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By Sastry Putcha, Santosh Mummaneni, Avasarala Swamy

"Inspection of bored pile hole bottom prior to placement of concrete is one of the most crucial element of foundation design and construction, especially for end bearing piles. Pile hole bottoms that are not cleaned well for sediments could potentially result in settlement. Although many projects have specifications in-place for drilled pile hole inspection, they are rarely implemented as the current available tools are either unsafe or cumbersome and costly, thus making it very unattractive for owners and contractors. Further, sometimes the post-construction nondestructive quality control testing such as PIT or sonic logging on piles resulted in unanswered questions related to soft bottom. This generates costly disputes with additional testing including concrete coring and possible repairs. Currently, there are several bored pile bottom inspection devices in USA, namely, SID, DID, and SQUID which can either provide video and photo documentation or measure sediments.“ShaftCam”, a patented advanced Digital Borescope, was invented to address the issues related to pile hole bottom inspection with its ability to measure sediments as well as photo and video documentation. Shaftcam device consists of 8-inch diameter bell with a camera, led lights, air hose connection and penetrometer with digital measurement that are connected to a control power box and laptop through a cable. The bell is fitted with a round clear open fiberglass skirt to form an open chamber. A simple motorized winch frame allows the user to lower the ShaftCam equipment gently to the bottom of the shaft at the desired location. Once the bell with camera is lowered to the bottom of the hole, air is pumped into the clear chamber to displace the water/slurry/polymer and get a clear view of the hole bottom to record the conditions and measure the sediment thickness and resistance. The skirt can also be enclosed and lowered to the desired location to allow for inspection of shaft walls.ShaftCam weighs less than 15 lbs. (6.8 kgs) in water and allows for inspection of the hole by one person in less than 30 minutes. Use of ShaftCam has saved significant time and money and thus allowed owners and contractors to readily accept and implement the quality control measures in many projects in USA over past few years."

Jan 1, 1900

By William B. Conway

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

Jan 1, 2013

By Dr. Anup Kumar Mandal, Partha Roy, Shuvranshu Kumar Rout, Dipak Mandal, Biswajit Das

Installation of a new scalping station with bunker, apron feeder, scalping screen, ramp -retaining wall and approach bridge was planned in an existing integrated complex of phosphate fertilizer at a remote place in West Africa. Rock phosphate ROM, transported from mines by a combination of 100 Ton and 150 Ton dumper, would be fed to a steel bunker having capacity of 180 m3. Different options were studied for retaining wall at the junction of ramp and approach bridge. Initially options with conventional RCC Retaining Wall, Gravity Retaining Wall with Precast Concrete Blocks and Reinforced Earth walls were studied. Option with Reinforced Earth was selected as this option was much more cost effective compared to other options. But real engineering challenges cropped up when competent execution contractors were not available nearby the site. To minimize the cost, an innovative option with Stepped Retaining wall was then studied. Geotechnical parameters of native soils, selected for the construction of the approach ramp were determined and it was found that with available poor geotechnical parameters of the native soils, design of stepped retaining wall would not be feasible with respect to available bearing capacity, subjected dead load, live load, operational load and earth pressure. A conscious effort was then made to make the design feasible by improving the geotechnical parameters of the retained earth of ramp near the retaining wall. In view of that, mix design with locally available materials like Silexite, Sand, Laterite, Gravel and Silt at different proportions was made and samples were tested in the laboratory to determine relevant geotechnical parameters. Based on the test results, a suitable mix was selected that had high shear strength, enhanced bearing capacity and improved coefficient of earth pressures. Design of stepped retaining wall was then made with the selected construction materials and construction completed. The plant was successfully commissioned in December. 2021.

Sep 1, 2022

By Zia Zafir

"Levees in the central valley of California are primarily for flood control purposes and thus are subjected to infrequent hydraulic loading. The primary concern for these levees is their instability due to through and under seepage. Primary seepage control measures are seepage cutoff walls and/or seepage berms. The cutoff walls primarily consist of soil-bentonite (SB) slurry walls. The seepage berm could be a drainage blanket to allow the seepage with controlled exit gradient or an impervious layer to provide enough cover to protect any adverse effects of seepage in terms of sand boils. Although, Sacramento is an area of moderate seismic activity, levees protecting urban areas require assessment for the potential instability due to liquefaction and associated vertical and lateral deformations. In certain cases, the seismic deformations of the levee may not compromise the stability of the levees, but they may cause damage to the seepage control measures. Depending on the nature and extent of the damage, the mitigation measures may require limited or full replacement of the seepage control measures. This paper will provide a systematic assessment of these different types of seepage control measures under vertical and lateral deformations due to liquefaction and lateral spreading under seismic loadings.INTRODUCTIONThere are two broad categories of levees in Central California: levees that are subjected to continuous hydraulic loading such as delta levees and are called frequently loaded levees (FLL) and flood control levees that are subjected to seasonal or infrequent hydraulic loading, called infrequently loaded levees (ILL). This paper will focus on the seismic response of ILL. The probability of ILL experiencing an earthquake at the time of the design flood is very low. Therefore, consequences of seismic failure of flood control levees are only significant in terms of response time required to restore the level of flood protection provided by the levee before the next flood season. An example for this restoration is the restoration of the Pajaro River levees in Santa Cruz, California after the 1989 Loma Prieta Earthquake. Nevertheless, failure of flood control levees due to a seismic event could result in loss of the entire levee and/or loss of freeboard. In addition, some of the seismic failure of ILL levees may result in loss of seepage control measures such as the soil-bentonite wall.The State of California State approved Senate Bill (SB) 5 in 2007 that mandates for 200-year flood protection to be the minimum level of protection for urban and urbanizing areas in Central California (Sacramento-San Joaquin Valley) by the year 2025. This legislation also requires that urban and urbanizing areas protected by Federal project levees cannot use adequate progress as a condition to approve development after 2025. SB 5 requires that the urban level of flood protection be consistent with criteria used or developed by DWR (Government Code § 65007(k)). To avoid delaying urgently needed flood protection, Urban Levee Design Criteria (ULDC, 2012) was developed."

Jan 1, 2016

By Masaaki Terashi

The machine for the hybrid method called JACSMAN is ordinarily a dual shaft machine. Each shaft has augers at three different levels and nozzles for jetting at two different levels. The distance between two shafts may be changed according to the particular requirements. Figure 4 shows single shaft and a treated soil column created by the method. The diameter of the auger is 1.0 m. As the jetting nozzles locate at the periphery of the auger, jetting can achieve the additional treated soil column beyond the diameter of the auger. The diameter of the jetting improvement is fixed at 2.3 m.

Feb 10, 2003

By Jonathan G. Cannon

"This paper will describe dynamic pile testing conducted during installation of driven octagonal precast prestressed concrete piles used as the foundation for this bridge. The piles were long and hence spliced. A number of the piles showed damage near the splices and the damage location was near the ground surface so that the damage could be verified using visual inspection. The piles and splice configuration are still in use today without modification. Further WEAP driveability analysis has been conducted which demonstrates the effect of the splice on pile stresses and a likely failure mode. A slight modification is proposed to the splice that should prevent the damage on future projects.INTRODUCTIONThe bridge site is located on the Olympic Way, Route 41, about 20km north of the regional centre of Albury, NSW. For a long distance north of the site the Olympic Way ""shadows"" the main Melbourne to Sydney rail line and is located on the Western side and in close proximity. At the bridge site there was previously a sharp dog-leg in the road and a right angle level crossing with the road changing to the Eastern side of the rail line, eventually joining up with the Hume Highway, which in turn now becomes a ring-road through the eastern outskirts of Albury. The dog-leg and rail crossing had warning signs and bells, speed restrictions and rumble strips to warn approaching motorists to reduce speed. Site distance was exceptionally good.Approximately 2years before construction a group of five ""high spirited"" young men from the local area were driving south on the Olympic Way adjacent to a south-bound train. It is understood they interacted with the train crew for a period of time. Unfortunately the car and train collided at the level crossing and all of the young men were killed. There were outpourings of grief in the local community and a decision was made to replace the level crossing with a road-over-rail bridge.The bridge was highly skewed with two piers and two high level abutments with fill embankments on both approaches.GROUND CONDITIONSThe site is open grazing country with approximately level ground at the site with surrounding low hills. The geology was unremarkable with consistent stiff clays for a considerable depth.The design required driven precast prestressed pile foundations with the piles to be driven to a considerable depth.Hard driving with high tension stresses were evident from the start of driving and a variety of different pre-bore lengths were adopted in an attempt to minimise driving and potential for damage. At the abutments the pile locations were predrilled for at least the full embankment depth.PILESThe piles were 550mm octagonal prestressed concrete with the pier piles being single piece and the longer abutment piles being two-piece with a ""standard"" epoxy glued box splice. Pier piles and the initial length of the abutment piles were 24m. The add-on piece used at the abutments was 12m. Pile concrete was grade 50MPa."

Jan 1, 1900

By Spencer Ness, Yazen Khasawneh, William Tjaden, Mohammad Nassim

The evaluation of long-term performance of the wind turbine structures is essential in lowering the Levelized Cost of Electricity (LCOE) from wind sources. The required maintenance of the wind turbine foundation during the design-life time of the wind turbine may result in escalated cost, if not properly evaluated during the planning and designing phases. The degradation of the foundation soils’ stiffness due to the accumulation small plastic strains resulting from normal and/or extreme operating cyclic loading may result in escalating the O&M cost. The foundation’s stiffness degradation will result in a shift of the wind turbine system natural frequency, which may result in amplifying the vibrations generated at the hub. The anticipated shift of the wind turbine system natural frequency during the design-life time should be investigated through numerical simulations of the anticipated dynamic loading utilizing soil constitutive models that are capable of capturing the foundation stiffness degradation due to the accumulation of such small plastic strains. This study presents the validation of an element model that will be used to evaluate the performance of existing and/or proposed constitutive model.

Oct 1, 2022

By Ashley Shirer

Have you heard a geotechnical engineer rail against using the word "dirt"? The typical maxim is: "It's not dirt, it's soil!" This axiom is so prevalent that it is joked about on the construction site. How did we get to the point in our profession that soil is too technical to understand, while dirt is not viewed as important? Take a moment and think about the images that come to mind by the word soil. Responses range from the sand at a playground to the mud that sticks to the bottom of your shoe, the dark loam found in gardens to the firm earth under your feet. But do you know where the term soil originated? Or how it was intended to be used? This article looks at how word choice can lead to very different motivations for owners, designers and constructors.

May 1, 2023

By Andreu J. Ferrero

Polyurethane and acrylate resins are routinely injected into soils to gain strength and control water flow. However, most published data regarding strength gain is derived from laboratory samples created under ideal conditions. This study endeavored to inject resins into full scale mock-ups that could then be excavated and tested to yield results comparable to actual field conditions. To achieve this goal, a large container was filled with a silty SAND (SM), as defined by the Unified Soil Classification System (USCS). The soil was moisture treated and compacted in lifts of 0.3m. PVC pipes installed in a diamond grid into the soil were used to inject polyurethane and acrylate resins. Dynamic cone penetrometer (DCP) tests were conducted on the polyurethane treated soils, the acrylate treated soils, and the baseline untreated soils in the container. Testing results will be correlated to SPTn and CBR values to evaluate increases in the soil strength parameters in the treated soils. Cored samples of polyurethane and acrylate treated soils will be tested in compression, shear, and triaxial. These laboratory test results will focus on material property gains for the treated soils, in comparison to standard values for similar soil types. Complete documentation of the soil type, compaction methods, injection methods, and testing performed have been documented and will be presented in the final paper.

By Christopher Sammon, Nicholas Turus

"The demand for underground parking in South Florida has increased as a result of changes to the local building code, coupled with developers’ desire to improve building aesthetics and provide much needed walk in retail space for high-end structures. Historically, underground construction was uncommon in South Florida due to the high groundwater level and porous soil/rock. Conventional dewatering methods become ineffective only a short depth below the ground surface and deeper excavations have required a tremie seal solution consisting of wet excavation and the pouring a temporary unreinforced slab under a water head. However, as excavation area and depth increase, the cost and schedule of the tremie seal method become problematic. For these reasons developers and construction teams alike have looked to contractors in South Florida for alternative means of construction.This paper details the construction of two sites in South Florida where Deep Soil Mixing (DSM) technology offered an efficient alternative to tremie seal construction. The Brickell City Centre required excavation of 8 acres to depths of 30 feet, and augercast piles up to 36” diameter and 110 feet in depth. The second site, Jade Signature, required an excavation of up to 41 feet directly adjacent to the Atlantic beachfront. Due to the concerns over differential settlement, the project featured a soil mixed gravity wall that was designed and installed to allow for completion of the tower prior to excavating the adjacent garage.Both projects involved improving every square inch of ground beneath the planned project excavation. The developed DSM seal slab solution creates a nearly impervious excavation at excavation invert with the strength to resist hydrostatic uplift forces. Low permeability site perimeter walls are constructed to complete the sealed excavation and reinforced with either beams or sheet piles for structural support. Augercast piles required for the permanent hydrostatic concrete slab supplement the uplift capacity of the DSM. After DSM and augercast piles are installed from grade, the site is excavated in dry conditions."

Jan 1, 2017

By D. Vanni

Constructing new infrastructure in urban areas increasingly entails the use of sophisticated techniques for soil improvement in order to minimize surface disturbances in adjacent areas and damage to existing structures. In Naples, at the new Piazza Garibaldi subway station, TREVI built a 45 m deep shaft using a hydromill, and utilized soil freezing for the excavation of the four station's tunnels, fifty meter long, located approximately 30 meters below the water table. An innovative use of directional drilling was specially developed by TREVI to successfully complete this challenging job.

Jan 1, 2006

By Karsten Beekhaus, Sander W. Odijk, Rabea Bahlum, Mazin Adnan, Ayman Abdelh Al Nuaimat, Hassan Farhat

The Arab Potash Company, APC, is one of the 10 largest potash producers of the world. The solar ponds at the Dead Sea, used for the enrichment of the salt content in the brine, are of crucial importance for the first step in the exploitation of the potassium salt. Targeting at the expansion of production in the since over 50 years utilized facilities, the increase of the brine exploitation capacity, reducing the substantial brine seepage losses from the ponds, becomes a crucially required measure. In this context, the remediation measures on the over 11 km long Dyke 1, being a main dyke of the solar ponds system, became inevitable to reduce the brine losses, prevent further development of sinkholes and cavities and hence assuring the stability of the dyke. The highly aggressive environment, the acting hydraulic conditions and the sensitive stratification and nature of the existing ground represented remarkable challenges for the design, as well as its implementation by the construction activities. Royal Haskoning developed a solution addressing the challenges above and targeting at a high sustainability of the executed structure, especially in view of the various geological and hydrological hazards repeatedly occurring in this Dead Sea region, including sinkholes of several meters by diameter and depth. The construction works, consisting of a cut-off wall, with depths reaching down to 31 m, were awarded to Bauer International FZE, a subsidiary of Bauer Spezialtiefbau GmbH. Upon the execution of the first section of 4.2 km length, additional sections were subsequently commissioned, also on further dykes, totaling to about 300,000 m² of cut-off wall. The specific project conditions, such as utilization of cutter technique for the excavation in Halite rock, the stability of open trench exposed to hydrostatic pressure of salt-saturated ground water, resulted in unconventional requirements towards the supporting fluid. The extremely aggressive saline conditions –with a Dead Sea water density of 1.25 tons/m3; one of the world's saltiest water–, were further a decisive factor for the definition of the backfill material concept. Despite its clear advantage for construction of cut-off walls with installed sheet piles, the single-phase system with hardening slurries, fulfilling both functions of excavation support and cut-off wall backfill material, had to be abandoned in favor of the two-phase system, to construct a hybrid cut-off wall made of sheet piles and plastic concrete.

May 1, 2022

By Mark Koelling

This paper presents a case history of a ground improvement program conducted in a soft soil environment and seismically active region in the northwest corner of Washington State near the Canadian border. The program was performed over several years, and provided adequate soil bearing conditions for the construction of several structures. Completed development includes separate construction of four adjacent structures, each with unique total and differential settlement requirements and built at approximate two year intervals. Site soils consist of 45 feet of loose saturated sand and silt overlying 70 feet of very soft to stiff (N60 = 0 to 7) normally consolidated clay. Adding to the complexity of the site is the owner?s requirement that all existing structures remain open and in service during construction of each subsequent structure. The paper presents the site geotechnical information and the foundation design issues. Details of a combination of ground improvement methods is presented, including stone columns, wick drains, a preload surcharge, and staged construction to provide soil support for shallow foundation construction of all structures at this site. The soil test results and settlement observations are presented along with QA/QC measures. Lastly, a brief method sustainability comment will be made.

Jan 1, 2010

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 Gordon Chen

As part of a value engineering envisioned by East Coast Slurry, Weidlinger Associates, Inc. designed a unique elliptical slurry wall cofferdam for construction of the 65 ft. deep MWRA North Dorchester Pump Station. A conventional rectangle cofferdam with multiple levels of bracing would have been time consuming and costly and imposed a significant obstruction to the pump station construction. A circular slurry wall, while eliminating the bracings, conflicted with adjacent structures and required excessive backfilling around the final pump station structure. The ellipse shaped cofferdam fit the needs of the project well; however, it created a significant design challenge without the use of bracings. Unlike a circular cofferdam which primarily only has hoop stresses, the ellipse still has to be designed for horizontal bending moments in each panel because of the non-axial symmetric conditions. The more eccentric the cofferdam shape; the higher the horizontal bending. The challenge was to develop a three dimensional finite element model that could analyze both the hoop stresses and horizontal bending stresses above and below the bottom of excavation induced by soil and water pressure and unbalanced construction surcharge loads. This paper discusses the techniques used to model the soils and structure interactions and results of stresses on this challenging unbraced configuration.

Jan 1, 2010

By Franz-Werner Gerressen

"New developments are required day by day. On the one hand site to improve the actual situation, on the other hand site to create the future and to ensure that future demands can be fulfilled. This requires for instance the development of technical support systems, which enable a more constant and quality ensured installation of special foundation products like piles. As part of the quality control, real time installation control of the production process, data transfer and reporting systems become more and more important ensuring the five dimensions of a jobsite. That means not only the three well known dimensions (width, height, depth) are cover, but also the dimension of time and money. Beside small, but important, details, also the demand of extending the use of methodologies in terms of getting deeper or allow their use in various soil conditions require the development of new tools and equipment. Therefore, the paper will describe some of these new approaches and activities required for these new developments. It will describe also the main equipment which will be needed to execute these works under the various conditionsINTRODUCTIONNew developments are required day by day. Either to improve the actual situation, or to create the future and to ensure that future demands can be fulfilled. Therefore, there is an increasing demand for the development of e.g. “Little Helpers”. “Little helpers” are for example technical support systems, which enable a more constant and quality ensured installation of special foundation products like piles, for example an assistance system like the later explained “drilling” assistant. As part of the quality control, real time installation control of the production process, data transfer and reporting systems become more and more important ensuring the five dimensions of a jobsite. In a second part the focus will be given to new approaches for soil mixing application. Adjustments of tools or equipment to extend the range of possible usage as well in terms of soil conditions as in treatment depth.“LITTLE HELPER”GeneralThe B-Tronic System enables you to efficiently operate, maintain, and administer individual machines as well as entire fleets. It helps you to securely monitor and precisely evaluate your projects and work processes. The system is an integrated system for controlling all operations and visualizing actual operating parameters in real-time on a large interactive touch-screen monitor."

Jan 1, 1900

By Shamsher Prakash

Estimation of vertical load carrying capacity of a single vertical pile under earthquake loading is an important task of a design engineer. Lateral vibration of vertical pile is highly influenced by the magnitude of vertical load. Several load reversal, during earthquake loading introduce gap between pile soil interface which reduces its load carrying capacity and increases lateral motion. This paper presents a simple time domain numerical scheme to estimate the lateral pile response, considering the loss of contact of pile at pile soil interface, during impact and earthquake loading. The motion of the pile is limited in the vertical plane. Time domain has been discretised into small intervals. The non linearity of soil properties has been taken into account by discretised Winklers model with Wolfes frequency independent mass spring dash pot coefficient for geometric damping. Suitable software has been developed which keeps track of the load reversal point of each elements.

Jan 1, 1996

By Sherrill Gardner

Vibratory drivers have been used since the 1930s to drive and extract piles. Vibratory pile drivers have the capability of significantly decreasing pile installation time, especially in granular type soils. However, they have not been widely accepted because of the uncertainty in estimating the bearing capacity of the driven pile. When driving bearing piles, the industry standard method for obtaining load carrying capacity of a pile installed with a vibratory driver is to redrive with an impact hammer. The advantage of improved productivity is lost with the redrive procedure. Currently, there is no other method to predict the capacity of these bearing piles installed with a vibratory driver. The Naval Civil Engineering Laboratory (NCEL) is making progress towards being able to estimate the bearing capacity of these piles. This paper describes field testing and corresponding analytical modeling of the vibratory driver-pile-soil system. The following sections describe the development of the numerical model and techniques for collecting field data. A discussion of the prediction of the pile driving process based on field test data is followed by suggestions as to the additional work that should be done to further verify the model to a point where it can be used with confidence.

Jan 1, 1987

By Jonathan Ernst

The Bruce Museum is an art, science and natural history museum in Green- wich, Connecticut. The museum was originally built as a private residence in 1853, and has undergone several reno- vations, the most recent dating to 1992. The current renovation is part of a $60 million capital expansion plan for the "New Bruce." The renovation includes a 43,000 sf (4,000 m2), three-story addition that will more than double the size of the museum, adding space for new ex- hibitions, education and community spaces. The proposed bottom of the foundations for the renovation sit up to 16 ft (5 m) below the Bruce Museum's existing shallow foundations.

Aug 1, 2023

By Tsuda Wakaki, Naoki Takahashi, Natsuki Okuno, Hidenori Takahashi, Ikuo Towhata, Yoshiyuki Morikawa

"Deep mixing (DM) method has been increasingly employed as a countermeasure against subsoil liquefaction in recent years. Pile-type DM, however, is considered to have little effect as a liquefaction countermeasure, because the shear deformation of unimproved soil around the piles cannot be reduced. However, experimental results, which imply that shear deformation of unimproved soil around DM piles can be reduced, were reported. Furthermore, a new plane-arrangement of DM piles has been proposed to mitigate lateral flow induced by liquefaction. The DM piles in this arrangement confront the lateral flow in any direction, compared with the piles arranged in conventional pattern such as square and triangular arrangements. In this study, a series of dynamic centrifuge model tests was conducted to verify the lateral flow resistance of DM plies in the new arrangement. The results indicate that the DM plies can reduce the lateral flow of liquefied ground when the pile displacement and the pile head rotation are restricted. In addition, lateral load acting on DM pile from liquefied ground, which is required for design strength of the DM pile, was investigated.INTRODUCTIONDeep mixing (DM) method has been increasingly employed as a countermeasure against subsoil liquefaction in recent years. The solidified body formed by the deep mixing method is usually block or lattice shape, composed of solidified columns that overlap each other horizontally. Lattice-type solidification has been shown to be effective as a liquefaction countermeasure despite the presence of unimproved soil inside the lattice wall, because the shear deformation of the interior soil is restrained by the wall (Suzuki et al., 1989). On the other hand, it has been thought that pile-type DM cannot reduce shear deformation of unimproved soil around the piles, because the displacement of the pile is less restricted than that of the lattice wall. DM piles have been reported to have little effect as a liquefaction countermeasure, but to be superior in terms of construction cost and applicability around existing underground structures (Koga et al., 1986). However, there are experimental results implying that DM piles have reduced the shear deformation of unimproved soil and mitigated its liquefaction (Yasuda et al., 2003; Tanaka et al., 2003). Yamamoto et al. (2006) conducted dynamic analyses of ground improved with lattice- and pile-type DM. Their results showed that pile-type DM with an improvement ratio of more than 35% reduces excess pore water pressure generated by earthquakes. Furthermore, the new pile arrangement shown in Fig. 1(a) has been proposed to mitigate lateral flow induced by liquefaction. It was developed and has been verified using dynamic model testing in a 1 g field (Takahashi et al., 2010a; 2010b; 2013; Towhata et al., 2010, Morikawa et al., 2014). The DM piles in this configuration interrupt lateral flow in any direction, unlike those placed in square and triangular arrangements."

Jan 1, 2015