Carrollton, TX, United States
Carrollton, TX, United States

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Hossain M.S.,University of Texas at Arlington | Haque M.A.,Bryant Consultants Inc. | Hoyos L.R.,University of Texas at Arlington
Geotechnical and Geological Engineering | Year: 2010

Bioreactor landfills are operated to enhance refuse decomposition, gas production, and waste stabilization. The major aspect of bioreactor landfill operation is the recirculation of collected leachate back through the refuse mass. Due to the presence of additional leachate and accelerated decomposition, the characteristics of Municipal Solid Waste (MSW) in bioreactor landfills are expected to change. About 50% of the continental United States comes under the designated seismic impact zone. The federal regulations have focused increase attention on seismic design of solid waste fills, and have mandated that the solid waste landfills located in the seismic impact zones should be designed to resist the earthquake. Accordingly, assessment of dynamic properties of landfills is one of the major geotechnical tasks in landfill engineering. In order to understand the changes in dynamic properties of bioreactor waste mass with time and decomposition, four small scale bioreactor landfills were simulated in laboratory and samples were prepared to represent each phase of decomposition. The state of decomposition was quantified by methane yield, pH, and volatile organic content (VOC). A number of Resonant Column (RC) tests were performed to evaluate the dynamic properties (stiffness and damping) of MSW. The test results indicated that the normalized shear modulus reduction and damping curves are significantly affected by the degree of decomposition. The shear modulus increased from 2.11 MPa in Phase I to 12.56 MPa in Phase IV. The increase was attributed to the breakdown of fibrous nature of solid waste particles as it degrades. Therefore, considering MSW properties to be uniform throughout the bioreactor landfill is not a reasonable assumption and the shear modulus reduction curves should be evaluated based on the degree of MSW decomposition, rather than the sample composition itself. © 2010 Springer Science+Business Media B.V.

Hossain M.S.,University of Texas at Arlington | Haque M.A.,Bryant Consultants Inc.
Journal of Materials in Civil Engineering | Year: 2012

To estimate the generated leachate and design of a leachate recirculation system, a clear understanding of the hydraulic conductivity of municipal solid waste with degradation, and the effects of intermixed cover soils, is necessary. Two sets of laboratory-scale bioreactor landfills were simulated and sampled at various phases of decomposition. The state of decomposition was quantified by methane yield, pH,and volatile organic content. The matrix structure of the degradablesolid waste component was broken down because of decomposition. However, daily cover soil, a nondegradable constituent of municipal solid waste, remained constant. Therefore, interaction between daily cover soil and municipal solid waste particles are expected to affect hydraulic characteristics resulting from degradation. The current study shows that the hydraulic conductivity of municipal solid waste with cover soil is lower than that without any intermixed cover soils. Based on experimental results, hydraulic conductivity of municipal solid waste samples in (aerobic) phase I is 5.8 × 10-3 cm/s, and drops to 2.6 × 10-3 and 1.7 × 10-3 cm/s, with 20 and 30% cover soils, respectively. Hydraulic conductivity decreases with increasing soil percentage. Therefore, the effects of cover soils on municipal solid waste hydraulic conductivity should be evaluated and taken into consideration during the design and operation of a landfill recirculation system. © 2012 American Society of Civil Engineers.

Bryant J.T.,Bryant Consultants Inc. | Haque M.A.,Bryant Consultants Inc.
Unsaturated Soils - Proceedings of the 5th International Conference on Unsaturated Soils | Year: 2011

The design of foundation systems on expansive soils requires knowledge of unsaturated soil mechanics. Expansive clay minerals are electrochemically active particles, especially in the presence of water. This affinity for water leads to soil mass volume changes with changes in soil moisture content. When a cohesive soil mass hydrates, the materials experience a volume change (termed swelling or heaving), the magnitude of which depends on the clay chemistry and the initial degree of saturation. The results from the swell test method, which tends to provide a conservatively higher estimate of movement due to the lateral confinement of the soil sample in a steel ring, is used as a basis to design most of the foundation systems. However, this test is not representative of conditions in nature, where the vertical swell strain is only a portion of the total volume change. This test method can also produce conservative estimates of movement due to complete inundation of the sample with water throughout the entire active zone depth, which is not generally typical in-situ. In order to avoid overly conservative design and to provide better performing foundation systems, in this study a heuristic approach is revealed for producing guidelines to design efficient foundation systems at a reasonable cost. The heuristic approach will also be shown to comport with principles of unsaturated soil mechanics. © 2011 Taylor & Francis Group, London.

Haque M.A.,Bryant Consultants Inc. | Bryant J.T.,Bryant Consultants Inc.
Electronic Journal of Geotechnical Engineering | Year: 2010

Vert Wall Systems (VWS) is a proprietary construction process developed, designed, and constructed by Geo-Con to support excavations. The VWS is a top-down, in-situ gravity wall system, which primarily uses deep soil-mixing method (DMM) technology. The DMM technology involves in-situ mixing of existing weak soil with cementitious materials like lime, cement, or combination of both. There are no standard designs available for the VWS; as such, the size, strength, and spacing of the components are site specific. In this study, the reported movement into the VWS system constructed in Irving-Las Colinas area in Texas was evaluated. Visual assessment of the problems indicated failure of a substantial body of soil at the site. The movement involved the failure of VWS retaining wall. Evaluation of the VWS design was checked using finite element program PLAXIS and limit equilibrium program GSTABL. The general trend between the soil movement measured by inclinometers and the wall movement predicted by FEM appeared to be in reasonable agreement with each other. The evaluation also elucidated some salient issues concerning the application of the VWS at this site and the reasonableness of the design assumptions used. This engineering evaluation also demonstrated that testing coupled with experience and engineering judgment should be used to provide design parameters and should be the basis of the VWS design assumptions. © 2010 ejge.

Bryant J.T.,Bryant Consultants Inc. | Haque M.A.,Bryant Consultants Inc. | Douglas B.L.,Bryant Consultants Inc.
Forensic Engineering 2012: Gateway to a Better Tomorrow - Proceedings of the 6th Congress on Forensic Engineering | Year: 2013

A heuristic approach was adopted to solve a time dependent geothermal problem. Freezer floors in a cold storage was replaced due to frost heaving of subgrade soils. The failure of previous heating system below the floor slab was attributed to the frost heave of subgrade soils. The heating system was fixed and the floor slab was replaced. Subsequent to the completion of the project, slab distress was soon noticed on the replaced slab. Several geotechnical investigations were performed both prior to and after replacement of the slab by others. Review of previous (pre slab replacement) geotechnical reports revealed that the incorrect estimation of thaw consolidation was the primary reason for the observed slab distress. A geothermal analysis was performed using TEMP/w to estimate the amount of time it would have taken by the frozen soil present at this site to thaw to the current condition. The settlement estimates from thaw-consolidation test and the time rate of settlement estimates from geothermal analysis correlated well with the observed slab settlement. In addition, it was also proved that the deformation (settlement) of frozen soils during thaw cycle is not completely reversible due to local soil consolidation caused by cryosuction forces. © ASCE 2013.

Haque M.A.,Bryant Consultants Inc. | Bryant J.T.,Bryant Consultants Inc.
Forensic Engineering 2012: Gateway to a Better Tomorrow - Proceedings of the 6th Congress on Forensic Engineering | Year: 2013

A building pad was certified for an allowable bearing pressure of 191.5 kilopascal (KPa). Subsequent to the pad certification the site contractor had repeatedly driven across the building pad with heavy equipment. Due to this, the surficial soils in the building pad yielded in some of the areas. Subsequently, standard penetration test (SPT) test and laboratory unconfined compressive strength (UCS) tests were performed by others on the prepared pad and it was concluded that the bearing pressure should be significantly lowered to 71.8 KPa from 191.5 KPa. The UCS test used to estimate the shear strength of soils is most common test in engineering practice. However, engineers often overlook one of the important soil parameters, the soil suction, which considerably affects the soil behavior. The increase in soil suction considerably increases the soil shear strength. A simplistic approach was adopted to measure the shear strength of partially saturated soils. A series of unconsolidated undrained (UU) tests were performed at different matric suction and by maintaining the same lateral confining pressure. Since the shear strength measured in the UU test reflects in-situ matric suction of the soil, an increase in matric suction significantly increased the undrained shear strength of a partially saturated soil. This in turn increased the bearing capacity of the soil and thereby the factor of safety. Based on the results from the test, it was concluded that the subsurface soils present at this site had adequate strength to support an allowable bearing pressure of 191.5 KPa. Further, it was also proved that the cause of pad rutting was not due to lower bearing capacity, but it was due to the trucks exerting 40% more load than the allowable bearing pressure of 191.5 KPa. © ASCE 2013.

Bryant J.T.,Bryant Consultants Inc. | Haque M.A.,Bryant Consultants Inc.
Geotechnical Special Publication | Year: 2011

A gas leak at a residence caused an explosion. It was hypothesized that the soil shrink/swell potential caused a break in the polyethylene (PE) gas pipe-coupler connection, which subsequently resulted in a leak and an explosion. However, this claim was without any scientific reasoning or engineering principles such as soil-structure interaction. Review of prior information indicated that sometime prior to the explosion a water line was installed below the PE gas pipeline and a BOMAG multipurpose compactor was used to compact the backfill in the water pipe trench. The waterline and PE gas pipeline were perpendicular to each other. Using finite element method (FEM) analysis of the soil-pipe system and the scientific method using site-specific soil, geophysical, and geotechnical data it was shown that the break in the PE pipeline and coupler was due to deformation (displacement) of the soils in the trench area, where the PE gas service line was present and not due to soil movement alone. This deformation is the result of external and applied loads from the BOMAG compactor in the static and dynamic compaction modes. A field re-creation of the construction sequence on a later date corroborated very similar pipe displacements as that predicted by the numerical modeling. This confirmed the results from numerical modeling and confirmed that the construction activities during the installation of water service and/or sewer lines underneath the gas line caused the gas line to sag and pull out at the adjacent pipe-coupler connection. © ASCE 2011.

A system and method is provided for on-site site risk assessment and to encourage collaboration between professional disciplines related to land development and construction projects. A graphical risk analysis system is provided based on answers to interdisciplinary questions related to risks. Use of the system promotes a complete checklist of interdisciplinary and informational consultation which, when completed for a project, assesses the risk related to construction site development and allows for reduction in risk as the project progresses.

Bryant Consultants Inc. | Date: 2015-06-02

A system and method for moisture control includes a computer, a probe controller connected to the computer, a set of probes connected to the probe controller, a sprinkler controller connected to the computer, and a set of sprinklers connected to the sprinkler controller. The set of probes are driven into the ground according to a predetermined set of positions. A set of high voltage currents is injected into the ground through the set of probes and measurements are taken. A three-dimensional resistivity model is generated from the measurements and is compared to a set of moisture requirements. A set of sprinkler commands is generated based on the three-dimensional resistivity model and the set of moisture requirements. If the three-dimensional resistivity model meets the set of moisture requirements, the set of sprinklers are activated in each of a set of sprinkler zones according the three-dimensional resistivity model where watering is needed.

Bryant Consultants Inc. | Date: 2011-03-01

Subsurface geological detection equipment, namely, computer controlled resistance meters.

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