Influence Of Near Horizontal Filling Mud Cavern On Tunnel Surrounding Rock Stability And Treatment Technology Research

To carry out tunnel engineering construction in karst area,encountering the underground geologic disasters such as collapse,water inrush,mud and karst,and so on,if the geological disasters are not handled well,it will bring some threat to the construction of the tunnel and the safety of the related staff and the subsequent safe operation.Due to the technical limitation in the exploration and design stage,it is difficult to find these underground disasters accurately before the tunnel construction,how to effectively find and effectively treat these underground disasters has become an important technical problem concerned by construction technicians.Taking the typical Karst cave section of Dongyue Tunnel of Lian Le Railway as the research object,this paper studies the investigation and detection method of horizontal-filled mud karst cave on the basis of hydrological environment investigation,and uses FLAC3 D and ANSYS numerical simulation analysis software,The influence of the size of the near-horizontal mud-filled karst cave on the stability of the tunnel surrounding rock and the treatment effect of the different shape concrete-filled steel tubular piles on the mud-filled karst cave are simulated.The main findings are as follows:(1)For the geological prediction of the tunnel in karst area,it should be based on the hydrogeological background,and on the basis of ascertaining the development characteristics of the karst system,using the targeted geophysical prospecting method.The method of geological investigation,electromagnetic wave detection and infrared water method should be used to detect the mud-filled karst cave near the horizontal direction.For Karst cave with fractured zone,we should pay attention to the karst in the process of tunnel excavation,there are some indications that the surface of the palm is mixed with mud and seepage,and the attenuation of the boundary,amplitude and filling material of the karst body should be paid attention to in the corresponding characteristics,such as the geological radar and infrared water exploration.Because the horizontal karst often leads to the change of the surrounding rock groundwater,the seepage range in the geologic body is deduced according to the characteristics of the GPR response,and the result is good.(2)According to the typical engineering conditions,the influence of 10 different sizes of mud-filled karst caves on tunnel surrounding rock was studied by Flac3 d software.The numerical simulation shows that,in a certain range,the width and thickness of the mud-filled karst cave are larger,the deformation of the hole wall and the hole bottom is bigger,and the width of the mud-filled karst cave is more obvious than the thickness of the surrounding rock stability,The broad and generous index of the vertical displacement under the tunnel wall is 7.64,the width and width index of the horizontal displacement of tunnel wall is 5.42,and the broad and generous index of the vertical displacement in the middle of the tunnel bottom is 1.40;when the cave is wider than a certain number(twice times the height of the tunnel),the horizontal displacement of the tunnel wall will be opposite to the normal force displacement The horizontal displacement of the tunnel wall reaches the maximum value when the cave thickness exceeds a certain value(twice times the diameter of the hole).(3)With the idea of calculus,the dense spiral hoop is reduced infinitely and arranged closely,and the spiral hoop reinforced concrete pile is approximately equivalent to the steel tubular pile.Based on the formula of the bearing capacity of the spiral reinforced concrete pile,the calculating formula of the normal triangular concrete-filled steel tubular pile is deduced and compared with the actual test results,the result shows that the error between the calculated results and the actual test results is 3%.(4)By using Ansys software,the treatment effect of the square steel tubular pile with the same circumference and the circular concrete-filled steel tubular pile in the mud-filled karst cave is treated as the pile foundation under normal train load.The numerical results show that under the condition of the same steel consumption,the deformation of the upper concrete slab is not considered,the displacement of the circular pile is the least,the stress of the square pile structure is the smallest and the strain is the smallest.There is obvious stress concentration in the joint area of pile and concrete slab,and the reinforcement of joint part should be paid attention to.It is concluded that the displacement of the circular concrete-filled steel tubular pile is the least,and the stress of the square concrete-filled steel tubular pile is the smallest.Among them,the displacement of square concrete-filled steel tubular pile Foundation is 140% larger than that of circular concrete-filled steel tubular pile foundation.The displacement of the concrete-filled steel tubular pile Foundation is 675% larger than that of the circular cfst pile.The strain of square concrete-filled steel tubular pile foundation is smaller than that of circular concrete-filled steel tubular pile foundation,and the strain of normal triangular concrete-filled steel tubular pile foundation strain is smaller than that of circular cfst pile 55.1%.The maximum stress of the square concrete-filled steel tubular pile Foundation is less than 71.56% of the maximum stress of the circular Cfst Pile Foundation,and the maximum stress of the rectangular cfst pile Foundation is less than 19.79%.The displacement distribution of square concrete-filled steel tubular pile is regular and the stress distribution of square concrete-filled steel tubular pile is relatively uniform,without stress alienation,and the strain distribution of circular concrete-filled steel tubular pile is relatively uniform.In the Pile Foundation and the panel joint,the Indexes of circular steel tubular pile are much smaller than the other two kinds of concrete piles.To sum up,when the surface area of steel pipe is equal,it is most scientific and reasonable to use circular concrete-filled steel tubular pile as the reinforcing pile foundation of mud-filled karst cave.