裂隙性膨胀土抗剪强度的试验研究

摘要

Fissures give expansive soil special structural,which destroys the integrity of the soil, so the expansive soil′s strength test and evaluation become very difficult. In order to study fissures′impact on shear strength of expansive soil and the strength of crack surface, the paper conducted quick shear and “Pre⁃section” triaxial tests on expansive soil in Cixian County of Hebei Province of South⁃to⁃North Water Diversion Project. Studies have shown that, whether quick shear, saturated quick shear, or saturated consolidated quick shear, the shear strength of remodeling comp decreases, comparing with undisturbed samples; residual strength also decreases relatively. Undisturbed expansive soil′s fracture strength is lower than that of the peak strength of undisturbed samples, slightly higher than the residual strength;the soil shear strength measured by triaxial tests with different inclination section appears the phenomenon of first decreasing and then increasing with the inclination′s increasing; when fracture surface′s inclination is approximately equal to (45°+φ/2), the soil strength is mainly controlled by fracture surface′s strength.%裂隙赋予了膨胀土特殊的结构性，裂隙的存在破坏了土体的整体性，使土体强度试验及评价变得十分困难。以南水北调磁县段膨胀土为研究对象，通过直接快剪、反复直剪和“预切面”三轴试验，来研究裂隙对膨胀土体强度的影响规律以及裂隙面的强度特性。结果表明：无论是直接快剪、饱和快剪或是饱和固结快剪试验，得到的重塑样的抗剪强度均较原状样的有所减小，残余强度也相对减小；原状膨胀土的裂隙强度低于原状样的峰值强度，略高于残余强度；采用含有不同倾角的“预切面”三轴试验测得的土体抗剪强度随切面倾角增大出现先减后增的现象；裂隙面倾角近似等于（45°＋φ／2）时，试样土体的强度主要由裂隙强度所控制。