新旧规程土压力分布下支护结构嵌固稳定对比分析

Comparative Analysis of Embedded Stability of Support Structures Under the Distribution of Soil Pressure in New and Old Regulations

《建筑基坑支护技术规程》对基坑单支点支护结构的抗倾覆稳定性、嵌固稳定性、土压力计算模式等计算给出了较为具体的规定,土压力按照经典的朗肯土压力理论计算,主动土压力分布模式为三角形。但目前未有规范对多支点支护结构的土压力计算模式给出规定,使该类工程的设计更加困难,本文以此为突破点进行探究并以贵州省毕节市某基坑支护工程为例,分别以《建筑基坑支护技术规程》(JGJ 120—2012)和《建筑基坑支护技术规程》(JGJ 120—99)新旧两规程为计算的理论依据,对坑底主动土压力分别呈三角形分布和矩形分布的2种不同状态下多支点支护结构的嵌固深度和嵌固稳定性进行计算分析,并利用大型有限元模拟软件Midas GTS对计算所得的不同嵌固深度进行数值模拟。结果表明:新规程土压力分布模式下计算得出的最小嵌固深度与旧规程相比较小、抗倾覆稳定系数增幅较大、整体稳定性安全系数略微增大、嵌固稳定性较好。对于该类基坑的多支点支护结构设计,采用新版规程中的土压力计算模式更符合实际的土压力分布并能提供更高的安全储备,降低工程造价,可供此类工程参考。

“Technical Specification for Building Foundation Pit Support,”provides specific provisions for the calcula-tion of anti overturning stability,embedded stability,and soil pressure calculation mode of single support point sup-port structures in foundation pits.The soil pressure is calculated according to the classic Rankine soil pressure theory,and the active soil pressure distribution mode is a triangle.However,there is currently no specification for the calcula-tion mode of soil pressure for multi support point support structures,making the design of such projects more difficult.The article explores this as a breakthrough point and takes a foundation pit support project in Bijie City,Guizhou Prov-ince as an example.The theoretical basis for calculation is based on two new and old regulations,namely"Technical Specification for Building Foundation Pit Support"(JGJ 120—2012)and"Technical Specification for Building Foun-dation Pit Support"(JGJ 120—99),Calculate and analyze the embedding depth and embedding stability of multi sup-port structures under two different states of triangular and rectangular distribution of active soil pressure at the bottom of the pit,and use the large-scale finite element simulation software midas GTS to numerically simulate the calculated different embedding depths.The results show that the minimum embedding depth calculated under the new regulation's soil pressure distribution mode is smaller than that of the old regulation,with a larger increase in anti overturning sta-bility coefficient,a slight increase in overall stability safety coefficient,and good embedding stability.For the design of multi support structures for this type of foundation pit,using the soil pressure calculation mode in the new version of the regulations is more in line with the actual soil pressure distribution and can provide higher safety reserves.Re-duce costs of the project and can provide reference for such projects.