Geomaterial characterization with displacement measurement technique and finite element simulation.

摘要

The characterization of soil properties is required for analyses and design of structures built on or in the earth. Traditional soil testing methods, however, are expensive and time consuming, due to the requirement of complicated testing procedures and equipment.; This dissertation describes a new testing method for determining shear strength properties of soil. First, the literature on soil testing methods was reviewed, and a new method of testing soil shear strength properties was developed. In the initial stage, surface deformations due to strip loading and subsidence on a dry sandy soil were measured and recorded with a newly developed testing apparatus. The apparatus is composed of a sand box that holds the soil specimen to be tested and a laser-optical distance measurement device with a position sensor. The surface displacements caused by strip loading and subsidence were measured without placing gauges on the granular soil surfaces. The data on surface displacement and strip loading was used for estimating shear strength properties of soils.; To interpret data, simple analytical solutions were established through the limit equilibrium analysis by way of measuring the surface displacement and failure loads. Equations were derived and established for determining shear strength properties, including both internal friction angle, &phis;, and cohesion, c.; To verify the soil strength properties obtained from this new soil testing method, test results were compared with direct shear test data, and simulations were carried out using the finite element method (FEM). The initial research results are encouraging.; Additional research was conducted to further develop the soil testing technique by measuring and analyzing surface subsidence induced over a cavity created on the bottom of the soil specimen. This method can be extended to establish the relationship between surface deformations and soil strength properties.; This investigation paved a new way for determining soil shear strength properties and proved that the newly developed testing methods are a practical way for testing soil strength properties and subsidence simulation. The dissertation also provides recommendations for further research.