土的膨胀性对微型桩支护参数的影响研究

发布时间：2018-06-06 03:16

本文选题：微型桩 + 膨胀土滑坡　；参考：《西安工业大学》2017年硕士论文

【摘要】：微型桩作为一种新兴的边坡支护结构,具有施工灵活方便、对地形限定条件要求低、能够承受较大的轴向载荷和适度的横向载荷、对周围土壤和环境扰动小、经济效应好等特点。但是我国引入微型桩技术的时间较短,对微型桩的受力机理认识有很大的局限性,导致微型桩在工程实际中的应用缺少技术指导,因此严重制约了微型桩的发展与推广。本文主要通过大型物理模型试验研究了膨胀土堆积层滑坡发生机理,土的膨胀性对微型桩支护参数的影响,通过监测桩顶位移、桩前土压力、桩身弯矩等数据,分析数据得到微型桩加固膨胀土堆积层滑坡的合理布设方式。并将微型桩加固黄土堆积层滑坡与微型桩加固膨胀土堆积层滑坡进行对比,力求获得一个可靠的比例系数,使微型桩加固黄土堆积层滑坡与微型桩加固膨胀土堆积层滑坡可以相互参照,可以迅速提出一套治理方案。通过大量的大型物理模型试验研究为微型桩在工程中的应用提供理论基础。1.通过模拟降雨与蒸发,并在滑坡体上进行加载试验,经过三组干湿循环,结合坡脚位移曲线图得知:膨胀土遇到降雨开始膨胀,蒸发时,开始收缩,但是由于其膨胀与收缩的不完全性,导致坡体产生一些细小的裂缝,随着干湿循环的进行,降雨不断冲刷裂缝,裂缝开始扩张,同时雨水的冲刷也会带走土体中的细小颗粒,严重破坏土体结构。当在滑坡顶部开始加载时,由于加载量的不断增加,流入滑体内部的水分会一直渗入堆积层内部基岩表面与堆积层接触的软弱层(即滑面)附近,雨水形成的水流带走了土体内部的细小结构,土体变得松弛且土体强度急速降低,在荷载的作用下,便沿着软弱面开始位移,当荷载达到一定量时,产生滑坡;2.通过大型物理模型试验,分别在桩间距为8d、10d(d表示微型桩桩径),排间距为5d、8d、10d的情况下,对各排测试桩的桩顶位移、桩前土压力、桩身弯矩数据采集和分析得到:1)桩顶位移方面,当桩间距一定时,随着排间距的增大,桩顶位移逐渐减小;当加载至1516kg时,桩间距8d,排间距10d时的最大桩顶位移为38.632mm,当加载至1870kg时,桩间距10d,排间距8d、10d的最大桩顶位移为42.582mm,37.83mm。2)桩前土压力方面,主要表现为当桩间距一定时,随着排间距的增大,桩前土压力逐渐减小,5d桩间距情况下桩前土压力最大,当加载至1516kg时,桩间距为8d,排间距10d时,三排桩受力比例为1:0.674:0.554;当加载至1870kg时,桩间距为10d,排间距为8d、10d的三排桩受力比例为1:0.738:0.638,1:0.709:0,615。3)桩身弯矩方面,通过观察桩身弯矩曲线图发现,距桩顶40cm处和距桩顶60cm处分别出现最大桩身弯矩,并距桩顶60cm处为滑面附近,为微型桩桩身在滑面段设计方面提供了指导。3.本文首次提出在桩顶布设纵横向"X"型连系梁,经过试验研究与仅在微型桩桩顶布设纵向连系梁桩顶位移相比减小了 14.4%,能够减少抗滑段桩身弯矩变形,并表现为三排桩作为一个整体共同承载桩滑坡推力。4.通过微型桩加固黄土堆积层滑坡与微型桩加固膨胀土堆积层滑坡的对比,并考虑工程实际情况,认为微型桩加固黄土堆积层滑坡与微型桩加固膨胀土堆积层滑坡的比例系数为1.3～1.5。
[Abstract]:As a new type of slope support structure, micro pile has the characteristics of flexible and convenient construction, low requirement for terrain conditions, large axial load and moderate lateral load, small disturbance to the surrounding soil and environment and good economic effect. However, the time of introducing microtype pile technology in China is short, and the mechanism of micro pile is stressed. It has a lot of limitations, which leads to the lack of technical guidance for the application of micro pile in engineering practice, so it seriously restricts the development and popularization of the micro pile. This paper mainly studies the mechanism of the landslides in the expansive soil pile through the large physical model test, the influence of the expansibility of the soil on the support parameters of the micro pile, and the displacement of the pile top by monitoring the displacement of the pile. In order to obtain a reliable comparison, the micro pile is used to reinforce the landslide of the loess accumulation layer. It can be referred to each other by micro pile reinforcement of expansive soil stacked landslides, and a set of control schemes can be put forward quickly. Through a large number of large physical model tests, a theoretical basis for the application of micro piles in engineering.1. is provided by simulating rainfall and evaporation, and carrying out loading tests on the landslide body, after three groups of dry and wet cycles, combined with the foot position of the slope. It is found that the expansive soil begins to expand when rainfall begins to expand and begins to shrink when evaporation is evaporated, but due to the incompleteness of its expansion and contraction, it causes some fine cracks in the slope body. With the dry and wet cycle, the rain continues to scour cracks, and the cracks begin to expand, and the scour of rain will take away the fine particles in the soil, and it will also take away the small particles in the soil. When the load is added at the top of the landslide, the water flow into the sliding body will penetrate into the weak layer (the slippery surface) of the inner bedrock surface and the accumulation layer. The water formed by the rain takes away the small structure inside the soil, and the soil becomes relaxed and the strength of the soil is rapid. Under the action of load, the displacement is started along the soft surface, and the landslide occurs when the load reaches a certain amount. 2. through the large physical model test, the pile top displacement, the soil pressure before the pile and the bending moment of the pile body are collected and collected at the pile spacing of 8D, 10d (D indicates the micro pile diameter) and the spacing of 5D, 8D, 10d. The analysis is obtained as follows: 1) pile top displacement, when the pile spacing is fixed, the pile top displacement gradually decreases with the increase of row spacing. When loading to 1516kg, the maximum pile top displacement is 38.632mm when the spacing of pile is 8D and spacing 10d. When loading to 1870kg, the pile spacing is 10d, the spacing 8D, the maximum pile top displacement of 10d is 42.582mm, 37.83mm.2) before the pile. The main performance is that the soil pressure in the front of the pile is gradually reduced with the increase of the spacing between the piles and the maximum pressure in the front of the pile with the spacing of 5D piles. When loading to 1516kg, the pile spacing is 8D, and when the distance between the piles is 10d, the force ratio of the three row piles is 1:0.674:0.554; when loading to 1870kg, the pile spacing is 10d, the spacing of 8D and 10d three row piles are received. By observing the bending moment curve of pile body, it is found that the maximum pile bending moment is found at the top of the pile top 40cm and the top of the pile top 60cm, and the distance from the top 60cm of the pile to the sliding surface is found, which provides guidance for the design of the micro pile body in the sliding surface section for the first time in the pile top layout, through the observation of the bending moment curve of the pile body. The transverse "X" type connecting beam has been reduced by 14.4% compared with the displacement of the vertical connecting beam pile top of the micro pile top. It can reduce the bending moment deformation of the anti slide pile body, and shows the three row pile as a whole common bearing pile landslide thrust.4. through the micro pile adding the loess accumulation layer landslide and the micro pile to reinforce the expansive soil. Compared with the actual situation of the engineering, the ratio coefficient of the micro pile reinforcement of the loess accumulation landslide and the micro pile to the expansion of the expansive soil landslides is 1.3 ~ 1.5.
【学位授予单位】：西安工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU473.1

【参考文献】