Terracon Consultants Inc.

Midland, TX, United States

Terracon Consultants Inc.

Midland, TX, United States
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Swaminathan “Vasan” Srinivasan has been elevated to president of Terracon Consultants Inc. from chief operating officer. In the new role, Srinivasan succeeds David Gaboury, who continues as chairman and CEO. An environmental and geotechnical consultant, Terracon ranks at No. 30 on ENR’s list of the Top 500 Design Firms, with $602 million in revenue and 3,500 employees. Vanderbilt University, Nashville, has re­appointed Philippe Fauchet to a second five-year term as dean of its school of engineering, beginning on July 1. The school says undergraduate enrollment rose 15% since 2012, and graduate enrollment is up 11%. It had about 2,000 students enrolled as of fall 2015, says its website; about 30% of undergraduates are women. The school also says it is experiencing “negative attrition,” contending that more students are earning undergraduate engineering degrees than the cohort that declared the major as freshmen. U.K.-based contractor Laing O’Rourke plc has named Sir John Parker chairman, effective later this year. He is set to succeed firm founder Ray O’Rourke, who remains CEO. Parker is former president of the Royal Academy of Engineering and a visiting fellow at Oxford University. He also held senior roles in several business sectors, including chairman of global mining firm Anglo-American plc, which he left in February. Richard McKinney has joined AECOM as vice president of IT strategy in its management services group’s systems engineering and information solutions business. He had been chief information officer of the U.S. Transportation Dept. and a senior adviser to the secretary of transportation on IT issues.

Thakur J.K.,Terracon Consultants Inc. | Han J.,University of Kansas | Parsons R.L.,University of Kansas
Journal of Materials in Civil Engineering | Year: 2017

A significant amount of recycled asphalt pavement (RAP) material is produced from flexible pavement rehabilitation projects. RAP can be used as a base course material for sustainable pavement construction. Performance of a pavement largely depends on the strength of its foundation, which consists of the subgrade and base course layers. Geocell was used in this study to increase the strength of RAP bases. Nine large-scale laboratory cyclic plate loading tests were conducted on unreinforced and geocell-reinforced RAP bases with three different thicknesses (150, 230, and 300 mm) over weak and moderate subgrades to investigate the influence of geocell confinement, base course thickness, base course strength, and subgrade strength on permanent and resilient deformations of RAP bases. The subgrade was prepared by mixing Kansas River sand with kaolin and compacted at weak [target California bearing ratio (CBR)=2%] and moderate (target CBR=5%) strengths. The test results showed that geocell confinement improved the performance of reinforced RAP bases by reducing permanent surface deformations and increasing resilient deformations and percentages of resilient deformation as compared with those of unreinforced bases. The RAP bases over the moderate subgrade performed better than those over the weak subgrade. Subgrade strength had a more pronounced effect than geocell confinement on the properties of RAP bases. Geocell confinement was more beneficial for the bases over the weak subgrade than those over the moderate subgrade. The relative improvement factors (RIFs) of the reinforced bases with respect to the unreinforced bases and the bases over the moderate subgrade with respect to the bases over the weak subgrade ranged from 1.1 to 11.4 and 1.2 to 17.2, respectively. The permanent deformation increased with the number of loading cycles and the RIFs increased with the permanent surface deformation of RAP base sections. © 2016 American Society of Civil Engineers.

Tannoury G.A.,Terracon Consultants Inc. | Schrock S.D.,University of Kansas
2016 Joint Rail Conference, JRC 2016 | Year: 2016

Trackbeds are typically composed of all granular materials comprised of ballast and subballast over compacted subgrade. Most poor performances of railroads can be attributed to poor and unstable subgrade conditions. Below the surface, the instability of the subgrade material can propagate through the granular zone leading to excessive settlements and deformations of the railway. Conventional subgrade restoration in the trackbed system requires the removal of the granular materials and over-excavation of soft unstable subgrade materials, moisture adjustment, re-compaction, and sometimes chemical stabilization of the subgrade soils. Since these procedures are considered very expensive in terms of construction equipment, railway outage time, and labor force, alternative solutions for consideration and evaluation are essential. Injection of expansive foam (polymer based) materials is a relatively recent method that has been used in various applications of soil stabilization in the roadway industry. This technique relies on the injection of rigid-polyurethane foam, which is a high-density, expanding, thermoset, hydroinsensitive and environmentally neutral polyurethane-resin product, into the soft and unstable soil to improve their shear strength and stability index. In addition, the stabilized zone acts as a waterproof membrane protecting moisture sensitive subgrade, and acting as a separation layer to eliminate pumping and contamination of the granular subballast at saturated fine grained conditions. The objective of this paper is to evaluate the practicability of polyurethane stabilized soft and unstable subgrade under unbounded granular trackbeds to mitigate future deformation, restore railway foundation, and reduce trackbed repair cost and outage time. Copyright © 2016 by ASME.

Thakur J.K.,Terracon Consultants Inc | Han J.,University of Kansas
Transportation Infrastructure Geotechnology | Year: 2015

Recycled asphalt pavement (RAP) has increasingly been used as a base material for highway construction as a sustainable solution. Due to the existence of asphalt, 100 % RAP typically has low strength and high potential of creep and permanent deformations. RAP can be blended with virgin aggregate, stabilized by cement and fly ash, or confined by geocell to increase its strength and reduce its creep and permanent deformations. This paper examines several recent experimental studies on treated RAP bases (blended RAP aggregate, cement and fly ash-stabilized RAP, and geocell-confined RAP) and discusses the key findings from these studies including the proportion of RAP to virgin aggregate, type and percent of stabilizing agent, strength, modulus, and creep deformation of treated RAP under static loading, and permanent deformation of treated RAP under cyclic loading. © 2015, Springer New York.

Le M.,Terracon Consultants Inc. | Abrams T.,Terracon Consultants Inc.
Geotechnical Special Publication | Year: 2017

Load carrying capacity of bedrock is needed for the design of foundations for structures in the Dallas-Fort Worth area. The load carrying capacity of bedrock can be estimated by testing rock core samples and by pressuremeter testing. These methods are time consuming and/or rather expensive to implement. An alternative method is to estimate the loading carrying capacity of bedrock in the field using Texas Cone Penetration's (TCP) measurements (number of blows per 12 inch cone travel distance or cone travel distance per 100 blows) and charts developed by Texas Department of Transportation (TxDOT). Moon et al. (2004) have developed empirical equations to mathematically predict the compressive strength of shale in Dallas area. However, the rock quality designation (RQD) and rock percentage recovery, which measure the degree of jointing or fracture in a rock mass, have not been included in the published correlations. This study presents a new approach to incorporate RQD and rock percentage recovery as another contributing factor in new empirical correlations along with the TCP's measurements to better estimate the unconfined compression strength of Eagle Ford shale in particular. This new strength correlation that was developed has a better statistical fitness compared to other previously developed correlations by other researchers. © ASCE.

Han J.,University of Kansas | Bhandari A.,University of Kansas | Bhandari A.,Terracon Consultants Inc. | Wang F.,Nanjing Southeast University
International Journal of Geomechanics | Year: 2012

The geosynthetic-reinforced pile-supported embankment is one of the favorable ground improvement techniques used in the construction of earth structures over a compressible soil when limited construction time is available and limited deformation is permissible. Various methods are available for the design of the geosynthetic-reinforced platform basedon various load transfer mechanisms from the embankment to the piles and the compressiblesoil. The existence of the geosynthetic layer makes the mechanisms more complex. This study focuses on the behavior of geogrid-reinforced embankments over piles compared with thebehavior of unreinforced embankments. The numerical simulations of the unreinforced and reinforced pile-supported embankments were conducted using the discrete element method (DEM). The embankment fill was simulated using unbonded graded aggregates of diameters ranging from 9.2 to 20.8 mm and the geogrid was simulated using bonded particles. This study investigated the changes of vertical and horizontal stresses and porosities, the vertical displacements within the embankment fill, and the deflection and tension in the geogrid. The simulation results showed that the coefficient of lateral earth pressure in the embankment fill changed from an initial at rest condition to a passive condition at certain locations after the compression of the compressible soil. The embankment fill dilated during the development of soil arching. The embankment load was transferred to the piles owingto the reorientation of the principal stresses. The results also showed that the geogrid reinforcement significantly reduced the total and differential settlements at the top of the embankment. © 2012 American Society of Civil Engineers.

Tetrachloroethene (PCE) releases at a former dry cleaner resulted in impacts to soil and shallow groundwater beneath and adjacent to the building. Subsurface impacts led to vapor intrusion with PCE concentrations between 900 and 1,200 micrograms per cubic meter (μg/m3) in indoor air. The migration pathways of impacted soil vapor were evaluated through implementation of a helium tracer test and vapor sampling of an exterior concrete block wall. Results confirmed that the concrete block wall acted as a conduit for vapor intrusion into the building. A combination of remediation efforts focused on mass reduction in the source area as well as mitigation efforts to inhibit vapor migration into the building. Excavation of soils beneath the floor slab and installation of a spray-applied vapor barrier resulted in PCE concentrations in indoor air decreasing by over 97.9 percent. Operation of an active ventilation system installed under the floor slab and groundwater remediation via injections of nano-scale zero valent iron (nZVI) further reduced PCE concentrations in indoor air by over 99.8 percent compared to baseline conditions. While significant reductions of PCE concentrations in groundwater were observed within two months after injection, maximum reductions to PCE concentrations in indoor air were not observed for an additional 12 months. © 2014 Wiley Periodicals, Inc.

Rollins K.M.,Brigham Young University | Jessee S.J.,Terracon Consultants Inc.
Journal of Bridge Engineering | Year: 2013

The passive force-deflection relationship for abutment walls is important for bridges subjected to thermal expansion and seismic forces, but no test results have been available for skewed abutments. To determine the influence of skew angle on the development of passive force, laboratory tests were performed on a wall with skew angles of 0, 15, 30, and 45. The wall was 1.26 m wide and 0.61 m high, and the backfill consisted of dense compacted sand. As the skew angle increased, the passive force decreased substantially, with a reduction of 50% at a skew of 30. An adjustment factor was developed to account for the reduced capacity as a function of skew angle. The shape of the passive force-deflection curve leading to the peak force transitioned from a hyperbolic shape to a more bilinear shape as the skew angle increased. However, the horizontal displacement necessary to develop the peak passive force was still between 2 and 4% of the wall height. In all cases, the passive force decreased after the peak value, which would be expected for dense sand; however, at higher skew angles, the drop in resistance was more abrupt. The residual passive force was typically 40% lower than the peak force. For nearly all skew angles, the transverse shear resistance exceeded the applied shear force on the wall so that transverse movement was minimal. Computer models using the plane strain friction angle were able to match the measured force for the no skew case as well as for skewed cases when the proposed adjustment factor was used. © 2013 American Society of Civil Engineers.

Tan Y.,Tongji University | Tan Y.,WPC Inc. | Lin G.,Terracon Consultants Inc.
Journal of Geotechnical and Geoenvironmental Engineering | Year: 2013

Although many studies have been done to investigate the axial behaviors of open-ended piles in sands, few studies have been reported for weak clayey silts. To develop reliable models for the design of open-ended steel-pipe piles driven into 29-m-thick varved clayey silt deposits, a series of full-scale field load tests including large-strain dynamic tests and static cyclic axial-compression-load tests was conducted on two groups of instrumented piles. Through analysis of the test data, soil parameters were back-calculated for estimation of pile capacities using the static-bearing-capacity formulas and cone-resistance-based methods. The comparisons between the calculated results and the field load test data demonstrated that the following considerations can be adopted in the design of static compression capacities of an open-ended pipe pile penetrating through thick varved clayey silts to end-bearing in dense cohesionless soils: (1) a fully plugged condition can be assumed, (2) cone resistance with an upper limit of 4,788 kPa (100 ksf) can be used for unit base resistance on the soil plug, and (3) exterior unit shaft resistance can be estimated using two-thirds of the total unit shaft resistance. © 2013 American Society of Civil Engineers.

Sebastian Bryson L.,University of Kentucky | Ortiz R.,Terracon Consultants Inc
Geotechnical Special Publication | Year: 2016

Cementitous grout is often used in permeation grouting applications, such as in seepage cutoff. However, ordinary Portland cement can be ineffective for permeation grouting of fine-grained sands or in sands with significant amounts of fines. Ultrafine cement grout thus becomes a viable alternative material for grout applications in these types of soils. While a major benefit of ultrafine grout is its penetration ability into the soils with relatively low hydraulic conductivity, the strength of the ultrafine grouted soil mass is not thoroughly discussed in literature. This study investigated initial conditions that could affect grout application effectiveness. An apparatus was developed so that a controlled volume of grout could be injected into a soil specimen. This study found that increases in water-To-cement ratio have a significant effect on the unconfined compressive strength of the neat grout. Grout penetration rates through the samples decreased as matric suction increased. The observed grout penetration rates were observed to be an inverse function of the unsaturated hydraulic conductivity. Also, the strength of the grouted sand was observed to increase as the matric suction increased. The results of this study suggest that knowledge of matric suction may be useful for estimating injection penetration rates and strength of ultrafine grouted sand. © ASCE.

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