水库运行期岸坡消落带红砂岩抗剪与抗压强度劣化机制
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摘要
目前在水库运行期岸坡消落带环境条件模拟方面,对消落带岩石在库水位周期性升降条件下宏观强度劣化规律进行研究时,主要侧重于"湿干"交替作用环境条件的单一模拟,鲜见对水库运行期岸坡消落带岩石所处的岸坡应力、"湿干"交替和库水渗透综合作用的真实环境条件进行模拟。自主研发了能模拟岸坡应力、"湿干"交替和库水渗透综合作用环境的水库岸坡消落带软岩三轴试验系统,以三峡库区马家沟滑坡红砂岩为研究对象,开展红砂岩的单轴、三轴压缩试验,并分析了岩石试样的破坏模式;同时,通过扫描电镜(SEM)和X射线衍射(XRD)等测试方法,获得红砂岩的微细观结构和黏土矿物成分随"湿干"交替作用次数增加的变化规律。研究结果表明:红砂岩的峰值抗压强度随"湿干"交替作用次数增加逐渐劣化,其中前4次"湿干"交替过程中,峰值抗压强度劣化幅度较大;第6～8次"湿干"交替过程中,劣化幅度逐渐减小。随"湿干"交替作用次数的增加,红砂岩的黏聚力也逐渐下降,第1～4次"湿干"交替过程中,黏聚力的下降幅度较大;第6～8次"湿干"交替过程中,黏聚力的下降幅度明显减小。随"湿干"交替作用次数的增加,红砂岩的内摩擦角有所降低,但变化规律不明显。红砂岩中的黏土矿物因水化反应产生不均匀膨胀、收缩,导致碎屑矿物颗粒之间的胶结作用遭到一定程度的弱化,在宏观上表现为抗剪强度、抗拉强度的劣化;抗剪强度、抗拉强度的劣化使得红砂岩在轴向荷载的作用下更容易发生破坏,是导致峰值抗压强度发生劣化的直接原因,而红砂岩中胶结物胶结作用的变弱是红砂岩峰值抗压强度发生劣化的根本原因;同时,渗透压对峰值抗压强度、抗剪强度的劣化具有一定程度的促进作用。研究成果可为水库运行期岸坡稳定性动态分析与评价提供科学的依据。
So far, the researches on the degradation of macroscopic strength of rock under cyclic wetting-drying conditions in the course of reservoir operation mainly focus on simulations of single environmental conditions without considering the combined actions of slope stresses, wetting-drying cycles and seepage water pressures. The triaxial test system of soft rock in the drawdown areas is developed independently to simulate the combined actions of slope stresses, wetting-drying cycles and seepage water pressures. The red sandstone from Majiagou landslide is selected as the study object. The uniaxial and triaxial compression tests on the red sandstone are carried out, and the failure modes are analyzed after each wetting-drying cycle.Meanwhile, the variation of microstructure and clay mineral content of red sandstone undergoing different numbers of wetting-drying cycles is always explored by means of the scanning electron microscopy(SEM) and X-ray diffraction(XRD).The results show that with the increasing number of wetting-drying cycles, the peak compressive strength of red sandstone decreases gradually. In the first four wetting-drying cycles, the peak compressive strength decreases obviously. After the sixth wetting-drying cycle, the decline trend of the peak compressive strength decreases gradually. With the increasing of wetting-drying cycles, the cohesion of red sandstone decreases gradually either, and the cohesion decreases a lot during the first four wetting-drying cycles. The reduction extent of cohesion is obviously reduced in the sixth to eightth wetting-drying cycles. The friction angle of red sandstone decreases with the increasing number of wetting-drying cycles, but the change rate is small. The uneven expansion and shrinkage of clay minerals caused by hydration reaction weaken the cementation between clastic mineral particles to a certain extent, which embodies the deterioration of shear strength and tensile strength on the macro level. The deterioration of shear strength and tensile strength makes red sandstone more vulnerable to failure under the action of axial loads, which is the direct reason for the deterioration of the peak compressive strength. The weak cementation of detrital minerals is the fundamental reason for the deterioration of the peak compressive strength. Meanwhile, the seepage water pressures can promote the deterioration of the peak compressive and shear strength to a certain extent. The research results can provide a scientific basis for the dynamic analysis and evaluation of the slope stability during the operation of reservoirs.
So far, the researches on the degradation of macroscopic strength of rock under cyclic wetting-drying conditions in the course of reservoir operation mainly focus on simulations of single environmental conditions without considering the combined actions of slope stresses, wetting-drying cycles and seepage water pressures. The triaxial test system of soft rock in the drawdown areas is developed independently to simulate the combined actions of slope stresses, wetting-drying cycles and seepage water pressures. The red sandstone from Majiagou landslide is selected as the study object. The uniaxial and triaxial compression tests on the red sandstone are carried out, and the failure modes are analyzed after each wetting-drying cycle.Meanwhile, the variation of microstructure and clay mineral content of red sandstone undergoing different numbers of wetting-drying cycles is always explored by means of the scanning electron microscopy(SEM) and X-ray diffraction(XRD).The results show that with the increasing number of wetting-drying cycles, the peak compressive strength of red sandstone decreases gradually. In the first four wetting-drying cycles, the peak compressive strength decreases obviously. After the sixth wetting-drying cycle, the decline trend of the peak compressive strength decreases gradually. With the increasing of wetting-drying cycles, the cohesion of red sandstone decreases gradually either, and the cohesion decreases a lot during the first four wetting-drying cycles. The reduction extent of cohesion is obviously reduced in the sixth to eightth wetting-drying cycles. The friction angle of red sandstone decreases with the increasing number of wetting-drying cycles, but the change rate is small. The uneven expansion and shrinkage of clay minerals caused by hydration reaction weaken the cementation between clastic mineral particles to a certain extent, which embodies the deterioration of shear strength and tensile strength on the macro level. The deterioration of shear strength and tensile strength makes red sandstone more vulnerable to failure under the action of axial loads, which is the direct reason for the deterioration of the peak compressive strength. The weak cementation of detrital minerals is the fundamental reason for the deterioration of the peak compressive strength. Meanwhile, the seepage water pressures can promote the deterioration of the peak compressive and shear strength to a certain extent. The research results can provide a scientific basis for the dynamic analysis and evaluation of the slope stability during the operation of reservoirs.
引文
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[8]傅晏,王子娟,刘新荣,等.干湿循环作用下砂岩细观损伤演化及宏观劣化研究[J].岩土工程学报,2017,39(9):1653-1661.(FU Yan,WANG Zi-juan,LIU Xin-rong,et al.Meso damage evolution characteristics and macro degradation of sandstone under wetting-drying cycles[J].Chinese Journal of Geotechnical Engineering,2017,39(9):1653-1661.(in Chinese))
[9]ZHANG Z H,JIANG Q H,ZHOU C B,et al.Strength and failure characteristics of Jurassic Red-Bed sandstone under cyclic wetting-drying conditions[J].Geophysical Journal International,2014,198(2):1034-1044.
[10]邓华锋,李建林,王孔伟,等.饱和-风干循环过程中砂岩次生孔隙率变化规律研究[J].岩土力学,2012,33(2):483-488.(DENG Hua-feng,LI Jian-lin,WANG Kong-wei,et al.Research on secondary porosity changing law of sandstone under saturation-air dry cycles[J].Rock and Soil Mechanics,2012,33(2):483-488.(in Chinese))
[11]邓华锋,李建林,刘杰,等.浸泡-风干循环作用对砂岩变形及破坏特征影响研究[J].岩土工程学报,2012,34(9):1620-1626.(DENG Hua-feng,LI Jian-lin,LIU Jie,et al.Influence of immersion-air dry circulation function on deformation and fracture features of sandstone[J].Chinese Journal of Geotechnical Engineering,2012,34(9):1620-1626.(in Chinese))
[12]邓华锋,李建林,朱敏,等.饱水-风干循环作用下砂岩强度劣化规律试验研究[J].岩土力学,2012,33(11):3306-3312.(DENG Hua-feng,LI Jian-lin,ZHU Min,et al.Experimental research on strength deterioration rules of sandstone under“saturation-air dry”circulation function[J].Rock and Soil Mechanics,2012,33(11):3306-3312.(in Chinese))
[13]邓华锋,周美玲,李建林,等.水-岩作用下红层软岩力学特性劣化规律研究[J].岩石力学与工程学报,2016,35(增刊2):3481-3491.(DENG Hua-feng,ZHOU Mei-ling,LIJian-lin,et al.Mechanical properties deteriorating change rule research of red-layer soft rock under water-rock interaction[J].Chinese Journal of Rock Mechanics and Engineering,2016,35(S2):3481-3491.(in Chinese))
[14]邓华锋,张恒宾,李建林,等.水-岩作用对砂岩卸荷力学特性及微观结构的影响[J].岩土力学,2018,39(7):2344-2352.(DENG Hua-feng,ZHANG Heng-bin,LI Jian-lin,et al.Effect of water-rock interaction on unloading mechanical properties and microstructure of sandstone[J].Rock and Soil Mechanics,2018,39(7):2344-2352.(in Chinese))
[15]张振华,黄翔,崔强.水库运行期岸坡消落带红砂岩抗拉强度劣化机制[J].岩石力学与工程学报,2017,36(11):2731-2740.(ZHANG Zhen-hua,HUANG xiang,CUI qiang.Experimental study on tensile strength deterioration mechanisms of red sandstone during the operation of reservoir[J].Chinese Journal of Rock Mechanics and Engineering,2017,36(11):2731-2740.(in Chinese))
[16]SL264-2001水利水电工程岩石试验规程[S].2001.(SL264-2001 Specifications for rock tests in water conservancy and hydroelectric engineering[S].2001.(in Chinese))
[17]周辉,孟凡震,刘海涛,等.花岗岩脆性破坏特征与机制试验研究[J].岩石力学与工程学报,2014,33(9):1822-1827.(ZHOU Hui,MENG Fan-zhen,LIU Hai-tao,et al.Experimental study on characteristics and mechanism of brittle failure of granite[J].Chinese Journal of Rock Mechanics and Engineering,2014,33(9):1822-1827.(in Chinese))
[18]刘长武,陆士良.泥岩遇水崩解软化机理的研究[J].岩土力学,2000,21(1):28-31.(LIU Chang-wu,LU Shi-liang.Research on mechanism of mudstone degradation and softening in water[J].Rock and Soil Mechanics,2000,21(1):28-31.(in Chinese))
[19]凌建明.压缩荷载条件下岩石细观损伤特征的研究[J].同济大学学报(自然科学版),1993,21(2):219-226.(LINGJian-ming.Study on the mesoscopical characteristics of rock damage under compressive loading[J].Journal of Tongji University(Nature Science),1993,21(2):219-226.(in Chinese))
[2]周翠英,彭泽英,尚伟,等.论岩土工程中水-岩相互作用研究的焦点问题特殊软岩的力学变异性[J].岩土力学,2002,23(1):124-128.(ZHOU Cui-ying,PENG Ze-ying,SHANG Wei,et al.On the key problem of the water-rock interaction in geoengineering:mechanical variability of special weak rocks and some development trends[J].Rock and Soil Mechanics,2002,23(1):124-128.(in Chinese))
[3]周翠英,邓毅梅,谭祥韶,等.饱水软岩力学性质软化的试验研究与应用[J].岩石力学与工程学报,2005,24(1):33-38.(ZHOU Cui-ying,DENG Yi-mei,TAN Xiang-shao,et al.Experimental research on the softening of mechanical properties of saturated soft rocks and application[J].Chinese Journal of Rock Mechanics and Engineering,2005,24(1):33-38.(in Chinese))
[4]姚华彦,张振华,朱朝辉,等.干湿交替对砂岩力学特性影响的试验研究[J].岩土力学,2010,31(12):3704-3708.(YAO Hua-yan,ZHANG Zhen-hua,ZHU Chao-hui,et al.Experimental study of mechanical properties of sandstone under cyclic drying and wetting[J].Rock and Soil Mechanics,2010,31(12):3704-3708.(in Chinese))
[5]LI K G,ZHENG D P,HUANG W H.Experiment research on shear characteristics of sandstone considering cyclic drying-wetting effect[J].Disaster Advances,2013,6:83-87.
[6]刘新荣,李栋梁,张梁,等.干湿循环对泥质砂岩力学特性及其微细观结构影响研究[J].岩土工程学报,2016,38(7):1291-1300.(LIU Xin-rong,LI Dong-liang,ZHANGLiang,et al.Influence of wetting-drying cycles on mechanical properties and microstructure of shaly sandstone[J].Chinese Journal of Geotechnical Engineering,2016,38(7):1291-1300.(in Chinese))
[7]傅晏,刘新荣,张永兴,等.水岩相互作用对砂岩单轴强度的影响研究[J].水文地质工程地质,2009,36(6):54-58.(FU Yan,LIU Xin-rong,ZHANG Yong-xin,et al.Study of the influence of water-rock interaction to the strength of sandstone[J].Hydrogeology&Engineering Geology,2009,36(6):54-58.(in Chinese))
[8]傅晏,王子娟,刘新荣,等.干湿循环作用下砂岩细观损伤演化及宏观劣化研究[J].岩土工程学报,2017,39(9):1653-1661.(FU Yan,WANG Zi-juan,LIU Xin-rong,et al.Meso damage evolution characteristics and macro degradation of sandstone under wetting-drying cycles[J].Chinese Journal of Geotechnical Engineering,2017,39(9):1653-1661.(in Chinese))
[9]ZHANG Z H,JIANG Q H,ZHOU C B,et al.Strength and failure characteristics of Jurassic Red-Bed sandstone under cyclic wetting-drying conditions[J].Geophysical Journal International,2014,198(2):1034-1044.
[10]邓华锋,李建林,王孔伟,等.饱和-风干循环过程中砂岩次生孔隙率变化规律研究[J].岩土力学,2012,33(2):483-488.(DENG Hua-feng,LI Jian-lin,WANG Kong-wei,et al.Research on secondary porosity changing law of sandstone under saturation-air dry cycles[J].Rock and Soil Mechanics,2012,33(2):483-488.(in Chinese))
[11]邓华锋,李建林,刘杰,等.浸泡-风干循环作用对砂岩变形及破坏特征影响研究[J].岩土工程学报,2012,34(9):1620-1626.(DENG Hua-feng,LI Jian-lin,LIU Jie,et al.Influence of immersion-air dry circulation function on deformation and fracture features of sandstone[J].Chinese Journal of Geotechnical Engineering,2012,34(9):1620-1626.(in Chinese))
[12]邓华锋,李建林,朱敏,等.饱水-风干循环作用下砂岩强度劣化规律试验研究[J].岩土力学,2012,33(11):3306-3312.(DENG Hua-feng,LI Jian-lin,ZHU Min,et al.Experimental research on strength deterioration rules of sandstone under“saturation-air dry”circulation function[J].Rock and Soil Mechanics,2012,33(11):3306-3312.(in Chinese))
[13]邓华锋,周美玲,李建林,等.水-岩作用下红层软岩力学特性劣化规律研究[J].岩石力学与工程学报,2016,35(增刊2):3481-3491.(DENG Hua-feng,ZHOU Mei-ling,LIJian-lin,et al.Mechanical properties deteriorating change rule research of red-layer soft rock under water-rock interaction[J].Chinese Journal of Rock Mechanics and Engineering,2016,35(S2):3481-3491.(in Chinese))
[14]邓华锋,张恒宾,李建林,等.水-岩作用对砂岩卸荷力学特性及微观结构的影响[J].岩土力学,2018,39(7):2344-2352.(DENG Hua-feng,ZHANG Heng-bin,LI Jian-lin,et al.Effect of water-rock interaction on unloading mechanical properties and microstructure of sandstone[J].Rock and Soil Mechanics,2018,39(7):2344-2352.(in Chinese))
[15]张振华,黄翔,崔强.水库运行期岸坡消落带红砂岩抗拉强度劣化机制[J].岩石力学与工程学报,2017,36(11):2731-2740.(ZHANG Zhen-hua,HUANG xiang,CUI qiang.Experimental study on tensile strength deterioration mechanisms of red sandstone during the operation of reservoir[J].Chinese Journal of Rock Mechanics and Engineering,2017,36(11):2731-2740.(in Chinese))
[16]SL264-2001水利水电工程岩石试验规程[S].2001.(SL264-2001 Specifications for rock tests in water conservancy and hydroelectric engineering[S].2001.(in Chinese))
[17]周辉,孟凡震,刘海涛,等.花岗岩脆性破坏特征与机制试验研究[J].岩石力学与工程学报,2014,33(9):1822-1827.(ZHOU Hui,MENG Fan-zhen,LIU Hai-tao,et al.Experimental study on characteristics and mechanism of brittle failure of granite[J].Chinese Journal of Rock Mechanics and Engineering,2014,33(9):1822-1827.(in Chinese))
[18]刘长武,陆士良.泥岩遇水崩解软化机理的研究[J].岩土力学,2000,21(1):28-31.(LIU Chang-wu,LU Shi-liang.Research on mechanism of mudstone degradation and softening in water[J].Rock and Soil Mechanics,2000,21(1):28-31.(in Chinese))
[19]凌建明.压缩荷载条件下岩石细观损伤特征的研究[J].同济大学学报(自然科学版),1993,21(2):219-226.(LINGJian-ming.Study on the mesoscopical characteristics of rock damage under compressive loading[J].Journal of Tongji University(Nature Science),1993,21(2):219-226.(in Chinese))
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