【作者】 刘建文；

【导师】 苗晨曦； 张军；

【作者基本信息】 太原理工大学 ， 土木工程（专业学位）， 2024， 硕士

【摘要】 中西部地区的公路项目大多穿越山区,地形复杂且地质条件多变,特殊的地形地质条件为挡土墙结构工程的进一步应用带来了巨大挑战。虽然加筋土挡墙以其独特的优势被广泛应用于各个应用环境中。但是,在斜坡地段的加筋土挡墙设计与施工中仍面临诸多难题,尤其是斜坡地段面临的复杂交界面问题以及筋材的可布设长度受限问题,一旦处置不当就会增加支挡结构整体滑塌和失稳的风险。目前,针对此类问题,工程中经常采用直接削坡或分级开挖台阶等方式来调整坡体形态,通过减小坡度或降低支护高度的方法降低整体失稳风险。但这样会导致原位稳定岩土坡的利用率较低,还会增加大量施工工作量和造成环境损害。因此,针对斜坡地段加筋土挡墙的特殊问题,亟待进行深入研究,探索更经济、高效且环保的解决方案。为解决目前加筋土挡墙存在的应用问题,本文依托国家基金面上项目,开展预应力锚杆-加筋土挡墙组合支挡结构室内缩尺模型试验和FLAC3D数值模拟研究。通过室内模型试验验证数值模型的可靠性,并在此基础上,充分发挥数值模拟的优点,就组合结构多因素分析和结构材料强度影响两个重要角度对新型组合支挡结构力学性能和作用机理开展研究,系统分析静载作用下组合支挡结构的承载特性、边坡的变形模式和应力应变特征,以及循环荷载作用下组合结构动力响应变化。揭示预应力锚杆的引入对组合支挡结构整体性能的影响,为预应力锚杆-加筋土挡墙组合支挡结构在山区斜坡地段的长期可靠应用提供可靠的理论和技术支持。主要研究内容包括:(1)根据相似比理论开展了预应力锚杆-加筋土挡墙组合支挡结构室内模型试验,然后以试验为基础,建立FLAC3D数值模型并对面板水平位移、沉降和筋材应变进行对比分析。对比结果表明:数值模拟能够较好的反应模型试验结果,具有较好的可靠性;模型试验和数值模拟结果均显示预应力锚杆-加筋土挡墙组合结构筋材应变相似,破裂面为双折线破裂面,发育趋势略有不同。(2)针对锚杆预应力、斜坡地段交界面状况、土工格栅布置各影响因素,开展数值模拟研究,为组合结构设计应用提供可靠的研究结论。模拟结论显示:随着接触面摩擦角的增大,边坡的破坏模式由沿接触面的楔形破坏逐渐变为圆弧破坏,并且由于预应力锚杆的引入,使得基底竖向应力的仍保持均匀分布;随着锚杆预应力的不断增加,潜在破裂面是先由加载板前侧(以临空面为正方向)下方向向中间格栅的中部发展,然后向面板底部延伸转为先由加载板前侧(以临空面为正方向)垂直向下发展,随后向混凝土面板底部发育;土工格栅变间距布置能避免在回填土与混凝土面板交界面处产生拉应力区。(3)利用数值模拟手段,研究各组成部分(预应力锚杆、加筋材料、挡墙和回填土)强度对组合结构承载能力影响程度和应力应变演变规律。研究结果表明:当回填土强度较高时,反而会导致基底压力过高,但是应在内侧优先采用强度较高的土壤作为回填土;锚杆预应力和锚杆强度均能影响锚杆的主动约束效果;土工格栅强度增加对破裂面产生的影响与锚杆预应力增加的作用效果极为相似,但其作用机理并不相同。(4)利用数值分析方法模拟复杂动态交通荷载,研究加筋土挡墙在动力作用下结构长期性能的变化。研究结果显示:加载范围为0-60 k Pa的正弦循环荷载最大沉降值约为60k Pa静力荷载沉降值的81.7%;沉降、面板水平位移和轴力均出现明显的滞后现象。更多还原

【Abstract】 Most of the highway projects in the central and western regions pass through mountainous areas,the terrain is complex and the geological conditions are changeable.The special geological conditions bring great challenges to the further application of retaining wall structure engineering.Although reinforced earth retaining walls are widely used in various application environments for their unique advantages.However,there are still many problems in the design and construction of reinforced soil retaining wall in slope section,especially the complex interface problem and the limited layout length of reinforcement material,which will increase the risk of overall collapse and instability of retaining structure once handled improperly.For the time being.In order to solve such problems,direct slope cutting or step excavation is often used to adjust slope shape,and the overall instability risk is reduced by reducing slope or reducing support height.However,this will lead to a low utilization rate of in-situ stable rock slope,but also increase a lot of construction workload and environmental damage.Therefore,for the special problems of reinforced earth retaining wall in slope section,it is urgent to conduct in-depth research and explore more economical,efficient and environmentally friendly solutions.Take advantage of a solid wall,this paper,relying on the national foundation project,carried out the indoor scale model test and FLAC3D numerical simulation of prestressed bolt-reinforced soil retaining wall composite retaining structure.The reliability of the numerical model was tested in an indoor model.On this basis,the mechanical properties and mechanism of the new composite retaining structure were studied from two important perspectives of multi-factor analysis of the composite structure and the influence of structural material strength on the numerical simulation.The bearing characteristics of composite retaining structure under static load,deformation mode and stress-strain characteristics of slope,and dynamic response of composite structure under cyclic load are analyzed systematically.The effect of the anchor post on the overall performance is demonstrated,which provides a solid theoretical and technical support for the long-term reliable application of the shock post on the high flank.The main research contents include:(1)Based on the similarity ratio theory,an indoor model test of prestressed bolt-reinforced soil retaining wall composite retaining structure was carried out.Then,based on the test,a FLAC3D numerical model was established and the horizontal displacement,settlement and reinforcement strain of the panel were compared and analyzed.The comparison of the results shows that the numerical model better reflects the results of the model and shows better reliability.The results of model test and numerical simulation show that the strain of the reinforcement of the prestressed bolt-reinforced soil retaining wall is similar,the fracture surface is double broken line fracture surface,and the development trend is slightly different.(2)Carry out numerical simulation research on the influence factors of anchor prestress,interface condition of slope section and gegrid layout,so as to provide reliable research conclusions for the design and application of composite structure.The simulation results show that with the increase of the friction Angle of the contact surface,the failure mode of the slope gradually changes from wedge failure to arc failure along the contact surface,and the vertical stress of the base is still evenly distributed due to the introduction of prestressed anchor rod.With the increasing prestress of the anchor rod,the potential fracture surface first develops from the front side of the loading plate(with the free side as the positive direction)to the middle of the middle grille,and then extends to the bottom of the panel,and then develops from the front side of the loading plate(with the free side as the positive direction)to the bottom of the concrete panel.The variable spacing of the geogrid can avoid the tension stress zone at the interface of the backfill soil and the concrete panel.(3)The foreign components used for camouflage(extrusion anchors,adjustable materials,repulsive forces and fossilization)were studied through genetic simulations,and the adaptive strength of multiple structures and how adaptive modes increase carrying capacity were investigated.The results show that when the backfill strength is higher,the base pressure will be too high,but the soil with higher strength should be preferred as the backfill in the inner side.Both prestress and strength of bolt can affect the active restraint effect of bolt.The effect of the increase of geoglage strength on the fracture surface is very similar to that of the increase of anchor prestress,but its mechanism is different.(4)Using a numerical analysis method to simulate a complex dynamic traffic load,The long-term change of the structure capacity of earth wall under dynamic action is studied.The results show that the maximum settlement value of sinusoidal cyclic load with the loading range of 0-60 k Pa is about 81.7%of that of static load with 60k Pa.The subsidence,horizontal displacement and axial force of the panel all show obvious hysteresis.更多还原