Peter M. Byrne

LONG-SPAN REINFORCED STEEL BOX CULVERTS

A comprehensive investigation of soil–metal structure interaction for long-span deep-corrugated reinforced steel box culverts was carried out in a project sponsored by the National Research Council of Canada in 1996. Two 12-m span box culverts were erected at a Dorchester, New Brunswick, test site using two backfill densities, one structural steel plate thickness, and a minimum cover of 300 mm. These structures are the largest steel box culverts erected to date. One structure was reinforced using continuous deep-corrugated crown stiffeners, and the other was intermittently reinforced using composite concrete metal-encased stiffeners. Strain and deflection of the structure were monitored in response to static axle loads positioned at six locations on the test surface. A finite element model was then used in numerical simulations of the soil–metal structure system. The measured culvert response was then compared with results from the finite element model. A nonlinear soil-structure interaction program (NLSSIP) was used to analyze the two long-span box culverts. NLSSIP was developed specifically for long-span soil–metal culverts and has been used for structures with and without stiffeners. The box culvert test provided a definitive relationship between soil stiffness and metal structure stiffness. The test was the first that evaluated intermittently reinforced composite concrete metal-encased stiffeners relative to conventional continuous reinforcement. The performance of the two types of stiffeners is evaluated and recommendations are made for future design and installation of long-span deep-corrugated steel box culverts.

Some Observations on the State of Stress in the Direct Simple Shear Test Using 3D Discrete Element Analysis

Assessment of the mobilized friction angle in a soil specimen tested in a given shear apparatus requires adequate information to establish the stress state at the instance of interest. In the most commonly used version of the direct simple shear (DSS) apparatus, where a cylindrical soil specimen is confined by wire-reinforced membrane, only the normal and shear stresses on the horizontal plane are measured. The knowledge of these stresses alone does not provide adequate information to construct the Mohr circle defining the state of stress. In this context, drained and constant volume (i.e., equivalent to undrained) discrete element simulations of a cylindrical DSS specimen were performed and the results are presented with emphasis on the DSS mobilized friction angle during shearing. It was found that planes of maximum stress obliquity rotate with the development of shear strain. This finding implies that it is not possible to calculate the friction angle accurately from typical DSS laboratory tests with unknown normal stress on the vertical plane. However, it seems that at large shear strains, the horizontal plane becomes a plane of maximum stress obliquity, and the friction angle calculated using the stress state on the horizontal plane is a good approximation to the mobilized friction angle at such shear strain levels.

SEISMIC ANALYSIS OF LARGE BURIED CULVERT STRUCTURES

Field experience indicates that large buried culverts have suffered essentially no damage during past earthquakes when no significant permanent ground movements have occurred. These soil structures, which generally comprise steel or concrete arch members and engineered soil, may have spans of 15 m. Static, pseudodynamic, and dynamic finite-element analyses have been carried out on these structures and indicate that for horizontal seismic loading, the surrounding soil is much stiffer than the arch and results in the seismic load being taken by the soil rather than by the arch. Under vertical seismic loading, the arch is stiffer than the surrounding soil and attracts significant load, which can essentially be accounted for by increasing the unit weight of the soil in proportion to the vertical acceleration. Thrusts and moments in a 10-m concrete arch are examined under combined static and seismic loading (both horizontal, and vertical). The results indicate that significant increases in thrust and moment in...

The Evaluation of the Break-Out Force For a Submerged Ocean Platform

Describes a mechanism which offers an explanation of the breakout phenomenon. This mechanism leads to a simple analytical method for predicting the breakout force. One of the most important factors controlling ability to predict breakout force is the proper evaluation of the strength of ocean sediments. The method is applied to the analysis of data obtained by the Naval Civil Engineering Laboratory at Port Hueneme from breakout experiments in the Gulf of Mexico and San Francisco Bay. It is also applied to the problem of raising a pedestal for a well-head from the ocean floor.

Evaluation of stress strain non-uniformities in the laboratory direct simple shear test specimens using 3D discrete element analysis

The direct simple shear (DSS) device is one of the commonly used laboratory element testing tools to characterize the shear behaviour of soil. The interpretation of results from an element test requires understanding of the degree of stress and strain non-uniformities in a given test specimen. So far, studies on stress and strain non-uniformities in the DSS test have been conducted using direct boundary measurements of stresses in laboratory specimens supported by a continuum based analytical approach. Discrete element modelling now provides a means of modelling the soil behaviour in a realistic manner using a particulate approach. Accordingly, the performance of a DSS specimen was modelled using discrete element modelling with emphasis on assessing stress and strain non-uniformities in the specimen during shearing. The approach allowed for the numerical determination of stresses not only at the boundaries, but also within the DSS specimen. It was shown that mobilised stress ratio distribution throughout the shearing phase for the majority of specimen volume at locations near the central planes parallel and perpendicular to the direction of shearing is fairly uniform. Finally, it was noted that the potential for particle slippage at locations near the specimen centre can result in non-uniform shear strain distributions.

Effects of Partial Saturation on Liquefiable Ground Response

Recent evidence indicates that partially saturated conditions may exist below ground water level. Laboratory test data have shown that the seismic resistance of sands to liquefaction increases as saturation decreases. This paper presents the results of an investigation on partial saturation effects on liquefiable ground response. Using a coupled stress-flow dynamic analysis procedure the ground response to seismic shaking has been analyzed in terms of excess pore pressure and deformations. The results indicate that displacements of a slope under partial saturation condition can be larger than that of fully saturated conditions when a low permeability sub-layer is present.

Seismic Retrofit of Tuttle Creek Dam

AbstractThis paper discusses the seismic retrofit of Tuttle Creek Dam near Manhattan, Kansas, including investigations, seismic analyses, design, construction, and stabilization techniques used. Original plans called for stabilization of the upstream and downstream slopes and installation of an upstream cutoff wall to reduce underseepage. However, constructability and dam safety issues, along with the results of refined seismic deformation analyses, led to cancellation of the jet grouted upstream slope stabilization and cutoff wall. Downstream slope stabilization was to be accomplished by jet grouting or soil mixing, but ultimately was accomplished using a self-hardening cement-bentonite (C-B) slurry to construct transverse shear walls. A total of 351 transverse shear walls were constructed along the downstream toe by primarily clamshell equipment. Typical shear walls are 13.7 m long, 1.2 m wide, and extend 18.9 m deep or about 6.1 m into the coarse foundation sands. The walls are spaced at 4.3 m on cente...

Soil improvement for seismic retrofit of Tuttle Creek Dam

This paper discusses the seismic retrofit of Tuttle Creek Dam near Manhattan, Kansas. Seismic analyses, construction, and stabilization techniques are presented. Constructability and dam safety issues, along with results of refined seismic deformation analyses, led to cancellation of the jet grouted upstream slope stabilization and cutoff wall. Downstream slope stabilization was to be accomplished by jet grouting or jet-assisted soil mixing, but ultimately was accomplished using self-hardening cement-bentonite slurry to construct transverse shear walls to reinforce the liquefiable foundation sands. A total of 351 transverse shear walls were constructed along the downstream toe by primarily clam shell equipment. Typical shear walls are 13.7 m long, 1.2 m wide, and extend 18.9 m deep or about 6.1 m into the foundation sands. The walls are spaced at 4.3m on center along the downstream toe for a replacement ratio of about 29%.

Analysis of Ocean Bottom Sediments

The Civil Engineering Dept. of the University of British Columbia was requested by Lockheed Offshore Petroleum Services Ltd. to perform laboratory tests on ocean bottom sediments taken from a depth of 1,200 ft in the Strait of Georgia, British Columbia. The main purpose of the tests was to determine the stability and settlement of a pedestal base to be placed on the ocean bottom. A secondary purpose was to estimate the force required to lift the pedestal base from the seabed. Samples of the ocean bottom sediments were obtained by dropping a 12-ft long x 2-3/8-in. diam gravity core sampler into the sediments. The sampler was weighted and was allowed to hit the bottom at considerable speed such that the whole sampler penetrated the sediments. During the first 2 sampling attempts, the core catcher placed at the bottom of the sampling tube seemed to prevent the soft material from entering the tube and only a small amount of material was recovered in the sampling shoe.