碱处理红黏土的力学强度试验研究

采用碱液加固红黏土,提高其力学强度,探讨在不同温度、不同干密度和不同加固方式下的碱液加固效果。并结合应力-应变控制式三轴仪对碱处理的红黏土进行了不同应力路径下的力学特性研究。结果表明:碱处理下,红黏土的力学强度随养护温度增加而明显上升,最优温度下无侧限抗压强度增强90.2%,最优干密度下的红黏土试样经过碱液处理后力学强度最大为162.1 kPa,碱液通过拌合的方式掺入加固效果最佳。不同应力路径下的红黏土三轴剪切试验表明,经过碱处理之后的红黏土在CTC(增P)、TC(等P)、RTC(减P)3种工况下,其抗剪强度均有所增加,有效应力路径的c值在CTC和RTC下增幅分别为77.84%和20.36%,φ值变化较小,但在TC路径下,c值基本未变,φ值增幅20.51%。研究成果对红黏土地基加固或基坑的支护设计具有实际意义。

Experimental Study on Strength of Alkali-treated Red Clay

The effect of alkali solution reinforcing red clay was investigated in this paper in the aim of improving its mechanical strength. Temperature, dry density of red clay, and reinforcement method were set varied in the test. The mechanical properties of red clay treated with alkali under different stress paths were examined using a stress-strain controlled triaxial apparatus. Results demonstrated that the mechanical strength of alkali-treated red clay increased with the rising of curing temperature. At optimal temperature, the unconfined compressive strength increased by 90.2%; and given optimal dry density, the alkali-treated red clay sample witnessed a peak mechanical strength of 162.1 kPa. The reinforcement effect reached the optimum when alkali solution was blended into red clay. Moreover, triaxial shear test under different stress paths unveiled that the shear strength of alkali-treated red clay increased under the following three conditions: CTC (Conventional Triaxial Test which simulates the loading process with mean principal stress rising), RTC (Triaxial Test which simulates lateral unloading process with mean principal stress reducing), and TC (Triaxial Test which simulates lateral unloading and axial loading in the meantime with mean principal stress unchanged). The c value of red clay under effective stress path increased by 77.84% and 20.36% under CTC and RTC, respectively, and the value of φ changed little, whereas under the TC path, the c value remained basically unchanged, and the value of φ increased by 20.51%. The research results are of practical significance for the reinforcement of red clay foundation or foundation pit support design.