微型桩—锚组合新结构的抗滑机理研究

发布时间：2018-04-30 10:24

本文选题：边坡工程 + 微型桩　；参考：《中国铁道科学研究院》2014年硕士论文

【摘要】：边坡工程涉及公路、铁路、矿山、水利水电、核电等众多工程领域，其中病害边坡的雨季抢险及滑坡引起的线路保通等工程普遍存在工期紧、施工场地受限等特点。抗滑桩、预应力锚索框架等传统大型防治结构的施工期周期长、圬工量大，无法满足快速治理的要求。因此，基于应急抢险和环保施工的需要，抗滑结构逐渐趋于向轻型化、快速化以及机械化方向发展，边坡工程界积极研发轻型支护体系以及组合型边坡支挡结构。微型桩由于具有非开挖施工、对土层适用性强、桩位布置灵活、施工速度快、对滑体扰动小等优点，近年来在边坡加固和滑坡治理尤其是一些应急抢修工程中得到了越来越广泛的应用。但由于微型桩长径比大、抗弯承载力不足，在外力作用下易产生侧向挠曲变形，作为独立措施加固边坡时难以严格控制变形。例如，加固隧道穿越的滑坡体时隧道-滑坡体系的变形仍易超出道路安全运行的允许位移量。因此，工程实践中通常将微型桩与其它滑坡支挡结构联合应用以达到防治边坡滑坡的目的，微型桩的应用推广仍具有一定的局限性。所以在现有微型桩的应用研究基础上，积极开发高承载力的微型桩结构新形式具有重大意义。本文主要依托科技部科研院所技术开发研究专项资金《灾后边坡病害快速治理新结构及防护技术》（2009E123201），对课题组提出的一种微型桩-锚组合抗滑新结构进行研究。在国内外相关研究的基础上，结合堆积层滑坡、堆载诱发型均质土滑坡及黄土滑坡三类典型灾害性滑坡，通过现场调查、理论分析、数值模拟、室内模型试验相结合的方法，，对普通微型桩结构及微型桩-锚组合新结构的加固效果及力学机理等进行了系统研究。研究表明微型桩-锚组合新结构应用于滑坡防治是可行的。取得的主要成果如下：（1）在系统总结实践中常用的微型桩结构类型的基础上，基于综合利用排桩刚架结构与拉锚式挡土结构两种结构形式优点的研发思路，提出了一种微型桩-锚组合抗滑新结构。该结构以预应力锚索作为外拉系统，一端通过桩顶系梁与微型桩相连，另一端锚固在稳定土层中，形成主动加固体系。改进的抗滑机理主要体现在：一方面，增大了刚架式挡土结构体系的侧向刚度，有效限制了结构的整体侧向变形；另一方面，挡土结构所承受的部分荷载，通过预应力锚索传递到锚固体周围稳定地层中，充分发挥了结构的整体受荷能力和地层的自承能力。（2）以一典型的折线型堆积层滑坡为工程对象，运用FLAC3D有限差分软件对微型桩-锚组合结构应用于滑坡防治的适宜性进行数值试验研究。分别计算了自然工况和普通平面刚架式微型桩结构及微型桩-锚组合结构两种防治方案加固该滑坡时的坡体变形、应力-应变特征和结构内力、外力分布规律及变形特性。对比分析得出，相比微型桩框架结构，新结构加固的边坡位移场、应力场、应变场的稳定性更好，新结构桩头位移小，与边坡协调变形性能优越，桩体内、外力分布相对均匀且峰值有所降低。（3）通过室内地质力学模型试验，对独立布置的微型桩、垂直布置的平面刚架式结构、倾斜布置的平面刚架式结构及预应力锚索作用下垂直和倾斜布置的平面刚架式组合结构共计五种结构的支挡效果及机理进行研究。结果表明，微型桩单桩的抗滑机理由抗剪、抗弯及独特的抗拔性能体现；在群桩顶部增设系梁可增强结构的整体性，形成桩土复合结构；桩轴倾斜至与滑面呈垂直角度时可增加结构的抗剪、抗弯性能，因此针对不同的滑面形态选择合适的布置角度可有效提高微型桩抗滑效果；在刚架结构顶部增设预应力锚索可有效增加结构整体刚度，限制侧向变形和桩头位移，均匀受力分布并减小内力峰值。根据模型试验结果，建议在新结构设计中桩锚荷载分担比取0.4～1.0。（4）基于新结构为横向受力的复合抗滑桩的假设，根据横向约束的Winkler弹性地基梁计算方法，按变形协调原理推导了微型桩-锚结构加固边坡时锚索拉力、桩身位移及内力的计算公式。在此基础上，提出了微型桩-锚组合结构的一种设计方法及步骤。（5）以新疆省道S316线一处路基黄土边坡为工程背景，对新结构的设计步骤进行了详细介绍。首先根据理正软件的边坡稳定性分析模块计算搜索最危险滑动面；然后计算滑坡推力；在拟定桩截面形式后，通过检算桩间土拱效应和扰流现象，确定组合结构间距；基于工程实践经验和相关规范要求，确定联系梁设计形式及尺寸；通过桩锚荷载分担比确定锚索设计荷载，计算锚固长度；最后基于桩截面极限抗力通过推导的解析公式计算桩长。
[Abstract]:Slope engineering involves many engineering fields, such as highway, railway, mine, water conservancy and hydropower, nuclear power, etc., in which the rainy season and landslides caused by the landslide are widely used in engineering, such as tight construction time, limited construction site and so on. The construction period of the large control structure, such as anti slide pile, prestressed anchor cable frame and so on, has long period of construction and large quantity of masonry. The method meets the requirements of rapid management. Therefore, based on the needs of emergency emergency rescue and environmental protection construction, the anti sliding structure has gradually tended to light, rapid and mechanized. The slope engineering community has actively developed a light support system and a combined slope retaining structure. The micro pile is characterized by a non excavation construction, strong applicability to the soil layer and a pile position. With the advantages of flexible arrangement, fast construction speed and small disturbance to the slide body, it has been used more and more widely in slope reinforcement and landslide treatment in recent years, especially in some emergency repair projects. However, due to the large length diameter ratio and insufficient bending bearing capacity of the micro pile, it is easy to produce lateral deflection under external force, as an independent measure to reinforce the slope. It is difficult to control the deformation strictly. For example, the deformation of the tunnel landslide system is more likely to exceed the allowable displacement of the road safe operation when the tunnel is strengthened through the landslide. Therefore, the micro pile is usually combined with other landslide retaining structures to prevent the slope landslide. Therefore, based on the applied research of the existing micro piles, it is of great significance to actively develop new forms of micro piles with high bearing capacity.
This paper mainly relies on the new structure and protection technology for the rapid control of post disaster slope diseases (2009E123201), which is based on the special funds of the technical development research of the scientific and Technological Research Institute of the Ministry of science and technology. Three typical catastrophic landslides of slope and loess landslide are systematically studied through field investigation, theoretical analysis, numerical simulation and indoor model test. The reinforcement effect and mechanical mechanism of the new structure of ordinary micro pile and micro pile anchor combination are systematically studied. The study shows that the new structure of micro pile anchor combination is applied to the prevention and control of landslide. It is feasible. The main achievements are as follows:
(1) on the basis of the type of micro pile structure commonly used in the systematic summary practice, based on the research and development ideas of the advantages of the two structural forms of the pile rigid frame structure and the anchorage retaining structure, a new type of micro pile anchor combination anti sliding structure is put forward. The structure is used as the prestressed anchor cable as the external pull system, and one end passes the pile top system beam and the minitype. After the pile is connected and the other end is anchored in the stable soil layer, the active reinforcement system is formed. The improved anti sliding mechanism is mainly embodied in: on the one hand, the lateral stiffness of the rigid frame retaining structure is increased, the overall lateral deformation of the structure is restricted effectively; on the other hand, the partial load of the retaining structure is transferred to the anchor through the prestressed anchor cable. In the stable surrounding strata, the overall loading capacity of the structure and the self bearing capacity of the strata are fully realized.
(2) taking a typical folded stacking landslide as an engineering object, the FLAC3D finite difference software is used to study the suitability of the micro pile anchor combination structure for the landslide prevention and control. The natural working condition, the ordinary rigid frame type micro pile structure and the micro pile anchor combination structure are respectively calculated and two kinds of prevention and control schemes are used to reinforce the slide. The slope deformation, stress strain characteristic and structural internal force, external force distribution law and deformation characteristics. Compared with the micro pile frame structure, the stability of the displacement field, stress field and strain field strengthened by the new structure is better, the displacement of the pile head is small, the deformation performance of the new structure is small, the deformation of the new structure is superior, the distribution of the internal force in the pile is relative to the pile, and the distribution of the force in the pile is relative to the pile. It is uniform and the peak value is reduced.
(3) through the laboratory geomechanics model test, the supporting effect and mechanism of five kinds of rigid frame structure, flat rigid frame structure, flat rigid frame structure and the vertical and inclined plane rigid frame combined structure under the action of prestressed anchor cable are studied. The anti sliding mechanism of pile is reflected in shear resistance, bending resistance and unique anti drawing performance. Adding a beam to the top of the pile group can enhance the integrity of the structure and form a composite structure of pile and soil. When the pile shaft inclines to the vertical angle to the slide surface, it can increase the shear and bending properties of the structure. Therefore, it is effective to select the appropriate layout angle for different sliding surfaces. Increasing the anti sliding effect of the micro pile, adding the prestressed anchor cable on the top of the frame structure can effectively increase the overall stiffness of the structure, limit the lateral deformation and the pile head displacement, the uniform force distribution and reduce the internal force peak. According to the model test results, it is suggested that the ratio of the pile anchor load to the load ratio of 0.4 to 1.0. in the new structure design is suggested.
(4) based on the hypothesis of the composite anti slide pile with the lateral force of the new structure, according to the lateral constraint Winkler elastic foundation beam calculation method, the formula of the anchor cable tension, the pile displacement and the internal force is derived according to the deformation coordination principle. On this basis, a design side of the micro pile anchor combination structure is put forward. Law and steps.
(5) taking a roadbed loess slope in the S316 line of Xinjiang provincial highway as the project background, the design steps of the new structure are introduced in detail. First, the most dangerous sliding surface is calculated by the slope stability analysis module of the software, and then the landslide thrust is calculated. After the cross section of the pile is drawn up, the soil arch effect and the disturbing current between the piles are checked. To determine the spacing of the composite structure, the design form and size of the connecting beam are determined based on the practical experience of the engineering and the requirements of the relevant specifications. The anchor length is calculated by the load sharing ratio of the pile anchor, and the length of the anchorage is calculated. Finally, the pile length is calculated based on the analytical formula derived from the ultimate resistance of the pile section.

【学位授予单位】：中国铁道科学研究院
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU473.1

【参考文献】