| With the deepening of China’s western development strategy implementation, theinfrastructure constructions of western areas have been vigorously developed. Due to therestricted factors such as the terrain fluctuation, the open cut tunnels of high backfill becomemore and more widely used in railway, highway and other large-scale infrastructureconstruction. Earth pressure is the main source of the load in structure of such engineeringdesign and construction. At present, however, in various criterions of our country, there is nota lot of the calculating method. According to General Code for Design of Highway Bridgesand Culverts, it causes great waste of engineering cost using pillar method z H.Therefore, finding out the factors influencing the earth pressure of the open cut tunnels ofhigh backfill and effective calculation method of earth pressure are of great significance forengineering construction in our country.In the present study, based on2#open cut tunnel of Changshou Mountain during theLanzhou-Chongqing railway, the previous theories of the earth pressure calculating areanalyzed. And whose advantages and disadvantages are evaluated. Through simplifying andprocessing of the engineering model, with the help of powerful simulation function of thelarge general finite element software ANSYS, the following work has been done:(1)We simulate the slope, the width of the groove and structure ratio, structure in theposition of the groove, and the volume-weight of backfill influence on the pressure of theopen cut tunnels of high backfill. And on the basis of the data, nonlinear calculation formulasof the open cut tunnels of high backfill are fit out.(2)Three deloading measures, including the EPS board of vault, the deloading ofReinforcement Bridge, dealing soil with jet grouting pile, are also studied. The current studyputting three aspects, which are the safety factor of structure, the secondary lining of concretecrack and bearing capacity of foundation soil, as the entry point, analyzes the safety ofstructure under three deloading measures. And the deloading results of three deloadingmeasures are evaluated.Through the work above, we finally arrive at the conclusion that:(1)The research results show that, comparing to theoretical value z H, the soilpressure of high filled open cut tunnel presents obvious non-linear relationship. When theheight of backfilling is below than20m, there is soil arching effect above the soil. With theincreasing of the backfilling height, the soil arching effect is more and more obvious.(2)The breadth ratio of side slope grade and structure, the location of the structure in thebottom of trench and the volume-weight of backfilled soil have effect on the soil pressure ofhigh backfilled of open cut tunnel. The steeper the slope, the smaller the ratio of the bottom oftrench and structure, and the soil arching effect is easier to form. Under the same backfilledheight, the soil pressure of arch crown is smaller. The soil pressure of structure on the toe of slope is smaller than in the center of the bottom of trench. Volume-weight has great impact onsoil pressure. And the bigger volume-weight is benefit to the form of the soil arch effect.(3)The deloading measures, EPS board of vault, the deloading of Reinforcement Bridgeand dealing soil with jet grouting pile, can decrease the soil pressure of vault of open cuttunnel effectively. And in which the jet grouting pile with soil has the best effect. Meanwhile,three deloading measures have great effect on the control of the crack of secondary liningconcrete. The deloading effect, however, is not obvious to the pressure of the inverted archfoundation. |
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