无填料振冲法在液化粉细砂中的应用研究

结合某电厂工程大面积吹填土的地基处理实践,从振冲法处理地基的加固机理出发,根据振动荷载作用下孔隙水压力的增长方式,由理论公式推导孔压变化的解析式,并由此得到砂土地基达到临界液化状态所需条件。考虑到孔压解析式为单调波动函数,求解困难,故在计算过程中将其分解为单调函数及波动函数两部分,利用图解法求解,得到一定条件下砂土地基临界液化时间的精确值。根据文献中最优密度的概念,经分析认为临界液化时间即为砂土达到最优密度所需的时间,据此可对振冲法施工中的留振时间进行优化设计。对振冲法的预振效应进行了分析,认为预振效应的机理是经过振动处理后,砂土地基的微观结构得到了优化。最后结合工程实例,探讨了无填料振冲法处理液化粉细砂地基的适宜性及处理效果。

Application of vibroflotation without backfill in liquefiable silty and fine sand

The application of vibroflotation without backfill in the improvement of liquefiable silty and fine sand at a power plant ground treatment is presented.On the basis of vibroflotation strengthening principle and the rising mode of vibration pore water pressure,the analytic solution of pore water pressure is deduced from the theoretical formula,and the sand critical liquefaction condition is presented.In view of the monotonic fluctuation function,the analytic solution is detached as monotonic function and fluctuation function and solved by the graphical method to get the exact solutions of sand critical liquefaction time.The paper takes the critical liquefaction time as the time to get the best density of sand and then optimization design for the vibroflotation load time can be made on the basis of the critical liquefaction time.The underlying mechanism of pre-vibration effect is also discussed,which is thought to be useful to improve the microstructure of sand.Finally,the suitability and effectiveness of vibroflotation without backfill on silty and fine sand are dicussed.