合肥地铁盾构施工模型试验及数值分析

发布时间：2018-10-21 08:16

【摘要】：盾构施工不可避免地会引起周围土层沉降和土压力变化,不同土质中土层的沉降规律和土压力变化规律是不同的。探究盾构施工中土质改变时土层沉降规律及土压力变化规律如何改变对保证盾构的安全顺利进行具有重要意义。以合肥轨道交通盾构施工为研究背景,首先采用合肥地区典型砂土和黏土作为试验材料进行模型试验,探究盾构开挖情况下两种土质的地表沉降和土压力变化规律。结果表明:与黏土相比,砂土对开挖扰动更加敏感。开挖后砂土的沉降和土压力变化较快,土体在更短的时间内恢复稳定,同时砂土模型中相邻沉降测点测得的沉降值相差较大,最终的沉降槽起伏明显。而黏土的沉降和土压力变化较慢,最终的沉降槽较平缓。对两种土质还均有如下试验结果:开挖阶段的沉降值占总沉降值的比例约为45%~50%,两种土质的这一比例相差在5%以内。四个试验阶段中土压力减小速度和沉降速度呈现相似的规律,土压力减小速度可反映地层沉降速度。试验中最大沉降值出现在先开挖侧而最大沉降速度出现在后开挖侧。最终的“双峰”状沉降槽可看作由两侧单独开挖形成沉降槽的叠加,但沉降槽并非完全对称,先开挖侧深于后开挖侧。其次,针对黏土和砂土性质的差异,采用有限差分和颗粒流软件对模型试验结果进行验证的同时,进一步探究盾构开挖引起土层沉降和土压力变化内部机理。有限差分法得到的砂土和黏土沉降云图、土压力分布及地表沉降最大值均与模型试验结果吻合,同时给出了隧道周围应力场的完整分布及其变化过程。颗粒流计算则完整地给出砂土开挖后土层沉降发展和土压力调整的具体过程,揭示了砂土中两种变化的内部机理。最后,将典型黏土和砂土施工断面的监测结果与模型试验及数值计算结果进行比对,再次验证了试验及计算的正确性。文中的结果可为后续合肥地区盾构施工提供一定的参考。
[Abstract]:The shield construction will inevitably cause the settlement of the surrounding soil layer and the change of the soil pressure, and the law of the settlement and the variation of the soil pressure in the different soil quality are different. It is of great significance to explore how to change the law of soil subsidence and earth pressure when soil quality changes in shield construction to ensure the safe and smooth operation of shield tunneling. Taking the shield tunneling construction of Hefei rail transit as the research background, the typical sand and clay in Hefei area are used as the test materials to model test, and the variation law of ground subsidence and earth pressure of the two kinds of soil under shield tunneling is explored. The results show that sand is more sensitive to excavation disturbance than clay. After excavation, the settlement and pressure of sand soil change rapidly, and the stability of soil is restored in a shorter time. At the same time, the settlement values measured by adjacent settlement measuring points in the sand model differ greatly, and the final settlement trough fluctuates obviously. The clay settlement and earth pressure change slowly, and the final settlement trough is more gentle. The results are as follows: the ratio of settlement value to total settlement value in excavation stage is about 45% and the difference between the two types of soil is less than 5%. In the four test stages, the decreasing velocity of earth pressure is similar to the velocity of settlement, and the decreasing velocity of earth pressure can reflect the velocity of ground subsidence. In the test, the maximum settlement value appears at the first excavation side and the maximum settlement velocity at the later excavation side. The final "bimodal" settlement trough can be regarded as the superposition of the settlement trough which is excavated separately by both sides, but the settlement trough is not completely symmetrical, and the excavation side is deeper than that of the later one. Secondly, according to the difference between clay and sand, the finite difference and particle flow software are used to verify the results of the model test, and the internal mechanism of soil subsidence and soil pressure caused by shield tunneling is further explored. The cloud map of sand and clay settlement, the distribution of earth pressure and the maximum value of surface settlement obtained by the finite difference method are in agreement with the results of the model test. The complete distribution of stress field around the tunnel and its variation process are also given. The calculation of particle flow gives the concrete process of soil settlement development and soil pressure adjustment after sand excavation, and reveals the internal mechanism of the two changes in sand and soil. Finally, the monitoring results of typical clay and sand construction sections are compared with the results of model test and numerical calculation, and the correctness of the test and calculation is verified again. The results in this paper can provide a certain reference for the shield construction in Hefei area.
【学位授予单位】：合肥工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：U455.43;U231.3

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