| Summary: | 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.
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