【作者】 张石磊；

【导师】 张孟喜；

【作者基本信息】 上海大学 ， 结构工程， 2010， 博士

【摘要】 水平-竖向(Horizontal-Vertical,简称H-V)加筋是一种新型立体加筋形式,即在传统的水平筋条上布置竖直筋片。已进行的三轴试验、平面应变试验结果证明了H-V加筋能有效提高土体强度,限制土体变形。本文通过对H-V加筋路堤的室内模型试验、颗粒流细观模拟及理论分析研究了H-V加筋路堤的承载力特性及机理,研究结果对H-V加筋土的工程应用及相关研究有重要的参考价值。本文针对H-V加筋路堤进行了一系列室内模型试验,试验模型设计了不同加筋层数、不同加筋长度、不同荷载分布方式、不同加筋形式等多种工况。通过H-V加筋路堤和传统水平加筋路堤的模型试验结果,证明了H-V加筋路堤能够更有效地提高路堤承载力、减小路堤沉降并且限制路堤边坡侧向变形。在模型试验中加筋路堤的承载力随着加筋层数的增加而增加,因此适量增加加筋层数可以提高路堤的承载力。当加筋位置较为接近路堤荷载作用处时,筋条能够充分发挥其加固功能,并能大幅减小路堤边坡顶部侧向变形。试验还研究了H-V加筋筋条的长短对加筋路堤承载力的影响,虽然短筋对路堤承载力的提高幅度没有长筋大,但节省材料,是更经济的设计方案。H-V加筋路堤的破裂面与未加筋路堤不同,表现为多个不连续的圆弧破裂面。筋条起到了隔开破裂面的作用,H-V加筋路堤的破裂面角度更大,位置更靠近路堤中央。在室内模型试验的基础上对加筋路堤进行了颗粒流离散元模拟分析。由路堤内部土颗粒受力分析和位移矢量图研究了H-V加筋路堤的作用机理。H-V筋条不仅提供了水平筋条的拉力,其竖向筋条还提供了侧阻力以限制土体位移,因而在H-V筋条周围形成了范围较大的“土体加固区”,使路堤内部力的分配更均匀。通过数值模拟得到的H-V加筋路堤破裂面形态与模型试验的结果一致,且发现路堤边坡的土颗粒以水平方向位移为主,因此H-V加筋中的竖向筋条能够充分发挥作用以限制土体侧向变形。在H-V加筋路堤室内试验和数值模拟的基础上,对现有加筋路堤边坡稳定性系数计算方法进行了修正,得到了适用于H-V加筋路堤边坡的稳定性系数计算方法。其中充分考虑了水平筋条对周围土体的影响及竖筋在提高路堤边坡稳定性系数方面产生的影响。更多还原

【Abstract】 Horizontal-Vertical (H-V) reinforcing element is a new type of 3D reinforcements, in which some vertical reinforcing elements were placed on the traditional horizontal inclusions to made the reinforcements. The results of triaxial tests and plain strain tests which had been carried out to investigate the behavior of soil reinforced with H-V inclusions have proved that the H-V reinforcing elements can improve the strength of soil and restrict the deformation of soil. In this dissertation the behavior of bearing capacity and mechanism of embankments reinforced with H-V inclusions were investigated by labortatory model tests, numerical simulations and theoretical analysis. The conclusions are available for reference practical application and related research of soil reinforced with H-V elements.A series of laboratory model tests had carried out on H-V reinforced embankment. In these model tests, the layer, length, and type of reinforcements and the size of footing were varied. The H-V reinforcing elements were proved in increasing the bearing capacity, reducing the settlements and restricting the lateral displacements of embankments, by the results of laboratory model tests. In model tests the bearing capacity of reinforced embankments were increased with the increment of the layers of H-V reinforcing elements. It can be found that the bearing capacity of embankments can be increased and the lateral displacements on top of the slop can be restricted more effectively, if the location of H-V reinforcing elements was closer to the footing in vertical direction. The short H-V reinforcing element was provided little lower increment in the bearing capacity of embankment but it can save material of reinforcements, according to this optimized design can be provided. The shear bands in H-V reinforced embankments were separated into several discontinuous arc bands by the reinforcing inclusions. The angle of the shear band was larger and the location was close to the middle of embankment.The PFC numerical simulations (Discrete Element Method) were carried out on the base of the results of model test. The working mechanism of H-V reinforced embankment was investigated by analyzing the contact force between soil particles and the displacement of ball units. When the embankment was under loading, besides the tensile force provided by the horizontal element, the vertical inclusions provided resistance to restrict the lateral displacements of soil. Soil near the H-V inclusions was been strengthened, and these“strengthened areas”made the stresses evenly distributed in filling. The shear bands obtained by the numerical simulations were in common with those observed from model tests. Most soil particles moved horizontally in the slope of the embankment, so the vertical inclusions of H-V reinforcing elements worked effectively and restricted the lateral displacement of the slop.By analyzing the result of laboratory model tests and PFC numerical simulations on embankments reinforced with H-V inclusions, the traditional equation to calculate the safe factor of reinforced embankments was been revised. The new equation is suit for calculate the safe factor of embankments reinforced with H-V inclusions, which considering the effect of both horizontal elements and vertical inclusions.更多还原