藏东南冰碛体剪切特性受冻融循环的影响及改良∗

藏东南地区广泛分布着冰碛体堆积体，此土体严重影响工程安全。为了研究冰碛体的剪切性能并对其进行改良，运用相似原理配制出级配良好的冰碛体相似材料，分别在不同冻融循环次数和不同含水率的条件下，对冰碛体相似材料开展了直剪试验，同时掺入机油和粉煤灰外加剂进行三轴试验，研究其对冰碛体相似材料抗剪强度参数的影响。结果表明：（1）直剪试验过程中，随着垂直压力的增大，冰碛体的位移?剪应力曲线由弱应变软化型转变为弱应变硬化型。（2）含水率变化对冰碛体抗剪强度的升降受到冻融循环次数的影响。（3）冻融循环为5 次是冰碛体材料抗剪强度的分界线。（4）机油和粉煤灰对冰碛体抗剪强度指标（咬合力和内摩擦角）的影响相反。

Influence of Freeze-Thaw Cycles on Shear Characteristics of Morainesin Southeastern Tibet and Their Improvement

Moraine deposits, which are widely distributed in southeastern Tibet, pose significant risksto engineering projects. In order to study and improve their shear performance, well-graded similarmaterials replicating moraines were prepared using the principle of similarity. Under different freezethawcycles and moisture content conditions, direct shear tests were conducted on these similar materials.Triaxial tests were conducted with the addition of engine oil and fly ash admixtures to study theirimpact on the shear strength parameters of the moraine-like materials. The results showed that: (1) Indirect shear tests, with the increase of vertical pressure, the displacement-shear stress curve of moraineschanged from a weak strain softening type to a weak strain hardening type. (2) The influence ofmoisture content on moraines'' shear strength was affected by the number of freeze-thaw cycles. (3) Afterfive freeze-thaw cycles, the material reached a threshold in shear strength. (4) Engine oil and flyash had opposite effects on the shear strength indices (cohesion and internal friction angle) of the moraines.