| In the field of rock engineering,foundation pit engineering is a very important content.During the excavation of foundation pit,how to do the support is a key factor affecting its depth level.Therefore,in-depth research on foundation pit support not only provides reference for similar areas and similar construction conditions,but also has certain significance for preventing construction risks.It is necessary to survey the geological conditions and other information of the site before excavation of the foundation pit.Due to the complexity of the soil layer,it is difficult to maintain the stability of the foundation pit in the excavation process,so it is of great significance to carry out proper support of the foundation pit.Pile and anchor support not only has a strong ability to restrain deformation,and strong applicability,higher safety,and convenient construction,so it is widely used in the process of deep foundation pit.Based on a foundation pit project in Changchun,this paper uses Midas GTS to establish a three-dimensional model,verifies the reliability of the model by analyzing monitoring data and simulation data,analyzes the embedded depth,pile diameter and pile spacing,analyzes the influence analysis on the horizontal displacement of the pile body and the settlement of the surrounding environment,and conducts the influence analysis through numerical simulation.The main research contents and achievements of the paper are listed below:(1)The variable analysis method was used to compare the change of design parameters of the envelope pile,and the results of the influence of changing parameters on the pile shape change and surrounding surface settlement were obtained,which were reflected in the form of curves.Midas DTS software was used to select different pile diameters,pile distances and embedment depths.It is concluded that the trend curves of the three factors affecting pile horizontal displacement and surrounding settlement are almost the same.(2)The large in the middle and the small on both sides are the variation trend of the uplift presented by the pit degree,which means that the uplift will be limited by the pit Angle.During the design of foundation pit support,we can properly design the strength of the support to be lower than the surrounding area,which not only meets the requirements,but also saves costs.(3)From the horizontal direction,the axial force of prestressed anchor cable shows a trend of large change in the middle and small change on both sides.From the vertical direction,the axial force of prestressed anchor cable gradually increases.(4)When the embedment depth is within a certain limit,the influence on the surrounding environment and pile level can be effectively reduced with the increase of embedment depth.However,once the embedment depth reaches a certain limit,the effect of the embedment depth on the surrounding environment will be weakened.(5)By analyzing the horizontal displacement of pile and surrounding settlement through pile diameter,it can be found that pile diameter has a positive influence on both horizontal displacement and settlement displacement,which are proportional to pile diameter,but when pile diameter exceeds a certain limit value The anti-stability efficiency of pile decreases with thickness.In a certain range,pile diameter can reduce the surrounding settlement and pile horizontal displacement by13.06% and 15.45%,respectively.(6)Within a certain range,pile distance is proportional to surrounding settlement and horizontal displacement.With the increase of pile distance,settlement and horizontal displacement also increase gradually,and pile distance reduces the surrounding settlement and pile horizontal displacement by 16.04% and13.81%,respectively.(7)The change of anchor cable inclination Angle has a positive effect on the horizontal displacement of pile.The optimal range is 10°～25°,but it should not be greater than 35°.When the inclination Angle is less than 25°,the maximum horizontal displacement of pile body is about the middle of the pile body;when the inclination Angle is greater than 35°,the maximum horizontal displacement of pile body is at the top of the pile body.(8)With the increase of free section,anchorage section decreases,anchorage depth increases relatively,and horizontal displacement of pile decreases successively,which is beneficial to foundation pit deformation.In order to ensure the anchorage length in a safe state,the length of free section can be increased appropriately,while the length of anchorage section can be reduced.(9)Based on the above analysis results,it can be seen that there is an upper limit on the resistance to foundation pit deformation of the five factors,such as the distance,diameter,embedment depth,anchor cable Angle and free section length,and there is little difference in the resistance to deformation after the upper limit is exceeded.Therefore,it is necessary to analyze the above five factors together in the optimization of pit design. |
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