The Research On The Mechanical Properties Of Underground Pipe Gallery In The Condition Of Changes Water Level

Due to the development of the city,the above-ground space has been reduced and the needs of urban management have led to the rapid development of underground integrated pipe corridors in recent years.In the water-rich areas,especially the southern river and sea areas,the groundwater situation is complex,which has a great impact on underground engineering.Whether it is the precipitation work required by the project or the fluctuation of the river,it has a great impact on the seepage of groundwater and changes in the water level,and it is also very easy to cause the safety of nearby underground projects.In this paper,through theoretical analysis and numerical simulation,the force and deformation characteristics of the pipe gallery structure and joints under different groundwater level changes are studied,and the influence rules are also summarized.The main research work and results are as follows.(1)The calculation method of water buoyancy reduction coefficient is proposed.The calculation theory of groundwater buoyancy is researched and deduced.Combining statics and soil particle models,through the law of conservation of energy and capillary model,the calculation method for determining the value of the reduction coefficient is further deduced.The value is mainly determined by the permeability coefficient and the properties of water,in order to be able to carry out more reasonable anti-floating calculations.(2)The mechanical model of the pipe gallery interface in the settlement difference is established.The stress and deformation of the pipe gallery interface of the post-tensioned steel strand connection mode during the settlement process are deduced,and the settlement deformation process is divided into three stages with the settlement difference as a variable.The displacement of the pipe gallery,the deformation force of the joint and the deformation force of the steel strand are respectively analyzed,and the water-proof sealing state of the joint of the pipe gallery and the pressure change of the upper and lower soil bodies are also analyzed.In the initial state,the mid-span part of each interface section is the first part that may be damaged.The four corners of the outer edge of the section are more likely to see water.(3)In the dewatering work,because the deformation of the pipe gallery is smaller than the deformation of the soil,the change of the ground settlement at the position of the pipe gallery is the smallest.Along the axis of this pipe gallery,the farther away from the pumping well,the smaller the change in settlement.The maximum settlement difference between the first and last ends of the pipe gallery is 1.43mm,which is 53%of the minimum settlement change.(4)In the dewatering work,the deformation of the mid-span position of the roof is most affected by precipitation.The vertical settlement change value and the lateral displacement generally increase with the increase of precipitation depth.The vertical settlement of the top slab in the middle of the span changes more and faster,and its lateral displacement is also large,the maximum being 103%of that of the bottom.The spinning of the gallery top plate and the bottom plate displacement may have adverse effects on the internal pipeline.(5)During the precipitation work,the force on the bottom plate changes more.The stress at the mid-span part of the bottom plate of the socket end changes the most.At the same port,the force change of the bottom plate is greater than the force change of the top plate,and the maximum can reach 2.01 times.The tensile stress on the inner side of the top and bottom of the pipe gallery increases,and the increasing trend is to decrease with the increase of the distance between the axis of the pipe gallery.The maximum tensile stress is 319.52kPa at the bottom plate of the socket end,which has a potential risk of tensile damage.On the whole,the roof and the side walls close to the river are more prone to fatigue damage.(6)In the water level rise and fall conditions,the vertical deformation of the top plate is smaller than that of the bottom plate,but the deformation amplitude in one cycle is greater than that of the bottom plate.The maximum vertical displacement is 4.7 times the minimum,which is more likely to cause fatigue damage.The lateral deformation of the wall near the river is smaller than that of the far river wall,but the amplitude of the deformation during the period is larger,and the maximum lateral displacement is 5.6 times the minimum.On the whole,the overall magnitude of change with the largest displacement is smaller.(7)In the water level rise and fall conditions,the stress value on the interface continues to increase with the passage of time,and reaches the peak value in the second year,and the cycle begins.In terms of stress,the stress value at the mid-span part of the top plate is the largest,which is 125%of the maximum stress of the bottom plate on the same section.In terms of interface normal stress,the normal stress value of the top plate of the socket end is smaller than that of the bottom plate.Since the bottom plate peaks more quickly in the first year,the bottom plate may be the first to undergo compression failure.In terms of tensile stress,the maximum tensile stress of the bottom plate is 51.3%of the top plate,and the minimum tensile stress is 48.6%of the top plate.The top plate is more likely to undergo tensile failure.On the whole,during the cycle of water level fluctuations,cracks or water seepage are most likely to occur at the roof.In summary,this paper mainly studies the law of the force deformation of the gallery under the conditions of water level.Through theoretical derivation,the theoretical calculation method of water buoyancy and the mechanical calculation model of the force deformation of the gallery interface under differential settlement has been determined.Through numerical simulation,the law of the stress deformation tube in different water levels has been explored.The above research results can be calculated for the theory of hydraulic force,and the stress calculation of gallery interfaces under differential settlement conditions and the design,construction and maintenance of underground integrated gallery in the rich area.