【作者】 朱伟；

【导师】 应宏伟；

【作者基本信息】 浙江大学 ， 岩土工程， 2014， 硕士

【摘要】 随着城市建设的发展,地下空间被广泛利用,地下建(构)筑物越来越密集。很多支挡工程中出现挡墙前后填土宽度有限的情况,例如临近既有地下室基坑支护结构、临近基岩面的边坡挡土墙、地铁车站狭窄基坑支护结构等。经典库伦或朗肯土压力理论,均假定刚性挡土墙平动且达到极限状态、挡墙后土体为半无限体,显然对于以上情形并不适用。本文针对有限土体的土压力问题,考虑挡墙变位模式和大小,开展模型试验和理论研究,主要工作和结论如下：1.针对有限土体土压力问题研制了1g缩尺模型试验装置,试验可以考虑墙后填土宽度、挡墙变位模式及变位大小等因素对土压力的影响。并将颗粒图像测速技术(PIV)应用于模型试验中,对墙后土体变形进行可视化观察,以研究土体变形、滑裂面发展规律。2.进行了四组不同n(墙后土体宽度与墙高比值)的T(平动)模式主动土压力试验,分析表明：土压力受挡墙位移和n影响显著,呈非线性分布；随着挡墙位移的增大,土压力逐渐由静止土压力减小到极限主动土压力,墙后形成一道通过墙踵的滑裂面,极限土压力与已有理论解吻合较好：随着n的增大,相同位移下土压力逐渐增大,滑裂面倾角逐渐减小；当n≥ncr时,极限主动土压力接近库伦主动土压力,滑裂面倾角接近库伦理论滑裂面倾角。3.进行了两组不同刀的T模式被动土压力试验,试验结果表明：土压力呈非线性分布,且沿挡墙深度逐渐增大。随着挡墙位移的增大,土压力由静止土压力逐渐增大；相同位移下,土压力随着刀的增大而减小。4.在试验和已有理论的基础上,建立了有限土体刚性挡墙RT、RB典型变位模式下主动土压力的理论计算模型,采用水平薄层单元法,将薄层单元层间等效内摩擦角与挡墙位移模式及n相关联,分段建立了挡土墙上土压力强度的一阶微分方程,给出了土压力强度、主动土压力系数和土压力合力作用点相对高度的理论计算公式。主要分析讨论了n和墙土摩擦角对两种不同模式主动土压力的影响,发现n、变位模式及土体参数是影响有限土体主动土压力的主要因素。算例理论分析结果与前人数值分析和试验数据吻合较好,验证了本文理论方法合理可行。5.考虑墙体最大变位点与滑裂面和临近挡墙交点的相对位置的变化,建立了有限土体柔性挡墙鼓形变位模式下主动土压力的理论计算模型,推导了土压力强度、主动土压力系数和合力作用点相对高度的理论公式。算例分析表明,此类问题土压力分布较简单变位模式复杂,退化到半无限土体情况下的土压力分布与已有试验和理论解进行对比,结果表明本文方法所得结果较已有理论解与试验数据吻合更好。更多还原

【Abstract】 With the development of urban construction, underground space is being widely used. Underground structures become more and more densely distributed. Some situations in which the width of the backfill near the retaining wall is limited begin to occur, such as the retaining wall adjacent to an exsiting basement or rockface, and narrow excavation of subway station etc. However, the classical Coulomb and Rankine earth pressure theory assume that the rigid retaining walls translate and reach the limited state, and the soil near the wall must be semi-infinite. So it is obviously inappropriate to calculate the earth pressure in above cases using the classical pressure theories. This paper focuses on model test and theoretical studies on the earth pressures for finite soils considering the displacement mode and magnitude of retaining wall. The main work and conclusions are as follows:1. Based on existing experiments, facilities for a1g scale model test were designed and produced to study the earth pressure problem for finite soils considering the displacement mode and magnitude of retaining wall. The particle image velocimetry(PIV) method was applied in the model test to visually observe patterns of soil deformation and development of the slip surface.2. Four T model active earth pressure tests were conducted under different n (the ratio of backfill width and wall height) and experimental results were analyzed. It was shown that the earth pressure was significantly affected by wall displacement and n in a non-linear distribution. With the increasing of the retaining wall displacement, the earth pressure gradually decreased from the rest earth pressure to the limit active earth pressure, and a sliding surface arose through the wall bottom.The limit active earth pressure was in good agreement with existing theoretical solution. With the increasing of n, the earth pressure increased and the slip surface inclination decreased gradually under the same wall displacement magnitude. While n≥ncr, the limit active earth pressure was close to Coulomb active earth pressure and the sliding surface inclination.was close to the theoretical Coulomb slip surface inclination.3. Two T model passive earth pressure tests were conducted under different n and experimental results were analyzed. It was shown that the earth pressures were in non-linear distribution and increased along the depth of the wall. With the increasing of wall displacement, the earth pressures gradually increased from the rest earth pressure. The earth pressures decreased with the increasing of n under the same wall displacement.4. Based on the experiments and existing theories, calculation models on the earth pressure of rigid retaining wall with wall movement of rotation about top and bottom for finite soils were presented. Horizontal thin-layer element method was used in which the equivalent internal friction angle between the horizontal thin layers were associated with retaining wall displacement modes and n. The differential equation of the first order was set up by the equilibrium of forces on the horizontal layer. The theoretical formulae of the unit earth pressure, the active earth pressure coefficient and the relative height of the application points of the resultant earth pressures on the retaining wall were obtained. The effects of n and wall friction angle on the active earth pressure under the two different modes were mainly discussed. It demonstrated that n, wall displacement mode and soil parameters were the major factors which had impact on the active earth pressure. The results by the method proposed here were in good agreement with those of the existed numerical analysis and experimental results. This verified the method presented here was reasonably practicable.5. Considering the relative position of maximum wall displacement point and the intersection of the slip surface and the adjacent retaining wall, theoretical analysis model on the earth pressure of a flexible retaining wall with drum deformation for finite soils were established respectively. The theoretical formulae of the unit earth pressure, the active earth pressure coefficient and the relative height of the application points of the resultant earth pressures on the retaining wall were obtained. It was shown that the earth pressure distribution about this problem was more complicated than other simple displacement modes. The results for Semi-infinite soil by the method proposed here were compared with those existed experimental data and theoretical solutions, and a better fitting than the existed theoretical solutions was achieved.更多还原