基于正交设计的红砂岩改良土抗剪强度试验和回归分析

Shear strength tests and regression analysis of red sandstone-improved soils based on orthogonal design

兰州地区地铁深大复杂基坑日益增多,为了保护生态环境和减少工程造价,通过试验将开挖后的红砂岩添加黄土和水泥进行改良作为路基填料。基于兰州某地铁工程,采用正交试验,对不同配合比下的改良土展开了击实试验和快剪试验,分析了红砂岩改良土抗剪强度的影响因素及其影响大小,给出各因素最佳配合比,并得出了红砂岩改良土抗剪强度的回归模型。试验结果表明:黄土对内摩擦角的影响显著,水泥和含水率对黏聚力影响显著,各因素对黏聚力影响的主次顺序为:水泥掺量→含水率→黄土掺量,对内摩擦角影响的主次顺序为:黄土掺量→含水率→水泥掺量。针对不同配合比下的试验数据,建立回归方程预测改良土的黏聚力和内摩擦角。试验结果对评价红砂岩作为路基回填料具有一定参考价值。

There are more and more deep foundation pits of subway in Lanzhou area. In order to protect the ecological environment and reduce the project cost, after excavation, adding the cement and loess into the red sandstone is used as the roadbed filler through experiments. Based on a subway project in Lanzhou, the compaction tests and the quick shear tests are carried out on the remolded soil with different mixing ratios by adopting orthogonal tests. The influence factors of the shear strength of the red sandstone-improved soil are analyzed, and the best mix proportion of each factor is given. The regression model for shear strength of red sandstone-improved soil is obtained. The test results indicate that the loess has significant influence on the internal friction angle, and the water content and cement have a significant influence on the cohesion. The order of main influence factors of cohesive force can be arranged as follows: cement→water content→loess, and the order of main influence factors of internal friction angle can be arranged as follows: loess→water content→cement. According to the test data of different mix proportions, the regression equation is established to predict the cohesion and internal friction angle of the improved soils. The results have certain reference value for the evaluation of red sandstone as the backfill material.