【摘要】：盾構(gòu)施工不可避免地會引起周圍土層沉降和土壓力變化,不同土質(zhì)中土層的沉降規(guī)律和土壓力變化規(guī)律是不同的。探究盾構(gòu)施工中土質(zhì)改變時土層沉降規(guī)律及土壓力變化規(guī)律如何改變對保證盾構(gòu)的安全順利進行具有重要意義。以合肥軌道交通盾構(gòu)施工為研究背景,首先采用合肥地區(qū)典型砂土和黏土作為試驗材料進行模型試驗,探究盾構(gòu)開挖情況下兩種土質(zhì)的地表沉降和土壓力變化規(guī)律。結(jié)果表明:與黏土相比,砂土對開挖擾動更加敏感。開挖后砂土的沉降和土壓力變化較快,土體在更短的時間內(nèi)恢復(fù)穩(wěn)定,同時砂土模型中相鄰沉降測點測得的沉降值相差較大,最終的沉降槽起伏明顯。而黏土的沉降和土壓力變化較慢,最終的沉降槽較平緩。對兩種土質(zhì)還均有如下試驗結(jié)果:開挖階段的沉降值占總沉降值的比例約為45%~50%,兩種土質(zhì)的這一比例相差在5%以內(nèi)。四個試驗階段中土壓力減小速度和沉降速度呈現(xiàn)相似的規(guī)律,土壓力減小速度可反映地層沉降速度。試驗中最大沉降值出現(xiàn)在先開挖側(cè)而最大沉降速度出現(xiàn)在后開挖側(cè)。最終的“雙峰”狀沉降槽可看作由兩側(cè)單獨開挖形成沉降槽的疊加,但沉降槽并非完全對稱,先開挖側(cè)深于后開挖側(cè)。其次,針對黏土和砂土性質(zhì)的差異,采用有限差分和顆粒流軟件對模型試驗結(jié)果進行驗證的同時,進一步探究盾構(gòu)開挖引起土層沉降和土壓力變化內(nèi)部機理。有限差分法得到的砂土和黏土沉降云圖、土壓力分布及地表沉降最大值均與模型試驗結(jié)果吻合,同時給出了隧道周圍應(yīng)力場的完整分布及其變化過程。顆粒流計算則完整地給出砂土開挖后土層沉降發(fā)展和土壓力調(diào)整的具體過程,揭示了砂土中兩種變化的內(nèi)部機理。最后,將典型黏土和砂土施工斷面的監(jiān)測結(jié)果與模型試驗及數(shù)值計算結(jié)果進行比對,再次驗證了試驗及計算的正確性。文中的結(jié)果可為后續(xù)合肥地區(qū)盾構(gòu)施工提供一定的參考。
[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.
【學(xué)位授予單位】：合肥工業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：U455.43;U231.3

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