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By Stephen Buttling

The construction of a water treatment plant in Dandenong, Victoria, required detention tanks and a pumping well. The design provided by the Engineer used conventional rectangular cast-in-situ reinforced concrete walls within a sheet piled cofferdam. It was decided to construct the tank and shaft using the diaphragm walling technique as an alternative and, for the shaft in particular, this involved a “circular wall”. Except where cutters are used, joints in diaphragm walls have to be made between colinear panels, with waterproofing provided by dumb-bell water stops held within trapezoidal forms. This means that the circle has to be approximated by a number of straight sides, which in this case was twelve. The requirement was to design the reinforcement for the strange shaped panels. Finite element analysis was used, in the first stage using an axisymmetric model to determine the profile of lateral earth pressures with depth. In the second stage a horizontal slice was modelled, without gravity which normally operates from the top to the bottom of the page. By considering appropriate possible earth pressures at different depths, a range of bending moments was calculated, which was used by the structural engineers to design the rebar. The tanks were successfully constructed, and inclinometers were installed in both the tank and the shaft. Measured deflection profiles show that the design was moderately conservative.

Nov 1, 2022

By Chu E. Ho

This paper reviews the design of jet grouting at re-entrant corners of excavations where the diaphragm wall and secant pile wall installation were interrupted by existing utilities in the streel sidewalk. Jet grout blocks were formed to seal the gaps in the walls for excavation support, consisting of four to six columns in clusters. Jet grouting was performed around an electrical duct bank which had to be maintained. Jet grouting was executed through stratified soils using various combinations of jetting parameters for different soil strata. The installation sequence and age of the neighboring columns within a cluster will affect the jet’s ability to form subsequent columns. When jet cutting is limited next to hardened grout columns or embedded obstructions (such as diaphragm walls or secant pile walls in this case), the specific gravity (SG) of spoils would be reduced and tend toward the value of the injected grout SG. The magnitude of spoil SG is also influenced by the variability of the grout mix supplied. Specific Gravity Ratio (SGR) defined as the ratio of spoil SG to the actual grout SG at the time of jetting can be used as an indicator of successful treatment, with SGR > 1.0 indicating effective soil erosion. Verification coring and testing were implemented to confirm target column diameter and strength of grouted soils have been achieved.

May 1, 2022

By Aaron L. Sacks, David R. Good, Srinivas Yennamanda, Joseph K. Carey

Construction of Parcels 6 and 7, the second phase of The Wharf, began in 2019 and geotechnical construction was completed by December 2020. The overall project consisted of horizontal site, parks, and office buildings. The Wharf’s Phase 2 development includes approximately 1.2 million ft2 (110,000 m2) of above-grade construction including five multi-story, mixed-use buildings constructed over up to three levels of underground parking. The site is located between the WMATA Green Line Tunnels to the north and the Washington Channel to the south; it is bisected by a 108-in. (2740-mm) diameter DC Water outfall pipe. This arrangement, along with very difficult ground conditions, created challenges in the geotechnical design and construction. The support of excavation for this complex project required several different methodologies, including sheet piles, soldier piles, displacement piles, tiebacks, deep foundation anchors, jet grouting, and internal bracing with multi-tier rakers. Ground improvement was also required for support of spread footings in soft soils over the garage footprint. Underpinning of the active 108-in. (2740-mm) diameter DC Water outfall pipe running on a north/south alignment through the center of the site between the two garage structures was also performed. Since portions of the support of excavation are below the groundwater table, an extensive pre-excavation dewatering program was necessary and was separate from the foundation package. On the north side of the project, support of excavation (SOE) was required on a curved alignment, offset approximately 10 ft (3 m) from the outbound Green Line tunnel. Due to the proximity of the tunnel, a stiff, near-zero displacement wall was required. A portion of the buildings extend over the tunnels, imparting load to the tunnels to approximately restore original overburden loads excavated for the basement space. The building foundation is a 3 to 4-ft (0.9 to 1.2-m) thick mat slab anchored into the Potomac clay formation. Continuous movement monitoring of the tunnels was performed by an automated system. This paper describes the design and construction of the SOE and foundations for this high-profile project, which required collaboration between the Owner, Engineer, Construction Manager, and Specialty Geotechnical Contractor to solve many challenges.

Oct 1, 2022

By Pete Howell, Patrick Granitzki, Alicia Plinio, Janitha Batagoda

The New York City Housing Authority (NYCHA) Red Hook Houses was subjected to damage during Superstorm Sandy. As a result, the NYCHA has an ongoing project known as Restoration Associated with Sandy Recovery Program to improve the resistance against future storms. The specific project included 28 residential buildings and several service buildings within the Red Hook Development. The subsurface conditions within the eastern portion of the site included existing fill material underlain by varying stratums of very loose, loose and medium dense silty sands followed by very soft to medium stiff clay or dense silty sands. The western portion of the site included existing fill material, very loose to medium dense silty sands and organic clayey silts underlain by very soft to medium stiff sandy silts. Based on the geotechnical report, a conventional driven steel pile system was specified containing two pile depths. As part of the project bidding, an alternative pile type was recommended and analyzed to provide quicker installation, reduce vibrations, reduce noise, and provide relatively large cost savings. Due to relatively high lateral loading, an innovative double steel casing drilled displacement piles was proposed as the alternative pile option. Field testing proved the piles capable of the required project capacities and the use of drilled displacement piles as the best alternative for the project and accepted by the NYCHA.

Oct 1, 2022

By Madhu. P, Srinivas. K

Measurement of thermal properties like thermal conductivity, thermal resistivity, heat capacity and thermal diffusivity for materials, it plays a crucial role in a wide range of various civil and electrical engineering projects, and many field applications like building’s basement, power generation, underneath soil heating, wastes from nuclear as well as thermal plants, and buried cables. Thermal conductivity of soil depends upon various geotechnical parameters such as type of soil, moisture content, particle size distribution, density, and compaction characteristics. Earlier studies, the measurement of thermal conductivity of soil by incorporating the heat source methods. Thereby expensive and time taken to conduct in laboratory as well as field measurements. The thermal conductivity is determined by fabricated probe and used in this work. Fabricated probe was calibrated with glycerin. The thermal conductivity of the soil increases as the water content and density increase because these factors are majorly influencing and water has a higher thermal conductivity than soil minerals, and grain to grain contact increases as density increases. therefore, Thermal conductivity is higher in coarser soils than in finer soils. The details regarding of this work as explained in this paper.

Sep 1, 2022

By Sarah Ramp, Daniel V. Cacciola, Justin Labrozzi, Shafiq I. Siddiqui, Faisal Ahmed

"Construction of embankments up to 34 ft in height for twelve ramps and roadways needed for the New Jersey Turnpike Interchange 14A project required ground improvement. The subsurface conditions, consisting of up to 30-ft thick layer of highly-compressible peat and organic soils, would induce up to 8 ft of primary and 4 in. of secondary consolidation settlements to the embankments over a long period of time. Innovative ground improvement solutions were needed to meet unique challenges posed by the poor subsurface conditions, space and existing utility constraints, aggressive construction schedule, and massive size of the project. A variety of ground improvement techniques were utilized in six different zones of the embankments to limit settlements and ensure stability of the embankments. These techniques included preloading with surcharge and prefabricated vertical drains (PVD), load balancing using light weight fill, and concrete column rigid inclusions (RI). Additionally, augercast piles with load transfer platform were used under an existing bridge with low vertical clearance. An innovative approach consisting of preloading with surcharge and PVDs followed by installation of RI was needed in one of the six embankment zones with the worst, i.e., very soft, soil conditions. The design of the RI was performed by a specialty ground improvement contractor (SGIC) using Plaxis 2D and 3D softwares. The performance of the ground improvement systems was verified and monitored by load tests and instrumentations. This paper presents details of the ground improvement design, construction, monitoring results, and lessons learned, with a focus on the RI.INTRODUCTIONNew Jersey Turnpike Interchange 14A is located within the cities of Bayonne and Jersey City, in Hudson County, New Jersey. The New Jersey Turnpike Authority (NJTA) identified Interchange 14A as an area of mass congestion in need of redevelopment to improve the increasing demand of traffic and roadway safety. The New Jersey Turnpike Interchange 14A project included the construction of twelve (12) new roadways, in addition to the construction of four new bridges. The limits of construction are shown in Fig. 1.The fill height required to construct the roadway embankments varied from 2 to 34 ft. The proposed embankment side slopes varied from 6H: 1V to 2H: 1V. Additionally, mechanically-stabilized-earth (MSE) walls were utilized to retain the embankment fill along some segments of the roadways. As shown in Table 1, the proposed roadways were divided into six zones, based on location, subsurface condition, and embankment height."

Jan 1, 2017

The development of Augered Cast-In-Place (ACIP) piles started in the late 1940's when several projects were performed by Intrusion-Prepakt, Inc. utilizing various techniques to place the piling. On some projects, a grout pipe was placed down the augered hole after the auger was withdrawn, and structural grout was pumped into the hole until grout appeared at the surface, after which the grout pipe was withdrawn. In some instances coarse aggregate was placed after a grout pipe was in place, and then the grout was intruded into the coarse aggregate, making a pile using the preplaced concrete method. Another method of forming augered piles used a system of driving or drilling a grout pipe through soils adjacent to the auger once the auger was drilled to the bottom elevation. The tip of the grout pipe was placed in close proximity to the tip of the auger. As the auger was withdrawn, grout was pumped through the grout pipe filling the augered hole from the bottom. After grout was observed at the surface, the grout pipe was withdrawn. In 1951, a patent was applied for by Raymond Patterson describing the above techniques along with a technique for placement of grout using a hollow stem auger and a removable plug or lead bit at the tip of the auger. The expendable plug or lead bit was removed by using grout pressure. The patent was granted in 1956. Around this same time other augered piling con-tractors began operations under licensed arrangements.

Jan 1, 2003

By Alessandro Bertero, Stefano Valagussa, Filippo Maria, Wesley Schmutzler, Leoni

"Abstract The Deep Mixing Method (DMM) represents a viable solution to improve the adverse geotechnical properties of foundation soils. Differences and the importance of performing pre-construction laboratory and field tests will be highlighted. Comparative analyses and interpretations between the various lab and field stages, along with accumulated information about soil properties and QC results, allowed fine-tuning of the production parameters throughout almost the entire project.Two projects where the US Army Corps of Engineers selected the Deep Mixing Method (DMM) for the required stabilizations, and a third project completed in Italy, will be illustrated:•,?the LPV 111 Project (New Orleans - LA – USA); DMM was used for groundimprovement/foundation strengthening and consequently stabilize and support the burden of the new levee.•,the Rio Puerto Nuevo Project (San Juan - PR - USA); DMM was applied to improve the soils adjacent to a 90” forced sewer main relocation and to improve the soils for the base of a new drainage channel•,the new Italian high speed railway project (Florence Italy); DMM technology was applied to realize a a TBM break in/break out, foreseen originally by jet-grouting.IntroductionThe Deep Mixing Method (DMM) represents a viable solution to improve the adverse geotechnical properties of foundation soils. The effectiveness of working parameters depends largely on the physical and mechanical properties of the soil to be treated. Therefore, well designed laboratory and field test programs, aimed to disclose the interaction between the site-specific soils and the mixing parameters, are essential to achieve the desired end product."

Jan 1, 2014

By Lorie M. Dilley

Alaska Village Electric Cooperative (AVEC), an electric utility cooperative providing power to 51 Alaska villages, has made a concerted effort to install wind turbines in the villages they serve in an effort to mitigate the growing costs of electrical power generation. The subsurface soils in several of these villages consist of sands and silts with ground temperatures of between 30°F and 32°F. The presence of warm, degrading permafrost in three of the villages has required innovative foundation designs, including the use of helical piers and piles to support steel and concrete wind turbine foundations. The design of the deep foundations had to account for the effects of degrading permafrost likely resulting from observed climate change patterns. Uplift forces imposed on the foundations were approximately 100 kips per pile. Uplift pile load testing was conducted on the installed piers and piles in order to determine the actual working load that each pier or pile could sustain. In addition, pile driving analyzer testing was conducted on several piles installed in the permafrost and compared to pile load tests. Results indicated that the installed piers and piles achieved the necessary capacity with sufficient factors of safety. Thermosyphons were installed near the foundations in order to limit the effects of climate change on the permafrost. The two to four wind turbines in each of the three villages are currently operational. Refinement of the design based on the pile testing from the first village to the third has decreased the cost of the tower foundations and improved our understanding of designing for warm, degrading permafrost.

Jan 1, 2010

By Sastry Putcha, Santosh Mummaneni, Swamy Avasarala, Vamshi Vemula

"This paper presents the results from a case study on the comparison of two strain acquisition instrumentation technologies, Geokon rebar strainmeters and Embedded Data Collectors (EDC) for the DC Water Main Pump Station project, in Washington D.C. These two instrumentation systems were installed by AVER in a single 18-inch (0.45 m) diameter augercast pile (with one-1.25 inch (3.175 cm) dywidag bar) at critical locations to determine the load transfer mechanism and establish a comparison between strain/load measured with these two systems along the pile. A quick static load test was performed on the test pile as per ASTM D1143 standard.Prior to the installation of the pile, a 24-inch (0.6 m) diameter outer casing was installed to the proposed cutoff elevation of -22.5 feet (-6.85 m) to discount the frictional resitance within the upper overburden zone. The pile was then drilled through the outer casing to the tip elevation of -65.02 feet (-19.8 m) with inner casing within the overburden zone. Strainmeters along with EDC were installed on dywidag bar at various locations and then wet set into the concrete following auger retrieval. The loads measured with EDC and Geokon sensors were within 15% percent of each other.PROJECT BACKGROUNDProject Background & Requirements:Like any other foundation piles, augercast piles are extensively used in the public and private sector structures in the United States for many years. It is a common practice to perform static compression (ASTM D1143), tension (ASTM D3689), and lateral load tests (ASTM D3966) depending on the project requirements. In recent years, embedded strain sensors, manufactured by Smart Structures, USA has gained prominence for its use to collect both static and dynamic measurements for driven piles. In addition, AVER has successfully used EDC for collecting long term static measurements for an abutment drilled shafts for I-95 Hotlanes project in Virginia, USA.Geokon sisterbar strain gages are widely used in the foundation industry to monitor the load transfer mechanism within pile foundations throughout the world. As the Geokon strainmeters are vibrating wire and are welded to a sister bar, there is often a debate within the engineering community with regards to what modulus to use when converting measured strains to loads. EDC sensors, unlike Geokon strain gages are embedded directly into the concrete and therefore do not have the same concern."

Jan 1, 1900

By William M. Tanner, Daniel C. Brahana

"A drilled pier foundation was originally designed to support the proposed G. Wayne Clough Undergraduate Learning Commons on the campus of Georgia Tech in Atlanta, GA. Reflective of the site geology, the original drilled pier foundation was divided into a Northern and Southern portion with an allowable end bearing capacity of 60 ksf and 100 ksf, respectively. After initial pricing on the original design, several value engineering options were submitted that featured changes to the original design capacity and construction method. The project team selected the value engineering option that involved conducting an Osterberg Load Cell test to assess end bearing of the site bedrock and skin friction. Results of the Osterberg Load Cell test justified increasing the allowable end bearing capacity of the site bedrock to 100 ksf in the Northern portion and 125 ksf in the Southern portion. Considering the final foundation design and Osterberg Load Cell test program, a net savings of approximately $259,000, or approximately 34%, was obtained over the original design.Project BackgroundThe G. Wayne Clough Undergraduate Learning Commons (CULC) is a 5-story academic building on the Georgia Tech campus in Atlanta, Georgia. The CULC was completed in 2011 and consists of a concrete frame structure supported on a drilled pier foundation.After pricing of the original drilled pier foundation design, several value engineering (VE) analyses were performed by the foundation contractor in an effort to demonstrate the potential for a reduced foundation cost. The VE analyses focused on variations in design assumptions, as well as construction techniques. This paper presents a case study that demonstrates how the value engineering process can be used to reduce foundation costs.Site Investigation and Subsurface ConditionsThe CULC building site is located within the Southern Piedmont Physiographic Province, an area underlain by metamorphic and igneous rocks. McConnell and Abrams (1984) indicate that the site is located at the boundary between two distinct geologic formations. The Northern portion of the site is underlain by the Wahoo Creek Formation while the Southern portion of the site is underlain by the Stonewall Formation. The following paragraphs briefly describe the geotechnical investigations performed by the project geotechnical engineer (GE) for the CULC."

Jan 1, 2015

By Lee R. Buhagiar

As a result of the increased seismic risk and the highly variable geology of Christchurch, finding costeffective foundation solutions has been a challenge for the Canterbury rebuild. The soil profile in Christchurch comprises both terrestrial (Springston Formation) and marine (Christchurch Formation) alluvial deposits with a high groundwater table. The result is a highly variable and interbedded soil profile which is prone to liquefaction and static settlement. Vibro-replacement stone columns are very effective in mitigating liquefaction in clean sand. However, the author’s experience has shown that vibro-replacement stone columns are also effective for treating silty and soft soil layers. Vibroreplacement stone columns can be used to treat these soft soils by increasing the composite soil stiffness and providing a load transfer path to the underlying dense soils. Another challenge encountered in the Canterbury rebuild is the cost of redevelopment of brownfield sites with contaminated fill. The costs of disposing this fill often make projects too expensive. Vibro-replacement stone columns have been used successfully to treat contaminated fill, providing a treated soil profile with uniform performance and reducing the cost of disposing of contaminated fill. This paper looks at several case studies in Christchurch, with highly variable soil profiles, where vibro-replacement stone columns have been used successfully to treat multiple soil layers, from contaminated fill to silty soils and soft and non-liquefiable silt.

Nov 1, 2022

By Seth K. Martin, Tony Nichlany, Alan R. Poeppel, Konstantinos Syngros

"This paper presents a case study on bored pile construction in challenging karst conditions below a supertall building in Kuala Lumpur. Innovative design and construction techniques helped keep the project moving through very difficult and unpredictable geological and drilling conditions. The development encompasses about 12,400 square meters and includes a 77-story tower, a 59-story tower, a five-story podium, and four contiguous basement levels. The site is underlain by a residual soil derived from a siltstone/claystone (the Kenny Hill formation), then limestone bedrock. Subsurface conditions are relatively uniform within the Kenny Hill and highly variable at the limestone surface. Extreme cases included 40-meter-tall underground caverns, 40-meter-tall pinnacles, and a 50-meter-tall underground rock ledge. Local piling practice in Kuala Lumpur involves deriving pile capacity entirely in the Kenny Hill formation to avoid the unpredictable limestone surface. However, the massive tower foundation loads and relatively shallow bedrock required the piles to be socketed in the limestone. The 77-story tower will be supported by 2.0- and 2.2-meter-diameter bored piles 50 to 100+ meters long, socketed in limestone, with working loads between 40 and 70 Meganewtons. Two Osterberg-cell load tests were used to develop a site-specific rock socket skin friction correlation with RQD. Exploratory rock probes were drilled at each pile location to design the rock socket length based on the rock quality and sloping rock conditions. The rock mass was pressure-grouted during each rock probe to improve the rock quality and fill voids in the rock.INTRODUCTIONThe Kuala Lumpur City Centre, home of the Petronas Towers and the world’s deepest foundations, will be the future home of a new supertall tower. The 77-story tower will be supported by a piled-raft foundation that relies on piles terminating in the highly erratic, karstic Kuala Lumpur limestone formation. The high building loads coupled with relatively shallow limestone across the majority of the tower footprint forced the piles to extend into the limestone."

Jan 1, 2016

By Song-yu Liu, Chao Yan, Yong-feng Deng

"In order to investigate the stability of embankment on soft subgrade improved by T-shaped deep mixed column composite foundation, the internal forces and failure modes of columns were analyzed on the shape of critical slip surface and the displacement fields of composite foundation through strength reduction method of three dimensional numerical simulation. Then comparison between T-shaped and conventional deep mixed column composite foundation were conducted. The simulation results indicate that the stability analysis was overestimated by limit equilibrium methods. Piles within the slope shoulder provide great resistance slide effect through the vertical bearing capacity, while the piles nearby slope shoulder and outside slope shoulder providing great moment to resistant slip. The embankment stability of T-shaped deep mixed column composite foundation is higher than that of conventional deep mixed column composite foundation while cost less cement and construction time.INTRODUCTIONThe soft soil has many unfavorable project properties such as high compressibility, low strength, and high water component. Embankment built on the soft soil will face subsidence, horizontal displacement and stability problems. Cement-soil deep mixed column composite foundation is more commonly used as a method for construction of embankment on soft ground [1-2]. For the existing problems of China's current cement-soil pile (wet jet mixing pile), including strength uneven, effective treatment with shallow depth and high cost, a new technique, T-shaped bidirectional deep mixed column, is introduced [3]. An automatic expanding mixing blade was developed by Liu et al. shown in Figure. 1, to install TDM columns [4].T-shaped deep mixed (TDM) column combines bi-directional deep mixing technique and T-shaped deep mixing technique: ?Using concentric biaxial drill pipe, opposite rotational direction of the blade on the inner drill pipe and the outer drill pipe. By squeezing action of the blade on the outer drill pipe, forward and reverse rotation of the blades bidirectional mixing at the same time, blocking the way to take the grout, the uniformity of cement mixing is improved. ?Scalable stirring blades, which can be stretched for two different radius at any depth below ground, expand cross-section of the upper pile (enlarged head), forming expanding cross-section within the upper part of a certain depth which is similar to the shape of nail. As a new composite foundation, T-shaped mixing pile composite foundation is widely applied. However, studies on the stability of T-shaped column treated soft subgrade are rare in the research. So the stability study on T-shaped column composite foundation under embankment for guiding the design and construction has important significance."

Jan 1, 2015

By Stephen Buttling, Zhong Rui

"A single unit gas fired power station was being built on the edge of the Gulf of Thailand in 2001. The soil conditions consisted of very soft to soft Holocene Marine Clay, and the site was part of a coast line which had been subsiding below high water mark for some time. In order to provide access around the power station a road system in a figure-of-eight formation was required, and this also needed to be above the design flood level, allowing for future settlement. A ground improvement scheme was proposed and constructed, which consisted of two spacings of prefabricated vertical drains (PVD) over two depth ranges, vacuum consolidation and pre-loading, and rigid inclusions.During the construction phase, the vacuum consolidation was applied for 202 to 221 days in different zones, and monitoring allowed a prediction that the future settlement, including secondary consolidation over a period of 25 years, would be within the range of 175 to 355 mm, which met the contract requirement of less than 400 mm.The power plant was completed and became operational in 2003. Monitoring of the road levels continued, as did the settlement, and in early 2010 the total settlement since the end of vacuum consolidation had reached about 800 mm. The monitoring data both during the ground treatment and for the following 7 years is presented and analysed. This is supported by numerical analysis using 3D finite element methods which shows good agreement with the measured data, and allows a preliminary explanation as to why the predictions were so far out.BACKGROUNDAfter a period of bidding and negotiation, the Eastern Power and Electric Co Ltd (EPEC), an Independent Power Producer, entered into an agreement with the Electricity Generating Authority of Thailand (EGAT) in November 1997 to sell them power. In 1999 an Engineering, Procurement and Construction (EPC) contract and an Operation and Maintenance contract were signed with a supplier to provide a gas-fired (with oil as a back-up fuel) 350 MW combined cycle power plant in Bang Bo, Samut Prakarn Province, east of Bangkok. The site of the plant at Bang Bo is located immediately to the east of the Samut Prakarn Wastewater Treatment Plant, adjacent to the Gulf of Thailand (see Figure 1) in an area of very soft to soft marine clay (Bangkok clay) having low shear strength and potential for excessive settlement. The site layout comprises the main Power Plant components of generating block, cooling towers, fuel unloading area and storage tanks, switchyard and administration block, separated by access roads."

Jan 1, 1900

By Venkata Krishnaiah Yeddala, Sai Vivek Adari, Suresh Kumar Velugu

Assam cancer care foundation (ACCF) proposed the construction of hospitals and related facilities across 18 locations in the state of Assam-India. Tezpur is one among the 18 locations of Assam with high seismic risk. The strata at the site are comprised of mostly fine silty sands of lower SPT- N values. The water table is also encountered and ranging from 1 m to 2 m below EGL. Since the site lies in seismic zone V as per IS 1893, detailed liquefaction analysis is carried out for all five boreholes and indicates that soil is liquefiable and ground improvement is inevitable up to a depth of 15 m below existing ground level. To mitigate the liquefaction potential and enhance the seismic performance of the soil, ground improvement using stone columns by Wet top feed Vibro-replacement method is proposed. Also, the differential settlements can be avoided effectively under the raft foundation with Vibro Stone Columns. In this paper, field test validation results such as Pre and post-SPTs and ECPTs to access the extent of ground improvement, along with other information adopted in this project presented.

Nov 1, 2022

By Lucie Spencer, Craig Butterworth

"This paper presents the design of a raft enhanced pile group recently constructed for a hotel development in Perth, WA. At the time of construction in 2016 the hotel was the tallest prefabricated hotel in Australia.The structure covers the entire 12 m by 32 m development footprint, located in an inner city environment, and directly surrounded by existing structures. The small site and lack of space required innovative thinking in terms of the substructure design.The ground conditions comprise a layer of medium dense sand underlain by variable layers of stiff clay, silts and sands. Groundwater was around 1.5 m below ground level.The substructure design was carried out on the basis of a raft enhanced pile group. This allowed the use of much shorter piles than a conventional pile solution, thereby permitting the adoption of CFA piling techniques. This also allowed the raft thickness to be reduced to such that the substructure works were maintained above the groundwater level.The design was carried out in general accordance with the Australian Standard AS 2159 and using conventional piled raft design techniques involving iteration between elastic soil settlement software and structural analysis software until spring reactions were obtained with convergence of the two models. Following this springs were introduced to model piles in the structure.Due to the variable nature of the ground and resulting uncertainty in pile base capacity it was not considered appropriate to design the system as a pile assisted raft with piles loaded beyond their ultimate geotechnical design strength. As a result, all piles were designed based on a maximum load maintained within the elastic response region, with the majority of the load taken by the piles. However, the combined capacity of the raft and the piles allowed for a saving in pile lengths and numbers of around 40%, when compared to a conventional pile group designed in accordance with the Australian Standard AS 2159.The raft slab was monitored during construction in order to check the actual displacements against the design displacements. At the end of construction, the settlements were found to be within 2 mm of the design values.INTRODUCTIONThe Wellington Street area of Perth in the CBD is undergoing recent regeneration which includes the King’s Square development, Perth Arena and the Wellington Street Bus Station. The proposed hotel development is close to the recent developments on a Lot previously occupied by a low rise development. Due to the small size and constrained nature of the site, the substructure design for the tower needed to take into account available space and the impact of the works on adjacent properties. This paper presents reasoning for the choice of substructure design, details of the design methodology adopted, results from limited post construction monitoring and potential improvements that could be considered for similar future developments."

Jan 1, 1900

By Craig M. Shillaber, Joseph E. Dove, James K. Mitchell

"This paper addresses two primary factors affecting the sustainability of Deep Mixing Methods (DMMs): construction materials and handling of the spoil from wet mixing methods. We examine these factors within a life-cycle embodied energy (EE) and carbon dioxide (CO2) emissions accounting framework, using the LPV 111 project in New Orleans, LA as a case history. The underlying assumption is that project planning and preliminary design have determined that a DMM is the best ground improvement alternative for achieving the broader aims of sustainable development. While EE and CO2 emissions are direct measurements of environmental impact alone, we illustrate how their minimization can also influence the social and economic consequences of the project. It is recommended that DMMs use lower energy and carbon material alternatives to Portland cement and lime in the binder whenever possible, with preference given to locally sourced materials. Currently available alternative cementitious materials include fly ash and slag, which are waste products from other processes. In addition, recycling the spoil material from wet mix methods on site is recommended. If the material cannot be recycled on site, transporting it to a processing and recycling center for later use as fill is preferred over landfilling. INTRODUCTIONWithin the geotechnical community there is an increased appreciation for sustainability considerations, which are an important component of the planning, design, construction, operation and maintenance of projects. An assessment of project sustainability includes holistic life cycle thinking, systems analysis, environmental impact assessment, use of safe and benign materials, awareness of local societies and cultures, social equity, protecting human health and well-being, and monetary costs (Abraham, 2006). Since ground improvement is a principal practice domain of geotechnical engineers, it is important that geo-professionals play a role in addressing the sustainability for these projects. In this paper, we illustrate by case history how different materials and methods associated with deep mixing projects can impact overall project sustainability through quantifying project embodied energy (EE) and carbon dioxide (CO2) emissions. EE is defined as all energy consumed to bring something into its present state (Chau et al., 2008; Inui et al., 2011; Soga et al., 2011; Chau et al., 2012). Recommendations are then made for how adverse environmental impacts of Deep Mixing Methods (DMMs) may be minimized, leading to more sustainable geotechnical construction."

Jan 1, 2015

By Challa Venkata Rami Reddy, Anindya Roy, G. R. Konni

This paper presents the results of pile lateral capacities obtained from both conventional design and fullscale pile lateral load tests. Conventional design using P-Y curve analysis is very commonly being used by designers; designers use well accepted software programs like Lpile and Allpile for analysis. However, these programs do not cover the soil models to simulate engineering behavior of marine carbonate sands; which generally have different engineering behavior than silica/quarts sands. In this study, the existing soil models for common sands have been used to assess pile lateral capacities and these results are compared with the results from full-scale instrumented pile lateral load tests performed in compacted marine carbonate sand fills of artificial island constructed for oil and gas facilities in Abu Dhabi. The objective of this study was to verify the applicability of the existing sand soil models for carbonate sands and also to verify the associated conservatism in the pile lateral capacities. This study shows that the actual pile lateral response is much stiffer than what was anticipated through the LPile analysis. Therefore, further research focus may be required to capture the engineering behavior of the marine carbonate sands to develop specific P-Y curves.

Sep 8, 2021

By Giulia M. B., Ferruccio Cribari, Alessandro Bertero, Eliano Romani, Roberto Sorge, Francesca Casini

"The use of Artificial Ground Freezing (AGF) to form earth support and seepage control barrier systems has had applications worldwide. These cover a variety of construction problems, including the formation of frozen earth walls to support deep excavations, structural underpinning for foundation improvement, and temporary control of ground water in construction processes. An application of AGF during construction of Line C of Rome underground is described in detail.The new line “C” of San Giovanni metro station was constructed adjacent to the existing line “A” of San Giovanni station; the new metro line “C” is deeper than line “A” and runs below the existing station. The underpass project envisages an Artificial Ground Freezing in order to create a structural and waterproof temporary cut-off suitable to the two new tunnels excavation, while keeping trains running in the safest possible condition. The excavation of tunnels under the water table, with a hydraulic head of over 10 m in not homogeneous soils having different mechanical properties and permeability and below existing sensitive structures, involves special ground freezing sequences and methods, as well as peculiar drilling systems and operations, such as TDDT (Trevi Directional Drilling Technology).Artifical Ground Freezing IntroductionNatural freezing occurs seasonally in many areas of the globe and can affect negatively the engineering performance of geotechnical structures; on the other hand, man-made freezing is a controllable process that can be used by civil engineers to stabilise temporarily the ground in order to support and/or exclude groundwater from an excavation until the final retaining and lining structures are constructed. Freezing and thawing of the pore fluid within soils involve complex thermal, hydraulic and mechanical processes that have significant mutual interactions. For example, phase changes of the pore fluid caused by temperature variations can modify the pore water pressure in the soil, which, in turn, can induce mechanical deformation. At the same time, any changes in the hydraulic and mechanical conditions affect the thermal processes by advection and changes of ice and water contents.An application of AGF which will be presented in the paper, refers to the construction works of Line C of Rome underground. In this case AGF was carried out to provide temporary support during excavation of the two Line C running tunnels directly underneath the existing S. Giovanni station of Line A, in the safest possible condition. In order to keep the trains of Line A operational during excavation, a temporary structure was installed and a real-time monitoring system was conceived in order to control the temperatures of the soil during freezing and the response of the structures of the existing station."

Jan 1, 2016