模拟干湿循环及含低围压条件的膨胀土三轴试验（双语出版）

针对膨胀土边坡坍滑多呈浅层性，取广西百色膨胀土为对象，设计并开展经干湿循环作用含低围压条件的重塑土饱和三轴固结排水试验，着重分析橡皮膜约束对围压的影响并做出校正，对比分析校正前、后的实测抗剪强度参数，探究不同干湿循环次数及试验围压下的强度及应力-应变关系。结果表明：经干湿循环作用，各级围压下试件的应力-应变均呈应变硬化特征；围压越大，初始模量越大，主应力差也越大；干湿循环作用下，橡皮膜约束等效围压σ_3e均随试验围压σ₃增大而减小；0次干湿循环下，σ₃由5 kPa增至200 kPa时，σ_3e从9.1 kPa减少至6.7 kPa，σ_3e/σ₃由181.8%减少至3.4%，橡皮膜约束对低围压的测试结果影响显著，须进行校正；干湿循环由0次增至6次，校正前低、高和全围压段的黏聚力分别衰减34.7%、27.7%和28.3%，校正后衰减达77.1%、31.9%和35.6%，但摩擦角变化小；橡皮膜约束影响后，经6次干湿循环作用，低围压段的黏聚力仅为0.8 kPa，趋于0，摩擦角为18.5°；膨胀土边坡稳定性分析时，宜采用低、高围压两段拟合校正围压应力圆的强度参数，以获得与实际坍滑破坏较吻合的计算结果。

Simulating Wet-dry Cycles and Low Confining Pressures Triaxial Test on Expansive Soil（in English）

According to the occurrence of shallow failure of most expansive soil slopes, consolidated drained triaxial compression tests on saturated Baise remolded expansive soil were carried out, considering the wet-dry cycles and low confining pressures. The influence of rubber membrane confinement on the confining pressure was analyzed and correction was made. The shear strength parameters measured before and after correction were compared. The strength and stress-strain relationship under different wet-dry cycles and experimental confining pressure were investigated. The results show that stress-strain relationships at all levels of confining pressures due to wet-dry cycles have a strain hardening characteristic. The greater the confining pressure, the greater the initial modulus and principal stress difference. Under the action of wet-dry cycle, the equivalent confining pressure of the rubber membrane σ_3e decreases with the increase in experimental confining pressure σ₃. In the zero wet-dry cycle, when σ₃ increases from 5 kPa to 200 kPa, the σ_3e decreases from 9.1 kPa to 6.7 kPa, and σ_3e/σ₃ decreases from 181.8% to 3.4%. The rubber membrane constraints significantly influence the low confining pressure test results, and correction should be made. When the wet-dry cycle increases from zero times to six times, the cohesion values of low, high, and all confining pressure segments without correction attenuate by 34.7%, 27.7% and 28.3%, while those after correction attenuate by 77.1%, 31.9% and 35.6%, respectively. However, the change in friction angle is small. Considering the influence of the rubber membrane constraint under the action of six dry-wet cycles, the corrected cohesive force value of the low confining pressure segment is only 0.8 kPa tending to zero, and the value of friction angle is 18.5. When analyzing the stability of expansive soil slope, the strength parameters obtained from the confining pressure stress circle fitted by two segments of low and high confining pressure should be used to obtain the calculation results in consistent with the actual collapse failure.