behind the latter method is densification and consolidation of soft soil in the radial direction by controlled displacement for which the process can be viewed as a cavity expansion problem (Vesic 1972)."

Jan 1, 2005

By Rahul Wankhade, Sunil S. Baswankar, Aditya S. Kharatkar

Despite advances in pile design methodologies and piling techniques at site, difficulties and uncertainties still exists for design of piles particularly in coralline deposits and weak carbonate rocks. Such deposits are known to be heterogenous in nature, and occupy major stretches of earth, where piling experiences are probably very scanty. Such deposits are associated with low unit weights and usually consist of weakly cemented calcareous and carbonate soils interbedded with coral rocks containing cavities, which are completely void or filled with coral debris. Many of the studies indicate that conventional parametric relationships are may not apply to such sediments and rock formations. This paper intends to provide an appraisal of the available information that cautions against risks involved in conventional design practice and also serve as a guideline for pile design in such formations despite being a grey area of research. Contents of the paper is expected to provide a basis for the pile design and likely to serve as an eye-opener for research into this important soil-pile structure interaction problem.

Sep 1, 2022

By Paul M. Schuman, Alessandro Bertero, Giuliana A. Zelada, Sharon G. Cranston

Many jet grouted columns were recently installed to create a jet grout-treated soil foundation for an earthen embankment used in a large shoreline stabilization project in the Mystic River in Charlestown, MA. A physical test program was used to determine whether the jet grouting parameters the Contractor selected would meet the design requirements given the local soil variability, including soft river sediments and organic soils. The presence of hydrocarbons encountered in the marine sediments during the test program caused concern that the design strength could not be achieved. The published literature discusses the environmental aspects of jet grouting with hydrocarbons. The literature did not include many studies of the effect on jet grout-treated soil strength for the types and concentration of hydrocarbons encountered on this project. The grout mix, air pressure, and number of passes of jet grouting were varied in a second field test program to determine jet grouting parameters needed to achieve the design strength of columns with hydrocarbons. A geo-probe study was performed to identify the type and concentration of hydrocarbons on the site. With few exceptions, the quality control core samples from the production columns met the design requirements with many strength values far exceeding the design strength. This paper presents the data, and reviews the lessons learned. PROJECT BACKGROUND The Charlestown Bus Garage, located in Cambridge, Massachusetts, is a Massachusetts Bay Transportation Authority (MBTA) bus maintenance facility located on the Mystic River. The site was home to a coal gasification facility before it was developed by the MBTA as a bus garage in 1978. A deadman-anchored steel sheet pile bulkhead wall installed along the Mystic river on the east side of the site supports the site grade at about El. 11 ft (NAVD 1988) (Figure 1).

Jan 1, 2019

By José Carlos do Amaral, Marcelo Groszownik, Jorge Beim

"Initiated in 2008, the project of this 1800 km long Electrical Transmission Line is a job of extreme technical complexity, crossing regions of major forests and rivers. When ready, it will allow the large Brazilian states of Amazonas, Amapá and Pará to use the energy from hydroelectric plants, thus eliminating the need for the use of diesel fuel thermal plants, with their much larger environmental footprint. Due to its extraordinary characteristics, the Green Peace and the Discovery Channel constantly visited the job. The part between the Amazon and the Xingu rivers started in 2012, and encompassed about 100 transmission towers with up to 150 m height, through a region known as “Alagados”. This region exhibits a 1.5 m water level during the rainy season, and soaked ground the rest of the year. Navigation of regular vessels is impossible during the flood season, when a dense vegetation called “bulhado” fills the riverbed, and vehicle traffic is impossible during the dry season, due to the extremely low surface soil resistance. Great logistical and technical difficulties were encountered for driving and determining the capacity of the piles. New systems had to be developed for driving the piles, with the simultaneous use of 15 small piling rigs. The final penetration, total number of hammer blows during driving, plus Dynamic and Static Load Tests were used for determining the driving and acceptance criteria.The geographical challenge and initial conditionsThis paper describes the execution of foundations for a 500 kV Electrical Transmission Line in a region that becomes flooded during the rainy season and heavily muddy during the dry season. This is the monsoon climate, typical of the equatorial region of Brazil, where there is a rainy season lasting for about half the year, followed by a very dry season. The temperature varies very little throughout the year, due to the proximity to the equator. The locals call the rainy season “winter” and the dry season “summer”.The most important part of the so-called “Alagados” region is situated inside an Environmental Extractive Reserve (RESEX) called “Verde para Sempre” (Forever Green), created in 2003. This is one of the largest environmental reserves in Brazil. It is an area controlled by the Brazilian Environmental Control Department, the Chico Mendes Institute (ICMBio). The environment control parameters are very strict.No deep foundation had ever been executed before along the “Alagados” region. The main challenge faced on this job, however, was working in a place where self-propelling vessels or land vehicles and equipment cannot be used. During the rainy season there is a dense and intricate vegetation called “bulhado”, which prevents the movement of outboard motor boats with propellers going deeper than 50 cm. In the dry season, the heavy mud prevents the movement of foundation equipment, excavators, trucks and other machinery."

Jan 1, 2015

By Bengt H. Fetlenius

The "Pile Prediction Event" at the ASCE GeoInstitute's Deep Foundation Conference in February 2002 involved prediction of drivability and capacity of three 14m long, 324mm diameter, closed-toe pipe piles driven into loose to compact fine sand to slightly silty sand. Predictors were provided the results of two soil borings and three cone penetrometer tests, as well as type and model of hammer to be used for the pile driving. A total of 33 persons submitted predictions. As to penetration resistance distribution, many predictions were far below actually observed values. As to capacity in compression, the predicted values ranged from 270KN through 2,340KN with a mean of 1,070KN. As to capacity in tension, the predicted values ranged from 100KN through 1,650KN. The maximum load applied to the compression pile in the static loading test was 1,25OKN, at which no more reaction load was available. The reaction system for the tension test failed early in the test. CAPWAP analysis on End-of-Driving blows showed capacities at the end of the driving for the push and pull piles of 670KN, and 710KN, respectively. No restrike tests were made. Additional CPT soundings indicate that the pile driving had densified the soil. Static analysis and calculations from the CPT indicated that capacities ranged from 1,000KN through 2,000KN. The paper presents the data and discusses the various methods of determining pile capacity and addresses influence of set-up Lessons useful for future similar events are indicated.

Jan 1, 2004

By Peter Middendorp, David J. Tara, Gerald E. Verbeek, Jan Fischer

"For pile driving simulation the model used must be accurate for the entire process, i.e. from the start of pile driving until the pile has reached its target depth. Of the various model components (hammer, pile and soil), the soil is the most difficult to characterize accurately. This is well known, but the aspect that is not as well understood (and therefore commonly misapplied) is the fact that the soil properties and thus the soil parameters do not remain constant during the pile driving process. Furthermore, this phenomenon of soil fatigue, mainly for skin friction, as a continual change of soil resistance during pile installation, is not implemented into all commonly applied pile driving simulation software and could therefore not be taken into consideration. In this paper the effect of soil fatigue will be described by numerous research results, showing that this effect will occur regardless. Different methods to consider the change of soil resistance during pile installation will be presented, some applying soil fatigue while others merely reduce soil resistances. Using currently available wave equation software that can take soil fatigue into consideration, the importance of doing so will be shown on the basis of the back calculation of a monopile installed offshore in Germany.THEORY BEHIND SOIL FATIGUESkin friction and toe resistanceTo simulate pile installation as accurately as possible, detailed geotechnical knowledge about the mechanical behavior of the soil surrounding the pile is necessary during each step of the installation process. Therefore, to ensure ""geo-mechanical correctness"" of a pile driving simulation, the shaft friction and the toe resistance have to be recalculated at each penetration level. For the skin friction parameters this is especially important since they change significantly during pile installation because of soil fatigue. Depending on the pile and soil type, the toe resistance can experience changes as well due to soil fatigue during to pile driving. However, in this paper the toe resistance values were kept constant over the entire penetration depth.In general, the unit skin friction can be derived from measured values (CPT, qs) or calculated as a function of the horizontal effective stresses dh acting perpendicular to the pile wall of a vertically driven pile. The horizontal stresses can then be converted into the unit skin friction qs using the Mohr-Coulomb failure criterion:"

Jan 1, 2017

By Andrew Moran, William H. Walton, Matthew D. Emrick, Mary C. Nodine

"A rapidly growing company in the northern US needed a large auditorium built into a dolomite bedrock hillside. The structure required an 80-foot-deep earth retention system independent of the auditorium foundation and superstructure. Allowable wall movements were limited to less than two inches. A 60-foot-tall permanent shotcreted soil and rock nail wall was designed for excavation support. The soil and rock nail wall utilized both active (post-tensioned) and passive nails, with capacities and installation angles optimized to address varying soil and rock conditions and to support heavy surcharges. The wall was configured with three two-foot-wide benches to facilitate controlled blasting and removal of more than two million cubic yards of soil, limestone and dolomite bedrock, and featured a permanent cast-in-place concrete face and a robust waterproofing and drainage system. A 20-foot-high reinforced concrete retaining wall was required at the top of the soil and rock nail wall to raise grades, resulting in a large surcharge.Design of the soil and rock nail wall was initiated less than three months before the start of construction, requiring expedited geotechnical explorations, analyses, design, and construction that would occur simultaneously. Design changes were made to address the discovery of a weak clay residuum seam at depth running along the base of the excavation, as well as significant changes to the building footprint made after the start of construction. Extensive performance monitoring was conducted during construction to measure vibrations and movements.Introduction and Project BackgroundA fast-growing company in the northern United States had a need for 600,000 square foot, 11,000 seat auditorium as part of its campus expansion. The auditorium was built underground, into a hillside to preserve the views of rolling terrain and farmland beyond. It featured a green roof and rockwork facing that mimicked regional geologic formations. The sixstory building required up to 80 feet of earth retention, including 60 feet of excavation beneath existing grades.As concepts for the project evolved, it became apparent that due to the geologic conditions, space limitations on site and the depth of cut required, a standard counterfort wall system would not be feasible. With groundbreaking for the building three months away, Thornton Tomasetti (structural engineer) engaged GEI Consultants, Inc. (wall design engineer) to design a 1,600-foot-long permanent soil and rock nail wall to support the excavation. The wall design engineer implemented a geotechnical exploration program immediately and began the design process, coordinating closely with Nicholson Construction (specialty"

Jan 1, 2017

By Karl A. Higgins

In August 2004, the long-awaited National Harbor project in the DC metro area sprang to life with the design of Gaylord National Resort and Convention Center. When the project was in its final stages of construction in 2007, it was noted as largest building development of the east Coast and the 4th largest Building project in the U.S. The final construction costs were above $900M and it served as the catalyst for the overall National Harbor development which added another $1B in construction costs over the next few years. The Gaylord Hotel is supported by approximately 150,000 linear-feet of driven precast concrete piling, one of a handful of major DC area projects in the early 2000s that were supported by this pile type. The project overall was a success, but the fast-paced construction schedule created significant challenges to the designers and contractors. Piling installation was the first major building construction task, and it did not start out well. While the test piles were installed without damage, when production pile driving began in the summer of 2005, pile head and body breakage soon became evident. Typical of most highprofile projects, there are many stakeholders involved and an equal number of opinions on why the piles were breaking. The financial and contractual implications of starting the project off awkwardly were evident to all. The pile driving criteria was scrutinized by the contractor, and the engineer’s had reservations about the size and type of the hammers used for pile driving. Ultimately, it was proven the leading cause of pile breakage was neither the pile driving criteria nor equipment, rather the pile materials themselves. The author of this paper is also the Geotechnical Engineer of Record for Gaylord National and many of the adjacent National Harbor buildings including the recently completed MGM casino. About 100 piles were damaged during Gaylord’s construction some requiring multiple piles for replacements. Over the past decade or so, rumors on the causes of the pile breakage have spread in the market, with some alleging this pile type is not compatible with the geologic setting. I have purposely avoided writing this case-study due to the controversy surrounding the subject, but now some 15 years later it seems appropriate to do so considering DFI’s annual conference location. This will be a fact-based assessment of pile breakage at Gaylord and will also include a comparison to the neighboring buildings where far fewer driven piles were damaged, once a more appropriate concrete mix design was required. The pre-cast supplier is no longer in business.

By I. D. McPherson, Dominic P. Mahoney

The Metro Sports Facility is currently under development in Christchurch, New Zealand and is a key Anchor Project in the city’s post-earth quake recovery. When completed it will be largest indoor sports and swimming pool complex in New Zealand, with a building footprint in the order of 22,000m2. The site is underlain by poor performing soils comprising interbedded layers of soft compressible silts and loose liquefiable sands to over 20m depth. The site is typical for Christchurch with a shallow groundwater table and artesian conditions. The site performed poorly during the 2010-2011 Canterbury Earthquake Sequence with extensive liquefaction, and associated ground damage. To provide a resilient and economical foundation system for this key development project, deep ground improvement comprising of a uniform grid of some 7,200 stone columns in conjunction with robust shallow foundations has been adopted. This paper discusses the geotechnical site constraints, and ground performance under earthquake loading and describes the various options considered for the development. The foundation option selected, the design considerations of the adopted stone column ground improvement, and foundation solution are described in detail, as well as, construction observations. The paper aims to provide insight into an urban large-scale ground improvement project for the engineering practitioner.

Nov 1, 2022

By Nadir Ansari, Brian W. Wilson, Marina S. W. Li

"A hybrid Deep Mixing (DM) shoring system was recently constructed for a high-rise development in downtown Vancouver, British Columbia, Canada for the temporary support of a five-level basement excavation. The site is bounded by an existing bridge off-ramp structure along its longest side and by city streets on the other two sides, which formed a truncated triangle in plan. A conventional secant pile wall was installed along the longest side, about 380 ft (116 m) in length, of the site. Hybrid shoring walls (HSW) 1 and 2 were installed along two shorter sides with each being 235 to 246 ft (72 to 75 m) long. HSW 3 completed the excavation support system along the shortest side with a length of about 55 ft (17 m). Cutter soil mixing (CSM) was proposed by the excavation and shoring design-build team in lieu of conventional secant piling. CSM was the preferred method to construct the infill panels between soldier piles because of the speed at which the shoring system could be constructed in the variable fill, peat, wood waste and overburden. Design ConsiderationsTo minimize the impact on buried utilities along the outside perimeter of the excavation, the temporary shoring was designed to limit the lateral displacements to less than 0.8 in (20 mm). Factors taken into consideration for shoring design included the lateral earth pressures from the fill and native soils, groundwater pressures, temporary construction loads (e.g., crane or heavy plant/equipment), and permanent structural requirements. The subsurface conditions at this site typically consisted of fill (cohesive and granular), overlying peat and/or wood waste, overlying clayey silt to sandy silt, overlying weathered to dense to very dense clayey silt till to sandy silt till with silt layers. Localized, perched groundwater was observed within the fill, peat, wood waste and sandy silt layers above the dense till."

Jan 1, 2017

By Min Sunn Ye, Wei Wang, Huawen Xiao, Kai Yao, Fook Hou Lee, Siang Huat Goh

"Previous research have shown that introducing fibers to cement soil mixture is effective in improving the ductility as well as maintaining the strength of cement-treated soil. A good knowledge of stiffness of the improved soil at small strain is essential for realistic predictions of ground movements that may affect adjacent buildings or underlying infrastructure. This paper presents a triaxial system with local strain measurement developed for studying shear modulus degradation of cement treated clay with fibers. Cylinder specimens (70mm diameter by 140mm height) with 50% cement, 100% water, 0% to 1% polypropylene fibers by mass, and 7 days of curing period were used. A local strain measurement system with floating type miniature submersible LVDT is introduced in this paper. Configuration of the mounts including the pin size, length and distance are presented and discussed. Based on the experimental results, a reasonable configuration of the mounts is recommended for fiber reinforced cement treated clay. Results showed that the proposed local strain measurement system is effective for testing the shear modulus degradation of cement treated clay with fibers under both unconfined and confined condition. Comparisons with results from resonant column and bender element tests served to verify the reliability of the local strain measurements using the proposed method.INTRODUCTIONIn many geotechnical engineering problems, the operational strain domain ranges from 10-3% to 10- 1%. A good knowledge of stiffness at small strains is essential for realistic predictions of the ground movements that may affect adjacent buildings or underlying infrastructure. As such, during the last 3 to 4 decades, the importance of using the small strain stiffness of soils for the design of foundation and underground structures has widely been accepted. Triaxial testing has been widely used to study the stress-strain behavior of soil in the laboratory. However, the stiffness obtained from the conventional triaxial apparatus is usually far smaller than those back-calculated from field measurements. This is mainly attributed to the overestimation of axial strains from the external strain measurements, which usually includes compliance effects of the loading and load measuring system as well as sitting, bedding and alignment errors between sample and system (Baldi et al., 1988). The poor resolution of the external strain measurements is another important contribution. Therefore, conventional procedures are inappropriate for small-strain stiffness evaluation due to low accuracy and resolution."

Jan 1, 1900

By Jason Herron, Joseph Brown

The common couplings for joining sections of helical piles with an outside diameter of 6.625 inches and 8.625 inches are square on square, flange to flange, external pipe sleeve, internal pipe sleeve, and welded joint. Each coupling type has advantages and disadvantages in efficiency, capacity, installation, and economics of the installed pile. All these coupling types have been used in the helical pile market in North America for various applications and designs. Many of these applications require on-site testing, but test records are not typically shared with the helical pile industry. Due to the lack of information available for square on square and flange to flange couplings, testing was done to compare the efficiency of installation, load to deflection response, and torque to capacity ratios of external pipe sleeve, square on square, and flange to flange couplings. Field installations and tension tests were performed in non-cohesive (sand type) soil near Caseyville, IL and in cohesive (clay type) soil in Centralia, MO. The data collected during these tests included rotations per foot during installation, installation torque, applied pressure, and deflection. The results of this testing are analyzed and discussed within this paper. The results indicate that the square to square coupling is the most efficient of the designs tested, but this conclusion cannot be fully justified without further testing due to the variability in the data gathered and the small number of piles tested. INTRODUCTION A helical pile is typically assumed to be a medium-displacement pile when its outside diameter is between 4.5 inches and 8 inches and a high-displacement pile when its outside diameter is greater than 8 inches. A helical pile designer has multiple options when selecting a coupling type for medium- to high-displacement helical piles. Each type of coupling has advantages and disadvantages and must be analyzed on the bases of efficiency, capacity, installation, and economics of a project. Typical couplings that are chosen by designers include square on square, flange to flange, external pipe sleeve, internal pipe sleeve, and welded joint. A helical pile must transfer axial, lateral, bending moment, and torsional loads, and the coupling must be designed to effectively and efficiently transfer each type of load. During the installation of a helical pile, the rate of penetration and the disturbance of soil layers play a critical role in the efficiency and torque to capacity ratio (Kt) of the pile. It is common for a coupling to protrude beyond the outside diameter of the pipe section being used. This is necessary for the function of certain coupling types and can facilitate the connection of couplings. However, it causes increased soil disturbance and reduce the rate of penetration due to soil bearing against the protruding portion of the coupling. A helical pile designer typically will work to minimize the coupling protrusion and create a pile with optimal installation efficiency but may choose a design with lower installation efficiency if it offers sufficient economic advantage.

Jan 1, 2019

By Yazen Khasawneh, Yao Zhang

Upgrading and maintenance programs were proposed at a power generating plant in Indiana. To perform construction activities associated with the proposed upgrading and maintenance, a LR11350 crawler crane with a dead load of 1,500 ton was required in the vicinity of existing plant structures. The contact pressure from the crane tracks for the heaviest lift, maximum reach and angle (worst loading condition) were estimated by the rigging engineer to be on the order of 84 psi. Several concerns were raised regarding the total and differential settlements while the crane is in operation and the induced stresses on existing underground utilities due to crane loads. Three-dimensional finite element simulations were conducted using hardening soil model for the subsurface soils and elastic model for the other structural elements (underground utilities and crane mats) to optimize the configuration of the proposed crane foundation. It was found 1-foot thick engineered steel mats underlain by a 1.5-foot thick crushed stone pad will provide enough support to the crane. It will also control the settlement to the allowable limit and maintain the stresses in the underground utilities within tolerance. INTRODUCTION A LR11350 heavy lift crawler crane was proposed as part of an upgrade program at an existing power plant in the state of Indiana. The proposed crane will be sitting on an open ground in the vicinity of existing plant facilities, with multiple underground utilities going beneath the proposed footprint of the new crane pad. The existing utilities are of diverse kinds, including sanitary sewer corrugated metal pipes, electrical conduits and variable steel water/oil drain pipes. The safety and functionality of these underground utilities are critical to maintain the proper operation of the power plant. Therefore, the design of the new crane pad foundation system is of essential to control the ground settlement and the imposed stresses to the existing utilities (Davie et al., 1998, Scott 2017). To ensure all utility locations and depths are identified, the proposed footprint was thoroughly surveyed. Information in regard to each identified utility was provided by the owner. Subsurface explorations were conducted using geotechnical soil borings and soundings to evaluate the ground conditions and generate soil profiles. Numerical simulation and analysis utilizing finite element method were performed to design the crane pad foundation system and evaluate the responses of the utilities. This paper summarizes project information, geotechnical conditions and then focuses on the finite element analysis in assisting the design of crane pad and the utilities evaluation.

Jan 1, 2019

By A. Paviani

The subject of this session is "Equipment Installa­tion, Recent Developments". This is a subject which is not usually addressed at conferences of Foundation Engineering. It is rare to find sessions dealing with the technological side of deep foundations, a subject which only recently seems to have aroused sufficient interest at national and international conferences. It is therefore natural for the subject of "Equipment", or the tools used to implement the various "technologies", to be over­looked or mentioned only occasionally during the discussion of other issues. At conferences, most of the attention is attached to research and to the theoretical interpretation of the performance and behaviour of deep foundations, as well as to establishing the most suitable calculation algorithms and approaches for the study, design and control of foundation structures. It is almost as if the subject of equipment is felt to be less important or, perhaps, that it is considered to belong more strictly to mechanical engineering than to civil engineering.

Jan 1, 1994

By Schmitz Stefan, Stephan Jee-Sun

"Due to the reunion of Western and Eastern Germany in the late 80’s, a multitude of infrastructure projects had to be executed. A good portion of these projects required improvement of the motorway system. In the southern region of Leipzig, in the eastern part of Germany, it was required to connect two existing motorways. Parts of the new motorway pass old strip mining areas. These strip mining areas consist of up to 70m thick backfill material. Especially the upper 20m are very inhomogeneous soil material with a very low bearing capacity. In order to increase the bearing capacity, to decrease the differential settlements and to homogenize the soil parameters, soil improvement using sand-gravel columns was required. Bauer Spezialtiefbau GmbH executed the installation of approx. 711,000 linear meters of columns with a length from 5 m to 25 m. For the project, 11 rigs with frame leads up to 40m were used to install the 43,000 columns with a diameter of 0.8m in 27 weeks.1. INTRODUCTION1.1 Site LocationThe construction site is located in the south-eastern part of Germany, in the south west of the city Leipzig.The area to be treated had a size of approx. 500,000 m² to allow the construction of dam/embankments and a highway bridge.1.2 Required WorkIn addition to the general earthworks and the installation of geogrids and fibre mats, a total amount of more than 710,000 linm of Gravel-Sand Columns with different lengths due to the given soil conditions had to be installed:•nos. 4,206 Columns length 5m ? 21,030 linm•nos. 4,581 Columns length 10m ? 45,810 linm•nos. 10,820 Columns length 15m ? 162,300 linm•nos. 19,634 Columns length 20m ? 392,680 linm•nos. 3,574 Columns length 25m ? 89,350 linmFor the installation of the columns Gravel-Sand with the grain size of 0/32mm was used. The total amount of Material was 580,000mt"

Jan 1, 2015

By Sudhir Kumar Das

"The exorbitant price of the land in the metropolis has restricted the horizontal expansion and compelled the owners, the developers and the engineers to opt for vertical expansion. This has resulted in the construction of high rises by extending floors of the existing buildings and developing the new ones for which deep excavation is a must. The multistoried buildings up to a certain height can be founded on shallow depth if the soil beneath can withstand the load. If not, the soil can be stabilized by the latest improvement technology to change the properties of soil to cater the desired load of the superstructures. By such practice the cost and time of completion of the substructures can be reduced in comparison to the substructures needed for deep excavation.The necessity of deep excavation cannot be ignored to create housings, underground parking lots and the other public amenities for the urban migrants in the metropolis.Although most of the metropolis have underground mapping the developers, before starting excavation should be hundred percent sure about the alignment and depth of the utilities so that the excavators do not snap the same to bring cut in water supply, power lines, telephone lines etc, resulting in hue and cry in the neighborhoods of the metropolis due to no availability of the essential services The building/structures coming on the influence zones of the deep excavation should be monitored in all sequences of excavations. In case of building underground corridors for rail or road through open deep excavation under a traffic road the developers, before commencing excavation should shift/divert the dry and wet utilities coming on the way of excavation to suitable locations. The surface traffic need to be diverted either temporarily to an adjacent alternative road or allowed to pass over a decking built over the trench of excavation for the affected length of construction. The soil support system is necessary longitudinally on the two sides covering the width of trench for building corridors. In case of building substructures of flyovers built at different plots along the alignment of the flyover or a multistoried complex built at an isolated plot, the soil support system would be necessary on all the sides covering the plot of construction.The material of construction of soil support depends on the depth, type of soil and the type of permanent structure to be developed. Probable geo-hazards inviting casualties in the deep excavation projects occur due to caving of soil, leakage of wet utilities, seepage through honey comb concrete surfaces, failure of pump used for dewatering etc. A detailed comprehensive planning, management and determination of the project authority is essential for marginalizing the casualties. These prevent unforeseen expenditure in mitigation and help to control the time and the cost over run of overall project. The engineer at site should be more a professional manager than an engineer at site. He should be conversant with the safety and environment rules and regulations applicable to deep underground projects."

Jan 1, 2015

By Jeremy Butkovich

Dynamic soil-structure interaction (DSSI) analyses are becoming more common in bridge designs, especially in seismically active areas. Because of its proximity to two active fault zones, the Evergreen Point west approach bridge replacement will be base isolated, and will be designed using DSSI. The project team completed two independent bridge designs to satisfy peer review requirements. The designs required substantial characterization of the soil dynamic behavior using both laboratory and in-situ testing. The analyses made use of earthquake time histories spectrally matched to conditional mean spectra. This led to reduced, and more realistic seismic demands on the structure, compared to conventional uniform hazard spectrum matching. The bridge analyses suggest that the preliminary bridge design is relatively conservative. This will allow the design team to potentially reduce shaft/column diameters and reinforcement. The design team estimates that the dynamic analysis design could represent a net savings of around $60 to $90 million compared to a conventional design.

By M. Kitazume, H. Imai

The deep mixing method was developed in Japan and put into practice in the middle of 1970s. Since then, the wet and dry type methods have been applied for various improvement purposes in Japan. One stork of mixing tool produces a column shape of stabilized soil in a ground. By the series of productions, arbitrary shape of improved ground can be constructed by overlapping each columns. It is specified to complete the overlapping within 24 hours in order to ensure the tight connection of the columns. However, it can not be completed within the specific time in some cases due to bad weather or machine trouble, which causes a cold joint in the improved ground. In this study, the influence of the cold joint to the behavior of the block type improved ground is examined by a series of centrifuging model tests and FEM analyses. It is found that the ground behavior is influenced by the position of the cold joint, where the cold joint at the sea side shows a little influence to the behavior but one at the port side causes large decrease in the stability of the improved ground.

Sep 8, 2021

By David W. Martel, Tom George

"As part of the regional water authority review and upgrade of local dams a 35m x 5m x 3m wet soil mixed block was required for stabilisation of a dam wall toe in remote Victoria, Australia. Remote access, extremely poor roads and high mobilisation costs made more traditional CSM and deep mixing methods cost prohibitive. The dam required a redesign to raise the wall by 2.0m to increase water storage. Additionally, the dam required additional stabilisation to reduce the risk of liquefaction during an earthquake event. Soil testing indicated loose, cohesionless, high permeability soils to a depth of 3.0 to 3.5m across the toe of the wall. This resulted in high dam seepage through the toe of dam wall potentially causing the factor of safety during a seismic event to decrease to a dangerous level. A number of laboratory trials were completed to determine the mix ratio of cement required to improve the strength of the saturated, liquefiable soil.Wagstaff Piling was responsible for achieving the required soil/cement strength and mix depth on site. As the ground conditions were too soft for conventional soil mixing equipment, an excavator mounted Mitsui road header was modified to fit a 20 tonne excavator. A purpose built remote batching plant was set up on more stable ground approximately 200m from the wall and utilised for preparation of cement and water slurry for supply to the machine. As the ground was too soft to support the excavator, the progressively improved ground was used as the working platform. Both wet grab sampling and in situ testing was undertaken to determine the UCS of the improved soil. These results indicated several variations in the results due to size effects.1 INTRODUCTIONA small town in remote Victoria relies totally on its water supply from a small dam. The dam wall required stabilisation works by ground improvement as studies completed on the dam classified it as a high risk of failure under an earthquake event. In addition, the earth fill dam had high levels of seepage and poor control measures, requiring the dam to be upgraded to comply with all regulations.The relevant water authority engaged a contractor under a design and construct contract to complete the works. Wagstaff Piling was engaged as the Subcontractor to provide design and construction advice including the contract for the ground improvement works. Initial discussions involved CSM walls, cut-off walls and mass soil mixing solutions. However, due to the access restrictions for piling equipment, mass soiling mixing was the chosen method of ground improvement."

Jan 1, 2015