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Strength and mechanical behavior of short polypropylene fiber reinforced and cement stabilized clayey soil

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Geotechnical engineers face several challenges when designing structures over soft soils. These include potential bearing failure, intolerable settlement, large lateral pressures and movement, and global or local instability. Geosynthetic-reinforced and pile- supported earth platforms provide an economic and effective solution for embankments, retaining walls, and storage tanks, etc. con- structed on soft soils; especially when rapid construction and/or strict deformation of the structure are required. The inclusion of geosynthetic~s! in the fill enhances the efficiency of load transfer, minimizes yielding of the soil above the pile head, and potentially reduces total and differential settlements. A numerical study has been conducted to investigate pile-soil-geosynthetic ~s! interactions by considering three major influence factors: the height of the fill, the tensile stiffness of geosynthetic, and the elastic modulus of pile material. While current methods have not fully addressed important effects of the geosynthetic stiffness and pile modulus on the soil arching ratio, numerical results suggested that the stress concentration ratio and the maximum tension in geosynthetic increase with the height of the embankment fill, the tensile stiffness of geosynthetic, and the elastic modulus of the pile material. The distribution of tension force in the geosynthetic reinforcement indicated that the maximum tension occurs near the edge of the pile.

Numerical Analysis of Geosynthetic-Reinforced and Pile-Supported Earth Platforms over Soft Soil

A theoretically based design method for the thickness of the base course of unpaved roads is developed in this paper, which considers distribution of stress, strength of base course material, interlock between geosynthetic and base course material, and geosynthetic stiffness in addition to the conditions considered in earlier methods: traffic volume, wheel loads, tire pressure, subgrade strength, rut depth, and influence of the presence of a reinforcing geosynthetic (geotextile or geogrid) on the failure mode of the unpaved road or area. In this method, the required base course thickness for a reinforced unpaved road is calculated using a unique equation, whereas more than one equation was needed with earlier methods. This design method was developed for geogrid-reinforced unpaved roads. However, it can be used for geotextile-reinforced unpaved roads and for unreinforced roads with appropriate values of relevant parameters. The calibration of this design method using data from field wheel load tests and laboratory cyclic plate loading tests on unreinforced and reinforced base courses is presented in the companion paper by the authors.

Design Method for Geogrid-Reinforced Unpaved Roads. I. Development of Design Method

Field observations and numerical studies demonstrated that stone columns could accelerate the rate of consolidation of soft clays. A simplified method for computing the rate of consolidation is presented in this paper by assuming that stone columns; (1) are free draining; (2) have higher drained elastic modulus than soft clay; and (3) are deformed 1D. The formats of the final solutions in vertical and radial flows are similar to those of the Terzaghi 1D solution and the Barron solution for drain wells in fine-grained soils, respectively. Modified coefficients of consolidation are introduced to account for effects of the stone column-soil modular ratio. The new solutions demonstrate stress transfer from the soil to stone columns and dissipation of excess pore water pressures due to drainage and vertical stress reduction during the consolidation. Comparisons between the results from this simplified method and the numerical study by Balaam and Booker in 1981 exhibit reasonable agreement, when the stress concentration ratio is in the practical range (2-6). The discrepancies in the results from these two methods are discussed. This paper also includes design charts and a design example.

Simplified method for consolidation rate of stone column reinforced foundations

A theoretically based base course thickness design method for unpaved roads was developed in the companion paper. This paper presents a calibration of the design method using data from field wheel load tests and laboratory cyclic plate loading tests on unreinforced and reinforced base courses. The constants in the design method are determined during the calibration. The calibrated design method is used for analyzing the test data through three case studies. In addition, the design procedures and a design example are provided in this paper to demonstrate the use of the design method.

Jie Han

Papers

Numerical Analysis of Geosynthetic-Reinforced and Pile-Supported Earth Platforms over Soft Soil

Design Method for Geogrid-Reinforced Unpaved Roads. I. Development of Design Method

Simplified method for consolidation rate of stone column reinforced foundations

Design method for geogrid-reinforced unpaved roads. ii. calibration and applications

Investigation of factors influencing behavior of single geocell-reinforced bases under static loading