干湿循环下复合改良黄土剪切力学特性试验研究

纤维可有效改善土体的力学特性。通过不固结不排水三轴剪切试验,研究了玻璃纤维掺量、纤维长度、养护龄期及干湿循环次数对纤维-秸秆灰-石灰复合改良黄土剪切力学特性的影响规律。试验结果表明:随着纤维的掺入,复合改良土的应力-应变曲线逐步转为应变硬化型,极限偏应力、黏聚力及内摩擦角随着纤维掺量及纤维长度的增加,呈现先增加后减小的趋势,当纤维掺量为0.4%、纤维长度为9 mm时为最优配比。干湿循环条件下,复合改良土的极限偏应力、黏聚力及内摩擦角逐步减小,前期衰减速率较大,后期基本趋于稳定,衰减幅值受纤维掺量、纤维长度影响明显。养护龄期越长,改良土在不同干湿循环下的强度越高,稳定性越好。

Experimental Study on Shear Mechanical Properties of Composite Improved Loess under Wet and Dry Cycles

Fibers effectively improve the mechanical properties of soil. In this paper, the influences of glass fiber content, fiber length, curing age, and drying-wetting cycles on the shear mechanical properties of fiber-straw ash-lime improved composite loess were examined through unconsolidated and undrained triaxial shear tests. Results demonstrated that with the addition of fiber, the stress-strain curve of the improved soil gradually displayed strain hardening features. With the rise of fiber content and fiber length, the ultimate deviatoric stress, cohesion and internal friction angle first increased but then decreased. The optimal ratio is that the fiber content is 0.4% and the fiber length is 9 mm. Under drying-wetting cycles, the ultimate deviatoric stress, cohesion and internal friction angle of the improved soil decayed gradually; the rate of such decay was large in the early stage and tended to be stable in the later stage. The decay amplitude was obviously affected by fiber content and fiber length. Regardless of the number of drying-wetting cycles, the strength and stability of the composite improved soil enhanced with the expansion of curing age