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在人工冻结加固盾构到达端头土体施工过程中,土体温度是关系到冻土帷幕发展情况以及确定盾构机推进时机的重要参数。以南京地铁二号线集庆门车站北端头盾构进洞冻结加固工程为背景,利用大型有限元数值分析软件建立数学模型对冻结和自然解冻温度场进行计算,研究了多圈水平冻结条件下温度空间分布及温度随时间变化规律,并对左线开挖后垂直冻结管停冻和不停冻两种方案对温度场的影响进行对比,研究表明:采用多圈水平冻结并合理布置冻结圈径可以显著加快冻结壁的形成,从而缩短工期;自然解冻时存在两个解冻锋面,其中管片散热对解冻影响较大;自然解冻时温度上升速率先快后慢,而解冻锋面推进速度则越来越快;在左线开挖后可以停止左、右线洞门之间垂直冻结管的冷媒循环,同样能够保证右线冻结壁厚度达到设计要求。
During the construction of artificial frozen reinforced earth shield body, soil temperature is an important parameter that is related to the development of frozen soil curtain and the timing of advancing shield machine. Taking the freeze-hardening project of shield tunnel into the north end of Jimei Gate Station of Nanjing Metro Line 2 as the background, a mathematical model was established by using a large-scale finite element numerical analysis software to calculate the temperature field of freezing and natural thawing. The spatial distribution of temperature and the variation of temperature with time, and contrasts the effects of freezing and non-freezing vertical freezing pipelines on the temperature field after excavation of the left-hand excavation. The results show that the multi-circle horizontal freezing and reasonably arrangement of freezing rings Diameter can significantly speed up the formation of the frozen wall, thereby shortening the construction period; there are two thaw front during natural thawing, of which the heat dissipation of the tube has a greater effect on thawing; the temperature rising speed is faster at first and then slower than that at thawing, To the faster; in the left line after excavation can stop the left and right vertical freezing pipe between the door of the refrigerant circulation, the same can guarantee the frozen wall thickness to meet the design requirements.