J. Hossain

Evaluation of Unknown Foundation Depth Using Different NDT Methods

Many of the older bridges in the United States have no original contract documents available, and about 26,000 bridges that are rated as scour critical have unknown foundation conditions. Thus, no information is available regarding the type, depth, geometry, or material of these scour critical bridge foundations. The unknown bridge foundations pose a significant problem to bridge owners because of safety concerns. This paper presents the determination of an unknown bridge foundation depth at Forth Worth, Texas. The bridge was supported by driven steel H-piles. Three nondestructive testing (NDT) techniques were utilized: (1) the parallel seismic (PS) method, (2) the sonic echo (SE) method, and (3) resistivity imaging (RI). The main objective of this present study was to compare the suitability of NDT techniques to determine the unknown bridge foundation depth. Based on the field test results, both PS and RI methods provided foundation depth close to actual foundation depth. However, the SE method was determined to be unsuitable for determining the unknown steel H-pile depth.

Effects of Backfill Soil on Excessive Movement of MSE Wall

AbstractThe use of mechanically stabilized earth (MSE) retaining walls has gained popularity as an alternative to conventional cast-in-place concrete walls. The construction of MSE walls is cost effective, requires less site preparation, and is technically more feasible compared with conventional concrete retaining walls. However, use of backfill with high fine content and poor drainage behavior can cause excessive wall movement or even failure. The current paper presents the case study of a MSE wall located at State Highway 342 in Lancaster, Texas. The top of the MSE wall has moved as much as 300–450 mm only 5 years after construction. An extensive site and laboratory investigation testing program was conducted to determine the possible causes of the MSE wall movement. The site investigation included soil test boring and resistivity imaging (RI). Perched water zones were identified at a few locations in the backfill area using RI. The bulging of the MSE wall facings was observed where the perched water z...

Assessment of geo-hazard potential and site investigations using Resistivity Imaging

The use of geophysical methods for evaluating subsurface contamination of sites is becoming increasingly popular all over the world. The paper presents the assessment of geo-hazard potential of a site in the City of Duncanville, Texas using Resistivity Imaging (RI). Resistivity Imaging was being used to identify areas of environmental concern and to develop a detailed image of subsurface conditions. Both two dimensional (2D) and three dimensional (3D) resistivity imaging were conducted for the site. A geotechnical site investigations program, which included three test soil borings, was conducted, to confirm the finding from resistivity imaging.

Performance Evaluation of a Slope Reinforced with Recycled Plastic Pin

The shallow slope failures are predominant in the North Texas area and pose significant maintenance problems for the Texas Department of Transportation (TxDOT). Typically, TxDOT maintenance team considers the traditional slope stabilization techniques, mainly concrete retaining wall. However, conventional remedial methods can be expensive in some instances and Recycled Plastic Pin (RPP) could be utilized to stabilize the shallow slope failure as a cost effective alternative. RPP are fabricated from recycled plastics and waste materials (i.e. polymars, sawdust, fly ash). It is a lightweight material and less susceptible to chemical and biological degradation compared to alternative reinforcing element. RPP are driven into the slope face that provides an additional resistance along the slip plane and increase the factor of safety. During the current study, a highway slope located over highway US 287 near the St. Paul overpass in Midlothian, Texas was stabilized using RPP. Surficial movement and cracks over the shoulder were observed near the bridge abutment due to rainfall. Two cracked section of US 287 slope were selected and reinforced using RPP in March 2011. The width of each reinforced section was 15.25 m (50 ft). Another 15.25 m (50 ft) section between two reinforced sections was used as a control section. To monitor the performance of the reinforced and control section, RPPs were instrumented with strain gauges and were installed in all sections. Based on the performance monitoring data of first year, the instrumented RPP at the unreinforced control section had larger strain due to rainfall compared to the reinforced section. In addition, no significant increment in strain was observed in the instrumented RPPs driven at the reinforced zone.

Determining Unknown Bridge Foundation Depth by Resistivity Imaging Method

Determining unknown foundation length and type of bridge foundation is becoming an important concern for state departments of transportation (DOTs) to ensure the safety of the bridge. Based on specific site conditions and type of foundation to be tested, there are several methods available to determine unknown foundation depth. Resistivity Imaging (RI) is a nondestructive method to investigate the subsurface condition. The objective of the current paper is to investigate the applicability of RI for determining unknown foundation depths. RI tests were conducted on two bridges located in North Texas. The first investigated bridge was supported by driven steel H-pile and the other bridge had drilled shaft as foundation. The investigated bridge foundation depths were compared with the actual foundation depths. The determined foundation depth utilizing RI was found very close to actual foundation depth for the first bridge supported by steel H-pile. However, for the second site, the determined depth of foundation did not match with actual depth of foundation.

Investigation of geohazard potential of highway embankment slopes on expansive clay by using geophysical methods

Natural disasters due to failure of geo-structures present an important threat all over the world. Each year, rain induced slope failures cause significant damages in infrastructures and environments, as well as tragic losses of human lives around the world. Therefore, it is important and necessary to improve our knowledge of slope failure mechanism and ways to mitigate slope failures. At present, soil drilling and sampling method are used for the determination of geo-hazard potential of a site. However, this method offers information at certain points, not a general view of the site. Geophysical methods have the possibility to give an image of the subsurface. The objective of the current paper is to present the results of a site investigation using Resistivity Imaging (RI) and Multi-channel Analysis of Surface Wave (MASW) for a highway slope failure in Texas, USA. The site investigation was also conducted using soil test borings. The investigation results were utilized to identify possible failure plan and to determine the associated geo-hazard potential of the site. The preliminary results indicate that geophysical methods can be successfully utilized to determine the geohazard potential of a site.

Investigation of Moisture Variation of Backfill Soil in MSE Wall

The use of mechanically stabilized earth (MSE) retaining wall has gained popularity as an alternative of conventional cast in place concrete walls. The construction of MSE wall is cost effective, requires less site preparation and technically more feasible. However, the performance of MSE wall strongly depends on the backfill soil condition. Backfill soil with high percentage of fine content can cause excessive movement or even failure due to their poor drainage behavior. This paper presents a study on the investigation of backfill soil condition of MSE wall located at state highway 342, Lancaster, Texas. The top of the wall has moved as much as 300 mm to 450 mm at some locations, in only five years after construction. Site investigation included soil test boring, installation of inclinometers and resistivity imaging (RI). The soil samples collected from backfill zone were classified as clayey sand (SC) according to Unified Soil Classification System (USCS). Laboratory testing conducted on the collected soil samples showed 29% to 39% of fine content in backfill soil. RI was performed twice during the investigation period to monitor the moisture condition within the backfill soil. Based on the RI, perched water zones were encountered in two locations near inclinometers. Moreover, increase in perched water zones were observed from March 2010 to July 2010. Moisture content of backfill soil was determined using RI along two profiles in the perched water zones. Increase in moisture content along profiles was observed during investigation period. The rate of wall movement also increased from 1 mm/month to 4 mm/month during this period.

Numerical modeling for remedial measures of shallow slope failure using recycled plastic pins

Highway embankment in North Texas is constructed mainly on expansive clays. However, due to wetting and drying cycles over years, clayey soil in embankments are expected to change their engineering characteristics. Therefore, sloughing and shallow slope failures are predominant in North Texas area and posses a significant maintenance problem for Texas Department of Transportation (TxDOT). Recycled Plastic Pins (RPP) had been utilized in other states (Missouri, Iowa) as a cost effective solution for slope stabilization compared to conventional slope stabilization methods. The objective of this paper is to investigate the possibility of utilizing RPP for slope stabilization in Texas. The slope failure mechanism and stabilization of slope using RPP will be modeled and presented here. The finite element program PLAXIS was used for the modeling. Based on the numerical modeling, the factor of safety without RPP is 1.01. For different RPP spacing, the factor of safety of the modeled slope varies between 1.4 and 1.8. The preliminary results indicate that recycled plastic pins can be utilized for shallow slope failure to increase the stability of soil slope.