| The mechanical characteristics and deformation mechanism of foundation pit is complex,and have strong regional characteristics,so the engineering experience analogy is always used in supporting design and construction of foundation pit.To eguarantee the stability,detailed analysis on the foundation pit's stability is needed.Aimed at large deep foundation pit engineering of Hechang Trading Center in Quanzhou,and based on summarizing the stability analysis principle and calculation formula of foundation pit,the article checks global stability,anti heave stability,anti overturning stability and anti punching shear stability,and four stability safety factors are obtained to verify the stability of this foundation pit.On this basis,the relationship between four kinds of stability safety factors of foundation pit and cohesion,weight,internal friction angle of soil and buried depth of pile is studied,which has some reference significance for stability analysis in some similary engineering.The main conclusions of this paper include:(1)Safety factor of global stability in this foundation pit is 2.362,which meets the requirements of the specification.It increases linearly as the increase of soil internal friction angle and cohesion,but decreases as the increase of soil weight;And it increases as the increase of buried depth of pile,and the growth rate is fast.(2)In the foundation pit,the anti uplift safety coefficient under the mode of foundation bearing capacity is 11.98,the safety coefficient is positively correlated with soil weight outside the pit,but negatively related to soil weight inside the pit.The anti heave stability safety coefficient under the mode of circular sliding whose center is the pit bottom is 2.987,The anti heave stability safety coefficient under the mode of circular sliding whose center is the lowest support point is 2.329,the safety coefficient increases linearly as the increase of ultimate resisting moment of supporting structure but decrease as the increase of soil weight.As buried depth of pile is getting deeper,the safety coefficient goes down firstly and then rises,and the former reaching the minimum value of 3 in the insertion ratio of 0.5,the latter reaching the minimum value of 2.26 in the insertion ratio of 0.66.The anti heave stability safety coefficients under the three kinds of calculation modes of foundation pit increase as the increase of the cohesion and the internal friction angle of soil,linearly changing with cohesion,and three kinds of anti heave stability safety coefficients are satisfied with the requirement of the standard.(3)The modified anti heave stability calculation formula under the mode of circular sliding whose center is the pit bottom and the lowest support point are used to get the anti heave stability safety factors of foundation pit that are 3.096 and 2.564,which can meet the requirements of specification.The changing characteristics between the modified anti heave stability safety coefficients and factors is the same as the unmodified.(4)The anti overturning stability safety coefficient of this foundation pit is 2.95,and the anti punching shear safety coefficient is 2.35,which can both meet the requirements of the specifications.The anti overturning safety coefficient increases with the increase of soil cohesion,internal friction angle,soil weight inside pit,insertion ratio of pile and the distance between bottom support and pit bottom,but decreases with the increase of soil weight outside pit,changing linearly with the soil cohesion inside pit.The changing features of punching shear stability safety coefficient is the same as anti overturning stability,except which decreases firstly but then rises with the rising of insertion ratio of pile,reaching the minimum value of 2.24 in 0.36. |
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