| This article relies on the Nanjing Metro Line station in Nanjing. By means ofthe theoretical analysis, measured analysis and numerical analysis method,systematic study of the stratum deformation law, the intermediate pile and platesettler law and blasting vibration on completed construction while the station is builtby using the combination of blasting and cut-and-cover top-down method. The mainresults are as follows:(1) The earthwork excavation follows the principle of "hierarchical, block,symmetry, balance, limit". Dig the middle soil first, and then dig the both sides ofthe soil until the middle of laminates pouring. That is feasible to control thehorizontal displacement of envelope structure, the surrounding surface depositionand the basal rebound.(2) This project has taken in the precisely locate and skew control technology ofthe intermediate pile, large cover situ technology and the key inverse nodeprocessing technology.That have a good effect on controlling the subsidence, heaveand differential vertical displacement of the laminates,as well as intermediate pile.(3) The rock blasting of this project using equally spaced millisecond to layoutthe blasting network. The time interval is100ms. Select the non-electric,half-a-second detonator as the arithmetic interval detonators. Blasting is in the wayof the stratified sub-step drill blasting. The charge is coupling charge and explodingin packet segmentation interval. That can avoid the stress wave superposition, createa full on face for subsequent blasting and is helpful to control the impact of theblasting vibration on the laminates and intermediate piles.(4) The numerical simulation results and field measured results of thehorizontal displacement of the envelope structure as well as the surrounding groundsurface settlement are in a comparative analysis. Their trends are basically the same,and the deviation of them is not big, indicating that the model is feasible, and theresults are available. Horizontal displacement of the pile occurs mainly in the pitoverburden excavation process. After the roof pouring, the horizontal displacementof envelope is less then before.(5) Surface settlement curve is "spoon-shaped". A certain distance outside theenvelope, there is a sedimentation tank. The location where the maximum of thesettlement happens is essentially the same. The role of subsidence of the soil nearthe envelope relative to other soil is slightly slow, due to frictional resistance of the envelope. Experienced local typical settlement, the settlement value becomes smaller.The impact of the foundation pit excavation on surface settlement, mainly hanppensin the range of1times final excavation depth from the pit. Surface subsidenceoccurrs mainly in the overburden excavation and roof pouring process. It uplift bythe "squeeze push" effect of the closed main structure. While the closed mainstructure becomes larger, the uplift rate is increasing.(6) The settlement of the intermediate piles with "uninstall-load" during theexcavation, uplift and subside. At last, the settlement uplift with the elevation of theentire main structure. The vertical displacements of the piles are different. Thedifference between the pile vertical displacement increases with the increase in thepile vertical displacement. The settlement of the laminates is similar to that of thepiles. Differences in vertical displacement of the laminates and piles will cause thestructure to generate additional moment.(7) The impact of the blasting load on laminates, piles are mainly in the verticaldirection than in the horizontal direction. The size of the impact of the blasting loadon building is related to its distance from the blast center. The closer it is from theblast center, the greater impact caused by the blasting load. The blasting vibration ofthe underground structure is a problem of transient dynamics. Building and soilstress is mainly concentrated within the two times of blasting area near the blastingcenter, smaller in other region. |
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