交叠车站下穿段MJS+水平冻结温度场分析

Analysis on MJS + Horizontal Freezing Temperature Field in Underpass Section of Overlapping Station

以南京地铁7号线中胜站下穿既有10号线中胜站工程项目为研究背景,提出了富水承压含水砂层交叠车站下穿施工MJS+水平冻结新工法,通过ADINA有限元软件进行水平冻结温度场数值模拟,获得了富水砂层交叠车站下穿段人工水平冻结的冻结温度场变化规律,并对比分析了MJS加固端部采取保温措施与否的冻结温度场发展规律,研究了因MJS水化热产生的不同地层初始温度和不同季节施工对冻结温度场的影响。结果表明:随冻结时间增加,冻结锋面发展速度先快后慢,冻结40 d时,冻结区内土体温度维持在-13℃以下;无论是在MJS加固区的顶部、中部还是底部,距离冻结管越近,其温度下降速度越快,最终土体温度也越低;MJS加固区中地层初始温度平均每升高4.54℃,内部土体达到设计厚度所需时间延长1 d;夏季必须对端部采取保温措施,否则无法形成所需厚度,对端部采取保温措施后,端部冻结交圈时间减少2 d,冻结40 d时端部冻结壁厚度增加了2.6倍。相同地层初始温度和冻结设计方案下,冬季施工能有效增强端部位置的冻结效果。研究成果可指导实际工程施工,同时为国内相似地层类似工程设计、施工提供技术支撑。

The paper put forward a new construction method of MJS + horizontal freezing method for the construction of water rich sand overlapped station by taking Zhongsheng station of Nanjing Metro Line 7 under the existing 10 Line Zhongsheng station project as the research background,and then numerical simulation was carried out by finite element software ADINA to obtain the variation law of frozen temperature field of the end and the inside of the soil and the soil on different sections of water rich sand layer overlapped station under section which was reinforced by MJS and then freezing. The following is analyzed and compared: the development law of freezing temperature field after it was took insulation measures in end position;effect of different initial temperature and different seasons on freezing temperature field. The results show that: the development speed of frozen front from fast to slow with the increase of freezing time,the soil temperature in the frozen area is below-13℃ when it is frozen for 40 days. The soil closer the freezing pipe and the faster the temperature drop and the final temperature is also lower whether in the top,middle or bottom of the MJS reinforcement area. In the MJS reinforcement area,the time required for the internal soil to reach the design frozen thickness is prolonged by one day for every 4. 54 C rise in the middle stratum temperature. The freezing time of the ends is reduced by 2 days and the thickness of the frozen wall at the end is increased by 2. 6 times when the soil is frozen for 40 days after the end is taken thermal insulation measures in the summer. Freezing in winter can effectively enhance the freezing effect of the end position under the same initial stratum temperature and freezing design scheme. Above the research results can guide the actual project construction,and provide technical support for similar stratum design and construction in China.