海底隧道衬砌上孔隙水压力的估算(英文)

EVALUATION OF RESIDUAL PORE WATER PRESSURES ON LININGS FOR UNDERSEA TUNNELS

从长期观察的结果来看,隧道表现出两种不同方式:一种是对于全封闭隧道表现出渗流量的增加;另一种是对于排水隧道表现出的渗流量减少。渗流量的增加有可能超出排水系统排水能力的情况,而渗水的减少则有可能导致衬砌发生不可预测的水压力增加或减小。由于这种渗流量的增加或减少都将对隧道产生不良的影响。因此,在隧道正常运行中,应对隧道周边的地下水进行适当地控制。在隧道安全性评价上,其最重要的因素之一就是研究排水系统劣化而导致衬砌的作用水压力增大(在此称为孔隙水压力)。为了保障隧道的安全运行,应该对此进行严密的监控。然而,对于大部分运行已久的海底隧道而言,其不仅缺乏装备优良的监视系统,甚至连运营仅几年的新隧道也常常出现监测仪器发生故障的问题。以间接和非破坏的方式,通过数值模拟,将所获得的孔隙水压力进行曲线拟合,以便对作用于衬砌的孔隙水压力进行合理地评价。对于给定的隧道内渗流量、地下水位及地基渗透系数,采用本法可以评估孔隙水压力。对于缺乏监测数据和监视系统运行较长的隧道,所提出的方法较为适用,最后通过实例来说明其合理性。

Long-term observations for tunnels have shown two interesting aspects:an increase in leakage for watertight tunnels;and a decrease for leaking tunnels. An increase in leakage may exceed the capacity of drainage system and a decrease in leakage cause unexpected water pressure on the lining. Both excess leakage and additional water pressure are detrimental to running tunnels. Therefore,during tunnel operation,the flow behaviors around tunnel should be appropriately controlled. One of the most significant key elements in evaluating tunnel safety is the development of water pressure on the lining due to the deterioration of the drainage system. The increased water pressure on the lining is termed here as 'residual water pressure'. The subsea tunnels generally need strict and careful monitoring of hydraulic effect to keep safe operation. Establishment of a well-organized maintenance program is therefore essential during operation. However,most aged-subsea tunnels do not have well-equipped monitoring systems,in addition even in new tunnels,the monitoring systems are often malfunctioned just after several years of operation. In this study,a new indirect and nondestructive method evaluating residual water pressure on the lining is proposed based on a characteristic water pressure curve obtained by numerical analysis. If the amount of water inflow,the height of water table and average ground permeability are known,the water pressures on the lining can be evaluated using the proposed analytical equations and the characteristic curves. It is shown that the method is particularly useful for tunnels of which measured data are not available and particularly for the aged-tunnels without monitoring systems. Applicability of the proposed method is illustrated by solving an example problem.