水泥改性土削坡余料二次利用研究

The Reusing of Surplus Soil from Slope Cutting of Cement-modification Soil

选取南水北调中线南阳段膨胀土,进行水泥改性,对渠道边坡削坡余料进行二次利用时发现现场碾压干密度达不到最低设计要求.通过室内试验对削坡余料的压实性能进行了分析,得出了3个关键影响因素,即龄期、颗粒组成和水泥有效成分,最大干密度随着龄期的增加而逐渐降低,欲使最大干密度满足设计要求,二次利用时间必须控制在水泥改性土换填后5 d之内,施工工期紧凑;与天然膨胀土相比,由于削坡余料级配不良,影响压实性能.在此基础上,对削坡余料进行了改良试验研究,提出3种改良方法,分别是混合非膨胀土、混合天然膨胀土再掺水泥和再掺水泥的改良方法.通过工程造价分析,对以上改良方法进行方案比选,从技术、经济上合理选择最佳方法,得出前两种改良方法具有较好的可行性和经济性,解决最大干密度无法满足最低设计要求的工程难题.

Expansive soil in the midline of South-North Water Transfer Project at Nanyang was selected to conduct cement modification laboratory tests. The dry density on the spot can not meet the minimum design requirements, when reusing the surplus soil after cutting the channel slopes. The factors affecting compaction capacity were studied. Three critical factors were proposed as following：age,particle composition and effective components of cement. The maximum dry density would be decreased with the extension of age,only the reusing time controlled in 5 days after replace cement-modified soil that the maximum dry density can meet design requirements,but it is urgent in construction period. Compared with natural expansive soil,its compaction capacity will be affected due to the bad gradation of surplus soil from slope cutting. Based on the above,the surplus soil from slope cutting was selected to conduct modification laboratory tests,three improved methods were proposed as following：mix with non-expansive soil,mix with natural expansive soil and to add cement,addition to cement. The above improved methods are compared by making use of the engineering cost,with optimum method chosen from the view of technology, economy and rationality. The analysis results show that the first two methods are of fairly good feasibility and efficiency,the engineering problem that maximum dry density can not meet the minimum design requirements was successfully solved.