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By Dario Libano, Luis Carlos Tenuta, Juliano Penteado

"Subway Line Number 4 is one of the newest additions to the Rio de Janeiro subway network. Built for the 2016 Olympic Games, the 16 km (10 mi) subway line connects the south of the city, with the famous beaches Copacabana and Ipanema, to Barra da Tijuca, west of the city, where the Olympic Village and Park are located. This new line, which is estimated to cost USD 2.2 billion, is composed of six new stations: Jardim Oceanico, São Conrado, Gavea, Antero de Quintal, Jardim de Alah (JA) and Nossa Senhora da Paz Station.Brasfond participated in the construction of foundations and retaining structures for all the stations, and each presented unique challenges. This is not surprising considering the difficulties present in a highly-dense urban environment including utilities, nearby buildings, traffic limitations and noise.Of all the stations, JA Station was the most challenging to construct. It was located in the middle of an avenue between residential high rises supported on shallow foundations as well as below sea level in sands with high groundwater. The other five stations were located in small parks and squares, with no buildings in the immediate proximity.The interaction between designer, owner, and the general and foundation contractors during execution was key in safely reducing the construction schedule. This was significant given the unforeseen construction delays the client, Linha 4 Sul JV, faced due to permitting, utility and traffic relocation so that the owner could fulfill their final goal: making the line operational by the Olympic Games. The GeologyGeologically, the state of Rio de Janeiro is formed by Pre- Cambrian crystalline basement rock. Its geological formation is very old and comprises two major orogenic cycles, a Mid-Precambrian formation, called “Transamazonian” (Proterozoic Era), and an Upper-Precambrian to Cambrian called “Brasiliano” (Proterozoic-Paleozoic). The soil structure of the city of Rio de Janeiro is represented by a core of crystalline rocks, usually granite-gneiss, covered with a layer of residual soil and/or partially weathered rock.JA Station is located in a Rio de Janeiro neighborhood called Ipanema, between the Atlantic Ocean and Lagoon Rodrigo de Freitas. Local geology is composed of a superficial soil, consisting of medium to coarse grained sands. Top of rock varied significantly from 20 m (66 ft) deep on one side of the station to 33 m (108 ft) on the other. Water is at a depth of 3 m (10 ft)."

Jan 1, 2016

By Bao K. Le, Khang T. Truong, Masaki Kitazume, Toru Kobayshi, Long P. Le, Tanaka Hitoshi, Makoto Kamimura, Hoang-Hung Tran-Nguyen

"Earth levees constructed using dredged materials taken from a river along an earth levee have annually damaged in the Mekong Delta due to high void spacing in earth levees and floodwater. Sliding and internal erosion due to floodwater or piping are two key factors causing earth levees’ failures. This study proposed to apply Deep Mixing Method (DMM) to reinforce earth levees in the Mekong Delta, Vietnam. The DMM creates a soil cement wall or soilcrete wall having better engineering properties such as higher strength and low hydraulic conductivity than those of the in-situ soils. The DMM can be applied to reinforce earth levees with limit additional materials that provinces in the Mekong Delta are difficult to supply. The study investigates capacity of the DMM to reinforce earth levees in the Mekong Delta, Vietnam against annual floods. Seepage and slope stability analyses under various conditions were performed with various scenarios of earth levee’s body. The analysis results indicate that the DMM can create a wall that cuts off piping across earth levee significantly and can improve stability against deep sliding due to rapid drawdown of the floodwater.INTRODUCTIONThe Mekong Delta produces agriculture products of 50% of the whole country even though the Mekong Delta has an agriculture area of 30% of the country (Wikipedia 2014). Rice is the main product for the domestic demand and export. This is the main reason why the local people want to cultivate rice 3 times per year to increase the total rice product for export. To do that, the local provinces have constructed earth levees surrounding each area of 100-200-hectare against annual floods to protect rice fields, and farmers can grow rice in the whole year. There are thousands of kilometers long earth levees in the Mekong Delta, and the local governments have spent millions of US dollars to repair and to maintain their earth levees yearly (reports of Dong Thap province 2012; 2014).Earth levees in the Mekong Delta have often failed in flood seasons (e.g., from August to December), especially in Dong Thap and An Giang provinces – the two provinces confronting directly the annual floods from the Mekong River when the floods reach the Vietnam land. The main failure of earth levees is piping, and then causing collapse of some section of an earth levee. An earth levee was usually constructed by piling up dredged materials along a river with minimum compaction. Subsequently, floodwater flows through connected void spacing and washes out soil particles in the body of an earth levee slowly to create piping. Annual wet-dry cycles make the top clay layer swelling and shrinking to form cracks that can store rainwater to trigger sliding (whitlow 2001; Ton That Vinh 2003)."

Jan 1, 2015

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

"A hybrid shoring system consisting of cast-in-place soldier piles with Cutter Soil Mixing (CSM) infill panels was constructed for temporary support of a 19.8 m (65 ft) deep excavation in Vancouver, British Columbia, Canada. Deep Mixing (DM) was completed up to 9.7 m (32 ft) in fill, peat, wood waste and clayey silt with embedment in dense till, and soldier piles constructed through the dense till extending to below final excavation level. Two trial CSM panels were installed ahead of production to assist with developing the termination criteria of the CSM panels in the dense till. The constructed depth of the CSM panels was based on interpretation of real-time monitoring data obtained through the Bauer B-tronic system. Inclinometer monitoring data from two CSM panels and two soldier piles, as well as soldier pile survey target data was used to assess and monitor the performance of the hybrid shoring system throughout bulk excavation. The objectives of this paper are to provide an overview of the design and construction aspects of the hybrid DM shoring system and to present inclinometer and pile target data to demonstrate the lateral performance of the CSM infill panels and soldier piles. This paper also discusses the merits of using real-time monitoring data as part of the engineering decision-making process for validating CSM panel construction. BACKGROUND A hybrid DM shoring design was recently completed for a high-rise development in downtown Vancouver, British Columbia for temporary support of a five level basement excavation. Deep mixing was proposed by the excavation and shoring design-build team as the preferred method to construct infill panels between soldier piles because of the speed at which the shoring system could be constructed in variable fill, peat, wood waste and overburden compared with traditional secant piling methods. The development site is generally a truncated triangle in plan, with the longest side of the triangle being approximately 115.7 m (380 ft) long and the two shorter sides being approximately 71.6 m (235 ft) (Hybrid Shoring Wall 1) to 75.0 m (246 ft) (Hybrid Shoring Wall 2) long. The site is bounded by an existing bridge off-ramp structure along its longest side, and by city streets on the other two sides, as shown in Figure 1. The truncated section is approximately 16.8 m (55 ft) (Hybrid Shoring Wall 3) long. Due to project constraints, the hybrid DM and soldier pile shoring system was only proposed for the two shorter sides of the triangle and the truncated section. Traditional secant piles were installed for the longest side. This paper focusses on the hybrid shoring system. A typical detail showing the CSM infill panel with the soldier piles is presented in Figure 2."

Jan 1, 2017

By David A. Hart, Barry P. Osborn, Richard J. Totty, Ana T. Carvalho, Max B. Elliott

This paper addresses the experience designing and installing bored piles for the King’s Cross area. This includes continuous flight auger and rotary bored piles, with a range of diameters between 600 mm and 1200 mm, reaching a maximum depth of 56 m below ground level. Existing Network Rail Thameslink twin bored running tunnels are located directly beneath the subject plots. These tunnels have an external diameter of 6.6 m and the crowns of the tunnels are very shallow, in some cases just 10 m below the existing ground level. Some plots needed piles to be installed in close proximity to the tunnels, which required additional control measures and contingency plans. Pile verticality was monitored as the tip of each pile advanced and in-tunnel monitoring readings were verified and are presented. Lessons learned from designing, installing and testing the piles and monitoring the tunnels are addressed in this paper.

May 1, 2022

By Kevin Kuhl

With the destruction of the US-90 Bridge spanning St. Louis Bay by Hurricane Katrina, the State of Mississippi awarded its first major design-build contract in order to have a completed four-lane bridge in a period of less than two years. The structure consists of 76 pre-cast concrete beam spans with a total bridge length from Bent 1 to Bent 77 of 11,124 ft (2.1 miles). All 77 bents are founded on pre-cast, pre-stressed concrete piles and consist of two foundation types: pile bents and water line footings. A total of 53 pile bents were utilized where the deck is less than 52 ft above the water. Further divided, 10 pile bents, supported by 24 in. square, solid piles, are located on land. The remainder of the pile bents are located within St. Louis Bay and supported by 36 in. square, voided piles. All the waterline footings are supported by 30 in. square, voided piles. In total, 138 -24 in., 437 -30 in., and 463 -36 in. piles support the structure. Production pile design was based upon information gathered from the subsurface investigation, design soil profile and 23 out-of-position test piles. Verification of the design was established by monitoring the first production pile driven at each bent using the Pile Driving Analyzer. Particular challenges included highly variable coastal deposits, loads in excess of 1600 kips per pile and a compressed construction schedule. Initial drive capacity of a portion of the production test piles was less than expected resulting in a minimum 14 day setup. Following the setup period, restrikes were necessary to verify capacity. Project production piles ranging from 50 ft in length to in excess of 160 ft in length were used to achieve the required resistance. This paper includes a brief overview of the foundation design and indicator test pile program. The main objective is to provide a summary of the quality control procedures including establishing the driving criteria for each bent and to present issues that arose during production pile driving and the solutions that followed.

May 11, 2007

By Richard J. Hartman

This presentation identifies some of the more common problems associated with cofferdam construction. After the various problems are identified, they are briefly explained and possible solutions and preventive measures are noted. Photographic slides used during the seminar illustrate the conditions. This discussion is limited to cofferdams which are braced structures excavated inside to allow access for construction. The common procedure is to drive sheet piling and then alternatively install bracing and excavate. They can be located either on land or in water. Loads are applied by soil, water, surcharge pres-sure, eccentricities, and impact loads. The loads are resisted by the sheet piling, the bracing, and the soil below the bottom of the excavation; each of these three components must be capable of resisting the applied loads.

Jan 1, 1987

By R. J. Yan

There was a plant equipped with a 32000t Hydraulic Press to be built, under which a box foundation of 22.5m x 15m x 14.25m (depth) with a base slab of, varying thickness was proposed. The subgrade reactions, bending moments and settlements needed to be determined by means of in-situ model test. A model of the same materials as the prototype scaled to l/10 was embedded in-situ with simulated depth in the bedrock. A lot of data obtained from 39 bench marks, 32 elongation measuring points, 30 couples of electric resistance strain gauges and 24 pressure cells attached to the model foundation enables all the quantities required to be found out. Since it was put into operation, the settlements measured has reasonably agreed with the test results and the foundation has been in good condition.

Jan 1, 2010

By Richard T. Stain

"In 2001, a pile trial site was established at Limelette in Belgium consisting of 25 displacement screw piles and 5 driven pre-cast piles. Interested parties were invited to participate in a pile prediction event, whereby they would submit predicted static load test behaviour in the form of load settlement plots. These predictions could be based on soil investigation results supplied by the organizers, or dynamic load test measurements.Following the submission deadline, the organisers released the results of static load tests for comparison.Of all the six participants, including Statnamic, the SIMBAT method was independently accredited with achieving the best predictions.This paper examines at the differences between SIMBAT and other systems, and presents the correlations from the Limelette trial.INTRODUCTIONThe Belgian Building Research Institute (BBRI) initiated an ambitious research programme involving the construction and testing of some 60 trial piles spread between two sites, a clay site at Sint Kateline Waver and a sandy site at the BBRI headquarters at Limelette. The project was financed largely by the Belgian Ministry of Economic affairs. (ref 1.) This paper refers only to the second site.At Limelette, six different types of displacement pile were installed: one driven pre-cast and five cast in place screw piles - Atlas, DeWaal, Fundex, Olivier and Omega. A detailed site investigation was carried out including in-situ and laboratory tests.An international pile capacity prediction event was publicised, participants being invited to predict static pile behaviour. Predictions could be based on:"

Jan 1, 2005

By Brian Metcalfe, Kord Wissmann, Gianni Martinez

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

May 1, 2022

By Jean-Louis Briaud

The following is a summary of a very recent report prepared at Texas A&M University for the National Cooperative Highway Research Program and entitled "Downdrag on Bitumen Coated Piles". Anytime the soil settles more than the pile, downdrag or negative skin friction will develop. The load in the pile increases with depth up to a certain point and then decreases down to the pile point. This phenomenon has been quoted as being the number one culprit for deep foundation failures. In Chapter 1, an introduction to downdrag is given. The most common criterion for downdrag is to consider it in design as soon as the settlement of the soil surface after pile driving exceeds 0.5 in. Coating piles with bitumen is an effective way of reducing downdrag forces and therefore allows to use smaller piles for the same load. This results in cost savings. Coating piles with bitumen increase the cost of piles by about 33% and therefore the decision to use bitumen is generally based on economic considerations.

Jan 1, 1989

By Graeme Smart, Thomas Fiala

"Yorkville Plaza II, a 40-storey signature condominium residence, is scheduled to open on Avenue Road in Toronto’s prestigious Bloor-Yorkville neighbourhood in spring 2017. In close proximity to Toronto’s subway system, the new tower requires six levels of underground parking, founded in wet, silty sand.Isherwood Geostructural Engineers (Isherwood) was retained in April 2012 by developer Camrost-Felcorp to provide a shoring and excavation solution to address the challenging site conditions. A 31-storey upscale residential building under renovation with three levels of parking, owned by Camrost-Felcorp, flanks the site on the north. Situated on the eastern border is a 7-storey building with three levels of parking. Avenue Road, a four-lane arterial road that brings heavy commuter traffic into downtown Toronto, runs along the western border, and on the southern border of the site is a busy City road that brings traffic into the popular Yorkville area. The tunnel for the Toronto Transit Commission’s (TTC) overburdened east-west subway is located 14.5 m to the south, running below an existing 26-storey neighbouring building. Electrical and communication utilities (Bell) are closely located along the southern side. Non-documented existing excavation shoring, installed in the early 1970s, on the southern and western sides compounded the difficulties presented by the TTC tunnel.This paper presents the unique, non-conventional hybrid shoring solutions Isherwood developed to address the challenges presented by the site, as well as other complications that surfaced during the project: non-encroachment requirements (no tiebacks) beneath uncooperative neighbours, tight geometry to install shoring, and Toronto’s two coldest winters in decades.THE PROJECTBecause of circumstances associated with this site, for this project Isherwood designed two unique shoring walls which drew on their experience and expertise they had gained over the last 40 years. The following is the story of this site:Yorkville is an affluent neighbourhood in the heart of Toronto with a vibrant mix of high-rise towers, residential homes, tony restaurants and flagship shops. The development requires six levels of underground parking (a 20m deep excavation), with three levels undermining the high-rise buildings to the north and east and extending into wet, silty sand.Isherwood was retained in the spring of 2012 to design the excavation shoring. Isherwood’s scope also included field support, design, verification and monitoring. Finite Element Analysis was employed to confirm Isherwood’s design and anticipated movement of the south shoring wall and the TTC subway tunnel.The existing site was severed in two, with the proposed condominium tower slated for the southern portion. On the north half of the site stands a 31-storey building (Yorkville Plaza I at 21 Avenue Road), with three levels of underground parking, sitting on belled caissons which were one foot from the back of the proposed shoring wall so this would have to be considered in relation to the design and drilling methods. Constructed in the early 1970s, Yorkville Plaza I is currently being converted from the Four Seasons hotel to luxury condominiums by Camrost-Felcorp. To the east, directly adjacent to the proposed shoring, stands a 7-storey building (164 Cumberland Road) with three levels of parking, supported on spread footings founded on stiff clayey silt. The tunnel for the TTC’s busy east-west subway, a double box structure built by cut-and-cover in the 1960s, is located 14.5 m to the south, 9 m below grade, and running below an existing 26-storey building. Bell fibre optic communication cables and electrical lines, along with storm and sanitary sewers, are situated on the south and west sides of the site, leaving limited room to install shoring. Due to the heavy volume of commuter traffic on the four-lane arterial road (Avenue Road) to the west, site access and lane closure were not permitted here."

Jan 1, 2015

By John C. Niedzielski

The existing US-70 Bridge over the Gila River at Bylas, Arizona is planned to be replaced due to its current poor condition. The replacement bridge is planned to be a 15-span, 1,904-foot (580 meter) long bridge, the third-longest bridge in the state highway system. Within the Gila River floodplain, granular alluvial soil is underlain by cohesive lacustrine soil; bedrock was expected due to nearby terrain but not encountered within the geotechnical exploration depth of 166.5 feet (51 meters) or less. Based on the anticipated loading conditions, design scour depths and the soil conditions, the full structural loads are carried by large diameter drilled shafts; therefore accurately determining the axial capacity of the proposed drilled shafts has important practical and safety implications. The conventional methods for axial capacity determination may be overly conservative to use for design in the site?s layered granular and hard clay soils. An Osterberg cell load test was performed to obtain detailed information on the load transfer from the drilled shaft in side friction and base resistance to allow optimization of the bridge foundation design. The full-scale field test played a significant role in the design of the project?s deep foundations, notably, by incorporating the specific subsoil properties and consequently, an exact prediction of the load-settlement behavior under loading. This paper provides the results of the geotechnical site investigations, drilled shaft load testing procedures, and shaft load distribution from the load test results. Comparisons were developed between predicted axial capacities of drilled shafts using several design methodologies and the axial capacity measured from static load testing. The load test results showed that underestimation of the axial capacity is evident using conventional methodologies. The exact prediction of the load-settlement behavior under loading combined with a site-specific design approach, resulted in a substantial reduction of foundation costs due to reduced drilled shaft dimensions.

By Kazunori Matsushita, Masaru Sakakibara, Kenji Harada, Naotoshi Shinkawa, Mitsuo Nozu

The Sand Compaction Pile (SCP) method has been widely used as a typical countermeasure against liquefaction in Japan, and its effectiveness has been confirmed in many case histories of damages caused by the past large-scale earthquakes. A series of studies were conducted to evaluate the effectiveness of the compaction method and other factors, if any, in sustaining a seismic force that is greater than the assumed one and caused no damage. Based on the results of these studies, the Architectural Institute of Japan (AIJ) has indicated in its “Recommendations for Design of Ground Improvement for Building Foundations” published in 2006 that the liquefaction resistance ratio (tl/sz) of the composite ground, which consists of sand piles and surrounding compacted ground, is higher than the RL calculated by using the SPT N-values of the ground in-between the sand piles. In this paper, statistical analysis of safety factor against liquefaction, FL, was performed by using the SPT N-values of ground in Port Island and Rokko Island which were both fully reclaimed islands in Kobe city during the 1995 Hyogo-ken Nambu Earthquake (classified as intense shaking) and, together with the consideration of relative settlement, resulted in tl/sz of the composite ground being 1.5~2.5 times of tl/sz of the soil in-between piles after improvement. Furthermore, the liquefaction resistance curve of SCP-improved sites obtained from the relationship between SPT N-values and cyclic shear stress ratio during the 2011 off the Pacific Coast of Tohoku Earthquake, which was regarded as long-duration earthquake, was plotted to the left side of the curve originally proposed by Japan Road Association. Thus, the liquefaction resistance of the improved ground was found to be higher than that of the natural ground, even for the same SPT N-values, verifying the validity of the AIJ recommendation.

Jan 1, 2017

By Brian Wilson, Megan Atkinson, Richard Diggle, Nathan Sweeney

"Ruskin Dam, located near Mission, British Columbia, was constructed in 1929 and 1930 and comprises of a concrete gravity dam structure founded on bedrock. At the right abutment, which consists mostly of dense to very dense sands and silt, the dam abuts against overburden soils, and connects to a cutoff wall system consisting of sloping concrete slabs. Significant seepage and piping issues were encountered during first filling of the reservoir in 1930. In 2012, BC Hydro, the owner of the dam, awarded a contract for the construction of seepage control measures at the right abutment, including construction of a plastic concrete cut-off wall extending upstream of the dam, a plastic concrete seepage training wall extending downstream of the dam, tie-in of the new cutoff wall to the dam, consisting of jet grouting of the soils adjacent to the dam to allow for the construction of the special cutoff connecting the cutoff wall to the dam, and construction of additional jet-grouting ground improvement downstream of the dam.Integral to the upgrade was the requirement for the special tie-in cutoff wall, consisting of a highly flexible, impermeable membrane to connect the concrete dam to the new, 1 m thick plastic concrete cutoff wall. The tie-in extends vertically into bedrock through the dam and jet grout columns constructed adjacent and beneath the overhanging portion of the dam at the right abutment. The membrane is required to survive the anticipated earthquake induced deformation between the dam and the abutment soils.This paper describes the processes used to develop a material suitable to meet the specified flexibility and permeability criteria, as well as the innovative construction techniques utilized to construct the slot and place the bituminous material within it. The final dimensions of the slot were in the order of 7 m long by 25 m deep by 0.17 m wide. The bituminous material was placed under a head of water which was required to maintain stability of the slot, and was placed at temperatures in excess of 120 degrees Celsius."

Jan 1, 2017

By Roger A. Bullivant

As the UK's foremost domestic foundation underpinning contractor over the last 25 years it has become abundantly clear that the size of the repair market, some £500m per annum is a significant waste of resource and cost. To experience this scale of foundation failure in mainly new construction less than 20 years old is unacceptable. This is being further endorsed by our contracting experience in the USA over the last 10 years. Our foundation repair systems are mainly based upon the use of driven mini piles and it was considered appropriate that this type of pile should be upgraded and used on new build construction where the ground was marginal or bad.

Jan 1, 1995

By Mike Muchard

STATNAMIC load testing augmented with embedded instrumentation has been successfully used to obtain structural and geotechnical design information on large diameter spun cast concrete cylinder piles on many large marine construction projects. The paper focuses on one particularly interesting large marine project involving a new bridge to St. George Island, Florida where instrumentation and STATNAMIC load testing was used in conjunction with static load testing on high capacity piles. The information presented includes embedded instrumentation measurements taken during pile fabrication (post-tensioning), during pile driving, during static load testing, and STATNAMIC load testing. As much of this data is the first of its kind on concrete cylinder piles, it is exciting to present the foundation industry with this additional insight as to the behavior of this pile type and the accuracy of the methods used to test them.

Jan 1, 2013

By D. K. ] [Gupta

The Foundations of the Shear keys and alround cut off for Power House -IV of the Western Yamuna Canal Hydroelectric Project at Bhudkalan, Haryana were to be laid at a depth of 26M below the N.S.L and 24.4M below ground water table. The foundation of the drainage sump was to be laid at still higher depth, Viz 29.OM below N.S.L. The Sub soil at the site consisted of Gravel with some amount of sand. The laying of the foundation at such a great depth, at a large depth below the ground water table and that too under such difficult sub-soil conditions encountered a large no of Geotechnical problems-viz excessive seepage, side slope sloughing and sand boiling during excavation. Under the circumstances at the site, the modified foundation construction procedure i.e a battery of M. S. Troughs was placed in flowing water conditions and concreted thereafter, resulting in a sizable cut in dewatering and reducing a significant amount of time and cost of construction affecting a saving of crores of rupees at the state exchequer. Sheet Piling was used to prevent side sloughing in the foundation pit.

Jan 1, 1996

By Emilie Lapointe, Fernando Famania

"A reliable determination of the in-placed cement factor, as defined by mass of cement over volume of final element of treated soil, allows the optimization of cement usage to achieve treated soil requirements. Cement determination tests were performed on soil-cement samples, both fresh (as per ASTM D5982) and hardened (as per ASTM C1084). This paper reviews the calibration work required for the D5982 determination of cement content by the heat of hydration method used on soil-cement samples obtained by wet-grabbing. Using the correlation curves in the field provides a rapid assessment of cement content hence optimizing the cement injection rate to match laboratory tests previously conducted. Cement determination tests on hardened soil-cement specimens from wet-grabs and cores were performed using the oxides method. Samples, both cored and wet-grabbed, were tested in a given cement-treated element, and in different soils to inform on the expected variation in cement content from field installation. Results indicate that both cement determination methods are valid for forensically determining cement contents and that they provide better assessment than the conventional field reporting methods. The methods can be used to optimise the cement usage as well as for Quality Assurance, especially when coring quality is poor.INTRODUCTIONThe degree of improvement, and inherent strength, which is attained in a deep-mixed soil is a function of many factors. The binder type, the existing soil, the mixing conditions and the curing conditions are the categories of factors influencing the strength of a given cement-treated soil as agreed by the deep mixing community and as summarized by the Coastal Development of Technology [CDIT] (2012). Given a site with existing soils and conditions requiring soil improvement using a given binder, the designer and/or contractor can control the mixing conditions. Mixing conditions are inclusive of the degree of mixing, mixing duration and the quantity of binder. Once a deep mixing method has been chosen to mix optimally the in-situ soil, the quantity of binder is the only remaining factor to be optimized. The quantity of binder, in the construction industry is commonly referred to as the field binder factor [ar] and defined by the mass of binder over the volume of soil treated with kg/m3 as unit. In research, the quantity of binder is referred to as the binder content [Cc] and expressed as a ratio of the mass of binder over the mass of dry soil mixed."

Jan 1, 2015

Jan 1, 1991

By Michael Perlow Jr

A modification of the original Davisson Offset Limit (DOL) is presented for drilled foundations using soil quake (QDOL) factors ranging from 2 to 6. A further modification of the Davisson Offset Limit has also been developed using helical pile soil quake values (HDOL) based upon helix diameter. In addition, the initial tangent slope (IS) of the pile load test displacement curve is used in lieu of the calculated elastic slope (ES) to eliminate many of the uncertainties associated with determining the drilled foundation pile elastic modulus. The QDOL and HDOL load test methods do not require any graphical interpolation and provide easy simple ultimate pile capacity interpretation methods where drilled foundation pile load tests are not carried to plunging failure. Drilled foundation and helical pile load test case studies are presented to demonstrate the use of the modified soil quake QDOL and HDOL Methods.