| After the excavation part of the foundation pit is completed,the project transfer,the capital chain break and other factors affect the suspension of work,and the situation of resuming work after long-term placement occurs from time to time,but the foundation pit support is generally designed according to the temporary structure,resulting in many overdue service foundation pits.The construction duration of the overdue service foundation pit project is long,and due to the influence of soil rheology and water level fluctuations,the deformation and force of the foundation pit will change,time effects and groundwater are well worth investigating in the design and performance evaluation of pile anchor supports.In this paper,considering both soil rheology and anchor cable prestress loss,combined with the deformation coordination relationship between anchor rod and pile body,the displacement and anchor rod tension calculation formulas of anchor support structure of foundation pit pile under different influencing factors were derived,and the evaluation method of support structure of overdue service foundation pit pile was further explored.The specific work and results of this article were as follows:(1)On the basis of referring to the characteristics of the relevant literature model,considering the rheological characteristics of the soil and the time-varying loss of the anchor cable prestress,the calculation formulas of the horizontal displacement of pile anchor support and the tension of the anchor rod considering the aging period were derived,and the reliability of the solution was verified by example,and the influence law of the stiffness of the support structure on the deformation of the supporting structure was further analyzed;(2)The groundwater prediction model was introduced,considering the effect of water pressure on the support structure,the analytical expressions of the horizontal displacement and anchor rod pull of pile anchor pit support considering aging and groundwater were obtained,and applied to the Hunan Cultural Square project,the reliability of the solution in this paper was verified;(3)Considering the influence of seepage on the water and soil pressure on the pile side,the calculation formulas of horizontal displacement and anchor rod tension of pile anchor foundation pit support considering aging and seepage were derived,and the influence of water level amplitude change,excavation depth and embedding depth of support pile on the support structure of foundation pit were analyzed,the two-dimensional analytical solution of ultrastatic pore pressure under water level fluctuation was solved,the distribution law of superstatic pore pressure in soil layer was studied,and the relationship between ultrastatic pore pressure and the width inside and outside the foundation pit was further analyzed;(4)Considering different influencing factors: aging,groundwater,seepage effect and water level fluctuations,the performance evaluation method of the support structure of the foundation pit that had been overdue for service was proposed,and the calculation formula of residual performance coefficient was proposed. |
