泥质页岩隧道施工开挖与支护力学特性研究

发布时间：2018-07-13 08:01

【摘要】：随着我国公路交通的迅猛发展,在中西部多山地区地质条件复杂,在隧道的建设过程中经常要穿越地质条件差的地层,泥质页岩地层就是其中一种。由于泥质页岩遇水软化等特性,使得隧道在施工过程中经常发生大变形、塌方,严重威胁着工作人员的生命安全,带来经济损失。泥质页岩隧道设计与施工是目前的一道难题,因此,有必要结合工程实际对泥质页岩隧道开挖与支护过程中围岩遇水软化情况进行系统研究。本文依托在建的宜昌陆城至渔洋关一级公路延伸段新建工程簸箕山隧道,根据现场实际采取的设计和施工方法,结合理论研究、现场实验和数值模拟的研究方法和思路,对该隧道围岩和支护结构进行了系列研究。通过对现场实时监测的变形数据进行分析,结合隧道地质勘探结果,得出该地层泥质页岩在遇水软化前后各项力学参数的变化情况,围岩在遇水软化后,弹性模量和粘聚力都降低,泊松比增大,内摩擦角减小,围岩抵抗变形的能力减弱;泥质页岩隧道变形大,ZK55+590断面上台阶周边收敛61.05mm,下台阶周边收敛3.50mm,拱顶沉降37mm,围岩遇水软化后,隧道变形更大,ZK55+610断面上台阶周边收敛287.60mm,下台阶周边收敛18.30mm,拱顶沉降226.85mm。变形速率随着围岩的软化逐渐增大,后随着围岩应力的释放又逐渐减小。通过对现场情况的数值模拟分析,围岩在没有遇水软化的计算结果与实测结果基本相符,围岩遇水软化后的计算结果相对略小于实测结果。得出了在不同时期围岩遇水软化各分步开挖阶段围岩的位移、应力场变化规律,支护衬砌结构的变形、应力分布及内力分布情况。围岩遇水软化后,由于隧道的变形,锚杆与围岩发生相对滑动,锚杆嵌入隧道围岩,隧道变形大的部位也是锚杆受力大的部位,同时该部位锚杆与围岩的相对滑动也最大,数值模拟结果与现场锚杆滑移的实际情况相符。隧道下台阶一次性开挖后施作的锚杆受力左右成对称分布,下台阶左右分步开挖施作的锚杆受力成不对称分布,后面施作的锚杆受力小于前面施作的锚杆受力,可以考虑折减最后施作锚杆的力学效应。通过研究发现,隧道围岩遇水软化后初期支护发生整体下沉,沉降量由拱脚向拱肩逐渐增大,拱顶沉降相对小于拱肩沉降;通过对不同阶段隧道围岩遇水软化下二次衬砌和仰拱的受力分析,发现在围岩软化的情况下进行隧道的开挖时,下台阶一次性开挖、仰拱一次性施作对隧道的安全性和稳定性方面都有提高,并得出不同阶段隧道围岩遇水软化隧道在后期运营阶段均处于安全状态。
[Abstract]:With the rapid development of highway traffic in China, the geological conditions in mountainous areas in the central and western regions are complex. In the process of tunnel construction, it is often necessary to pass through the strata with poor geological conditions, among which the shale-shale formation is one of them. Due to the characteristics of shale-water softening, large deformation and collapse often occur in the construction process of the tunnel, which seriously threaten the safety of the workers and bring economic losses. The design and construction of shale tunnel is a difficult problem at present. Therefore, it is necessary to systematically study the surrounding rock softening in the excavation and support process of shale tunnel combined with engineering practice. This paper relies on the newly built Boji Mountain Tunnel in the extension section of the first class highway from Yichang Lucheng to Yuyangguan. According to the actual design and construction methods adopted on the spot, combined with theoretical research, field experiments and numerical simulation research methods and ideas, The surrounding rock and supporting structure of the tunnel are studied in a series. By analyzing the deformation data of real-time monitoring in the field and combining with the geological exploration results of the tunnel, the variation of the mechanical parameters of the shale in the formation before and after the water softening is obtained, and the surrounding rock after the water softening, The elastic modulus and cohesive force decrease, Poisson's ratio increases, the angle of internal friction decreases, and the ability of surrounding rock to resist deformation is weakened. The deformation of muddy shale tunnel in section ZK55590 converges to 61.05mm in the upper step periphery, 3.50mm in the lower step periphery, 37mm in the dome settlement. After the surrounding rock is softened, the deformation of the tunnel is greater than that of the ZK55610 section. The convergence of the upper step perimeter is 287.60mm, the lower step peripheral convergence is 18.30mm, and the dome settlement is 226.85mm. The deformation rate increases gradually with the softening of surrounding rock, and then decreases with the stress release of surrounding rock. Through the numerical simulation and analysis of the field conditions, it is found that the calculated results of the surrounding rock without water softening are basically consistent with the measured results, and the calculated results of the surrounding rock after the water softening are relatively smaller than those of the measured ones. The displacement, stress field, deformation, stress distribution and internal force distribution of surrounding rock in different stages of excavation are obtained. After the surrounding rock softens in water, because of the deformation of the tunnel, the relative sliding between the anchor rod and the surrounding rock occurs, the anchor rod is embedded in the surrounding rock of the tunnel, and the large deformation part of the tunnel is also the part where the anchor rod has a large force, at the same time, the relative sliding between the anchor rod and the surrounding rock is also the largest. The results of numerical simulation are in agreement with the actual situation of anchor slippage in situ. The anchor force applied after one-off excavation of the lower steps of the tunnel is symmetrical distributed on the left and right side of the tunnel, and the stress on the anchor rod after the step excavation of the lower step is asymmetrical, and the force applied at the end of the tunnel is less than that of the anchor rod applied in the previous step. The mechanical effect of reducing the final application of anchor rod can be considered. Through the research, it is found that the initial support of tunnel surrounding rock softens in the initial stage, the settlement gradually increases from arch foot to arch shoulder, and the settlement of arch roof is relatively smaller than that of arch shoulder. Through the stress analysis of secondary lining and inverted arch of tunnel surrounding rock under water softening in different stages, it is found that when tunnel excavation is carried out under the condition of surrounding rock softening, the one-off excavation of lower steps is carried out. The safety and stability of the tunnel are improved by the one-off operation of inverted arch, and it is concluded that the tunnel surrounding rock in different stages is in the safe state in the later stage of operation.
【学位授予单位】：武汉理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U455

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