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By Ross Cutts

As a public servant geotechnical engineer, I observed how costly and valuable geotechnical field explorations are to the success of every project. Often however, the field exploration is a long and complex process that is made less efficient by the difficulty of retrieving and utilizing nearby internal or external historic geotechnical datasets. As an employee of a public agency, we would often start our investigations for every project from scratch, given the difficulty of locating and utilizing historic geotechnical data. This is an ethical and technical failing of our profession. When we start subsurface explorations from scratch, not only do we often duplicate investigations, we are also likely defaulting to reapplying tradi- tional test methods that yield con- servative geotechnical parameters, resulting in overly conservative and potentially costly construction. To address this issue while working as a public servant, I started a research program with Yunfeng Zhang, Ph.D., of the University of Maryland, to build a tool that could compile internal historic geotechnical data and extract additional value from it, using machine learning. This tool was able to provide, upon request, nearby historic geotechnical data, estimated soil parameters and recommendations for geotechnical test methods best suited for a given project site. This prevented common field ex- ploration problems such as, requesting duplicate data, requesting test methods that were not applicable for the project geology, not realizing presence of karsts, missing permits for wetlands, private property and others. This tool allowed for more efficient field investigations with regards to time and money saved. There was one problem with this tool: it could only be used by internal employees of a single state's depart- ment of transportation (DOT) for which this data was compiled. I realized at that point that it would be of tremendous value to make this concept universally accessible to the geotechnical engi- neering profession. I left public service to devote time to building a platform that would host historic geotechnical data from publicly funded sources throughout the country. The tool I helped build as a public servant was the foundation of Geosetta, a nonprofit company dedicated to serving the geotechnical profession. The nonprofit structure was adopted to prevent acquisition by a for-profit company and to ensure that Geosetta remains an independent steward of our profession's valuable data. Geosetta provides a GIS (geographic information system) platform that enables users to view historic geo- technical data and extract value from it with machine learning-based predictions and visualization tools. This data is provided in an open and interchangeable format called DIGGS, which stands for Data Interchange for Geotechnical and Geoenvironmental Specialists, making it easy for users to integrate it into their workflows. Geosetta is collaborating with the American Society of Civil Engineers' Geo-Institute and other sponsors to extract public data at no cost to the agency and provide the profession with free access to the existing data and access to advanced tools through a subscription to support the nonprofit mission.

Nov 1, 2023

By James Warner

Although use of low mobility grout is just now beginning in some parts of the world, its advantage for many applications has been well established through more than 50 years of positive experience. The single largest area of application continues to be densification of soil by way of compaction grouting. Because it is often the safest and least costly method for soil improvement in general, and virtually always that in connection with soil improvement under, or adjacent to structures or in developed areas, use will undoubtedly increase both geographically and in diversity of application.

Feb 10, 2003

By A. Flora, E. Bilotta, F. Foria, V. Nappa

"All the typical applications of deep mixing rely on the good mechanical properties of the improved columns to strengthen or stiffen the ground for a number of geotechnical applications.This paper focuses on a completely different kind of deep mixing, carried out in order to obtain columns much softer than the surrounding soil. This kind of deep mixing, named Soft Deep Mixing (SDM), is introduced as an original means to tackle seismic risk, and can be convenient when the existing structure to be protected has a historic relevance that cannot be altered with structural modifications. The idea is that properly assembled layers made of partially overlapped SDM columns, with dynamic impedance much smaller than that of the surrounding soil, will filter and reflect most of the seismic energy.The paper presents the results of some 2D parametric numerical analyses aimed to investigate the seismic performance of this innovative approach. Simplified dynamic inputs (Ricker wavelets, having only one largely predominant frequency) were adopted to better understand the effect of signal frequency. The analyses show that the effectiveness of the soft grouted isolating barrier depends on soil and SDM geometrical, physical and mechanical properties, as well as on the frequency content of the seismic input.INTRODUCTIONPassive structural systems installed at the foundation level of existing buildings are a common solution to protect them against earthquakes. However, installation procedures are expensive and not always feasible, as for instance in the case of valuable buildings. As an alternative, ground improvement techniques can be used to modify ground properties, in order to mitigate the intensity of shaking at ground level. The propagation of shear waves in the ground can be modified by introducing a layer of artificially modified material, having a dynamic impedance (defined as n =p VS, where p is the material density and VS the velocity of shear waves) very different from that of the natural soil. Both very high or very low values of the dynamic impedance of the grouted soil (nt) can be effective in reducing the overall transmitted energy, with the difference that – for a given reduction of the transmitted energy - stiff grouted layers tend to filter the low frequency components of the amplitude spectrum without modifying in a significant way the high frequency components, while soft grouted layers have the opposite effect. Then, ideally the choice of the best grouting technique should be made considering the effects of the different frequency components on the building to be protected. These effects are detrimental for the structure when they are close to its natural frequency: high frequency components result into large structural loads on massive squat structures (high natural frequency), and low frequency components may be critical for tall and flexible structures (low natural frequency). Therefore, the typical procedure of stiffening the uppermost soil layers regardless of the kind of building to be protected is not necessarily beneficial, and for the case of squat structures soft grouting should be preferred. However, this procedure has not been taken into account yet in the engineering practice, and may pose static problems at ground level (i.e. excessive static settlements)."

Jan 1, 2015

By John Davie

We used a Remtek survey in Glenrock and had very good luck with it when we first started the initial investigation. We would have loved to have used that more but my understanding is the equipment is hard to find. It also requires a flooded mine workings. If you're in a dry mine the communication between the two holes is not quite as successful.

Feb 10, 2003

By Don C. Warrington

This paper describes a new wave equation analysis program called ZWAVE, which is a program specifically for external combustion hammers. The program is de-scribed in detail, the discussion dealing with topics concerning the program such as 1) the numerical method the program uses to integrate the wave equation, which is different from most other wave equation programs; 2) the modelling process of both cushioned and cushionless hammers; 3) the automated generation of mass and spring values for both hammer and pile; 4) the method of dealing with plastic cushions; 5) the use of a recently developed model for computing shaft resistance during driving; 6) the computation and generation of values based on basic soil properties such as shear modulus, Poisson's Ratio and soil density; 7) the completely interactive method of feeding data to the program; 8) the method used to compute the anticipated rebound and the energy used to plastically deform the soil; and 9) the format of the inter-active input of the program and the program's output. Sample problems for the program, along with comparison of the program results with data gathered in the field, are presented.

Jan 1, 1988

By Junho Lee, Leopoldo Bello, Mohammad Khan

Multiline ring anchor (MRA) was developed as a cost-effective solution for securing floating offshore wind turbines (FOWTs) to the seabed. Since FOWTs are placed in arrays compared to conventional oilgas platforms, the availability of multiple mooring lines attached to a single anchor can make FOWTs economically competitive. Additionally, the MRA can provide a small and light-weight anchor with high resistance to mooring line loads due to its deep embedment depth. The combined benefits of fewer and smaller anchors allow substantial reductions in anchor material, transport, and installation costs. Such cost reductions are critical to reducing foundation costs for the wind turbine, which can comprise well over 25% of the capital costs for offshore wind power development. Since it substantially reduces the required number of anchor footprints, the multiline anchor concept also permits significant reductions in seabed site characterization costs. This study evaluates how potential advantages of the MRA can reduce the capital costs and provide a reliable cost analysis of the foundation component for offshore wind farms.

By William M. Camp

Construction-induced earthborn vibrations have long been recognized as a potential problem with respect to the constructed environment and various vibration criteria are in use to prevent damage. A special case of construction vibration control is the protection of early-age or ?green? concrete. Unlike limits for damage prevention to building stock, there is no rational, widely accepted limit for protection of early-age concrete. Numerous criteria have been proposed or reported in the literature and the most relevant and rational proposals are summarized herein. These findings are applied to a case history involving both bored and driven piles. Vibration measurements were made during pile driving activities and the vibration magnitude was evaluated with respect to the exposure of freshly-placed and curing concrete to the earthborn vibrations. The maximum vibration magnitude at the applicable distances from pile driving was on the order of 0.3 inches per second. Based on the most persuasive literature, threshold values of 0.8 inches per second or even 1 to 2 inches per second for the protection of green concrete appear to be well-supported. Consequently, it was concluded that the pile driving activities and bored pile construction could proceed simultaneously.

Jan 1, 2010

By Dan Brown

Deep foundation contracting for transportation projects in the United States has typically followed the design-bid-build model in which contractors bid on a specific work product according to relatively inflexible prescriptive specifications. With continuous flight auger piling and the many types of proprietary drilled displacement auger piling, there appear to be advantages to contracting this work according to a different model. This paper provides a discussion of the use of a performance specification for this work in which the contractor has greater freedom to choose the most appropriate foundation system and also greater responsibility for the performance of the completed foundation. With public agencies subject to open bidding, this type of contractual arrangement presents opportunities to encourage innovation. There are also challenges for implementation in public works projects, notably the selection of qualified contractors and the verification of performance requirements on production foundations.

Jan 1, 2006

By Shawn Downey

A helical pile with in-situ grouted shaft was used to underpin the existing slab of a large retail store in the Edmonton, Alberta Canada area. The existing structural slab did not have the capacity to support the increased load requirements. The design to upgrade the capacity specified a drilled shaft as the deep foundation to underpin a portion of the slab. A helical pile was quoted as an alternate and ultimately won the bid based on the advantages of the system. After an ASTM D1143 Quick Load Test confirmed the axial compression capacity, 723 helical piles with grouted shafts were installed in 3 weeks underpinning 40% of the 93,000 ft2 (8,660 m2) building.

Jan 1, 2003

By Louay Owaidat

The United States Army Corps of Engineers (USACE) Sacramento District awarded a $64 million construction contract in February 2020 to the Maloney Odin Joint Venture for 3 mi (4.8 km) of levee improvements along the Sacramento River East Levee (SREL). This project kicked off approximately $1.5 billion of work to upgrade levees along the American and Sacramento Rivers and widen the Sacramento Weir and Bypass. The project received the 2021 ASCE Region 9 Project of the Year Award. Contract 1 improved levees along five segments of the river, the longest segment being a 2 mi (3.2 km) reach from Garcia Bend Park to the Freeport Intake Facility in the Pocket neighborhood of Sacramento.

Oct 1, 2022

By Takeru Fukaya, Tsutomu Namikawa

"The bending tensile stress occurs in the ground improvements when external forces are applied to the column and wall shaped ground improvements. Therefore, in the design of the column and wall shaped ground improvements, the tensile properties of the cement-treated soils become a predominant factor when the external forces induce bending moments. Then the tensile properties are required to design the ground improvements rationally.Three points bending tests are conducted to investigate the bending tensile properties of cement-treated soils in this study. Cement-treated soils mixed in a laboratory are used in the bending tests. The test specimens are prepared with the several mixing properties to study the relationship between the tensile properties and unconfined compressive strength qu. Bending tensile strength Tfb and fracture energy Gf of the cement-treated soils are evaluated from the load-deflection curves obtained from the bending tests. The experimental results indicate that Tfb and Gf are approximately proportional to qu.INTRODUCTIONThe ground improvement by deep mixing has been widely used for structure foundations, retaining walls and liquefaction mitigations. Recently column and wall shaped ground improvements by deep mixing method have been applied for economical reason. When external forces are applied to the column and wall shaped ground improvements, the bending tensile stress occurs in the ground improvements. Therefore, in the design of the column and wall shaped ground improvements, the tensile properties of the cement-treated soils become a predominant factor when the external forces induce bending moments. Then the tensile properties are required to design the ground improvements appropriately.Namikawa et al. (2007) conducted the finite element analysis to investigate the dynamic behavior of the lattice-shaped improved ground for liquefaction mitigation. In the analysis, an improved ground consisting of several grids in a line was chosen to study the basic behavior of the lattice-shaped improved ground. Fig. 1 shows a example of calculated tensile failure zones in the improved soil during the earthquake. Half of one section of the improved soil consisting of two grids in a line for the 8 m × 8 m grid was modeled in the case. In Fig. 1, the failure occurs at the bottom and upper corners of the improved soil grid. The analysis result indicates that the constitutive model which can appropriately evaluate tensile failure behavior of cement-treated soils is required to evaluate the performance of the lattice-shaped improved ground for liquefaction mitigation. In the analysis, the elasto-plastic model developed by Namikawa and Mihira (2007) was adopted for the cement-treated soil behavior. The elasto-plastic model can suitably describe the tensile failure behavior of cement-treated soils. In the elasto-plastic model, tensile fracture energy is adopted to determine a tensile softening relationship because it is difficult to directly measure the stress-strain relationship after the peak stress state in direct tension tests. However there is little experimental study on the tensile fracture energy of cement-treated soils."

Jan 1, 2015

By Don W. Dotson

In 1962, Kondner prepared several papers dealing with hyperbolic stress-strain response of cohesive soils. The following year, Brinch Hansen proposed 80% and 90% failure criteria for stress-strain behavior of cohesive soils. Fellenius was instrumental in popularizing these failure criteria for pile load tests and offered a direct solution equation for the failure load according to the 80% failure criterion. Since the 90% Criterion has been incorporated into the International Building Code, equations for the direct solution of the failure load at the 90% Criterion would be useful to practicing engineers. This Technical Note supplies the derivation methodology for the 80% Criterion and provides expressions to determine the load and deflection at failure for the 90% Criterion.

Aug 1, 2013

By Mamdouh Hamza

The construction of 1200 m length new quay wall located 1,300 m East of the existing Suez Canal bypass and about 1,000 m south of the Mediterranean shoreline is one of the main projects currently under development in Egypt. Due to very weak foundation soil, mainly soft clay, a particular effort, both in terms of design approach and construction feasibility, has been required. The execution of "barrettes" and T-shaped" diaphragm wall panels down to a depth of 65 m and under extremely severe soil condition has been required in order to pass through the upper soft soil and to reach a competent base layer. Very critical and variable hydrological conditions have been also encountered due to the contemporary nearby channel dredging activity, thus increasing the difficulty for maintaining the stability of the slurry trenches opened in soft material. This paper gives a general overview of the project with some emphasis to the most significant design aspects and to the construction of the deep foundation elements.

Jan 1, 2002

By P. V. Chandramohan

"The paper deals with the arrangement of structural members for a retaining structure used as a berth in the port of Krishnapatnam. The height of retention is 24.3m. A T-shaped diaphragm wall acts as the retaining surface. A relieving platform has been provided at the top to ease lateral earth pressure on the wall. The diaphragm wall is tied back to a combination of vertical and raker pile. Later, this arrangement was altered to replace the relieving platform with just lowering of ground level below the berth. The tie back was changed to a classical A-frame anchorage. At certain reaches, installation of piles pointing towards the rear was obstructed by a conveyor structure. The anchorage was then changed to include a vertical pile and a pile that points towards the front of the berth. Change in position of inclined pile alters the force in the pile from compression to tension.GeneralPort is a major link in the multimodal transport chain. Berth is the heart of the Port infrastructure. It is here the ocean freight changes to land transport. The change-over, warrants special type of heavy duty handling equipment. The equipment and the process necessitate deep seated foundations. On one side of the berth, deep drafted ships would be berthed. But adjacent to this heavy duty cranes would be operating at the deck level. Berths are of various types. Some are founded on piles and may project into water. Some operators prefer a retaining structure. At the port of Krishnapatnam, a retaining structure was preferred. Dredged level at the berth was to be -20. Deck of the berth was at +4.3. This meant that the height of retention of soil was 24.3m. Ports are generally located near the coast. Subsoil in the port area generally consists of cohesive material of low shearing strength. The berth has to cater to imposed vertical and horizontal loads.Structural functionFor bulk cargo and containers, berth has to support the two crane tracks. These tracks will carry heavy wheel loads of the crane. Besides, the space between the tracks would be used for stacking of cargo or hatch covers. In short, the deck will be subjected to heavy surcharge. This vertical load will manifest as additional lateral force on the retaining wall. Since the height of soil to be retained is high, it is a practice to relieve the lateral earth pressure due to the heavy surcharge of the wall. This is done by providing a relieving platform. The surcharge of superimposed load on the deck and the self-weight of the soil up to a few metres below would be relieved by a suitable platform. This vertical load would be transferred directly to deeper levels through piles. Mooring pull is a horizontal force exerted by the vessel on the bollards towards water side. Berthing force is exerted by the vessel during berthing, through fenders and acts towards land side.Diaphragm walls are usually employed as the retaining face. If the height of retention is less, these walls can cantilever out but in the case of large retention, they have to be tied back. The ties are to be anchored on to suitable arrangements like a dead-man or an A-frame. Berthing structure in the early stages at Krishnapatnam port is shown in fig 1."

Jan 1, 2015

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 Abdelmalek Bouazza, Aamir Mahawish, Will P. Gates

Bio-grouting by means of microbial induced calcite (calcium carbonate) precipitation (MICP) to improve mechanical properties of granular soils has gained much attention in recent years. The biogrouting process offers an alternative and environmentally friendly approach to conventional soil improvement techniques, such as cement. Bio-grouting by urea hydrolysis has been extensively applied to tackle various geotechnical problems. However, it has yet to be applied to improve engineering properties (compressive strength) of a coarse cohesionless material with the aim using it as sand/stone columns within soft and very soft soils. This paper investigates the effect of using light, moderate and heavy biochemical treatments on the unconfined compressive strength (UCS) of coarse sand columns. In addition, the microstructure of the bio-cemented coarse material has been analysed by X-ray computed tomography (XRCT). The experimental results revealed that the UCS could reach up to 200kPa, 1000kPa and 5500kPa for light, moderate and heavy bio-cemented coarse sand columns, respectively. The microstructure investigations showed that the deposited calcium carbonate can be identified using XRCT imaging and can be associated with the gain in UCS values. Various microstructure properties, such as void ratio, dry density and porosity were also identified and compared with the laboratory data.

Jan 1, 1900

By Barry C. Roth

Driving of large piles in water can impact marine wildlife. Bubble curtains can mitigate these adverse effects. The procedures for and preliminary results of monitoring airborne, waterborne and groundborne vibrations with and without bubble curtains on a test project involving 2.438 m piles to 110 m is reported here. We observed fish kills and sea lions apparently fleeing the area. These phenomena were presumably due to the extreme acoustic effects of the powerful hammers which generated waterborne sound intensities locally in excess of 240 dB. This waterborne pile driving noise data collection undertaking is believed to be the most extensive ever attempted.

Jan 1, 2001

By Ramanathan Ayothiraman, Anurag Singh

"An experimental program was undertaken to investigate the effects of randomly distributed basalt fibre on the index and engineering properties of Dhanori clay and to compare its performance with the properties of soil reinforced with polypropylene fibre. In the present investigation, 7 groups of soil samples were prepared at four different percentages of basalt fibre and polypropylene fibre content and tests were done for measuring their consistency limits, compaction characteristics, unconfined compression strength and consolidation properties. The test results indicate that the inclusion of basalt fibre in Dhanori clay resulted in significant improvement in properties. The improved properties are not comparable with polypropylene fibres, nevertheless, the improvement by basalt fibres is able to meet the typical design target values and the cost is very much less than synthetic fibres. More importantly, basalt fibres are environment friendly.INTRODUCTIONConstruction of buildings in low lands with engineered filling, flexible and rigid pavements for highways/airfields, and embankments for highways/railways are also part of major infrastructural development in addition to construction of tall buildings, bridges/fly overs, major dams and underground structures. The later projects require different improvement techniques than that is adopted in the former projects. Ground improvement techniques such as use of reinforcement inclusions within soil found as an effective and reliable technique. Especially such modification by fibre reinforcement, is primarily possible in engineered filling, pavements subgrade and embankments, where surface mixing is easier; and may not be feasible when stabilization/modification is required for deeper depths. In comparison with conventional reinforcement using geosynthetics (strips, geotextile, geogrid, etc.), there are some advantages in using randomly distributed fibre as reinforcement. In past few decades, the discrete fibres are simply added and mixed randomly with soil, in much the same way as cement, lime, or other additives.There are several studies (Ziegler et al. 1998; Puppala et al. 2000; Bei-xing et al. 2004; Cai et al. 2006; Tang et al. 2007, 2012, 2016; Abdi et al. 2008; Viswanadham et al. 2009; Le et al. 2015) that investigated the behaviour of polypropylene fibre-reinforced soil and reported that an increase in fibre content caused an increase in strength and shrinkage potential but brought on the reduction of swelling potential. The length of fibres had an insignificant effect on soil characteristics, whereas fibre contents proved more influential and effective. A study on rubber fibre conducted by Hambirao and Rakaraddi (2014) mentions that tensile cracking of clays can be improved with the inclusion of short rubber fibres, optimum fibre content was about 15 % of weight of soil. Several experimental studies (Babu et al. 2008; Chaple and Dhatrak 2013; Vibhakar and Nahta 2014; Soundara and Senthilkumar 2015; Goyal et al. 2015; Jayasree et al. 2014, 2015) were conducted on coir fibre-reinforced soil and concluded that it helped in reducing the swell potential and 1% fibre by weight of the soil almost doubled the CBR value. Martins et al. (2015) found that 4% of sisal fibre by weight of the soil reduced the visibility of cracks. Pillai and Ayothiraman (2012), Ayothiraman et al. (2014) and Sahu et al. (2016) have demonstrated that human hair fibres can be used to improve the properties of both fine grained and coarse grained soils."

Jan 1, 1900

By Ryan P. Sullivan, G. Alan Klevens, Jian Huang

"BACKGROUNDLake Hamilton in Hot Springs, AR was created in 1932 when the Arkansas Power and Light Co. completed Carpenter Dam on the Ouachita River to generate electricity. Today, the 7,200-acre (2,914 hectares) impoundment is one of Arkansas’s most popular recreational and residential lakes.U.S. 70 crosses Lake Hamilton by means of a seven-span bridge featuring nine steel girders per span. Constructed between 1982 and 1984, the 1,410-foot long (430m) bridge carries four lanes of traffi c across the lake. The bridge is supported by six intermediate reinforced concrete piers composed of hammer heads, stems, footings and seals, which sit on the underlying rock. (See Figure 1). The bridge rises to a maximum of 33 feet (10m) above the surface of the lake and the footings and seals extend a maximum of 29.5 feet (9m) below the surface of the lake. The seals are situated on hard, fractured sandstone and shale.Routine underwater inspections in 1993 revealed large cracks in the lean seal concrete and refl ective cracks in the reinforced concrete footings. Infrastructure Engineers, Inc., The Arkansas State Highway and Transportation Department’s (AHTD) design consultant, then conducted an in-depth underwater inspection of the pier foundations. The investigation included cross-hole sonic logging, singlehole sonic logging, visual examination and strength testing of core samples, and petrographic analysis.The investigation revealed extensive cracking and low-strength concrete within the seals of all intermediate pier foundations. Many voids within the seal concrete had become fi lled with silt. There was evidence of continued seal deterioration between underwater inspections.AHTD and its engineers considered three rehabilitation solutions in the preliminary engineering stage: micropiles, a cofferdam supported concrete jacket, or a pile supported concrete jacket. The three alternatives were estimated to cost $1,250,000; $4,320,000; and $3,030,000 respectively. All three options would transfer the loads from the pier footing directly to the rock below, bypassing the seal concrete."

Jan 1, 2007

By Ryan P. Sullivan, G. Alan Klevens, Jian Huang

"BACKGROUNDLake Hamilton in Hot Springs, AR was created in 1932 when the Arkansas Power and Light Co. completed Carpenter Dam on the Ouachita River to generate electricity. Today, the 7,200-acre (2,914 hectares) impoundment is one of Arkansas’s most popular recreational and residential lakes.U.S. 70 crosses Lake Hamilton by means of a seven-span bridge featuring nine steel girders per span. Constructed between 1982 and 1984, the 1,410-foot long (430m) bridge carries four lanes of traffi c across the lake. The bridge is supported by six intermediate reinforced concrete piers composed of hammer heads, stems, footings and seals, which sit on the underlying rock. (See Figure 1). The bridge rises to a maximum of 33 feet (10m) above the surface of the lake and the footings and seals extend a maximum of 29.5 feet (9m) below the surface of the lake. The seals are situated on hard, fractured sandstone and shale. Routine underwater inspections in 1993 revealed large cracks in the lean seal concrete and reflective cracks in the reinforced concrete footings. Infrastructure Engineers, Inc., The Arkansas State Highway and Transportation Department’s (AHTD) design consultant, then conducted an in-depth underwater inspection of the pier foundations. The investigation included cross-hole sonic logging, singlehole sonic logging, visual examination and strength testing of core samples, and petrographic analysis.The investigation revealed extensive cracking and low-strength concrete within the seals of all intermediate pier foundations. Many voids within the seal concrete had become filled with silt. There was evidence of continued seal deterioration between underwater inspections.AHTD and its engineers considered three rehabilitation solutions in the preliminary engineering stage: micropiles, a cofferdam supported concrete jacket, or a pile supported concrete jacket. The three alternatives were estimated to cost $1,250,000; $4,320,000; and $3,030,000 respectively. All three options would transfer the loads from the pier footing directly to the rock below, bypassing the seal concrete."

Jan 1, 2007