高含水量黏土填方地基强夯置换试验研究

Experimental study on dynamic replacement of high water content clay filled foundation

强夯置换主要用于既有软弱地基的加固,在分层建造以高含水量黏土为主要填料的高填方地基方面尚无工程先例。依托布拖(建昌)±800 kV换流站工程,以现场试验为主要手段,研究了采用强夯置换技术建造高含水量黏土填方地基的填筑方式、处理效果和关键强夯工艺参数等。研究表明:采用强夯能级3 000 kN·m、填筑厚度4 m、直接堆填方案(试验A区),复合地基承载力特征值、变形模量分别可达148 kPa、10.9 MPa,置换墩全着底;采用强夯能级3 000 kN·m、填筑厚度4.5 m、互层堆填方案(试验B区),复合地基承载力特征值、变形模量分别可达158 kPa、9.2 MPa,但置换墩未着底、底部填土未得到有效处理。采用互层堆填方式在一定程度上提高了夯间土的力学性质,但施工效率较低、置换比例较高;直接堆填方式施工效率较高、置换比例较低,经济性较好。

Dynamic replacement is mainly used to reinforce the existing soft foundation.There is still no engineering precedent in layered construction of high fill foundation with high water content clay as the main filler.Based on ±800 kV Butuo(Jianchang) converter station project, field test is used as the main means to study the filling method, treatment effect and key dynamic compaction process parameters of dynamic replacement treatment of high water content clay filled foundation.The results show that the characteristic value of bearing capacity and deformation modulus of composite foundation can reach 148 kPa and 10.9 MPa respectively under the scheme of dynamic compaction energy level 3 000 kN·m, filling thickness 4 m and direct filling method(test area A),and the replacement pier is fully bottomed.And, the characteristic value of bearing capacity and deformation modulus of composite foundation can reach 158 kPa and 9.2 MPa respectively under the scheme of dynamic compaction energy level 3 000 kN·m, filling thickness 4.5 m and interbedding filling method(test area B).However, the replacement pier is not filled with the bottom or bottom soil is not effectively treated.The mechanical properties of the soil between rammers are improved to a certain extent by using interbedding filling method, but the construction efficiency is low and the replacement ratio is high;the direct filling method has higher construction efficiency, lower replacement ratio and better economy.