This paper presents the results of field performance tests of 39 in-service corrugated steel highway culverts in Ohio. The culverts had span lengths varying from 3.23m(10.6ft)to7.04m(23.1ft) and backfill soil heights over the crown varying from 0.27m(0.9ft)to7.47m(24.5ft). Static and dynamic load tests were conducted by driving heavy trucks across the culverts. Static loads were applied at ten different locations above each culvert. Dynamic load tests were conducted at six truck speeds varying from 8km∕h(5mi∕h)to64km∕h(40mi∕h). A portable instrumentation frame was installed inside each test culvert to monitor deflections. Strains on the culvert walls were also measured at 14 locations using strain gauges. Effects of backfill height and loading conditions are investigated. According to the experimental results, a plot of maximum culvert deflection versus backfill height shows a nonlinear relationship. Maximum static load deflections were found to be consistently larger than the maximum dynamic deflections obtained using the same test truck. Deflections were nearly zero for deep culverts with backfill heights exceeding 4m(13ft). Maximum deflections correlate more closely to equivalent line loads than to total truck weight. The data also indicate that culvert behavior is more difficult to predict when backfill heights are shallow because other factors, such as culvert age and condition and soil type, likely play a significant role.
The main objective of this study was to evaluate and improve the Ohio Department of Transportation's (ODOT's) current load rating procedures for corrugated metal culverts. This objective is achieved by testing 39 in-service culverts under static and dynamic loads, by evaluating the response of test culverts using available theoretical methods and numerical simulations, and by evaluating and advancing the current analysis tools and load rating methods based on the analytical and experimental evidence generated in this research. The experimental program was conducted to investigate the influence of several parameters on the field performance of culverts in Ohio. These parameters include backfill height, various static and dynamic load applications, and existing condition, size, shape, and other properties of corrugated metal culverts. Experimental results show that culvert deflections decrease nonlinearly with increasing backfill height. Deflections and strains were nearly zero in deep culverts with backfill height larger than 13 ft (4 m). Under static and dynamic truck loading, culvert deflections and strains increased significantly when the backfill height was less than about 6.5 ft (2.0 m). Responses of some of the test culverts were simulated using the two-dimensional finite element program CANDE. Deflections predicted from CANDE analysis were larger than deflections measured in the field. However, the moments and thrusts calculated from experimental strains were similar to those calculated using theoretical methods and CANDE. Experimental data and available theoretical studies were used to evaluate the current load rating methods. Recommendations are made to improve the analysis and evaluation procedures for corrugated metal culverts. Recommendations are based on an extensive review of load rating procedures and design practices, experimental data from 39 test culverts, and theoretical and numerical investigations. The recommended load rating procedures do not consider the effect of cover depth. New capacity reduction factors are introduced for culvert wall and seam, which require different appraisals for wall and seam during annual inspections. The authors recommend changes to rating factors for deep culverts and culverts subjected to low live load stresses.
A 17 m-high steel strip reinforced soil retaining wall was instrumented to compare field measurements with predictions given by the design guidelines of the American Association of State Highway and Transportation Officials (AASHTO) 1996 Standard Specifications and the AASHTO 1999 Interim Revisions. The AASHTO models were conservative with respect to external lateral earth pressures and lateral earth pressures on the facing panels. On average, the AASHTO 1996 and 1999 models overestimated lateral pressure at the facing by 94 and 142%, respectively. Measured values of foundation bearing stress were generally in good agreement with values calculated using soil unit weight and depth, except that the average force from the facing panels on the leveling pad was twice that of the weight of the panels themselves. This discrepancy is attributed to shear stress on the back of the facing panels and vertical loads transferred to the panels through the strip connection clips. The location of the zone of maximum strip tension was in good agreement with the assumed failure surface. On average, the AASHTO 1996 and 1999 models underestimated maximum strip tensions by 17 and 8% and overestimated strip connection tensions by 127 and 154%, respectively. Finally, the apparent soil-reinforcement friction coefficient for the ribbed steel strips exceeded values specified in the AASHTO models by an average of 132%.
This paper presents a numerical investigation of the performance of geosynthetic-reinforced soil (GRS) bridge abutments under static loading conditions. Simulations were conducted using a finite-difference program to model the Founders/Meadows GRS bridge abutment during construction and service. Simulated results are in good agreement with field measurements, including displacements, lateral and vertical earth pressures, and tensile strains and forces in reinforcement. The simulations also indicate that horizontal restraint from the bridge structure has a significant influence on abutment deflections. A parametric study was then conducted to investigate the performance of a single-span full bridge system with two GRS abutments, including effects of bridge contact friction coefficient, backfill soil relative compaction, backfill soil cohesion, reinforcement spacing, reinforcement length, reinforcement stiffness, and bridge load. Results indicate that backfill soil relative compaction, reinforcement spacing, and bridge load have the most significant influence on lateral facing displacements and bridge footing settlements for GRS abutments. Differential settlements between the bridge footing and approach roadway were small for all simulated conditions.
The results of numerical simulations for coupled large strain consolidation and solute transport, obtained using the CST1 model, are presented. CST1 accounts for advection, longitudinal and transverse dispersion, first-order decay reactions, and linear equilibrium sorption. Verification checks of CST1 show excellent agreement with analytical solutions for one-dimensional (1D) transport in rigid porous media, including various Peclet numbers and concentration boundary conditions. Similarly excellent agreement is observed for two-dimensional advection-dispersion transport in rigid media and 1D advection-dispersion transport in compressible media undergoing large strain consolidation. CST1 is then used to investigate consolidation-induced solute transport for a single composite liner system and a confined disposal facility for dredged contaminated sediments. In both cases, solute transport was found to be strongly affected by consolidation-induced advection both during and after the consolidation period. Consolidation has a lasting effect on solute migration because transient advective flows change the distribution of solute mass, which then becomes the initial condition for subsequent transport processes.
This paper presents the results of performance tests of a large number of in-service corrugated metal culverts in Ohio. The test culverts had span lengths varying from 3.4 m (11 ft) to 6.4 m (21 ft) and backfill soil heights over the crown varying from 0.6 m (1.8 ft) to 7.6 m (22.3 ft). Static and dynamic loads were applied by using heavy trucks. The static loads were applied at ten different locations above each culvert. Dynamic load tests were also conducted at six speeds varying from 8 km/h (5 mph) to 64 km/h (40 mph). A portable instrumentation frame was installed inside each test culvert to monitor deflections. Strains on the culvert walls were also measured at fourteen locations using strain gages. Effects of backfill height and loading conditions are investigated. According to the experimental results, a plot of maximum culvert deflection versus backfill height shows a nonlinear relationship. Maximum static load deflections were found to be consistently larger than the maximum dynamic deflections obtained using the same test truck. Deflections are nearly zero for deep culverts with backfill height exceeding 4 m (13 ft). Maximum deflections correlate more closely to AASHTO equivalent line loads than to total truck weight. The data also indicate that culvert behavior is more difficult to predict when backfill heights are shallow because other factors, such as culvert age and condition and soil type, likely play a significant role.
This paper presents numerical analyses of one-dimensional heat transfer in layered saturated soil with effective porosity and under a periodic temperature boundary condition using the numerical model HT1. The model characterizes the soil layer using separate columns to represent solid matrix and mobile pore fluid components, and a series-parallel approach to model soil thermal conductivity. Numerical simulations are presented to illustrate the effect of fluid velocity, thermal retardation factor, thermal conductivity of solid particles, effective porosity and layer heterogeneity. Numerical results indicate that increasing downward fluid velocity and decreasing retardation factor can increase the distance that temperature oscillations from the surface can propagate into the layer. In addition, decreasing fluid velocity, increasing retardation factor, and increasing thermal conductivity of solid particles can decrease the temperature oscillation amplitude in the soil. Temperature profiles also indicate the significance of soil effective porosity and multiple soil layers on heat transfer behavior.
: This paper presents an invited update to our 2004 state-of-the-art report and provides a comprehensive source of information on the shear strength and shear strength testing of geosynthetic clay liners (GCLs). Essential concepts of shear stress–displacement behavior and shear strength are presented, followed by detailed discussions on the laboratory measurement of the shear strength of GCLs and GCL interfaces. The paper also provides recommendations for the selection of design strength envelopes for stability analyses and checklists to assist users in the specification of GCL shear testing programs. North American practice is emphasized and discussions are focused primarily within the context of landfill bottom liner and cover systems. Conclusions and recommendations are provided with regard to GCL shear strength behavior and current GCL strength testing practice, improvements for GCL strength testing are suggested, and future research needs are identified.
A study of the internal shear strength of adhesive-bonded, stitch-bonded, and needle-punched geosynthetic clay liners (GCLs) is presented. Tests were performed using a large direct shear machine capable of measuring peak and residual (or near residual) shear strengths. For each product, failure occurred at the woven geotextile/bentonite interface and excess pore pressures remained zero on the failure plane during shear. The peak shear strength of the needle-punched GCL increased significantly with increasing normal stress because of the frictional connection of the reinforcing fibers. The peak shear strengths of the adhesive-bonded and stitch-bonded GCLs showed smaller corresponding increases. The residual shear-strength failure envelope was essentially independent of product type. A two-stage procedure for specimen hydration is described, which reduced the required in-machine hydration time to reach equilibrium conditions. For the reinforced products, small decreases in peak and residual shear strengths were observed with decreasing displacement rate. The findings of the study have implications for the design of facilities incorporating GCLs and for the manufacturing and shear-strength testing of GCL products.
The assumption of local thermal equilibrium (LTE) between solid and fluid phases commonly is used for studies of heat transfer in saturated soil and is valid for a wide range of conditions. However, for certain conditions, the heat transfer process may give rise to local thermal nonequilibrium (LTNE) in which adjacent solid and fluid phases have different temperatures. This note presents the results of a numerical study of the validity of the LTE assumption for one-dimensional heat transfer in a saturated soil layer with fluid flow. For the conditions investigated, the LTE assumption holds for soil with particle sizes smaller than the gravel range. For soil with particles sizes in the gravel range and larger, the LTE assumption may be valid or invalid, depending primarily on fluid discharge velocity, with higher fluid velocity values more likely to produce LTNE conditions.
As part of an experimental program, a large number of in-service culverts were tested to investigate the influence of several parameters on field performance of culverts. These parameters included cover depth, load application, size, shape, and other properties of corrugated metal culverts. Response of 14 test culverts was simulated using a two-dimensional finite element program and a three-dimensional finite difference program. Deflections predicted from the two-dimensional analyses were larger than the deflections measured in the field. However, the experimental and calculated thrust forces were similar. Deflections and thrust forces predicted from the three-dimensional analysis were similar to the experimental results. The critical factors affecting the response of the culverts include cover depth, culvert size, metal thickness, and elastic modulus and other properties of backfill soil. The influence of these parameters on the culvert behavior is investigated through numerical simulations using the established modeling properties.
