Pressure Analysis Of Surrounding Rock And In-situ Monitoring Of Jiexia No.2 Joint Arch Tunnels In Partial Pressure

With the rapid growth of Chinese national economy, transport has fast development. To keep up with the pace of economic development, highway reached high levels. Taking into account the balanced development of regional economies, high-grade highways gradually built from rolling plains area to the mountain extension heavy hill region. In China, mountains, hills and plateaus account for about 69 percent of total area. In the past, building roads in the mountain or the mid-levels, the most choice is winding road, which is not only low levels, bypass miles long occupation of arable land and has high energy consumption, but also has security risks, the ecological damage to the environment and huge economic losses and casualties. In view of this, highway tunnel has been widely used in highway constructions, which improve the route alignment, reduce journey mileage and improve operational efficiency advantages. In China, separated tunnel was usually used in highway construction, which was accumulated rich experience in the theory and practice. But the types of tunnel's distance should be at least greater than one to four times of the tunnel diameter. In the special geological conditions and terrain areas, considering the overall line alignment, bridge and tunnel convergence of factors to consider, are often more limited, especially in the mountain-hill region. So the joint arch tunnel has become an important form structure.The application of joint arch tunnel satisfactorily resolved separated single-tunnel with the existing problems, which has many advantages such as linear smooth, small footprint, space utilization, avoiding the hole at the rate of the bridge and convenient connection with horage lines .At the same time, its also has many advantages in adapting to terrain conditions, environmental protection and the number of projects. However, with the applications of joint arch tunnel in practical engineering, it exposed many problems. For example, the long-span arch tunnel excavation, construction processes, and supporting interactive excavation, the construction process so that the entire system had changed surrounding rock pressure distribution and the load become very complicated .Also, the effects is difficult to grasp that the care system in different parts of the force situation, the two hole that the interaction between the construction of the middle-wall. In addition, the joint arch tunnel also has a lot of problems after completed, which mainly concentrated in the wall, such as cracking, water seepage in the middle-wall.Surrounding rock pressure is that supporting contact with the surface of the rock, which generated by the disturbance stress redistribution in the process of deformation by supporting block. It includes stress caused by the structure of the surrounding rock stress and the totals force which hindered by deformation effecting supporting structure. According to the causes and rock characteristics of surrounding rock pressure, which will be divided into loose rock pressure, pressure for the deformation, the impact pressure. Due to topography, geology, construction methods and other factors influence, the pressure on the tunnel structure supporting is asymmetry and the tunnel has bias function. With the bias function caused by terrain, the surrounding rock pressure of the joint arch tunnel become more complicated. At present, it is not mature that the study of surrounding rock pressure of the joint arch tunnels in partial pressure, there are many research about the pressure and strain of the simulation of different excavation sequence of the joint arch tunnels in partial pressure. For a particular tunnel, there is little experience that combination with simulation and monitoring. Nowadays, many monitoring data has a simple curves and the data processing has no analysis so that we don't easily see the stability trend of surrounding rock pressure. Therefore, it is necessary to study the excavation process and supporting of joint arch tunnels in partial pressure, and research bearing rule of surrounding rock pressure, middle-wall, liner supporting, so as to provide guidance for design and construction of joint arch tunnels.The calculation-method and result of the surrounding rock pressure is limited because the complexity itself. Due to affect by the situation, the initial stress, the chamber shape and size, construction method and timing effects, supporting structure stiffness etc, it is difficult to consider all factors for studying the surrounding rock pressure. Therefore, this paper integrated in-situ monitoring and finite element numerical simulation for studying surrounding rock pressure of the joint arch tunnels in partial pressure and obtained the results of rule and number caused by the excavation and supporting.The surrounding rock pressure of actual measurement also called sit-monitoring measurement, which is a good method that the characterized is simple, intuitive, to reflect the actual situation. Through on-site measurement we have a well grasp of rock dynamics and supporting structure in the state of the work, using the measured to guide the construction. In this paper, the subject based on Jiexia No.2 joint arch tunnels in partial pressure for Zhu-Yong highway of Zhejiang province, selecting a typical cross-section and installing pressure cells for monitoring measurements of the surrounding rock pressure, which can obtain the actual size and change law. Due to the monitoring data affected by the external environment, operating conditions, the human factor etc, the data has inevitably accidental error. It is necessary to carry out mathematical regression analysis. This paper respectively used conventional regression analysis and genetic algorithm treating monitoring measurement data and obtaining the result. Through contracting between the two results and anglicizing reasonableness of the results, we select the most consistent result with the actual surrounding rock pressure curve for rock pressure prediction.Finite element method is a powerful tool which widely used in geotechnical engineering and structural analysis. Also, it is an effective numerical analysis method for discrete application, mechanics and computer technology to solve complex problems. It is suitable for the analysis of complex geometry continuous medium and adapt to all kinds of complex boundary conditions, which is difficult to achieve for other numerical methods. The paper introduce SIGMA module of GEOSTUDIO program to establish the model of the joint arch tunnels in partial pressure and adopt the calculation result contracting with monitoring data for studying and anglicizing change law and data of the pressure.