地下连续墙成槽施工引起的承压含水层——粉砂层的扰动机理分析及光纤传感验证
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摘要
通过标准贯入、静力触探等原位试验对比以及颗粒分析,研究了地连墙成槽施工对承压含水层——粉砂层的扰动作用,并分析了扰动机理。试验结果表明,苏州地区承压含水砂层的地质结构以及地连墙施工产生的超静孔隙水压力,泥皮不能有效阻止水力作用,距地连墙12m外的砂土层仍表现出较强扰动现象。中密—密实的不液化砂土,在水力作用下出现液化土现象。研究认为,施工扰动力范围内的砂层在超静正孔隙水压力作用下表现出全粒径流动性,流向基槽负压中心,引起砂土流失,密实性降低,形成液化土。推测外围存在管涌作用,并通过布拉格光纤光栅传感器验证了施工引起的超静孔隙水压力。
Through the comparison of the in-situ standard penetration test and the static cone penetration test data as well as the grade analysis before and after construction,the disturbance from underground diaphragm wall construction to the silt layer of the confined aquifer and the mechanism are studied. The tests show that the confined aquifer sand in Suzhou area,the excess pore pressure and the mud cakes from the construction could not effectively prevent the hydraulic action during underground diaphragm wall construction,and the sand layers with the range of 12 meters from the diaphragm wall are strongly disturbed. The saturated medium-dense non-liquefaction sand during the hydraulic action has liquefied.The study indicates that the excess pore pressure gives rise to the sand fluidity for all particle size range,and the negative cycle pore pressure gives rise to sand fluid to the foundation ditch,which result in the sand lost,density decreasing and liquefaction. It is inferred that the sand piping stochastically occurs far from the foundation ditch. The FBG fiber sensors are used to test the excess pore pressures.
Through the comparison of the in-situ standard penetration test and the static cone penetration test data as well as the grade analysis before and after construction,the disturbance from underground diaphragm wall construction to the silt layer of the confined aquifer and the mechanism are studied. The tests show that the confined aquifer sand in Suzhou area,the excess pore pressure and the mud cakes from the construction could not effectively prevent the hydraulic action during underground diaphragm wall construction,and the sand layers with the range of 12 meters from the diaphragm wall are strongly disturbed. The saturated medium-dense non-liquefaction sand during the hydraulic action has liquefied.The study indicates that the excess pore pressure gives rise to the sand fluidity for all particle size range,and the negative cycle pore pressure gives rise to sand fluid to the foundation ditch,which result in the sand lost,density decreasing and liquefaction. It is inferred that the sand piping stochastically occurs far from the foundation ditch. The FBG fiber sensors are used to test the excess pore pressures.
引文
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[2]张文龙.上海全新统地层中地下水类型和不良作用分析[J].上海国土资源,2008,(2):3~6.Zhang Wenlong. Analysis on groundwater types and adverse effects in Shanghai[J]. Shanghai Land&Resources,2008,(2):3~6.(in Chinese)
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[5]宋占璞,张丹,方海东等.大体积混凝土水化热温度变化光纤监测技术研究[J].工程地质学报,2014,22(2):245~249.Song Zhanpu,Zhang Dan,Fang Haidong et al. A study on fiber optic monitoring the temperature of concrete hydration heat release process[J]. Journal of Engineering Geology,2014,22(2):244~249.(in Chinese)
[6]汤永净,王丽平.地下连续墙中水化热对钢筋应力的影响研究[J].工业建筑,2006,36:670~672.Tang Yongjin, Wang Liping. Research on the influence of hydration heat on steel stress in diaphragm walls[J]. Industrial Construction,2006,36:670~672.(in Chinese)
[7] Mostaf A,Torsten G. Spontaneous Raman scattering in optical fibers with modulated temperature Raman remote sensing[J].Journal of Lightwave Technology,1999,17:1378~1391.
[8] Zhu H H,Ho A N,Yin J H et al. An optical fiber monitoring system for evaluating the performance of a soil nailed slope[J].Smart Structures and Systems,2012,9(5):393~410.
[9]王兴,施斌,张丹等. BOFDA分布式光纤监测技术及其在桩基测试中的应用[J].工程勘察,2015,43(12):13~17.Wang Xing,Shi Bin,Zhang Dan et al. The BOFDA based distribtued optic fiber sensing technology and its application in pile test[J]. Geotechnical Investigation&Surveying,2015,43(12):13~17.(in Chinese)
[10]张其琪,李文峰,王宝军等.基于DFOS的苏州地铁1号线隧道变形监测的三维可视化[J].工程勘察,2017,45(3):44~48.Zhang Qiqi,Li Wenfeng,Wang Baojun et al. 3D visualization of DFOS-based deformation monitoring on tunnel of Suzhou metro line 1[J]. Geotechnical Investigation&Surveying,2017,45(3):44~48.(in Chinese)
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