Analysis of Deep Penetration into Compressible Material using Strain Path Method

• Main Authors: Hsieh, Yo-Ming, 謝佑明
• Other Authors: Fushu Jeng
• Format: Others
• Language: zh-TW
• Published: 1997
• Online Access: http://ndltd.ncl.edu.tw/handle/57387096653232663061

碩士 === 國立臺灣大學 === 土木工程學系研究所 === 85 === The common deep penetration problems encountered in geotechnical engineering are pile foundation and soil sampling. However, due to its high gradients in stress and strain field around the penetrator, deep penetration problems can not be solved by using numerical methods such as finite element method and finite difference method. CEM (Cavity expansion method) proposed by Vesic(1972) uses spherical expansion and cylindrical expansion to approximate the strain field caused by penetrator, and then obtain the stress field by using the constitutive laws. But CEM is basically one dimensional analysis, therefore the two dimensional field caused by penetration could not be described completely and satisfactorily by such method. SPM (Strain path method) was first introduced by Baligh in 1985 to solve the deep penetration problem. It uses the combination of point source and ideal flow field to approximate the two-dimensional strain field, and then uses constitutive laws to calculate the stress field. The result of SPM did yield satisfactory solutions to deep penetration problem, but the compressibility of materials was not taken into consideration in 1985. In this research, the compressibility of materials is included in SPM, and then uses SPM to understand the effect of different material properties on penetration. At last, SPM is compared to other theories in deep penetration analysis.The result of this research shows: The compressibility of target materials lowers the stresses induced by penetration, and the influence of compressibility of materials are less than 10%. The mechanism of penetration is dominated by shear behavior of target materials. This research also indicated that the hardness of materials is not only affected by its compressibility, but also by its shear modulus. As the hardness increases, the compressibility decreases and the shear modulus increase.