【作者】 杨明；

【导师】 姚令侃；

【作者基本信息】 西南交通大学 ， 道路与铁道工程， 2008， 博士

【摘要】 我国中、西部地区地质环境脆弱,一些大规模基础设施建设对地质环境的影响很大,滑坡、泥石流、崩塌等斜坡重力灾害仍将保持增长趋势。边滑坡在重力作用下的破坏过程是岩土体发挥自稳能力与重力作用相抗衡的自组织过程,在外部因素扰动下,岩土体变形的过程即应力调整的自组织过程,其最终结果将使边滑坡系统达到另一个平衡状态,而这个平衡状态可能有两种表现形式:一是在工程意义上边滑坡达到最终稳定;二是工程意义上边滑坡失稳破坏。而采取有效的抗滑加固措施的目的即在于如何使这一自组织过程向有利于前一种平衡状态演化。根据自组织理论,当受到外界微小扰动时,系统表现为自组织行为;当受到外界强扰动时,自组织行为会屈服于外界的强扰动,即外界扰动成为系统行为的主导因素。对于边滑坡而言,在受到外界强扰动的情况下,如在地震工况下,边滑坡体即可能产生突然失稳。针对以上两种典型的边滑坡破坏过程,在进行抗滑加固设计时,应采用不同的设计理念。对于正常工况下的抗滑加固设计,应充分利用岩土体的自稳能力,抗滑加固措施着重于如何使岩土体自组织过程的演化朝有利于坡体稳定的方向发展。对于地震工况下的抗滑加固设计,则应加强整个边滑坡的抗震性能,减少和外界扰动的“耦合”放大作用,如改变坡体的动力特性,使其自振频率远离地震的卓越频率。抗滑桩作为治理斜坡重力灾害的一种较为常见和有效的措施,目前在设计上仍缺乏理论指导,尤其是在合理桩间距的确定方面,主要依靠工程经验进行设计。而常见的一些抗滑加固措施在地震条件下的抗滑加固机理的研究几乎是空白。本文在土工离心模型实验及振动台模型实验的基础上,结合数值模拟计算,研究了桩土相互作用机理及地震条件下的抗滑加固技术。主要工作及研究结论如下:(1)采用土工离心模型实验,结合数值模拟计算,再现了桩间土拱效应现象,在实验条件下得到临界桩净间距为桩径的5～6.25倍。离心模型实验及数值模拟结果表明土拱的形状大致相同,拱矢高度基本上随桩间距的增大而增大,矢跨比约为0.4～0.6。抗滑桩的受力及主应力场分布表明拱脚区域为控制截面,拱脚推力主要通过桩后受挤压土体传递给抗滑桩,桩侧面和土体的相互摩擦力所提供的拱脚反力仅约为前者的10%。通过敏感性分析,对于临界桩净间距而言,各影响因素的敏感性大小排序为:滑体剩余下滑力、土体内摩擦角、土体粘聚力、桩宽度。根据桩间土拱效应机理的研究结论,通过多元回归分析,建立了临界桩净间距计算模型,可据此判断桩间土拱的形成条件并进行桩间距优化设计。(2)基于拟静力法理论,采用离心模型实验和数值模拟计算研究了地震力作用下斜坡堆积体破坏模式和抗滑桩及锚杆框架护坡的加固效果。研究表明抗滑桩能够抵挡坡体沿基岩面的滑动,但仍有可能发生中上部坡体浅层坍滑从桩顶剪出。而锚杆框架护坡能够改善坡体内部的应力应变分布,有效地防止地震力作用下在坡体中可能形成的剪切带,控制坡体在地震力作用下的水平位移,防治坡体从桩顶剪出,同时能够较大幅度地减少抗滑桩受力。分析了高烈度地区斜坡堆积体破坏机理,提出设桩后发生越顶坍塌破坏模式的判定条件,可据此进行防治方案设计。在高烈度地区对于斜坡堆积体的工程设计应强调“固脚强腰”的防治原则,在增加了锚杆框架护坡工程后,可以适当地减少抗滑桩的工程数量,以实现技术和经济的优化设计。(3)通过不加锚杆和锚杆加固的边坡振动台模型对比实验,发现地震作用下,锚杆加固模型的加速度放大系数明显小于不加锚杆模型,说明锚杆加固边坡具有较好的抗震效果,尤其在中震和大震情况下更为显著。频谱分析结果表明,施加地震荷载前,锚杆加固边坡的自振频率比未加锚杆边坡的自振频率提高约20%,且历经中震、大震后,其自振频率无明显降低。而未加锚杆边坡的自振频率在历经中震、大震后降低达20%。说明锚杆加固能起到改善边坡地震动力特性的作用。对同一模型所进行的拟静力和动力分析的对比说明,根据设计规范所取的地震综合影响系数进行的拟静力计算结果在土体剪切应变及抗滑桩结构受力方面均小于动力计算值,在中震及大震工况下,采用拟静力计算偏于不安全。进一步计算表明,合理的地震综合影响系数取值约在0.45～0.5范围内。更多还原

【Abstract】 The geologic environment is friable in middle and west area of China. Some large-scale base establishment projects have influenced the geologic environment largely. The slope gravity hazards such as landslides, debris flow and collapse are retaining increased current. The destruction process of slope acted by gravitation is the self-organization process that rock and soil mass exert stabilization ability themselves to withstand the gravity action. In the process, the distortion behave as development from out-of-order to ordered. The anti-slide and reinforcement measure can change the the self-organization process and prevent the distortion of rock and soile mass developing from out-of-order to ordered. Based on self-organization theory, the strong outside disturbance can induce that the self-organization characteristic of system may disappear and behave as large-scale destruction abruptly, such as earthquake status, the slope may been destroyed abruptly. Aiming at upwards two typical destruct process of slope, different design idea should been adopted. For normal status, the main idea is to utilize the ability of rock and soil mass own stabilization adequately. For earthquake status, the main idea is to strengthen the aseismatic capability of the whole slope and reduce the coupling amplificatory effect of the outside disturbance, such as altering the dynamic characteristic of slope.As one kind of familiar and effective measures to deal with the slope gravity hazards, anti-slide piles are absence of theoretics guidance. Especially, in respect of confirming the reasonable pile space, engineering experience is main depended on. The mechanism of some familiar anti-slide and reinforce measures is studied rarely in seism condition. Based on geotechnical centrifuge model tests and shaking table model tests, combined with numerical simulation calculation, the pile-soil interaction mechanism and anti-slide reinforce technique in seism were studied. The main work and conclusion is as follow:(1) Geotechnical centrifuge model tests combined with numerical simulation calculation were adopted to reappear the soil-arching phenomena between piles. The critical net pile space is 5-6.25 multiple the pile width under experiment condition. The results of tests and calculation indicate that the form of soil-arching is same nearly, vector height increases with the pile space basically. Height-span ratio is 0.4～0.6 approximately. Force of pile and distributing of principal stress indicate that the foot of soil-arching is the dominate section. Thrust of foot is transferred to pile via soil at the back of pile mainly. The counter-force provided by the friction of pile flank and soil is 10% of the former. By sensitivity analysis, the sequence of factors that influence the critical pile space is: residual slip force of sliding mass, internal friction angle of soil mass, cohesion of soil mass, width of pile. Based on the research conclusion, the calculational model of critical net pile space is founded by multiple regression analysis, which can be used to estimate condition of forming the soil arching between piles and optimize the design of pile space.(2)Based on the pseudo-static method theory, the failure mechanism of slope accumulation reinforcement under earthquake was studied with centrifuge model tests and numerical simulation. In order to reinforce slope accumulation, anti-slide piles and anti-slide piles combined with anchor bolt frames were analyzed by means of contrast. Experimental results show that overtopping collapse possibly occur when anti-slide piles are used solely to reinforce the foot of slope accumulation. Anti-slide piles combined with anchor bolt frames can meliorate the distributing of stress and strain, and minish the deformation of slope and the force of anti-slide piles greatly. The determinant condition about failure mode of overtopping collapse is put forward, which can be used as guidance of prevention project design. It is suggested that the principle of "foot reinforcement and mountainside strengthening" should be emphasized for slope accumulation engineering design in high earthquake intensity regions. To carry out technique and economy optimum design, amount of piles project can be reduced when the anchor bolt frames are adopted.(3)Through Contrastive tests of no anchor bolt slope with anchor bolt reinforced slope by rockshaking table model tests, the phenomena is discovered that the acceleration amplificatory ratio of anchor bolt reinforced slope is less than no anchor bolt slope distinctly, which shows that anchor bolt reinforced slope has preferable effect, especially at the state of middle and high earthquake. The result of spectrum analysis shows that the natural frequency of anchor bolt reinforced slope is improved 20% than no anchor bolt slope before the earthquake forece is loaded, which does not reduce obviously after middle and high earthquake when the natural frequency of no anchor bolt slope redues 20%. This illuminates that anchor bolt can ameliorate the earthquake qualitative behavior of slope. Comparing pseudo-static with dynamical analysis about the same model, the shear stress of soil and force of pile of pseudo-static calculation are less than those of dynamical calculation when the earthquake comprehensive affecting coefficient is adopted from design criterion. Pseudo-static calculation is not safe at the situation of middle and high earthquake. Farther calculation indicates that the reasonable range of earthquake comprehensive affecting coefficient is in 0.45～0. 5.更多还原