冻融循环下红色砒砂岩水泥土力学性能试验研究

为实现砒砂岩作为一种自然资源的潜在利用价值,提高砒砂岩有效利用,将鄂尔多斯市准格尔旗的红色砒砂岩加入不同掺量水泥制成砒砂岩水泥土,进行不同围压、不同冻融循环次数条件下的不固结不排水三轴试验,得到了砒砂岩水泥土的各力学参数的变化规律,并通过超景深三维显微镜对砒砂岩水泥土的细观结构进行观测.结果表明:砒砂岩水泥土的应力-应变曲线呈应变软化趋势,随水泥掺量的增加其黏聚力和内摩擦角呈线性增长的趋势.砒砂岩水泥土的内摩擦角受冻融循环影响较小,而黏聚力受冻融循环影响较大.水泥掺量越多,砒砂岩水泥土的抗冻性越好,但其脆性特征越明显.对细观结构的观测进一步验证了冻融使得低掺量水泥的固化土细观结构发生较大改变,导致内部空隙增大,而水泥土随水泥掺量的增加其内部结构更加致密,从而提高了水泥土的抗冻性.

Experimental study on mechanical properties of red Pisha-sandstone cement soil under freeze-thaw cycles

In order to realize the potential utilization value of Pisha-sandstone as a natural resource, the effective utilization of Pisha-sandstone is improved. The red Pisha-sandstone in Zhungeer banner of Ordos City is added with different cement contents to produce the Pisha-sandstone cement soil,and the unconsolidated undrained triaxial tests under different cement mixing ratios, confining pressures and freeze-thaw cycles were carried out. The variation regularities of mechanical parameters of Pisha-sandstone cement soil were obtained, and the meso-structure of Pisha-sandstone cement soil was observed through ultra-depth three-dimensional microscope. The results show that the stress-strain curve of Pisha-sandstone cement soil presents a strain softening trend. The cohesive force and internal friction angle increase linearly with the increase of cement content. The internal friction angle of Pisha-sandstone cement soil is less affected by freeze-thaw cycles, while the cohesion is more affected by freeze-thaw cycles. The more cement content, the better the frost resistance, but the more obvious its brittleness. The meso-structure observation further verifies that the freeze-thaw cycle cause a large change in the meso-structure of cement soil with a small amount of addition, and the increased internal voids can be observed. With the increase of cement content, the compactness of cement soil structure is increased, and the frost resistance of cement soil is effectively improved.