【作者】 李长冬；

【导师】 唐辉明； 胡新丽；

【作者基本信息】 中国地质大学 ， 岩土工程， 2009， 博士

【摘要】 滑坡是斜坡破坏型式中分布最广、危害最严重的一种地质灾害，我国是世界上受滑坡灾害损失最为严重的国家之一。随着我国经济建设的蓬勃发展，三峡工程、青藏铁路、西气东输、西电东送和汶川地震灾后重建等一大批关系国计民生的重大工程相继启动，项目实施过程中深受滑坡灾害的严重危害和潜在威胁。为了切实保障人民生命财产安全，有关部门对滑坡非常重视并采取了积极的治理措施。仅据不完全统计，三峡库区存在地质灾害点共4429处，其中淹没和移民迁建区较大规模的滑坡、崩塌体2490处，2002年至今两期专项地质灾害治理已投入120余亿元。因此，迫切需要对滑坡治理方法进行系统研究并以此为工程实践提供科学的依据。抗滑桩作为整治滑坡的主要手段之一，在滑坡治理工程取得了极为广泛的应用。但由于目前抗滑桩的理论研究与工程实践存在较大的差距，尤其突出表现在抗滑桩工程中抗滑桩设计参数确定具有很大的随意性，缺乏合理的标准和科学的理论依据，因此其设计方案很难达到安全和经济的双重目的，过于保守的设计会造成极大的投资浪费，而反之则会造成工程隐患，会造成更大的经济损失。为此，在深入研究抗滑桩与滑坡体相互作用机理的基础上开展抗滑桩优化研究是当前抗滑桩工程中迫切需要解决的重要应用课题之一。本文从分析典型堆积层滑坡的特征及形成机理入手，分析了堆积层滑坡的推力分布形式，并结合当前抗滑桩工程中的抗滑桩设计原则和内力计算方法，构建抗滑桩与滑坡体相互作用的相互作用模型。通过抗滑桩与滑坡体相互作用的过程分析，深入研究了抗滑桩与滑坡相互作用的机理，提出了基于土拱效应的抗滑桩最小桩间距计算模型和最大桩间距计算模型，并建立了包括桩后土拱、桩间土拱和桩前土体的三级荷载分担比模型。结合本文对于抗滑桩桩间距模型的研究、截面尺寸优化研究和锚固比优化研究的相关成果，开展抗滑桩优化研究，并提出了抗滑桩综合优化研究的方法。取得的主要研究成果如下：(1)考虑抗滑桩与滑坡体的相互作用的模型与太沙基活动门试验的模型具有相似性，在Chevalier对改进太沙基活动门试验的三个阶段划分的基础上，指出抗滑桩与滑坡体相互作用的过程亦应分为初始阶段、过渡阶段和最后阶段的三个阶段。从整个抗滑桩与滑坡体相互作用是三阶段过程的角度出发，提出了基于抗滑桩与滑坡体相互作用过程的桩土相互作用模型，以桩后土拱占主导作用的阶段为土拱效应的“过渡阶段”，以桩间土拱占主导作用的阶段为土拱效应的“最后阶段”。(2)根据基于抗滑桩与滑坡体相互作用过程的模型，建立了基于抗滑桩与滑坡体相互作用过程的桩间距计算模型。结合抗滑桩与滑坡体相互作用过程的分析，分别基于桩后土拱效应和桩间土拱效应建立了最小桩间距计算模型和最大桩间距计算模型，可以为堆积层滑坡抗滑桩工程中桩间距的确定提供科学的计算依据。(3)在理论分析的基础上提出了抗滑桩不等桩间距布设原则。在抗滑桩截面尺寸和滑体参数确定的条件下，经过公式推导发现滑坡推力和桩净距的乘积是一个不变量，基于此提出了抗滑桩根据滑坡推力空间分布的特征进行不等桩间距布设的原则。其核心内容是对于抗滑桩截面宽度已经确定的滑坡，在滑坡推力比较大的主滑剖面附近布设桩间距较小的抗滑桩，而滑坡两侧推力比较小的地段应根据滑坡推力的递减程度逐渐增加桩间距，最终形成的桩间距布设呈“中间密，两侧疏”的特点。(4)根据抗滑桩工程的特点，提出了基于抗滑桩与滑坡体的桩土荷载分担比概念。并定义桩体分担比用来表征滑坡土体将滑坡推力荷载转移到抗滑桩上的程度，由此来衡量抗滑桩的抗滑效果。根据抗滑桩与滑坡体相互作用土拱的传力特点不同，可将桩后土拱称之为“端承土拱”，而将桩间土拱称之为“摩擦土拱”。并对传统的两级桩土荷载传递模式进行了改进，提出了基于桩后的“端承土拱”、桩间的“摩擦土拱”和桩前土体的三级荷载传递模式。并在此基础上研究了抗滑桩与滑坡体相互作用过程中的荷载分担比变化规律。(5)开展系统抗滑桩与滑坡体相互作用的数值试验研究，对目前抗滑桩与滑坡体计算模型进行了改进。在桩型选择方面，克服圆桩或方桩模型的缺点，采用截面高度为1．5倍桩截面宽度的矩形模型来模拟抗滑桩；在桩土相互作用模型研究范围方面，为了避免边界条件对土拱效应的影响，计算宽度范围内选取四根抗滑桩，而重点研究中间两根抗滑桩的土拱效应规律；在桩土相互作用模型约束条件方面，根据三峡库区典型堆积层滑坡“后陡前缓”的特点，桩前的滑坡体应为自由临空面，而非约束边界条件。(6)为了研究不同参数条件下抗滑桩与滑坡体之间的土拱效应的变化规律和桩土荷载承担比规律，分为不同桩间距、不同滑体抗剪强度参数、不同桩土接触面参数和不同滑坡推力条件下土拱效应和桩土荷载分担比的变化规律进行了系统分析与研究。研究结果表明：①通过不同间宽比的土拱效应数值分析，可以发现最大主应力拱即为存在于相邻抗滑桩侧壁之间的土拱，其“拱脚”则为桩间土与抗滑桩侧壁的接触面。随着桩间宽比的逐步增大，最大主应力拱的土拱效应越来越不显著；最小主应力拱即为存在于相邻抗滑桩桩后之间的土拱，其“拱脚”为抗滑桩后壁。当间宽比逐步增大时，最小主应力土拱逐渐被桩后滑坡推力形成的应力“反拱”所破坏；②在抗滑桩截面宽度一定的情况下，随着桩间距的增大，桩后土拱承担荷载比例下降，而桩间土拱承担的荷载比例上升，表明间宽比的增加致使更多的荷载作用于桩间土拱上，但桩间土拱的承载主要依靠桩间土体和抗滑桩侧壁之间的摩阻力，有承载极限的制约，故其荷载分担比例线的趋势逐渐趋于平缓；③在抗滑桩截面宽度和桩间距一定的情况下，随着滑体粘聚力的增大(由0增大至某一界限值)，桩后土拱承担荷载比例下降，而桩间土拱承担的荷载比例上升，表明滑体粘聚力的增加直接导致桩间土拱承载能力的增加。当滑体粘聚力增大至某一临界值后桩后土拱、桩间土拱和桩前土体所承担的比例基本不变，这表明当滑体粘聚力增大至某一临界值后，桩后土拱和桩前土拱的强度已经达到足以承担滑坡荷载的分担部分，若再增加滑体的粘聚力对于土拱效应的发挥并不明显；④在抗滑桩截面宽度和桩间距一定的情况下，随着滑体内摩擦角的增大，桩后土拱承担荷载比例有轻微上升，而桩间土拱承担的荷载比例有轻微下降，表明滑体内摩擦角的增加导致桩后土拱承载能力有一定的增加。当滑体内摩擦角增大至某一临界值后桩后土拱、桩间土拱和桩前土体所承担的比例基本不变，这表明当滑体内摩擦角增大至某一临界值后，桩后土拱和桩前土拱的强度已经达到足以承担滑坡荷载的分担部分，若再增加滑体的内摩擦角对于土拱效应的发挥并不明显；⑤在抗滑桩截面宽度和桩间距一定的情况下，随着桩土接触面摩擦角的增大，桩后土拱承担荷载比例有轻微下降，而桩间土拱承担的荷载比例有轻微上升，表明滑体内摩擦角的增加直接导致桩间土拱承载能力有一定的增加；⑥在抗滑桩截面宽度和桩间距一定的情况下，随着滑坡推力荷载的增大，桩后土拱承担荷载比例明显下降，而桩间土拱承担的荷载比例明显上升，表明滑坡推力荷载的增加直接导致桩间土拱荷载承担比的增加，当滑坡推力荷载超过某一界限值时，桩后土拱已经破坏，而相应的荷载由桩间土拱承担。(7)在考虑沿滑体深度方向的三维土拱效应研究法方面，指出在三角形分布的滑坡推力荷载作用下，由于受到土拱效应的影响，滑体的最大主应力在抗滑桩前后发生了显著的变化，且可见桩后应力影响的范围自上而下逐渐减小，表明土拱效应的影响范围随着滑体深度逐渐变小。因此，在抗滑桩工程实践中，应考虑到堆积层滑坡土拱效应随滑体深度逐渐减弱的规律，并根据土拱作用的影响范围进行合理的抗滑桩设计。(8)在抗滑桩桩型参数的单因素优化研究方面，在满足加固后稳定性要求，抗滑桩抗弯、抗剪和侧应力复核及构造配筋要求的前提下，实现抗滑桩单桩费用的最小化即是求解的最优目标。根据黄金分割优化算法可以根据优化计算模型分别对锚固比和截面尺寸进行优化研究。(9)综合单因素条件下抗滑桩优化研究的方法和桩型参数与布设参数之间的相互影响关系，提出了抗滑桩综合优化研究方法。根据在一定条件下滑坡推力和桩净距的乘积为定值的不等桩间距布设原则，首先根据滑坡推力的大小给定初始桩间距，然后通过已知桩间距的前提下进行抗滑桩截面尺寸和锚固比优化，根据确定的截面尺寸和锚固比又反过来验算初始桩间距是否合适。通过循环迭代，可根据本文对于抗滑桩桩间距模型的研究、截面尺寸优化研究和锚固比研究的相关成果，为抗滑桩优化研究提供了一个切实可行的综合优化研究方案。(10)在对抗滑桩进行优化研究的前提是首先弄清楚抗滑桩与滑坡体相互作用的机理，研究抗滑桩外部因素(如滑坡推力、滑体抗剪强度参数、滑体厚度和滑体容重等)与内部因素(桩间距、锚固比和桩截面尺寸等)之间的关系，在考虑工程安全和经济双重标准要求下，确定抗滑桩间距时应该保证桩后土拱和桩间土拱共同分担滑坡推力荷载。同时，在进行单桩工程投资优化的前提下，亦应考虑抗滑桩桩排的平面综合布设，根据本文提出的不等桩间距布设原则，进一步使抗滑桩与滑坡体实现协同工作的最佳状态，以实现工程安全和投资经济的双重目标。本文的研究方法可为抗滑桩工程中抗滑桩的桩型参数和布设参数的确定提供科学的理论依据。更多还原

【Abstract】 Of all slope failure types, landslide is the widest distribution and the most severe geological hazard. Our nation is one of the countries suffering the most serious landslide hazard loss in the world. With the fast development of our national economic construction, the Three Gorges Reservoir project, Qinghai-Tibet railway project, West-East natural gas transferring project, West-East electricity transmission project, Wenchuan earthquake reconstruction, etc, a great number of key projects related to national welfare and the people’s livelihood are successively carried out. During the enforcement of the projects, many of them are suffered severe threaten or potential threaten. In order to protect the safety of national welfare and the people’s livelihood, the administration department paid much attention to the landslide hazard and took effective steps to control the landslides. Just in the Three Gorges Reservoir Area, of all the 4429 geological hazard points, there are 2490 large-scale landslides or collapses in the submerged area and immigration removal area. And the nation has spent about 12 billion RMB on controlling the landslides as well as other geological hazards. As a result, it is urgent to systematic study the way of controlling the landslides to provide scientific basis for the engineering practice.Anti-slide pile is one of the most significant measures for controlling the landslide, and it is widely used in the landslide control project. However, due to the gap between the theory study and the engineering practice of anti-slide pile, the determination of design parameters of anti-slide pile always depend on engineering experience, lacking of reasonable standard and scientific theory basis. As a result, the design scheme is difficult to achieve both safety and economy. If the design scheme is too conservative, a great deal of investment will be wasted. On the contrary, it will cause engineering hidden trouble and the cost is even more. Therefore, there is pressure on carrying out research on anti-slide pile optimization study on the base of studying on the interaction mechanism of anti-slide pile and landslide.On the basis of the study on the characteristics and formation mechanism of typical accumulation landslide, the pushing force patterns of accumulation landslide are analyzed in detailed. With the design principle and internal force calculation of anti-slide pile, the geological model for anti-slide pile and landslide interaction is established. According to the analysis on the process of anti-slide pile and landslide interaction, the interaction mechanism of anti-slide pile and landslide is studied deeply. In addition, the minimum pile interval model and the maximum pile interval model are proposed based on the soil arching effect. And the three-stage load sharing ratio model is given, including the soil arching behind the piles, the soil arching between the piles and the sliding mass in front of the pile. Combined with the related study results in the aspects of pile interval, section dimension and anchoring ratio optimization research, the optimization study on the anti-slide pile is carried out, and the way of comprehensive optimization study is pointed out as well. The main study results are as follows:(1) Concerning the model of anti-slide pile and landslide interaction is similar with Terzaghi’s mobile door test, on the basis of improved mobile door test by Chevalier, the process of anti-slide pile and landslide interaction can be also divided into three stages, which are initial stage, transition stage and final stage. From the point of anti-slide pile and landslide interaction is a three-stage process, the anti-slide pile and landslide interaction model which is based on the interaction process is proposed. The stage when the soil arching behind the piles plays a dominant role is called "transition stage", while the stage when the soil arching between the piles plays a dominant role is called "final stage".(2) According to the model based on the process of anti-slide pile and landslide interaction, the pile interval calculation model is established. With the analysis of the process of anti-slide pile and landslide interaction, the minimum pile interval model and the maximum pile interval model are proposed based on the soil arching effect respectively, and they can provide scientific basis for the pile determination for engineering practice.(3) The differential pile interval distribution principle is proposed based on the theory analysis. Under the condition that the parameters of section dimension and sliding mass are determinate, the product of pushing force of sliding mass and the clear distance is a constant, therefore, the differential pile interval distribution principle is proposed based on the characteristics of pushing force of sliding mass. For the landslide that the section dimension parameters have been determined yet, the pile interval should be smaller where the pushing force of sliding mass is larger, while the pile interval should increase when the pushing force of sliding mass becomes smaller. The final pile distribution on the plane should present the characteristics of dense in the middle and sparse in the both sides.(4) According to the characteristics of anti-slide pile engineering, the pile-soil load sharing ratio based on the anti-slide pile and landslide is proposed. It is defined to describe the extent of load transfer from the sliding mass to the anti-slide pile, and it can weigh the effectiveness of anti-sliding. According to the difference of load transfer process between anti-slide pile and landslide, the soil arching behind the piles can be called end-bearing soil arching, and the soil arching between the piles can be called friction soil arching. Instead of the traditional two-stage load transfer pattern, a new three-stage load transfer pattern including end-bearing soil arching, friction soil arching and the sliding mass in front of the pile is proposed. With the new load transfer pattern, the change law of load sharing ratio during the process of anti-slide pile and landslide interaction can be studied in detailed.(5) The systematic numerical modeling study is carried out to research the anti-slide pile and landslide interaction. An improved model for anti-slide pile and landslide is proposed instead of the traditional one. In the aspect of pile pattern choice, in order to overcome the disadvantage of the circular pile and square pile, a new rectangle section dimension with the length of the section height is 1.5 times of the section width. In the aspect of study range, in order to prevent the impact by the boundary condition, there are four piles chosen as the study range, and the emphasis is on the middle two piles. In the aspect of constraint condition, according to the steep back and gentle front characteristics of the accumulation landslide in the Three Gorges Reservoir Area, the boundary of the sliding mass in front of the piles should be free but not constraint condition.(6) In order to study different parameters conditions the change law of anti-slide pile and landslide interaction soil arching effect and the pile-soil load sharing ratio, the anti-slide pile and landslide interaction soil arching effect and the pile-soil load sharing ratio are studied systematically under different pile interval, different shear strength parameters, different pile-soil interface parameters, different pushing force of sliding mass. The main conclusions are as follows:①According to the numerical simulation under different ratio between pile interval and section width, it can be found that the maximum principal stress arching is the arching existing between the piles, and its arch springing is the interface between the pile and the sliding mass. With the increase of the ratio between pile interval and section width, the effect of maximum principal stress arching becomes weak. The minimum principal stress arching is the arching existing behind the piles, and its arch springing is the back of the piles. With the increase of the ratio between pile interval and section width, the minimum principal stress arching will be destroyed by the pushing force.②When the section width of the anti-slide pile is determinate, with the increase of the pile interval, the load sharing ratio of arching existing behind the piles decreases, and the load sharing ratio of arching existing between the piles increases. It shows that with the increase of the ratio between pile interval and section width, more loads are transferred to the arching existing between the piles increases. Due to the bearing capacity depend on the friction between the piles and the sliding mass, the bearing capacity of the arching existing between the piles is limited to a certain range, and its load sharing ratio line becomes gentle.③When the section width of the anti-slide pile and the pile interval are determinate, with the increase of sliding mass cohesion (from zero to a certain threshold limiting), the load sharing ratio of the arching existing behind the piles decreases, while the load sharing ratio of the arching existing between the piles increases. It shows that the increase of sliding mass cohesion can enhance the bearing capacity of the arching existing between the piles. When the cohesion increases to a certain threshold limiting, the load sharing ratio of arching existing behind the piles, arching existing between the piles and the sliding mass in front of the pile remain the same. It shows that when the cohesion increases to a certain threshold limiting, the bearing capacity of both the arching existing behind the piles and the arching existing between the piles have enough capacity against the pushing force, and even larger cohesion has little effect on soil arching.④When the section width of the anti-slide pile and the pile interval are determinate, with the increase of sliding mass internal frictional angle, the load sharing ratio of the arching existing behind the piles has a slight increase, and the load sharing ratio of the arching existing between the piles has a slight decrease. It shows that the increase of sliding mass internal frictional angle can enhance the bearing capacity of the arching existing behind the piles. When the internal frictional angle increases to a certain threshold limiting, the load sharing ratio of arching existing behind the piles, arching existing between the piles and the sliding mass in front of the pile remain the same. It shows that when the internal frictional angle increases to a certain threshold limiting, the bearing capacity of both the arching existing behind the piles and the arching existing between the piles have enough capacity against the pushing force, and even larger internal frictional angle has little effect on soil arching.⑤When the section width of the anti-slide pile and the pile interval are determinate, with the increase of pile-soil interface frictional angle, the load sharing ratio of the arching existing behind the piles has a slight decrease, and the load sharing ratio of the arching existing between the piles has a slight increase. It shows that the increase of pile-soil interface frictional angle can enhance the bearing capacity of the arching existing behind the piles.⑥When the section width of the anti-slide pile and the pile interval are determinate, with the increase of sliding mass pushing force, the load sharing ratio of the arching existing behind the piles has a significant decrease, and the load sharing ratio of the arching existing between the piles has a significant increase. It shows that the increase of sliding mass pushing force increases the load sharing ratio of the arching existing behind the piles. When the sliding mass pushing force reach a certain threshold limiting value, the arching existing behind the piles is ruptured, and the load is mainly supported by the existing between the piles.(7) With concerning the three-dimensional soil arching effect in aspect of the direction along the siding mass depth, under the pushing force with triangle distribution, the maximum principal stress has a significant change after and before the piles due to the soil arching effect. In addition, the impact range of the maximum principal stress becomes smaller with the increase of the depth of siding mass. It shows the impact range of the soil arching effect becomes smaller with the increase of the depth of siding mass under this situation. Therefore, during the anti-slide engineering practice, the law of soil arching effect becomes smaller with the increase of the depth should be concerned, and the reasonable anti-slide pile should be carried out based on the impact range of soil arching effect.(8) In the aspect of single design parameter optimization of anti-slide pile, under the condition both satisfying the engineering safety and the check of bending resistance, shear resistant, lateral stress and construction reinforcement, the main optimization aim is to make the cost of the anti-slide pile lowest. By using the golden section optimization method, the optimization study on anchoring ratio and the section dimension can be carried out.(9) Based on the study on the single design parameter optimization and the relationship between the pile pattern parameters and the distribution parameters, the comprehensive optimization study method for anti-slide pile is proposed. Firstly, the initial pile interval is given according to the law that under the condition that the parameters of section dimension and sliding mass are determinate, the product of pushing force of sliding mass and the clear distance is a constant. Secondly, the optimization study of section dimension and anchoring ratio are carried out based on the initial pile interval. Also, the section dimension and anchoring ratio can check whether the pile interval is proper. According to the loop iteration, the final comprehensive optimization scheme can be determinate based on the study on the pile interval model, section dimension and anchoring ratio optimization study.(10) The premise of anti-slide pile optimization study is the interaction mechanism between anti-slide pile and landslide, and the relationship between the external factors of anti-slide pile (such as pushing force, shear strengthen parameters, the thickness of sliding mass, the unit weight of sliding mass, etc.) and internal factors of anti-slide pile (such as pile interval, anchoring ratio, section dimension, etc.) should be studied in detailed. With concerning the standard both the engineering safety and the investment economy, the reasonable pile interval should assure the arching existing behind the piles and the arching existing between the piles work together. Meanwhile, under the premise of single anti-slide pile investment optimization, the comprehensive distribution of anti-slide pile on the plane should be concerned. According to the differential pile interval distribution principle, it is will make the anti-slide pile and landslide synergistic work together still further. The study method proposed above can provide scientific theory basis to determine the pile pattern and distribution parameters for anti-slide pile engineering practice.更多还原