| The excavation engineering is a vital geotechnical engineering problem,while the support structure design is the key factor to influence the stability of theexcavation.In recent years,many scholars in the same tradehave been in-depth studying the theoretical knowledge,strengthening the practical experience in ensuring the safety of excavation structure to achieve reasonable and economical.The excavation engineering should not only consider the regionalism and the risk in the design,but also should pay attention to the geotechnical engineering geological conditions,hydrogeological conditions,soil stress state and the effect of the surrounding environment on excavation support structure.Compared to other support structure,the pile-anchor support structure can not only utilize a smaller construction space,but also can effectively control the ground deformation,so it is widely used in excavation engineering.The excavation engineering of the 8# building of Hengda gorgeous mansion is taken as an example.Firstly,the geological condition of the Hengda gorgeous mansion 8# building excavation engineering in Hohhot is analyzed and collected the strata distribution and mechanical parameters.And a calculation of the excavation support condition is taken by using Lizheng design software(v.7.0PB1)according to the related laws,preliminarily verified the reliability and security of the support scheme;secondly,based on the FLAC3 D software building the three-dimension model,doing the numerical simulation of stress and displacement during excavation and support process;finally,by comparing the numerical simulation results with the actual monitoring results,the results show that the parameters selected by the three-dimensional numerical model are reasonable.The specific research conclusions are as follows:1.The Holocene(Q4)strata in the study area are mainly composed of silt,gravel,and gravel,and the Lower Pleistocene(Q2)strata are composed of fine sand and gravel sand.According to the regional experience and the survey data of adjacent sites in recent years,it is concluded that the groundwater belongs to the diving type.The depth of the groundwater level during the construction period is more than 13.0m.Therefore,it is not necessary to consider the influence of groundwater on the design of foundation pit.The seismic fortification intensity of this project is 8 degrees,the seismic acceleration is 0.20 g,the characteristic period is 0.35 s,the site is in the general earthquake area,there is no possibility of liquefaction,the site belongs to class ? field.2.According to the standard formula,the displacement,bending moment and shear force of the supporting structure are calculated by using Lizheng design software(v.7.0PB1).It is found that the maximum horizontal displacement of the supporting structure occurs at the top of the supporting structure,the maximum displacement is 1.65 mm under the working condition 1;the maximum horizontal displacement of the supporting structure occurs at the top of the support structure,the maximum displacement is 1.16 mm under the working condition 2;the maximum horizontal displacement of the supporting structure occurs at the lower part of excavation,the maximum displacement is 7.20 mm under the working condition 3;meanwhile,the overall stability safety factor K=2.320,the bottom of the support structure of the safety factor Kb=17.081.The results show that the displacement of each working condition is small,the overall stability of the excavation the stability of the anti-uplift and the stability of the embedding are in accordance with the specification.3.The results show that the stress in the horizontal direction of the foundation pit is more obvious than that in the slope near the slope.The distribution of the stress distribution in the other horizontal directions is basically consistent with the topography,and the excavation of the foundation pit is in the horizontal direction The effect of stress is about twice the excavation depth;the vertical stress of the foundation pit is more obvious near the position of the supporting pile,and the whole vertical stress distribution is basically the same as the terrain,The effect of vertical stress release on the vertical stress is about twice as deep as that of the foundation pit.In the process of excavation of the foundation pit,the foundation of the three working conditions Pit lateral wall displacement is smaller,the maximum displacement change and the depth of the pit is the ratio of 0.7‰,less than 1‰.4.According to the comparative analysis of the calculation,numerical simulation and the actual monitoring of the horizontal displacement of the pile can be seen:(1)According to the observation values of the horizontal displacement of the pile in the middle of the foundation pit,it is found that there are three displacements in the excavation process,which are excavated to 5.0m in the foundation pit,and the foundation pit is excavated and excavated to 10.0 M under the conditions of the conditions.(2)Based on the canonical formula,the maximum horizontal displacement of the pile top is 1.65 mm under the conditions of the deep foundation pit calculation software.The displacement value of the pile top is 0.9mm larger than the monitoring value and 0.85 mm higher than the simulated value.The maximum displacement of the pile top is 1.16 mm,and the displacement value of the pile is 0.02 mm smaller than the simulated value,which is 0.16 mm larger than the simulated displacement value,that is,the calculation of the condition The maximum displacement of the pile top is 3.11 mm,which is larger than the numerical simulation value of 0.61 mm,which is larger than the monitoring displacement value of 0.98 mm.In this paper,the maximum displacement of the pile top is 3.11 mm,which is larger than the numerical simulation.On the above,the theoretical calculation value and the numerical simulation displacement value of each working condition are all larger than the monitoring displacement value,and the deformation is within the specification requirement,but the numerical simulation displacement value is closer to the monitoring displacement value,proving that the numerical simulation method ratio Normative calculation method is more realistic,and that the support program is safe and reliable.According to the simulation results of the numerical calculation,the calculation results of the canonical formula and the size of the on-site monitoring data,it can be seen that the design of the pile-anchor support structure on the 3-3 side of the foundation pit support is reasonable,and the numerical simulation parameters are selected As well as the establishment of the model is correct,for the region similar to the foundation pit engineering design and research methods to provide reference and recommendations. |
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