【作者】 邓华锋；

【导师】 李建林；

【作者基本信息】 武汉大学 ， 水工结构工程， 2010， 博士

【摘要】 水-岩相互作用在自然界广泛存在,水是诱发各种地质灾害最活跃、最主要的因素。三峡工程竣工后,库水每年都将在145 m和175 m水位之间缓慢或快速的升降,在库水位大幅度涨落的情况下,库岸边坡部分岩体处于“饱和-风干”的循环状态,水-岩循环作用将造成岩体性质劣化,很可能使稳定的库岸边坡向不稳定方向发展。因此有必要对变幅带水-岩循环作用机理和效应进行系统研究,确定岩土体力学参数的变化规律,并将此规律应用到岸坡稳定性分析中。在理论分析的基础上,以试验为主要研究方法对此展开了详细的研究：(1)把超声-回弹综合法应用到岩石试样选择中,在正式试验之前,挑出那些可能会使试验结果很离散的试样,可以提高室内试验的测试准确程度。实践表明,这种综合选样方法具有较好的适用性,同时,超声-回弹综合法可以较好的预测岩石的抗压强度。(2)试样本身存在的初始差异性决定了初始强度存在差异,采用超声-回弹综合强度预测公式,根据初始纵波波速、回弹值对每个试样的实测强度值进行修正,相当于把每个试样的初始强度修正到同一个标准,然后再进行比较分析,这样可以更好的反映试验规律。(3)水-岩物理作用、化学作用和力学作用通常是不可分割的,库岸边坡的破坏,通常是三类作用的综合结果,在不同时期,各类作用所占的比例不一样,引起边坡岩体破坏的作用机理也不一样的,因此,对于库岸边坡岩体在库水位变化时水-岩作用机理的分析应该分三个阶段考虑：库水位上升期、相对稳定期和消落期,同时应该重点考虑“饱和-风干”的循环作用。把库岸边坡水-岩作用机制概括为五个方面：力学弱化机制、局部应力集中机制、物理弱化机制、化学弱化机制、“饱和-风干”循环作用累积损伤机制。(4)采用分段的方法,详细分析了库水位升降对库岸边坡岩体的力学作用,从力学机理上解释了库岸边坡在水位上升或下降过程中安全系数先下降后上升变化规律的原因,也能很好的解释一些库岸边坡失稳的原因。(5)从断裂力学角度分析了裂隙水压力对裂纹强度因子的影响,对考虑裂隙水压力作用的Ⅰ～Ⅱ型复合裂纹扩展进行了研究,结果表明Ⅰ～Ⅱ型复合裂纹的裂纹扩展角θ的变化,不仅与裂纹的闭合程度、斜裂纹倾角α、双向应力大小有关,还与裂隙水压力的大小、裂纹面的摩擦系数有关；并且,在相同情况下,未闭合裂纹的扩展角要大于闭合裂纹的扩展角：对于闭合裂纹,摩擦角φ越小,扩展角θ越大。(6)从试验结果来看,单纯的静水压力对水-岩化学反应的影响较小,其差别在于物理和力学损伤作用促进水-岩化学作用的发生,水压力的升、降和“饱和-风干”循环作用对岩体的损伤有累积放大作用,浸泡时水压力变化越大,对离子浓度和次生孔隙的影响越大,而且,浸泡时间越长,“饱和-风干”循环次数越多,岩体的损伤越严重。(7)提出了基于离子浓度变化计算岩石中次生孔隙率变化规律的方法,与实测次生孔隙率变化规律基本一致。(8)岩石试样显微结构照片显示,经过浸泡和“饱和-风干”循环作用后,矿物颗粒均发生了不同程度的溶解、溶蚀,颗粒界限边缘变的模糊,不规则状变的趋向圆滑,颗粒之间的钙质胶结趋向松散,说明水溶液对砂岩的物理化学细观损伤作用较强。(9)不同浸泡时期的砂岩试样的应力-应变曲线的形态基本一致,但曲线中压密段的长度差别较大,浸泡的时间越长,压密段的长度越大,弹性变形段的斜率越小,卸除荷载后的残余变形越大,岩石试样有明显“变软”的趋势,而且循环加卸载损伤试样“变软”的趋势更加明显。(10)在“饱和-风干”循环过程中,砂岩试样的纵波波速、回弹值、抗压强度、粘聚力、摩擦角、弹性模量、变形模量均出现不同程度的劣化,而且浸泡时的压力变化越大,下降的趋势越明显,同时,强度下降趋势与试验时加载的围压有关,围压越低,下降的趋势越明显,与“完整”试样相比,循环加卸载损伤试样的各参数劣化的更为严重。(11)随着围压的增大,弹性模量和变形模量有增大的趋势,而且随着浸泡时间(“饱和-风干”循环次数)的变化,这个差别越来越大。同时,随着围压增大,岩石试样张性破坏特征逐渐减弱,而剪性破坏特征逐渐明显,即由张性破坏过渡到张剪性破坏,由张剪性破坏过渡到剪张性破坏。(12)从总体统计规律来看,随着围压增大,砂岩试样破坏时的剪切角逐渐变小；相同围压破坏的试样,浸泡时水压力变化越大,其剪切破坏角相对越小；随着浸泡时间(“饱和-风干”循环次数)的变化,砂岩试样的剪切破坏角有逐渐变小的趋势,这与砂岩试样强度参数劣化的规律是一致的。(13)与“完整”砂岩试样相比,循环加卸载损伤试样破坏时的破碎程度要严重的多,各项力学指标也衰减的更快,说明损伤岩体对水软化作用更加敏感,长期浸泡“饱和-风干”循环作用后力学性质弱化明显,更易产生不稳定问题。(14)通过不同级配、不同含水率情况下的土石混合体直剪试验,建立了天然级配和设计级配土石混合体的c-ω,φ-ω之间的关系,为评价滑坡在库水位变化条件下c、φ值的弱化提供了量化依据。(15)建立库岸边坡数值分析模型进行了计算分析,计算结果和监测数据变化趋势基本一致,而且计算中的塑性区分布位置和宏观地质巡查发现的滑坡后缘和中部区域出现了的裂缝区域非常相似,但是计算结果偏小,说明在分析库水位升降循环作用时,必须考虑水-岩作用的长期时间效应；同时,降雨及库水位升降是滑坡加速变形的主要影响因素,滑坡表层土石混合体在“饱和-风干”循环作用下的力学参数变化规律同样值得进一步的研究。更多还原

【Abstract】 Water-rock interaction exists widely in nature, which is the most active and important factor for a variety of geological disasters. The three gorges project will be completed; and the reservoir water will be raised to 175m and reduced to 145m every year. During the fluctuation of the reservoir water level, the quality of rock mass of the bank slopes would be deteriorated in water-rock interaction of "saturation-air dry" cycles, and it would further cause great damage to stability of the bank slope. So it is necessary to study water-rock interaction mechanisms and effects at the fluctuation of reservoir water level systemically, and determine the physical parameters of rock and soil mass, which can be applied in slope stability analysis and it would reveal the impact of the water-rock interaction on the slope stability.Based on theoretical analysis,a detailed study have been launched and experiment is considered as a main research methods:(1)The ultrasonic-rebound comprehensive method was applied to the rock sample selection which has the advantages of two methods. In order to get the accurate results, the rock specimens which may cause discrete results can be selected out first before the laboratory test. Practice shows that such a comprehensive sampling method has good applicability. At the same time, the ultrasonic-rebound method is quit useful to predict the compressive strength.(2) The inherent differences in the sample determine the differences of initial strength. Here try to propose a strength correction method, a strength prediction equation considering rebound value and strength of rock. It is equivalent to revise the initial strength of each specimen to the same standard, and then the law can be better reflected by the experiment results in a comparative analysis.(3) Water-rock interaction includes three aspects:physical, chemical and mechanical effects, the destruction of bank slopes would be the comprehensive result of those three aspects effects. Due to the proportion of different effects changes at different periods of water-rock interaction, failure mechanism of rock slope is not the same as well. So, the impact of water-rock interaction mechanism on bank slope during fluctuation of reservoir water level should be considered to divide in three phases:the decrease, the rise and stationary of reservoir level. Meanwhile the effects of "saturation-air drying" should be mainly concentrated. The water-rock interaction mechanisms is summarized as five aspects:mechanical weakening mechanism, local stress concentration mechanism, physical weakening mechanism, chemical weakening mechanism, cumulative damage mechanism of "saturation-air drying".(4) Segmentation method is proposed, and the mechanical effect of reservoir rock slope in rising or drawdown of reservoir water levels is analyzed detailed.The variation that the safety factor change from decreasing to increasing along with the change of reservoir water levels are explained by mechanical mechanism, which also can explain some of the reasons for the bank slope instability.(5)The influence of fissure water pressure to the crack intensity factor is analysed in respect of the fracture mechanics. I - II composite crack propagation is studied by considering the fissure water pressure. The results show that the crack propagation angle (?) of composite crack is not only related to the degree of crack closure、the angleαof inclined crack and the size of two-way stress, but is also related to the size of the fissure water pressure and the friction coefficient of the crack surface. In the same circumstances, the propagation angles of non-closed cracks are greater than the propagation angles of closed cracks; and for the closed cracks, the smaller the friction angle, the greater the propagation angle..(6) From the test results of this paper, the effect of simple hydrostatic pressure to water-rock interaction is smaller, the differences is for that the physical and chemical role of water-roc、the rise or decline of water pressure and the role in cycle of "saturation-air dry" has cumulative and magnified effect to the damage of rock. Tests show that the greater the water pressure in immersion, the greater the impact to the ion concentration and secondary porosity, and more development the erosion-corrosion pores. At the same time, the longer of the soaking time, the more cycles of "saturation-air dry", the more serious damage to the rock mass.(7)Based on the change of ion concentration, the computational method of secondary porosity change law in the rock is proposed, which consistent with measured changes of secondary porosity.(8)The microstructure’s photographs of the rock samples show that, after cycles of "saturation-air dry" cycles, the mineral particles have undergone varying degrees of dissolution, corrosion, particle boundaries become fuzzy, and irregular shape become smooth, particles of calcium cement tend to be loose, which indicates that the effect of aqueous solution on the sandstone physical and chemical microscopic injury is strong.(9)The morphological characteristics of stress-strain curves of sandstone samples in different soaking times is basically identical, but compacting curve varied greatly in length, as soaking time is the longer, length of compacting would be larger, the slope of the elastic deformation’s section became smaller, residual deformation after unloading is increased. The rock samples obviously change soft, and the injury samples which have experienced the cyclic loading and unloading change soft more obviously.(10)In the cycle of "saturation-air dry", longitudinal wave velocity, rebound value, compressive strength, cohesion, friction angle, elastic modulus, deformation modulus of the sandstone samples has varied degrees of deterioration, the change law is consistent basically. Moreover, the greater pressure in the soaking time, the trend is more downward obviously. While the downward trend of strength is related to the confining pressure of the loading test, the lower the confining pressure, the more obviously the downward trend. Compared with the "intact" samples, all parameters of the injury samples deteriorate more severely.(11) With the confining pressure increasing, the elastic modulus and deformation modulus are increased, and changed along with soaking time ("saturation-air dry" cycles), the difference gets more obvious. At the same time,tensile failure characteristics of rock samples is gradually weakened, the shear failure characteristics becomes obvious, which transforms from tensile damage to tensile-shear damage, finally changes to shear tensile damage.(12)Statistical laws show that the shear angle of sandstone samples dwindles with the confining pressure increasing; when under the same confining pressure, the shear failure angle is relatively smaller when the water pressure during immersion is greater; as the soaking time ("saturation-air dry" cycles) goes on, shear failure angle of sandstone samples is progressively smaller, which is consistent with the deterioration law of strength parameters of the sandstone sample.(13)Compared with the compressive strength of the "intact" sandstone sample, the damage degree of injury samples which have experienced the cyclic of loading and unloading is more serious, and the mechanical parameters decay faster, it indicated that injury samples is more sensitive to water, the weakening of the mechanical properties is obviously after long-term "saturation-air dry" cycles and it is easier to generate instability problems.(14) The direct shear test of SRM with the different gradations and different moisture content has been carried out, and the relationship is established between c-ωand (?)-ωof SRM with natural gradation and design gradation, which provides a quantitative basis for evaluating weakening degree of c、(?) of landslide under the condition of the reservoir water level fluctuation.(15)The model for numerical analysis is established to calculate, the results are basically consistent with the monitoring data, and the location of plastic zone calculated is very similar to the cracks region found at the edge and centre of the landslide when macro-geological inspection, but the calculation is smaller.The results show that long-time effect of water-rock interaction must be considered; at the same time, rainfall and water level fluctuation are the main factors for accelerating deformation of the landslide, and the variation law of parameters is also worth further studying when SRM on the landslide surface is under "saturation-air dry" cycles.更多还原