基于实测内力的大直径水下盾构隧道荷载反演分析

作用在管片结构上的水土压力是管片设计的关键，但目前盾构隧道管片衬砌结构的荷载确定尚未有一个统一的方法，开展现场测试获取管片衬砌结构的水土压力是一个有效的解决途径，但受工法特性影响，所得测试数据通常具有一定的误差。依托武汉地铁8号线越江隧道工程，基于较为准确的结构内力实测值，针对岸边深埋段和水下浅埋段两种典型地层条件，对管片所受竖向水土压力和侧向压力系数进行双参数荷载反演分析。研究结果表明：隧道位于岸边深埋段、洞身穿越均一地层时选取竖向水、土压力作为反演参数，而隧道位于水下浅埋段，洞身穿越多种地层时选取竖向水压力和侧向压力系数作为反演参数是合理的。针对越江隧道岸边深埋段的地层特性，拱顶竖向土压力取等效于拱顶以上2倍洞径范围内土柱所产生的压力，水压力需根据地层渗透性予以折减，折减系数一般在070～085；对于水下浅埋段，竖向土压力可按照全土柱法计算，水压力取上部全部水压，侧压力系数反演值较隧道所处地层地勘值偏大。

Back analysis of load of large underwater shield tunnel based on#br# measured internal force

The water and earth pressure acting on the segment structure is the key to the design of the segment. However, there is no unified method for determining the load of the shield tunnel lining segment structure. Obtaining the water and soil pressures from field test is an effective solution, but certain errors in the test data may usually be observed depending on the characteristics of the construction method. Based on Wuhan Metro Line 8 cross-river tunnel project and the measured internal forces of the structure, dual-parameter load back analysis on the vertical water-earth pressure and lateral pressure coefficient of the lining segment is carried out for the two typical formation conditions of the riverside deeply-buried section and the underwater shallowly-buried section. The research results indicate that choosing the vertical water and earth pressures as the inversion parameters shall be reasonable when the tunnel is located in the riverside deeply-buried section and passes through the single stratum, while choosing the vertical water pressure and lateral pressure coefficient as the inversion parameters shall be reasonable when the tunnel is located in the underwater shallowly-buried section and passes through multiple stratums. According to the stratum characteristics of the riverside deeply-buried section, the vertical earth pressure is equivalent to the pressure generated by the soil column within the range of 2 times the tunnel diameter above the arch, and the water pressure needs to be reduced in terms of the permeability of stratum with the reduction factor ranging from 0.70 to 0.85. For the underwater shallowly-buried section, the vertical earth pressure can be calculated according to the whole soil column method. The water pressure takes the total upper water pressure, and the inversion value of the lateral pressure coefficient is larger than that in geological survey report of the tunnel.