Thesis (M.Eng.)--Chulalongkorn University, 2009

Chiang Mai province is located in northern part of Thailand, wherein low to medium earthquake can occur. Therefore, this research aims to present an assessment of dynamic properties of Chiang Mai sand using cyclic direct simple shear test. Two of the most important parameters of dynamic properties in any dynamic analysis related to soils are shear modulus and damping ratio. The monotonic direct simple shear apparatus, which is developed at Norwegian Geotechnical Institute by Bjerrum and Landva, is modified to cyclic direct simple shear so as to be able to determine dynamic properties of Chiang Mai sand. Drained (constant normal stress) tests are carried out with saturated sand sample reconstituted by water pluviation method, which can closely replicate the in-situ fabric of natural sand deposits. In this study, relative density, vertical stresses, shear strain amplitude, and frequency are varied to observe their effect on sand dynamic properties. It can be concluded from the testing results that shear modulus and damping values mainly depend on vertical stress and shear strain. Shear modulus decreases with increasing shear strain amplitude. Oppositely, it increases with increasing vertical stress. The value of hysteretic damping increases with increasing shear strain amplitude. In contrast, when damping ratio decreases with increasing values of vertical stress. The experimental results of present study compared with previous investigations are found to be in fair agreement. All in all, this research is the first work focused on dynamic properties of Chiang Mai sand, which gives great distribution to the calculation of ground response during an earthquake. It also facilitates the following researchers who want to conduct further research on advanced soil laboratory testing about cyclic soil response in Chiang Mai as well as in Thailand