Research On The Calculation Method Of The Support System Of The Single-story Pair-supported Foundation Pit With Asymmetric Load

As the construction environment around the foundation pit becomes more and more complex,asymmetric load foundation pits become more and more common,anchor rods and anchor cable supporting piles are difficult to meet the needs of foundation pit support,and internal support systems have been widely used.How to do a good design of foundation pit support under asymmetric loads is an important issue that cannot be ignored in foundation pit engineering.At this stage,the research on asymmetric load foundation pits mainly focuses on numerical simulation analysis,while the related calculation theory research is relatively lagging.Based on this,this article mainly focuses on the following points:1.The structural mechanics force method is applied to calculate the horizontal fixed point coefficients of the supporting points on both sides of the foundation pit under the action of asymmetric loads.The rigid connection and the articulated connection at the fulcrum of the bracing structure are considered,and the method in this paper is used.The calculation results of,and the methods of Jin Yabing and Sun Yong are compared and analyzed.2.Under the action of asymmetric load,the earth pressure on the supporting pile body is different from the traditional active earth pressure,and the earth pressure on part of the pile body is between the active earth pressure and the static earth pressure.If the design calculation is carried out according to the active earth pressure,it is easy to make the design result unsafe.Based on this,This paper derives the displacement earth pressure formula and applies it to the calculation of the finite rod element method,At the same time,according to the engineering example,the asymmetric load pair is calculated the displacement and internal force of the bracing support structure are analyzed and compared with the displacement and internal force obtained by the finite element method of the rod system considering the displacement and earth pressure and the result obtained without considering the relationship between the displacement and the earth pressure.3.Based on the foundation pit engineering example,with the help of Midas GTS finite element analysis software,combined with monitoring data,the applicability of the displacement earth pressure formula proposed in this paper in the design and calculation of asymmetric load foundation pit support is verified.Based on theoretical derivation and analysis and calculation,combined with finite element simulation software,this article mainly draws the following results and conclusions:1.Under asymmetrical loads,there are three main displacement modes for single-layer bracing piles in foundation pits.The fixed point coefficient defined in the code is only applicable to the situation where the supporting piles on both sides are displaced into the pit.When the supporting piles on both sides are displaced to the same side,the horizontal internal support fixed point coefficient loses its meaning.2.The relationship between the displacement at the supporting point and the fixed point coefficient is deduced,and then the structural mechanics force method is introduced to calculate the fixed point coefficient.The fixed point coefficients of rigid connection and hinged connection are calculated based on engineering examples.The calculation results show that rigid connection and hinged connection have little effect on the fixed point coefficient calculation results.At the same time,the calculation results of Jin Yabing and Sun Yong method are compared,and the force is found the calculation result of the method is quite different,and it is believed that the fixed point coefficient calculated by the displacement of the support point is more accurate.3.Analyze and compare the displacement and internal force obtained by the rod system finite element method considering the displacement and earth pressure with the results obtained without considering the displacement and earth pressure relationship.The results show that the results of the two calculation methods for the large side of the load are similar,and the load The calculation results of the small side are quite different,because the soil pressure on the large side of the load is closer to the active soil pressure than the small side of the load,and the calculation and design results using the displacement-earth pressure relationship formula are more safe in engineering.4.Based on an engineering example,combined with Midas GTS finite element analysis software,the three data of simulation calculation,theoretical calculation in this paper,and foundation pit monitoring are compared and analyzed.The results show that the results of theoretical calculation and numerical simulation are greater than the foundation pit monitoring data,but the overall displacement trends are in line with the actual deformation of the pile,verifying the applicability of the displacement and earth pressure formula.