【作者】 潘建平；

【导师】 孔宪京；

【作者基本信息】 大连理工大学 ， 水工结构工程， 2007， 博士

【摘要】 尾矿坝是用来阻挡尾矿使其沉积的土工构筑物，它的使用功能、建筑工艺、坝体结构和静动力特性均不同于一般的水工土石坝。随着我国经济的快速发展和工业水平的迅速提高，对矿山原材料产出的需求越来越大，尾矿坝数量也随之增加。尾矿坝按其构造形式可分成三类：上游式、中线式和下游式。上游式尾矿坝后继断面小及占地少，且工艺简单、造价低，我国大多数尾矿坝均采用上游式修建。国内外震害表明，因上游式尾矿坝浸润线较高，大部分坝体处于饱和状态，地震作用下易发生液化变形破坏。我国是一个多地震国家，而尾矿坝几乎是永久性建筑，在设计阶段、服务期及废弃后均需要进行抗震分析。因此，深入研究尾矿坝的抗震设计、稳定、变形及抗震措施就显得尤其重要和迫切。本文主要进行了以下几方面的研究工作：1．传统的场地液化评估法通常以安全系数的大小作为评估标准，安全系数的要求则由工程师经验确定，但不能给出相应的液化概率。首先阐述了砂土液化机理及场地液化评价方法，其次用对数退化模型分析国内外现场实测标贯数据，建立场地液化极限状态函数，然后将可靠度理论引入场地液化评价中，用一次二阶矩法建立场地液化概率评价模型，进行实例应用并与规范结果进行了比较。分析表明，建议模型具有较高的可靠性，相比传统的确定性分析方法，不仅能判定液化发生与否，还能给出液化概率，这为进行基于风险分析的抗震设计提供了可能。2．现有规范中尾矿坝抗震设计方法的计算过程相当繁琐，有必要提出一种实用的地震液化稳定分析简化法。结合《构筑物抗震设计规范》的修订，用有限元程序计算多个60m高的尾矿坝，确定坝顶加速度放大倍数、坝体加速度分布系数和应力折减系数，建立尾矿坝地震作用应力比的简化计算式。基于尾矿抗液化性能的影响因素分析，对规范中抗液化应力比计算式进行简化。液化分析简化法只要求简单的物理力学特性数据和地震烈度，避免了进行大量的土力学试验和数值计算来评价尾矿土层的液化特性。根据砂土抗液化安全系数与超孔隙水压力比的经验关系，建立了超孔隙水压力简化计算式，并应用到瑞典条分法中，克服了用传统拟静力法进行尾矿坝地震稳定分析时忽略超孔隙水压力带来的风险。综合中日尾矿坝抗震设计规范并进行比较分析，提出上游式四、五级尾矿坝在小于或等于8度地震时，用简化法进行抗震设计。3．以某上游式尾矿坝为例，用有限元法分析了坝体的地震反应、永久变形及超孔隙水压力的发展过程，研究了降低浸润线、碎石排水和加筋的抗震效果，提出了一种综合抗震措施，即在子坝区加筋、初期坝外坡增设反压体及坝基土密实。分析表明，采取综合抗震措施加固后坝体地震变形显著减小。4．应用二维商用软件ALID研究了Mochikoshi尾矿坝在不同条件下发生液化流动变形的特征，分析了降低浸润线、在上游增设稳定柱、下游施加反压体和坝基土密实对抑制尾矿坝液化流动变形的作用效果。从经济、方便施工的角度出发，提出了两种抑制尾矿坝液化流动变形的综合措施，即在坝基土密实加固，并同时在坝体外坡施加反压体和降低浸润线。分析表明，采取综合措施加固后坝体液化流动变形得到了有效控制。5．基于Watanabe提出的边坡地震稳定滑移分析法，以某上游式尾矿坝为例，研究了输入不同加速度峰值对坝体等价加速度时程、安全系数时程与潜在滑块滑移量发展过程的影响，分析了加筋对提高尾矿坝地震稳定及减小坝坡滑移量的有效性。分析表明，随着输入水平加速度峰值的增大，水平等价加速度与地震安全系数的变化幅值相应地增大，超越加速度的幅值增加、历时较长，地震滑移量增大；加筋能较好地改善尾矿的力学性能，大大提高坝体的稳定性，减小滑动位移；筋材间距的增大与设计强度的降低都会减小坝体的地震稳定系数。更多还原

【Abstract】 Tailings dam is a soil construction that encloses tailings and its using function,architectural technology and structure static and dynamic characteristics are different fromtraditional hydraulic structure. In recent years, Chinese economy and industry quicklyadvance. Tailings dam rapidly aggrandize along with the demand increase of mine rawmaterials. Basically, tailings dam falls into three basic construction types: upstream, centerline, and downstream. The upstream method is frequently the least expensive, occupyingplace less, technology simply, and it has been used on many dams in the past. However,earthquake disasters show that the upstream method is the most susceptible to excessivepost-earthquake deformation and liquefaction because loose saturated deposits may beincorporated in the mostly upstream zones. There are frequently earthquakes in China, andmoreover, tailings dam is almost permanent soil construction and must be done antiseismicanalysis in design, serve and after closure. Consequently, it is of great importance andurgency to study antiseismic design, stability, deformation, and antiseismic measures fortailings dam. The main research works of this dissertation are as follow:1. The traditional site liquefaction evaluation method usually uses a factor of safety asassessing standard and the specified safety factor is largely determined by engineer’sexperience, however, there is not a liquefaction probability. The paper firstly expatiates on themechanism of sand liquefaction and evaluation method of site liquefaction. Secondly, a limitstate function for site liquefaction is developed based on logistic regression analysis SPTdatum of 200 sets case histories of 23 earthquakes over the world. And then reliability theoryis introduced site liquefaction evaluation and testing datum statistics analysis is used inconjunction with the first order and second moment method to found the liquefactionprobability evaluation model of site. Finally, a bridge site as example is analyzed andcompared to design code’s results. The calculation result analyses show the proposed modelreliability is higher. Comparing to the deterministic method of site liquefaction evaluation, itcan not only assess if liquefaction occur but also give liquefaction probability, so it is possibleto make antiseismic design based on risk analysis.2. The calculation process of tailings dam antiseismic design is very complicated in code,so it is necessary to advance a practicably simplified method of earthquake liquefaction andstability analysis. Combining the editing of Antiseismic Design of Special Structures, two-dimensional seismic response analyse are carded out for many 60m high tailings dams.Analyzing the calculative results, acceleration amplification ratio of the crest, damacceleration distributing coefficient and stress reduction coefficient are concluded and thenthe simplified procedure for calculating the cyclic shear stress ratio is founded. Based on theinfluence factors analysis of tailings resistance, the formula of cyclic resistance ratio inChinese design code is simplified. The simplified liquefaction evaluation method only needsmall physical-mechanical properties datum of tailings and degree of seismic intensity andavoid making a lot of soil mechanical tests and numerical calculation to assess liquefaction oftailings. According to the relationship between sand liquefaction resistance factor and excesspore pressure ratio, a simple formula of excess pore water pressure is proposed and applied inSweden slope stability analysis method for tailings dam, and that to overcome the risk forignoring excess pore water pressure in traditional pseudo-static method. The specialities ofantiseismic design code for tailings dam in China and Japan are compared and then usingsimplified method to make antiseismic design for height less than 60 m and within 8 degree ofseismic intensity is proposed.3. Taking a tailings dam as example, dam seismic response, permanent deformation, andthe development process of excess pore water pressure are studied using the finite elementmethod. After comparing the effects of three antiseismic measures, such as falling soakageline, drainage by setting stone column and reinforcing with fibre, a synthetically antiseismicmeasure that is composed of fibre-reinforced in child dam, forcing buttress out of starter damand densification foundation is proposed. It is found that the synthetically antiseismicmeasure produces better antiseismic effect.4. By using the finite element code ALID (Analysis for Liquefaction-InducedDeformation), liquefaction-induced flow deformation of No. 1 Mochikoshi talings dam underdifferent conditions is estimated. Some measures, such as falling soakage line, settingstabilizing column, forcing buttress out of dam and densification foundation are analyzed toassess the effect on restraining liquefaction-induced deformation of tailings dam. Looking ateconomy and the convenience of construction, two synthetical measures, namely densificationfoundation and at the same time forcing buttress out of dam and falling soakage line, areproposed. It is found that the synthetical antiseismic measures can reduce theliquefaction-induced deformation of dam to considerable amount.5. Taking a tailings dam as example, the time history of acceleration, safety factor andslippage in different earthquake excitations are studied and then the effect of reinforcement toimprove dam stability and reduce slippage are analyzed, using the analyse method of slopeseismic stability and slip that is proposed by Watanabe. With inputting horizontal accelerationaugment, it is found that the variety value of horizontal equivalence acceleration and safety factor, exceeding acceleration and lasting time as well as slippage will be aggrandized.Reinforcement with fibre can improve the mechanical properties of tailings and stability ofdam and reduce slippage. Adding fibre space and reducing fibre intension can minish damsafety coefficient.更多还原