Sam Helwany

Applied Soil Mechanics with ABAQUS Applications

Chapter 1. Properties of Soil. Chapter 2. Elasticity and Plasticity. Chapter 3. Stresses in Soil. Chapter 4. Consolidation. Chapter 5. Shear Strength of Soil. Chapter 6. Shallow Foundations. Chapter 7. Lateral Earth Pressure and Retaining Walls. Chapter 8. Piles and Pile Groups.

GRS bridge abutments—an effective means to alleviate bridge approach settlement

Abstract Field tests of segmental block-faced geosynthetic-reinforced soil (GRS) bridge abutments and piers have demonstrated excellent performance characteristics and very high load carrying capacity. One important feature of GRS abutment is that it can potentially eliminate the use of piling when situated over a weak foundation. This will not only reduce the costs but also reduce “bridge bumps” often experienced at the ends of a bridge resting on a pile-supported abutment. This study was undertaken to investigate the potential of GRS bridge abutments to alleviate bridge approach settlements. The study was conducted by the finite element method of analysis using the computer program DACSAR. The program was first calibrated by comparing its results with the measured data of the Founders/Meadows bridge abutment recently constructed by the Colorado Department of Transportation. A parametric study was then conducted to examine the effects of different foundation soils, ranging from loose sand to stiff clay, on the performance of a GRS abutment. Special attention was placed on the maximum vertical and horizontal movements of the abutment as well as the approach settlement characteristics. The study indicated that the finite element computer code DACSAR is a reliable analytical tool for analyzing the performance of GRS bridge abutments and that the GRS abutment is an effective means to reduce differential settlements between the abutment and the approach embankment.

Effects of backfill on the performance of GRS retaining walls

Abstract In this study, a finite element program was validated by comparing its analytical results with the results of a well-instrumented large-scale laboratory test conducted on a geosynthetic reinforced soil (GRS) retaining wall under well-controlled test conditions. The validated computer program was then used to investigate the effects of backfill type on the behavior of GRS retaining walls. Three different geosynthetic reinforcements and sixteen different backfills were implemented in the analysis of three different wall configurations to produce 144 analysis combinations. It was shown that the type of backfill had the most profound effect on the behavior of the GRS retaining wall. It was also shown that the stiffness of the geosynthetic reinforcement had a considerable effect on the behavior of the GRS retaining wall when the backfill was of lower stiffness and shear strength. A parametric study was performed on GRS retaining walls based on the finite element analyses to assist the design engineer in choosing the appropriate backfill and the appropriate geosynthetic reinforcement for GRS retaining walls in order to satisfy the prescribed requirements of maximum lateral displacement, maximum axial strain in the reinforcements, and/or average safety factors.

Rapid-Construction Technique for Bridge Abutments Using Controlled Low-Strength Materials

The time required for building bridge abutments is one of the main obstacles facing rapid bridge construction. For typical span bridges, this can be remedied by using controlled low-strength materials (CLSM) as backfill materials placed behind full-height, precast concrete panels that are integrated with the CLSM backfill via steel anchors. The CLSM bridge abutments can be constructed in a short time as they require neither heavy machinery for excavation and compaction nor piling equipment. In addition to the speedy construction, the ability to use by-product material, such as fly ash and foundry sand, in CLSM backfill translates into greater economy and the potential for a sustainable design. This paper describes the behavior of an instrumented laboratory, large-scale CLSM bridge abutment with full-height, precast concrete panels that was subjected to a monotonically increasing sill pressure. The experiment showed that the CLSM bridge abutment is capable of carrying typical bridge loads with a large safety margin and with negligible deformations.

Examining the Effects of Reinforcement in U.S. Forest Service Deep-Patch Landslide Repair Technique: Full-Scale Model Tests

A study was undertaken to investigate the effectiveness of the geosynthetic reinforcement in a skin-flow landslide repair method, known as the U.S. Forest Service deep-patch technique. A test apparatus, which can model a full-scale patched slope in the plane stain configuration, was devised and manufactured for the study. The test apparatus allows the behavior of the patched slope to be investigated in well-controlled test conditions. The base panel of the test apparatus contains a section that can be lowered gradually to simulate progressive failure underneath the patched slope subsequent to the repair work. Two tests, one with layers of geosynthetic reinforcement incorporated into the patched slope and one without any reinforcement, were conducted under otherwise identical conditions. Both tests were instrumented to monitor their behavior as the movable section of the base panel was being lowered. The effectiveness of the geosynthetic reinforcement, in terms of its potential for alleviating subsequent failures and its effects on the response of a patched slope during a subsequent failure, is discussed.