【作者】 王新刚；

【导师】 余宏明； 胡斌；

【作者基本信息】 中国地质大学 ， 地质工程， 2014， 博士

【摘要】 在实施“西部大开发”的战略决策中,水电开发是其中的重要组成部分。西部建设的大型水电站大多地处崇山峻岭中的深山峡谷地区,地形地质条件复杂,因此,出现了大量的库岸高陡边坡。水库在运营过程中,将按计划周期性的蓄水和排水,库水位反复大幅升降对“消落带”的岩体来说是一种“疲劳损伤”和反复弱化作用,库水位涨落下,“消落带”岩体的饱水-失水循环劣化作用会加剧库岸边坡消落带岩体的流变性,甚至发生流变变形破坏。而坝址区的边坡由于离大坝较近,在水电站运行期库水位涨落影响下其长期稳定性对大坝的长期安全将有直接的影响。本论文结合国家自然科学基金项目“水位周期性大幅涨落下库岸高边坡软弱节理岩体流变机理与长期稳定性研究”(41172281),以国家重点工程龙滩水电站的坝址区库岸高边坡“消落带”砂岩、泥板岩为研究对象,考虑库岸边坡在水电站运营中经常遇到的库水位涨落情况,对“消落带”岩石试样在饱水-失水循环作用下劣化机理和效应进行研究,进行不同“饱水-失水”循环次数作用后的单轴、三轴抗压强度实验、抗拉实验以及三轴流变试验。对“消落带”砂岩、泥板岩饱水-失水循环作用后的损伤劣化规律进行了研究分析,在Hoek-Brown强度准则的基础上,引入饱水-失水循环作用后岩石累积损伤率,考虑了饱水-失水循环作用对岩石的损伤影响,改进了Hoek-Brown强度准则,并构建了改进的Hoek-Brown强度准则对应的“GSI量化取值表格”。在流变试验的基础上,提出了考虑岩石饱水-失水循环次数n损伤的“非线性黏弹塑性流变模型(DNBVP模型)”,使用VC++编程对该模型进行了基于FLAC3D软件的二次开发。选取龙滩水电站坝址区流变体B区域的典型剖面,进行饱水-失水循环劣化作用下的长期流变计算,采用"BP-PSO算法的边坡位移反分析方法”,反演获取考虑流变特性的数值计算模型中“岩体”相应的DNBVP模型最优流变参数,结合库水位涨落周期内坝区高边坡岩体现场监测成果,论证提出的流变本构模型,对库水位涨落下坝区高边坡长期稳定性进行了计算预测,并提出了相应的防治措施,为工程实践提供参考。在我国中西部众多水利水电工程先后竣工和蓄水运行的背景下,研究成果对揭示大量存在的库岸边坡岩体力学参数随库水位涨落的变化规律,并将此规律应用到库岸边坡岩土体的长期稳定性评价分析中,具有十分重要的理论和应用价值。取得了如下研究成果：(1)从室内单轴抗压、抗拉、三轴抗压、三轴流变试验以及三轴流变试验后岩样的宏、细观破坏形态分析发现“饱水-失水”循环对砂岩、泥板岩的物理力学性质具有明显的损伤劣化作用。(2)以试验为基础,揭示了砂岩、泥板岩在不同“饱水-失水”循环下抗压强度、弹性模量、抗拉强度、粘聚力、内摩擦角的损伤劣化规律。(3)在Hoek-Brown强度准则的基础上,引入饱水-失水循环作用后岩石累积损伤率,考虑了饱水-失水循环作用对岩石的损伤影响,改进了Hoek-Brown强度准则,为饱水-失水循环作用下现场岩体力学参数的获取,提供了理论依据和过渡的“桥梁”。(4)结合国内外研究成果,在E. Hoek提出的广义Hoek-Brown准则中GSI评分表格的基础上,对GSI评分系统进行量化取值,构建了包含岩体结构类型、岩体体积节理数JV、岩体完整性系数Kv、岩体结构等级SR、节理特征系数JC、结构面表面等级SCR的“新的GSI量化取值表格”,“新的GSI量化取值表格”解决了岩体节理体积系数JV通常不能合理确定的问题,并采用我国相关规范以岩体完整性系数KV替换岩块体积Jb来解决对岩体完整性合理的定量化取值问题,且采用定性化的结构面表面特征、结构面表面等级指标SCR、节理特征系数JC、岩石质量指标RQD四个指标,选择性对比验证岩体结构面特征的定量化取值。新的GSI量化取值表格采用了区间数理论,来表示地质强度指标GSI的不确定性,更为符合现场岩体力学参数取值的实际情况,且考虑了现场试验资料选择性获取的可操作性,并引入多指标联合确定GSI值的最终交集,确保了GSI定量化取值的合理性。为不同地质情况下定量地将岩石力学参数转换为岩体力学参数提供了新的依据。(5)以饱水状态(饱水-失水循环0次)的砂岩、泥板岩流变试验曲线为例,进行坝址区库岸高边坡“消落带”砂岩、泥板岩流变特征研究分析,发现：①砂岩、泥板岩的流变曲线均经历了瞬时弹性变形阶段、减速流变阶段、稳定流变阶段和加速流变阶段。在低轴向应力作用下,砂岩、泥板岩只出现前三种阶段,在轴向应力接近或达到临界破坏值时才依次出现上述四种流变阶段。②砂岩岩样在前四级轴向荷载作用下流变速率先减小后趋于零或稳定值；砂岩岩样在第五级轴向荷载作用下流变速率先减小后趋于零或稳定值,最后又加速直至岩样破坏。泥板岩岩样在前四级轴向荷载作用下流变速率先无规律的波动后总体上趋于零或稳定值,但局部仍有波动,这是因为泥板岩相对于砂岩有着更多的微裂隙、微缺陷或不均匀性更易受水的影响,在流变试验的长期作用下导致轴向应变不均匀波动；泥板岩岩样在第五级高轴向荷载应力作用下流变速率先减小后趋于零或稳定值,最后又加速直至岩样破坏。③砂岩、泥板岩的轴向应变和轴向应变速率曲线并不十分光滑,其局部应变曲线段和应变速率曲线段均发生了微小波动和突变现象,而泥板岩的这种微小波动和突变现象更为剧烈。造成这种现象的原因是由于流变试验过程中,砂岩、泥板岩内部结构存在非均质性,从而引起岩样的微观弱化和破裂,使得原有的应力平衡被打破,由于受到恒定轴向应力的长期连续作用,岩样内部的微缺陷发生损伤,经过较长时间的积累之后,岩石中强度较低的部位无法承受这些微缺陷的长期累积所引起的流变损伤,出现了非均匀的变形与破坏,从而造成岩石变形曲线产生了不规则波动和突变。在饱水状态下,泥板岩出现突变现象的次数明显高于砂岩,说明饱水状态下轴向应力对泥板岩的微观缺陷具有更明显的损伤效应,从而使泥板岩的轴向应变曲线多次出现突变现象。(6)针对线性流变体的元件组合模型构建的与岩石流变相关的本构模型将会与实际有所偏差的情况,在Burgers模型的基础上串联一个非线性黏性元件和塑性元件并联而成的非线性黏塑性体,进而提出了一种能同时描述岩石黏弹和塑性特性的非线性流变模型-NBVP模型,对NBVP模型的三维流变本构方程进行了推导。以饱水状态的砂岩、泥板岩流变试验曲线为例,分别采用三参量模型、Burgers模型、NBVP模型对试验实测数据进行拟合,对比分析后发现所建立的非线性黏弹塑性流变模型—NBVP模型曲线与砂岩、泥板岩的三轴流变试验结果较吻合,且NBVP模型可以较理想的描述岩石的加速流变阶段。(7)将损伤变量引入到NBVP模型中,建立了考虑岩石饱水-失水循环次数n损伤的非线性黏弹塑性流变模型—DNBVP模型,同时基于流变试验结果得到了相应的损伤变量表达式,并推导了DNBVP模型的三维流变本构方程,以试验数据为例进行分析可以看出DNBVP模型能够很好地描述饱水-失水循环后岩石流变的全过程曲线。(8)将非线性黏弹塑性流变模型(DNBVP模型)方程,进行详细推导,获得了其二次开发所需的应力增量三维中心差分格式,参照DNBVP流变模型的应力增量差分表达式,采用VC++编程,生成可调用的动态链接库(.d11),可以实现DNBVP流变模型在FLAC3D中的开发。以三轴岩样的数值模型试验计算结果分析发现二次开发的DNBVP模型是合理正确的；对不同饱水-失水循环次数n取值后,计算所得的岩样顶端轴向位移,进行分析可以看出,随着饱水-失水循环次数n的增大,轴向位移亦增大,既损伤亦增大,且其与试验数据较吻合,证明了所建立的DNBVP流变模型的正确性。(9)选取龙滩水电站坝址区流变体B区域典型剖面,进行饱水-失水循环劣化作用下的长期流变计算。将室内岩石流变试验与现场监测数据相结合,根据提出的“非线性黏弹塑性流变模型(DNBVP模型)”,采用"BP-PSO算法的边坡位移反分析方法”,反演得到了高边坡消落带“岩体”的DNBVP模型的最优流变参数,并将其应用于高边坡的长期流变计算中,再将监测点的反演计算位移值与现场实测位移值进行对比,发现,现场实测位移值与流变计算值的变化趋势基本相同,量值上也接近,表明了本文采用的通过“基于BP-PSO算法的边坡位移反分析法”和提出的“非线性黏弹塑性流变模型(DNBVP模型)”的正确性。最后对龙滩水电站坝址区左岸B流变体典型剖面高边坡模型进行了长期流变计算与预测分析,并提出了相应的防治措施,为工程实践提供参考。更多还原

【Abstract】 Hydropower development is an important part in implementation of the strategy of "West China Development". Large-size hydropower stations constructed in the west regions are mostly located in high mountains and deep canyon areas with complex topographic and geological conditions; as a result, there are plenty of high and steep reservoir bank slopes. During operation of a reservoir, water is impounded and drained periodically as planned; the substantial rise of fall of reservoir water level has an effect of "fatigue damage" and repeated weakening on rock mass in the hydro-fluctuation belt. Under fluctuation of reservoir water level, the deterioration effect of water saturation-dehydration circulation of rock mass in the hydro-fluctuation belt will intensify the rheological behavior of rock mass in the hydro-fluctuation belt of reservoir bank slope, or even lead to rheological deformation failure. Moreover, since the slope in dam site area is relatively close to the dam, under the effect of fluctuation of reservoir water level during operation of the hydropower station, the long-term stability of the slope will directly affect the long-term safety of the dam.In combination with the program of the National Natural Science Foundation of China titled "Study on the Rheological Mechanism and Long-Term Stability of Soft Jointed Rock Mass of High Reservoir Bank Slope under Periodic Substantial Fluctuation of Water Level"(41172281), this paper takes sandstone and argillite in the "hydro-fluctuation belt" of high reservoir bank slope in the dam site area of Longtan Hydropower Station, a national key project, as the research object. With consideration to the fluctuation of reservoir water level with which the reservoir bank slope can frequently encounter during operation of the Hydropower Station, a study is conducted on the deterioration mechanism and effect of rock samples from the hydro-fluctuation belt under water saturation-dehydration circulation; uniaxial and triaxial compression tests, tensile test and triaxial rheological test are performed after different times of "water saturation-dehydration" circulation. The rule of damage and deterioration of sandstone and argillite in the "hydro-fluctuation belt" after water saturation-dehydration circulation is investigated and analyzed. Based on the Hoek-Brown strength criterion, the cumulative damage rate of rocks after water saturation-dehydration circulation is introduced; the damage effect of water saturation-dehydration circulation on rocks is considered; the Hoek-Brown strength criterion is improved; and the "quantitative GSI table" corresponding to the improved Hoek-Brown strength criterion is established. On the basis of the rheological test, a nonlinear visco-elasto-plastic rheological model (DNBVP model) considering the damage after n time(s) of water saturation-dehydration circulation of rocks is proposed; VC++programming is used for secondary development of this model based FLAC3D software. A typical section of the zone where rheological body B is located in the dam site area of Longtan Hydropower Station is chosen for numerical simulation calculation and analysis of the stability of the high reservoir bank slope in the dam site area under the deterioration effect of water saturation-dehydration circulation, the "method of slope displacement back analysis based on BP-PSO algorithm’" is adopted to obtain through inversion calculation the optimum rheological parameters of the DNBVP model corresponding to the "rock mass" in the numerical calculation model considering the rheological property. The validity of the rheological damage constitutive model proposed is demonstrated in combination with the findings from field monitoring of the rock mass of high slope in the dam area within the fluctuation cycle of reservoir water level; then, this model is used to calculate and predict the long-term stability of the high slope in the dam area under fluctuation of reservoir water level, and relevant prevention and control measures are put forward for reference in engineering practice. In the context that a number of water conservancy and hydropower projects have been completed and put into operation in succession in Midwest China, the research findings are of great theoretical and application value for revealing the rule that the mechanical parameters of rock masses of numerous reservoir bank slopes change with the fluctuation of reservoir water level, as well as for applying this rule in evaluation and analysis of the long-term stability of rock and soil masses of reservoir bank slopes.The following research findings are achieved:(1) From the indoor uniaxial compression, tensile, triaxial compression and triaxial rheological tests, and the analysis of the macro-and micro-failure patterns of the rock samples after the triaxial rheological test, it is found that "water saturation-dehydration" circulation has an obvious damage and deterioration effect on the physical and mechanical properties of sandstone and argillite.(2) Based on the tests, the rule of damage and deterioration of sandstone and argillite under different times of "water saturation-dehydration" circulation is revealed in terms of compression strength, elasticity modulus, tensile strength, cohesion and internal friction angle.(3) On the basis of the Hoek-Brown strength criterion, the cumulative damage rate of rocks after water saturation-dehydration circulation is introduced; the damage effect of water saturation-dehydration circulation on rocks is considered; and the Hoek-Brown strength criterion is improved, which provides a theoretical basis for obtaining physical and mechanical parameters of field rock mass under water saturation-dehydration circulation, and also builds a "bridge" for parameter transformation.(4) In combination with the research findings at home and abroad, and based on the GS1scoring table in the generalized Hoek-Brown criterion put forward by E. Hoek, a "new quantitative GSI table", comprising structure type of rock mass, volumetric joint count of rock mass Jv, integrity coefficient of rock mass Kv, structure rating of rock mass SR, joint characteristic coefficient Jc, and surface condition rating SCR, is established. The new quantitative GSI table solves the problem that the volumetric joint count of rock mass JV usually cannot be reasonably determined; meanwhile, according relevant norms of China, the integrity coefficient of rock mass KV is used to replace the volume of rock mass Vb to solve the problem of reasonable quantitative determination of rock mass integrity, and four qualitative indices including surface characteristic, surface condition rating SCR, joint characteristic coefficient Jc and rock quality designation RQD are used to selectively verify the quantitatively determined value of surface characteristic of rock mass through comparison. The new quantitative GSI table, which utilizes the interval number theory to represent the uncertainty of GSI, is more aligned with the actual situation of value determination of mechanical parameters of field rock mass; it gives consideration to the operability of selective acquisition of field test data, and introduces multiple indices to jointly determine the final intersection of GSI, ensuring the accuracy of GSI quantitative determination. In the meantime, a new basis is provided for quantitative transformation of mechanical parameters of rocks to mechanical parameters of rock mass.(5) The rheological test curves of water-saturated (0time of water saturation-dehydration circulation) sandstone and argillite are taken as examples to investigate and analyze the rheological property of sandstone and argillite in the "hydro-fluctuation belt" of high reservoir bank slope in the dam site area. The findings are as follows:(a) The rheological curves of sandstone and argillite both undergo the instantaneous elastic deformation stage, the decelerated rheological stage, the stable rheological stage, and the accelerated rheological stage. Under low axial stress, sandstone and argillite only have the first three stages; the foresaid four rheological stages take place successively only when the axial stress is close to or reaches the critical failure value,(b) Under the first four levels of axial load, the rheological rate of the sandstone samples first decreases, and then becomes close to zero or reaches a stable value. Under the fifth level of axial load, the rheological rate of the sandstone samples first decreases, then becomes close to zero or reaches a stable value, and finally increases till failure of the samples. Under the first four levels of axial load, the rheological rate of the argillite samples first fluctuates irregularly, and then becomes close to zero or reaches a stable value on the whole; but local fluctuation still exists, because argillite is more sensitive to water than sandstone as it has more microfissures, microdefects or nonuniformity, and nonuniform fluctuation of axial strain is induced under the long-term effect of the rheological test. Under the fifth level of high axial load, the rheological rate of the argillite samples first decreases, then becomes close to zero or reaches a stable value, and finally increases till failure of the samples,(c) The axial strain and axial strain rate curves of sandstone and argillite are not quite smooth; the local strain curve segment and the strain rate curve segment are both subject to slight fluctuation and mutation, and this phenomenon is more violent in argillite. The cause of such phenomenon is as follows:the nonhomogeneity of the internal structures of sandstone and argillite leads to micro-weakening and fracture of the rock samples, upsetting the original stress equilibrium;under the long-term sustained effect of constant axial stress, the microdefect parts of internal materials of the rock samples gradually get damaged;after long-time accumulation, the positions in rock materials where the strength is relatively low exhibit inhomogeneous deformation failure at micro-parts due to incapability of bearing the rheological damage induced by the long-term accumulation effect of microdefects, further resulting in rock deformation which gives rise to irregular fluctuation and mutation. In water-saturated state, the mutation in argillite is more frequent than in sandstone, which indicates that in water-saturated state, the axial stress has more obvious damage effect on the microdefects of argillite, resulting in frequent mutation of the axial strain curve of argillite.(6) The constitutive model related to the rheological behavior of rocks established according to the element combination model of linear rheological body will deviate from the reality to some degree:a nonlinear viscoplastic body consisting of nonlinear viscous elements and plastic elements connected in parallel is connected with the Burgers model in series to further propose a nonlinear rheological model that can describe the viscous, elastic and plastic properties of rocks-NBVP model; the3D rheological constitutive equation of the NBVP model is derived. The rheological test curves of water-saturated sandstone and argillite are taken as examples, and the three-parameter model, the Burgers model and the NBVP model are respectively adopted for fitting of measured data. After comparative analysis, it is found that the established nonlinear visco-elasto-plastic rheological model-NBVP model is relatively consistent with the results of the triaxial rheological test of sandstone and argillite, and that the NBVP model can ideally describe the accelerated rheological stage of rocks.(7) The damage variable is introduced into the NBVP model to construct a nonlinear visco-elasto-plastic rheological model considering the damage after n time(s) of water saturation-dehydration circulation of rocks-DNBVP model:meanwhile, the corresponding damage variable expression is obtained based on the results of the rheological test, and the3D rheological constitutive equation of the DNBVP model is derived; from analysis of the test data, it can be seen that the DNBVP model can well describe the curve of the whole rheological process of rocks after water saturation-dehydration circulation.(8) The equation of the nonlinear visco-elasto-plastic rheological model (DNBVP model) is deduced in detail to obtain the3D central difference scheme of stress increment required for secondary development of the model; referring to the difference expression of stress increment of "the nonlinear visco-elasto-plastic rheological model (DNBVP model) considering the damage after n time(s) of water saturation-dehydration circulation of rocks", and using VC++programming, a callable dynamic linking library (.dll) is generated, which can realize the development of the DNBVP rheological model in FLAC3D software. After analysis of the calculation results of the triaxial numerical model test of the rock samples, it is found that the DNBVP model after secondary development is rational and correct. After determining the number of times n of water saturation-dehydration circulation, the axial displacement at the top of the rock samples is calculated; from analysis of the axial displacement, it can be seen that as the number of times n of water saturation-dehydration circulation increases, the axial displacement also increases, which also means the damage is aggravated; this result is relatively consistent with the test data, proving the correctness of the proposed "nonlinear visco-elasto-plastic rheological model (DNBVP model) considering the damage after n time(s) of water saturation-dehydration circulation of rocks".(9) A typical section of the zone where rheological body B is located in the dam site area of Longtan Hydropower Station is chosen for calculation of the rheological property under the deterioration effect of water saturation-dehydration circulation. Combining the indoor rheological test of rocks with the field monitoring data, using the proposed "nonlinear visco-elasto-plastic rheological model (DNBVP model)", and adopting the "method of slope displacement back analysis based on BP-PSO algorithm", the optimum rheological parameters of the DNBVP model of the "rock mass" in the hydro-fluctuation belt of high slope are obtained through inversion calculation and are used in calculation of the long-term rheological property of high slope. Then, the displacement values of the monitoring points obtained through inversion calculation are compared with the field measured displacement values, and it is found that the change trends of the field measured displacement values and the rheological calculated values are basically the same, and that the magnitudes are also close to each other, indicating the correctness of the adopted "method of slope displacement back analysis based on BP-PSO algorithm" and the proposed "nonlinear visco-elasto-plastic rheological model (DNBVP model)" Last, the model is used for calculation and predictive analysis of the long-term rheological property of the high slope of the typical section of the zone where rheological body B is located at the left bank in the dam site area of Longtan Hydropower Station, and relevant prevention and control measures are put forward for reference in engineering practice.更多还原