A multi-scale study on structure damage of granite residual soil under wetting-drying environments
AN Ran1，2，KONG Lingwei1，ZHANG Xianwei1，GUO Aiguo1，BAI Wei1
(1. School of Urban Construction，Wuhan University of Science and Technology，Wuhan，Hubei 430065，China；2. State Key Laboratory of Geomechanics and Geotechnical Engineering，Institute of Rock and Soil Mechanics，
Chinese Academy of Sciences，Wuhan，Hubei 430071，China)
Abstract：To study the environmental effect with hot and rainy feature to the structural characteristics of granite residual soil under multiple dry-wet cycles，the triaxial consolidation undrained(CU)，computer tomography(CT)，nuclear magnetic resonance(NMR) and scanning electron microscope(SEM) tests were performed. Then，a multi-scale study from microscopic，mesoscopic，and macroscopic perspective about the damage mechanism of the soil. The test results show that the wetting-drying effect shows a change in particle and pore structure at microscopic scale，an expansion of fractures at mesoscopic scale，and a decrease in strength at macroscopic scale. The effective cohesion decreases exponentially with the increase of the wetting-drying cycles and the effective internal friction angle decays in a small range. The development process of meso-fractures can be divided into three phrases，which are the germination stage(0 to 1 cycle)，the development stage(2 to 5 cycles)，and the stable stage(5 to 8 cycles). The pore volume distribution curves of granite residual soil show a bimodal shape. The pores can be divided into four types according to pore size. With the increasing number of wetting-drying cycles，the volumetric proportion of microscopic pores decreased，while that of medium pores and large pores increased drastically. During the wetting-drying process，the clay particles gradually loose and the intergranular pores expand and connect to form connected cracks. Due to the wetting-drying effect，the hydrophilic clay minerals expand during a humidifying process，the microscopic tensile stress increases during a drying process，and the cemented materials decompose and lose. The three factors jointly drive the expansion and connectivity of fractures and cause fatigue damage to the soil structure，leading to the attenuation of mechanical properties of soil. This study provides a useful reference for the understanding of mechanical properties and structural damage rules of granite residual soil in hot and rainy climate.
[1] 杨光华. 广东深基坑支护工程的发展及新挑战[J]. 岩石力学与工程学报，2012，31(11)：2 276–2 284.(YANG Guanghua. Development and new challenges of deep excavation supporting engineering in Guangdong province[J]. Chinese Journal of Rock Mechanics and Engineering，2012，31(11)：2 276–2 284.(in Chinese))
[2] 安 然，孔令伟，张先伟. 残积土孔内剪切试验的强度特性及广义邓肯–张模型研究[J]. 岩土工程学报，2020，42(9)：1 723–1 732. (RAN An，KONG Lingwei，ZHANG Xianwei. Mechanical properties and generalized Duncan-Chang model for granite residual soils using borehole shear tests[J]. Chinese Journal of Geotechnical Engineering，2020，42(9)：1 723–1 732.(in Chinese))
[3] XIA J，CAI C，WEI Y，et al. Granite residual soil properties in collapsing gullies of South China：spatial variations and effects on collapsing gully erosion[J]. Catena，2019，174：469–477.
[4] XU J C，NI Y D. Prediction of grey-catastrophe destabilization time of a granite residual soil slope under rainfall[J]. Bulletin of Engineering Geology and the Environment，2019，78(8)：5 687–5 693.
[5] 黎澄生，安 然，舒荣军，等. 花岗岩残积土初期崩解规律与数学形态学方法近似模拟[J]. 岩石力学与工程学报，2020，39(4)：845–854.(LI Chengsheng，AN Ran，SHU Rongjun，et al. Initial-disintegration analysis of granite residual soil and approximate simulation of mathematical morphology[J]. Chinese Journal of Rock Mechanics and Engineering，2020，39(4)：845–854.(in Chinese))
[6] 汪华斌，周 宇，余 刚，等. 结构性花岗岩残积土三轴试验研究[J]. 岩土力学，2021，42(4)：991–1 002.(WANG Huabin，ZHOU Yu，YU Gang，et al. A triaxial test study on structural granite residual soil[J]. Rock and Soil Mechanics，2021，42(4)：991–1 002.(in Chinese))
[7] 安 然，孔令伟，黎澄生，等. 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)：1 902–1 911.(AN Ran，KONG Lingwei，LI Chengsheng，et al. Strength attenuation and microstructure damage of granite residual soils under hot and rainy weather[J]. Chinese Journal of Rock Mechanics and Engineering，2020，39(9)：1 902–1 911.(in Chinese))
[8] SUN Y L，TANG L S. Use of X-ray computed tomography to study structures and particle contacts of granite residual soil[J]. Journal of Central South University，2019，26(4)：938–954.
[9] 刘 越，陈东霞，王 晖，等. 干湿循环下考虑裂隙发育的残积土边坡响应分析[J]. 岩土力学，2021，42(7)：1 933–1 943.(LIU Yue，CHEN Dongxia，WANG Hui，et al. Response analysis of residual soil slope considering crack development under drying-wetting cycles[J]. Rock and Soil Mechanics，201，42(7)：1 933–1 943.(in Chinese))
[10] 王德咏，周树津，韩雨薇，等. 干湿循环下花岗岩残积土路堑边坡稳定性研究[J]. 公路，2021，66(1)：1–6.(WANG Deyong，ZHOU Shujin，HAN Yuwei，et al. Research on the cut slope stability of granite residual soils under wet and dry cycles[J]. Highway，2021，66(1)：1–6.(in Chinese))
[11] 简文彬，胡海瑞，罗阳华，等. 干湿循环下花岗岩残积土强度衰减试验研究[J]. 工程地质学报，2017，25(3)：592–597.(JIAN Wenbin，HU Hairui，LUO Yanghua，et al. Experimental study on deterioration of granitic residual soil strength in wetting-drying cycles[J]. Journal of Engineering Geology，2017，25(3)：592–597.(in Chinese))
[12] SAYEM H M，KONG L W，YIN S. Effect of drying-wetting cycles on saturated shear strength of undisturbed residual soils[J]. American Journal of Civil Engineering，2016，4(4)：143–150.
[13] 刘俊东，唐朝生，曾 浩，等. 干湿循环条件下黏性土干缩裂隙演化特征[J]. 岩土力学，2021，42(10)：2 763–2 772.(LIU Jundong，TANG Chaosheng，ZENG Hao，et al. Evolution of desiccation cracking behavior of clays under drying-wetting cycles[J]. Rock and Soil Mechanics，2021，42(10)：2 763–2 772.(in Chinese))
[14] 汪时机，王晓琪，李 达，等. 膨胀土干湿循环裂隙演化及其土–水特征曲线研究[J]. 岩土工程学报，2021，43(增1)：58–63.(WANG Shiji，WANG Xiaoqi，LI Da，et al. Evolution of fissures and bivariate-bimodal soil-water characteristic curves of expansive soil under drying-wetting cycles[J]. Chinese Journal of Geotechnical Engineering，2021，43(Supp.1)：58–63.(in Chinese))
[15] 张先伟，孔令伟，陈 成，等. 炎热多雨和突降暴雨气候影响下玄武岩残积土的崩解试验研究[J]. 中国科学：技术科学，2016，46(11)：1 175–1 184.(ZHANG Xianwei，KONG Lingwei，CHEN Cheng，et al. Experimental investigation on relative contribution of hot and humid weather and heavy rainfall in disintegration of basalt residual soil[J]. Science China：Technological Sciences，2016，46(11)：1 175–1 184.(in Chinese))
[16] 于佳静，陈东霞，王 晖，等. 干湿循环下花岗岩残积土抗剪强度及边坡稳定性分析[J]. 厦门大学学报：自然科学版，2019，58(4)：614–620.(YU Jiajing，CHEN Dongxia，WANG Hui，et al. Analysis of the shear strength of granite residual soil and slope stability under wetting-drying cycles[J]. Journal of Xiamen University：Natural Science，2019，58(4)：614–620.(in Chinese))
[17] 安 然，孔令伟，柏 巍，等. 单轴荷载下残积土的电阻率损伤模型及干湿循环效应[J]. 岩石力学与工程学报，2020，39(增1)：3 159–3 167.(AN Ran，KONG Lingwei，BAI Wei，et al. The resistivity damage model of residual soil under uniaxial load and the law of drying-wetting effects[J]. Chinese Journal of Rock Mechanics and Engineering，2020，39(Supp.1)：3 159–3 167.(in Chinese))
[18] GUAN G S，RAHARDJO H，CHOON L E. Shear strength equations for unsaturated soil under drying and wetting[J]. Journal of Geotechnical and Geoenvironmental Engineering，2010，136(4)：594–606.
[19] AN R，KONG L W，ZHANG X W，et al. Effects of dry-wet cycles on three-dimensional pore structure and permeability characteristics of granite residual soil using X-ray micro computed tomography[J]. Journal of Rock Mechanics and Geotechnical Engineering，2021，https：//doi.org/10.1016/j.jrmge.2021. 10.004
[20] KONG L W，SAYEM H M，TIAN H. Influence of drying–wetting cycles on soil-water characteristic curve of undisturbed granite residual soils and microstructure mechanism by nuclear magnetic resonance(NMR) spin-spin relaxation time(T2) relaxometry[J]. Canadian Geotechnical Journal，2018，55(2)：208–216.
[21] 王 港，张先伟，刘新宇，等. 厦门花岗岩残积土的压缩变形特性及其微观机制[J]. 岩土力学，2021，42(12)：3 291–3 300.(WANG Gang，ZHANG Xianwei，LIU Xinyu，et al. Compression characteristics and microscopic mechanism of Xiamen granite residual soil[J]. Rock and Soil Mechanics，2021，42(12)：3 291–3 300.(in Chinese))
[22] ZHANG X W，LIU X Y，CHEN C，et al. Evolution of disintegration properties of granite residual soil with microstructure alteration due to wetting and drying cycles[J]. Bulletin of Engineering Geology and the Environment，2022，81(3)：1–15.
[23] LIU WP，SONG X Q，LUO J，et al. The processes and mechanisms of collapsing erosion for granite residual soil in southern China[J]. Journal of Soils and Sediments，2020，20(2)：992–1 002.
[24] PIRES LF，COOPER M，CÁSSARO FAM，et al. Micromorphological analysis to characterize structure modifications of soil samples submitted to wetting and drying cycles[J]. Catena，2008，72：297–304.
[25] TIAN H H，WEI C F，WEI H. An NMR-Based analysis of soil-water characteristics[J]. Applied Magnetic Resonance，2014，45：49–61.
[26] DAIGLE H，DUGAN B. Extending NMR data for permeability estimation in fine-grained sediments[J]. Marine and Petroleum Geology，2009，26：1 419–1 427.
[27] 张先伟，孔令伟，臧 濛. 雷州半岛玄武岩残积土的工程地质特性研究[J]. 岩土工程学报，2014，36(5)：855–863.(ZHANG Xianwei，KONG Lingwei，ZANG Meng. Engineering geological characteristics of basalt residual soils in Leizhou Peninsula[J]. Chinese Journal of Geotechnical Engineering，2014，36(5)：855–863.(in Chinese))
[28] 陈东霞，龚晓南，马 亢. 厦门地区非饱和残积土的强度随含水量变化规律[J]. 岩石力学与工程学报，2015，34(增1)：3 484–3 490. (CHEN Dongxia，GONG Xiaonan，MA Kang. Variation of the shear strength of Xiamen unsaturated residual soils with water content[J]. Chinese Journal of Rock Mechanics and Engineering，2015，34(Supp.1)：3 484–3 490.(in Chinese))
[29] 梁广川，汪时机，李 贤，等. 砂质黏性紫色土渗透特性试验研究[J]. 岩土工程学报，2018，40(增2)：220–224.(LIANG Guangchuan，WANG Shiji，LI Xian，et al. Experimental study on permeability characteristics of sandy clayey purple soil[J]. Chinese Journal of Geotechnical Engineering，2018，40(Supp.2)：220–224.(in Chinese))
[30] 唐朝生，施 斌，刘 春，等. 影响黏性土表面干缩裂缝结构形态的因素及定量分析[J]. 水利学报，2007，38(10)：1 186–1 193. (TANG Chaosheng，SHI Bing，LIU Chun，et al. Factors affecting the surface cracking in clay due to drying shrinkage[J]. Journal of Hydraulic Engineering，2007，38(10)：1 186–1 193.(in Chinese))
[31] 孙银磊，汤连生. 化学成分对花岗岩残积土抗拉张力学特性的影响[J]. 中山大学学报：自然科学版，2018，57(3)：7–13.(SUN Yinlei，TANG Liansheng. The effect of chemical composition on tensile mechanics of residual granite soils[J]. Journal of Sun Yat-Sen University：Natural Science，2018，57(3)：7–13.(in Chinese))
[32] XU X T，SHA L J，HUANG J B，et al. Effect of wet-dry cycles on shear strength of residual soil[J]. Soils and Foundations，2021，61(3)：782–797.
[33] 谭罗荣，孔令伟. 特殊岩土工程土质学[M]. 北京：科学出版社，2006：56–60.(TAN Luorong，KONG Lingwei. Engineering behavior of special rock and soil[M]. Beijing：Science Press，2006：56–60.(in Chinese))
2023, Vol. 42 
