基于正交试验的复合水泥土强度试验研究

Study on the Strength of Cemented Soil with Composite Additive Based on Orthogonal Design

为改善宁波地铁某工程场地深厚软土地基中水泥搅拌桩的加固效果,可开展水泥土复合外加剂设计试验研究。根据选定的水泥、氯化钙、二乙醇单异丙醇胺和氢氧化铝等外加剂,进行正交试验设计,采用4因素3水平正交试验方法,开展室内无侧限抗压强度试验和现场钻芯取样试验。室内试验表明,各因素影响程度由高到低排列顺序为水泥、氯化钙、氢氧化铝和二乙醇单异丙醇胺,最优配合比为水泥21%、氯化钙3%、氢氧化铝3%和二乙醇单异丙醇胺0.03%。与同掺入比的无外加剂水泥土相比,含复合外加剂水泥土7 d、28 d、90 d的最大强度分别提高了46.7%、41.5%和23.1%。现场钻芯取样试验结果表明,经水泥搅拌桩加固后的水泥土强度尽管在深度方向分布不均匀,但其强度均满足工程设计要求,说明正交试验结果是可信的。

To develop the reinforcement effect of cement mixing piles in soft soil of Ningbo,the composite additives for cemented soil were investigated by laboratory test.The three additives,such as Ca C;,Al (OH);,DEIPA,were selected based on engineering experiences.The four factors three levels method of orthogonal test was adopted to analysis theirs importance of several factors by the unconfined compressive strength tests and the core drilling tests.It was shown from laboratory test that the influence degree of each additive on cemented soil strength was ranked from high to low:cement>Ca C;>Al (OH);>DEIPA.The optimum mixture ratio was cement of21%,Ca C;of 3%、Al (OH);of 3%and DEIPA of 0.03%.Compared to the cemented soil with no additive,the maximum strength of cemented soil with composite additives were raised by 46.7%,41.5%and 23.1%under the conditions of 7 d,28 d and 90 d curing age respectively.By the in-situ drilling tests,it was illustrated that the strength of cemented soil along pile was nonuniform,but it met the design requirements.It was concluded that the results from orthogonal test was correct.