跨江大直径盾构隧道管片受力特征监测分析

Monitoring and Analysis of Stress Characteristics of Segments of Large Diameter Shield Tunnel Across the River

依托杭州地铁8号线文桥区间风井~桥头堡站区间项目,对3个不同地质条件下的断面进行了水、土压力和钢筋应力的监测,探究了覆土厚度和水位高度对盾构隧道受力特性的影响。结果表明:土压力峰值最大为断面Ⅰ的821 kPa,其次为断面Ⅱ的683 kPa,最小为断面Ⅲ的492 kPa;断面Ⅰ土压力数值随时间变化最为强烈,断面Ⅲ的土压力变化最小,随着时间增加呈现缓慢减小的趋势;断面Ⅰ和断面Ⅱ隧顶和隧底水压力数值较为接近,整体表现也比较稳定;断面Ⅲ处由于水位较浅,水压力受季节潮汐等自然因素影响较大,水压力随时间变化存在一定的波动;覆土厚度决定了隧道钢筋应力的大小,同一位置下钢筋应力表现最大为断面Ⅰ,其次为断面Ⅱ,最小为断面Ⅲ。对于未越江隧道,可对隧底和起拱线的内弧面处钢筋进行适当加强;而越江隧道应该注重隧顶和起拱线外弧面钢筋强度。

Based on the project of Fengjing-Qiaotoubao Station in Wenqiao section of Hangzhou Metro Line 8,the water,earth pressure and steel stress of three sections under different geological conditions are monitored,the effects of the thickness of overlying soil and the height of water level on the mechanical characteristics of shield tunnel are studied.The results show that the highest earth pressure peak is 821 kPa in section I,the second is 683 kPa in section II,and the smallest is 492 kPa in section III.The soil pressure value of section I changes most strongly with time,and the soil pressure of section III has the smallest change,showing a slow decreasing trend with the increase of time.The values of water pressure at the top and bottom of the tunnel of section I and section II are relatively close,and the overall performance is relatively stable.At section III,due to the shallow water level,the water pressure is greatly affected by natural factors such as seasonal tides,and the water pressure fluctuates with time.The thickness of the covering soil determines the stress of the tunnel reinforcement.At the same position,the stress of the steel bar is the largest in section I,followed by the section II,and the smallest is the section III.For tunnels that do not cross the river,the reinforcement at the bottom of the tunnel and the inner arc of the arching line can be appropriately strengthened;while for the tunnel across the river,the strength of the reinforcement at the top of the tunnel and the outer arc of the arching line should be emphasized.