Evaluating the Application of Surface Wave Method in Examination of Ground Improving Rate by Numerical Simulation
|Keywords:||地盤改良;表面波震測;有限差分法;ground improvement;surface wave method;finite difference|
研究成果顯示，表面波於改良後場址之行為，主要受到波長λ與改良柱間距t影響，當λ/t>4時，其波速之均質化可由其等效波速決定，當 λ/t<4時，則為等效串聯模數行為。透過對表面波震測 λ/t 的計算，判斷表面波均質化之行為模式，可有效得將表面波震測應用做為改良率的檢核工具，經與現場實測資料初步比對驗證後顯示，此檢核方法具有可行性且極具潛力。|
Ground improvement can improve the engineering properties of soil, such as shear strength, stiffness, and bearing capacity. But after construction, the improved site is highly heterogeneous. Experimental methods ( Standard Penetration Test, Sampling, etc.) used to assess such ground improvement are not effective due to small sampling volume. Surface wave method as a non-invasive and direct method for assessing the overall quality of the ground improvement is characterized by large sampling volume, efficiency, and cost effectiveness. However, how to interpret the shear wave velocity increase measured by the surface wave method remained to be discussed. In this study, numerical simulations were conducted to quantitatively investigate the relationship between shear wave velocity and improving rate (i.e. replacement ratio of ground improvement). Research shows that surface wave behavior in the improved site is mainly affected by the wavelength(λ) and column spacing( t ). When λ/ t > 4, the homogenization of shear wave velocity can be derived based on the equivalent velocity. When λ/ t < 4, the homogenization should be derived based on the equivalent modulus in series. Through the calculation of λ/ t to determine the homogenization behavior of surface wave, the surface wave method can be effectively used to inspect the improving rate. By comparison with field measurement data, the hypothesis is further verified and shows that the surface wave method has great potential and feasibility in assessment of improving rate.
|Appears in Collections:||Thesis|