Abstract
In order to design the soil-rock combination foundation pit more safely and effectively, this paper presents the investigations of the mechanical and deformational characteristics of end-suspended piles supporting the structures in Jinan CBD area. Based on the measured data, a finite element model was established through the two-dimensional numerical simulation method to study the deformational characteristics of the end-suspended piles, and the influences of the depth of socketed rock, the width of rock shoulder, and the prestress of anchor cables on the deformations and mechanical property of end-suspended piles were discussed. Some optimization methods are proposed based on these analyses. Results show the following: (1) Rock-socketed depths have boundary effect on end-suspended piles. Under the given geological conditions, the reasonable socketed ratio is within 0.158∼0.200. (2) The anchor cable prestress can effectively slow down the ground settlement, the force, and deformation of the pile body and can be set to 1P∼1.25P under the conditions of the site. (3) Rock-shoulder width has little influence on the ground settlement and horizontal displacement of piles. The reserved width of rock shoulder is suggested to be selected in the range of 1.0 m∼1.5 m.
Highlights
Subway is gradually becoming an important way to improve urban traffic, and the deep foundation pit engineering of subway station plays an important role in subway construction. ere are a lot of intrusive magmatic rocks in Jinan area, resulting in the fact that the thickness of soil layer is generally less than 30 m [1]. erefore, there are a large number of soil rock composite foundation pits in Jinan area; that is, the upper part of the foundation pit is soil layer and the lower part is rock layer. e supporting structure of endsuspended pile is a kind of supporting structure which is widely used in soil rock composite foundation pit at present
Based on PLAXIS 2D finite element numerical simulation of foundation pit deformation, this paper studies the stress and deformation characteristics of end-suspended pile support in Jinan area and analyzes the influence of anchor cable prestress, rocksocketed depth, rock-shoulder width, and other factors on foundation pit deformation and support structure stress, so as to put forward corresponding optimization design suggestions
On the basis of the measured data, the finite element model is established by two-dimensional numerical simulation method, and the stress and deformation characteristics of the support are analyzed
Summary
Subway is gradually becoming an important way to improve urban traffic, and the deep foundation pit engineering of subway station plays an important role in subway construction. ere are a lot of intrusive magmatic rocks in Jinan area, resulting in the fact that the thickness of soil layer is generally less than 30 m [1]. erefore, there are a large number of soil rock composite foundation pits in Jinan area; that is, the upper part of the foundation pit is soil layer and the lower part is rock layer. e supporting structure of endsuspended pile is a kind of supporting structure which is widely used in soil rock composite foundation pit at present. E research shows that the reciprocal first row of prestressed anchor cables set in the length range of the end-suspended pile play a significant role in controlling the horizontal displacement of the pile foot during the excavation of the foundation pit To sum up, these studies are mainly aimed at Qingdao, Dalian, and other areas, and the conclusions are of certain significance for the stress and deformation characteristics of end-suspended pile support. Based on PLAXIS 2D finite element numerical simulation of foundation pit deformation, this paper studies the stress and deformation characteristics of end-suspended pile support in Jinan area and analyzes the influence of anchor cable prestress, rocksocketed depth, rock-shoulder width, and other factors on foundation pit deformation and support structure stress, so as to put forward corresponding optimization design suggestions. E variation trend of maximum horizontal displacement of pile with foundation pit excavation is shown in Figure 5. e horizontal displacement of the pile increases rapidly in the soil excavation stage, and the horizontal displacement has completed 93.24% in this stage, which indicates that the horizontal displacement of the end-suspended pile mostly occurs in the soil excavation stage
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