| This paper is based on the project "Central Yunnan water diversion project for soft rock and soil engineering properties research".Main content is for the study on engineering properties of Tertiary soft rock along lines in Central Yunnan water diversion project and research on the possible engineering geological problem of the diversion tunnel of WAN JIA segment by the means of numerical simulation.The length of whole diversion line of Water diversion project in Central Yunnan is252.650km.The length of tunnel accounts for86.50%of the total line.In particular its WAN JIA segment passes through mass the third soft rock region. The lithological characters in the region is mainly mudstone in Jurassic and Cretaceous,argillaceous siltstone, siltstone (including marlstone) and sandstone. In this paper,by the section survey and indoor test the analysis of the third strata through central Yunnan water diversion line WAN JIA segment.It is concluded that the mechanical properties of soft rock. It combined with numerical simulation method to study on a series of engineering geological problems about the possible process of WANJIA section of tunnel and operation.The main results of this paper are as follows:(1)Through the research on mechanical properties of tertiary soft rock draw, third soft rock compressive strength and shear strength are relatively low, increased its strength with sand content increased, under saturated conditions, the intensity values will greatly reduce; And rock mass that shale content high will also lead the intensity values of the rock mass at a discount.(2)The tertiary soft rock often contains a large number of clay minerals, and the amount of clay minerals directly determines the mechanical properties of soft rock and water physical properties. Its content is higher, the mechanical properties are relatively poor, and the impact on water was more sensitive and on the contrary relatively good.(3) through the indoor experiment for tertiary soft rock, it is not difficult to see that the third soft rocks usually have the following characteristics:.firstly, the shear, compressive strength is low, poor bearing ability; secondly, the deformation modulus is small, easy to produce big deformation; finally, it is more sensitive to the water, it is easily softening and disintegration with water.(4) Combined with the numerical simulation calculation of seepage field for WANJIA section, we can conclusion, that the tunnel near Hongmei reservoir has little effect on the water diversion tunnel, because there is a complete the watershed between the two, so the source of tunnel water gushing is mainly caused by the surrounding groundwater infiltration, and through the calculation can be drawn, it is rarely that seepage flow of the surrounding groundwater in the tunnel.(5) From the numerical simulation of tunnel excavation by steps of WAN JIA segment, we can see that:the maximum principal stress, the minimum principal stress is mainly affected by gravity, so the maximum value is still in the bottom of the model. In the model, tunnel excavation stress parts appear a small range of distribution. From the calculation result of displacement deformation of view, natural stress field (before excavation), the location of the maximum displacement is appeared in the model of height relatively high position, and the lithology is mainly third parts of strata. The unloading effect of deformation in the tunnel, the bottom is always upward, tunnel deformation is downward. |
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