Research On Spatial Effect And Construction Effect Of Intensive Supporting Structure

With the development of society,the density of buildings and structures increases rapidly,which makes the underground structure co-exists and affect each other.It’s a big challenge for the existing theories and design methods of underground structure.Based on practical engineering,the characteristics of intensive underground structure is founded,the concept of intensive design is put forward.Through the numerical simulation and theoretical analysis method,the spatial and construction effect of intensive supporting structure are researched.The main conclusions are as follows:1.The intensive supporting structure should consider the lateral reinforcement of the active area and negative area when there exist the composite foundation and piles under the bottom of foundation pit.The double-row piles with prestressed anchor cables are used as the supported structures as well as the composite foundation.Compared with conventional design of pit supporting,the scheme adds the durability design of supporting structures,and the effect on the basis of raft caused by the difference of vertical stiffness should be eliminate,by adjusting the thickness of mattress layer.Compared with the natural foundation,the composite foundation has reduced the soil pressure and lateral displacement of the active zone by 20.5%and 66.7%respectively,and the impact range of excavation has been reduced from 2 times to 1.5 times.The earth pressure of passive area increases by 15.6%due to the reinforcement of the anti-pulling pile.It is suggested to attach importance to establish the theory of intensive design.2.The spatial effect of foundation pit under the environment of Jinan typical strata is analyzed,and the integral design method of the deep foundation pit is proposed.The influence range of the negative corner is about 2 times the depth of excavation,and the effect of positive angle raises with the decrease of the depth ratio of the foundation pit.When the ratio of length to depth is less than 1,it reaches the limit.The horizontal displacement of the supporting structure raises with the increase of excavation width and then remains stable.The deeper the foundation pit is,the more significant the influence of excavation width is.The effect of the width of the foundation pit cannot be ignored when the depth exceeds 15m.The horizontal displacement of the supporting structure raises with the increase of h/H and decreases with the increase of pit toe coefficient.When the coefficient of pit toe exceeds 2.5,the supporting structure is not affected by the excavation of inside foundation pit.Compared with the integral calculation results,the calculation results of the unit calculation and the plane calculation are conservative,and the integral calculation method should be adopted when the foundation pit exceeds 15m3.The construction effect of bored pile is clarified.The influence range of the single pile is about 3.4 times the pile diameter,and the influence range of the row pile raises with the increase of the number of piles.when the number of bored cast-in-place piles reaches 25,the construction influence reaches the peak,which is about 10 times the pile diameter.The deformation curve of borehole wall is affected by the distribution pattern of soil layer.However,the deformation value is only related to the soil properties and geometry parameters of borehole,which is not affected by other soil layer.4.The jet pressure decays with the radial distance of the pile axis,and the attenuation of jet pressure increases with the increase of depth.The effect of the jet pressure on the shallow soil is more significant than that of the deep soil,and the influence on the foundation of the silty clay is greater than that of the soil foundation.The influence range of the jet pressure is about 2.7 times the pile diameter.