炎热多雨气候下花岗岩残积土的强度衰减与微结构损伤规律

doi:10.13722/j.cnki.jrme.2020.0073

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摘要对花岗岩残积土开展反复干湿循环下的三轴固结不排水(CU)剪切试验与核磁共振成像(MRI)扫描试验，通过应力–应变关系、抗剪强度参数、孔隙体积含量等指标，评价炎热多雨气候对土体性质的损伤效应。研究结果表明：经历0～2次干湿循环的残积土的应力–应变关系曲线在低围压下表现为应变软化型，在高围压下表现为弱应变硬化型，经历3次以上干湿循环的土体应力–应变曲线均为弱应变硬化型；随着循环次数增加，残积土的有效黏聚力和有效内摩擦角逐渐减小，且有效黏聚力的衰减幅度明显更大；通过求解表面弛豫系数，经由T2分布曲线获得了孔隙体积分布曲线，并根据直径将孔隙划分为微孔隙和裂隙；微孔隙的含量随干湿循环次数增加略有减小，裂隙的含量大幅增长；孔隙体积含量与有效抗剪强度指标呈负相关的线性关系，表明力学性能与孔隙结构的演化特征具有同步性；干湿循环对花岗岩残积土的损伤效应主要是由脱湿时的基质吸力增长、吸湿时的孔隙壁膨胀及胶结物分解、流失引起的。

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关键词 ：土力学, 花岗岩残积土, 干湿循环, 三轴剪切试验, 核磁共振成像, 强度指标, 孔隙结构

Abstract：The triaxial consolidation undrained(CU) shear tests and magnetic resonance imaging(MRI) scans were conducted on undisturbed samples of granite residual soils under multiple dry-wet cycles，and the stress-strain curves，shear strength parameters and pore volume content were obtained to evaluate the damage effect of hot and rainy weather on the soil. The experimental results show that，after 0–2 dry-wet cycles，the stress-strain curves of the samples present strain softening and weak strain hardening behaviors under low and high confining pressures，respectively. However，the stress-strain curves of the samples after 3–8 cycles all present weak strain hardening behavior. With increasing the dry-wet cycle number，the effective cohesion and effective internal friction angle gradually decrease，while the attenuation amplitude of the effective cohesion is more obvious. Based on the surface relaxation coefficient of granite residual soils，the pore-volume distribution curves were acquired from the T2 distribution curves，and subsequently，the pores were divided into micropores and cracks according to the pore diameter. It is also revealed that，with increasing the dry-wet cycle number，the content of the micropores declines slightly while the content of the cracks increases significantly. The pore volume content and the effective strength index show a negatively correlated linear relationship，indicating that the decaying patterns in mechanical properties are synchronized with the evolution laws of the pore structure. The damaged effects of dry-wet cycles on granite residual soils are caused by the increase of the matrix suction during dehumidification，the expansive force and the loss of cements during moisture absorption.

Key words： soil mechanics granite residual soil drying-wetting cycle triaxial shear tests magnatic resonance imaging strength index pore structure

引用本文:

安然1，2，孔令伟1，2，黎澄生1，2，罗晓倩1，2. 炎热多雨气候下花岗岩残积土的强度衰减与微结构损伤规律[J]. 岩石力学与工程学报, 2020, 39(9): 1902-1911.
AN Ran1，2，KONG Lingwei1，2，LI Chengsheng1，2，LUO Xiaoqian1，2. Strength attenuation and microstructure damage of granite residual soils under hot and rainy weather#br#. , 2020, 39(9): 1902-1911.

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http://rockmech.whrsm.ac.cn/CN/10.13722/j.cnki.jrme.2020.0073 或 http://rockmech.whrsm.ac.cn/CN/Y2020/V39/I9/1902

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