An Experimental Study On Post-Earthquake Settlement Behaiors Of Stone Columns Composite Foundation

There are agreements that Vibro replacement stone columns are in use can mitigate liquefaction hazards in sandy soils for almost three decades.But the post-earthquake settlement of stone columns can also induce earthquake disaster.The research of earthquake response and post-earthquake settlement of stone columns composite foundation during dynamic load is not enough now.And actual measurement and earthquake disaster information of stone columns com-posite foundation is fewer. So the research to stone columns composite foundation settlements is a important part and supplement to the whole theory of composite foundation.A shaking table experiment for stone columns have been made to find the characteristic of stone columns settlement.The following work have been made in this project.1. Technical development has been made to the laminar shear model box after the comprehensive analysis of the key accessories of the laminar shear model box.The deadweight of the new devel-oped model box decreases, and the force mechanism of the model box is more close to the actual one of soil. Equipment can be reused, and its operation capability is better than before.2. The whole scheme of shaking table test have been made. During stone column installa-tion,vibrator have been used to simulate the real construction of stone column installation in this experiment. Support system which inside with adjustable steel pipe have been used to solve the water creep problem in the laminar box.3. Analyse and research have been made to saturated sandy soil foundation and stone columns composite foundation earthquake acceleration response and the rule of development of excess pore water pressure. And analyse have been made to pile-soil stress ratio under upper load during dynamic load.4. A shaking table experiment for saturated sandy soil foundation and stone columns composite foundation have been made,and stone columns composite foundation use the different stone column installation and the different diameter of column and the different pile spacing. The pro-portion between instantaneous settlement and total settlement have been found through the ex-periment. And drawing the post-earthquake settlement curve in 12 hours of stone columns com-posite foundation and saturated sandy soil foundation.And elaborate analyse have been made to post-earthquake settlement.Assess of minishing settlements result have been made based on ex-periment result.5. Adopting dynamic parameter of sandy soil, a simple and practical method of estimating soil set-tlements is established. The shaking table test data have been used to verify the proposed method. And numerical simulation also have been made to shaking table test.