Equations For Calculating The Foundation Settlement Of Zhanjiang Formation Clay Considering The Influence Of Multiple Factors

Zhanjiang Formation clay is the most widely distributed soil mass in the coastal area of the Beibu Gulf.This clay has physical properties similar to those of muddy clay in other regions,such as large void ratio and high water content,and has mechanical properties that are different from those of muddy clay in other regions,such as high strength and low compressibility.When calculating foundation settlement,using the foundation settlement calculation formula recommended in the current code(GB 50007-2011)often has the problem of taking a small modulus value,which leads to a large calculation value.Studying the settlement calculation formula of clay foundation in Zhanjiang Formation has important theoretical significance for engineering construction in the coastal area of Beibu Gulf.Through carrying out plate load model tests on clay foundations of Zhanjiang Group with different natural densities,water contents,and over consolidation ratios,the effects of soil natural densities,water contents,and stress histories on the load-settlement curve and deformation modulus are revealed,and empirical formulas for soil deformation modulus and natural densities,water contents,and stress histories are established.Based on the comprehensive structural potential theory,the empirical formula is modified by introducing the structural index sensitivity of soil mass.The modified empirical formula is applied to the foundation settlement calculation formula recommended in the current specifications.A settlement calculation formula for clay foundation in Zhanjiang Formation is proposed that comprehensively considers the effects of soil mass natural density,moisture content,and stress history,and the validity of the calculation formula is verified.The main research work and conclusions are as follows:(1)Based on the similarity theory,it is demonstrated that the results of the plate load model test can reflect the prototype plate load test with a size of 1m×1m.Prepare clay foundations of Zhanjiang Group with different natural densities,different water contents,and different over consolidation ratios,and conduct plate load model tests to obtain load-settlement curves and corresponding deformation modulus of clay foundations of Zhanjiang Group under different natural densities,different water contents,and different stress histories.(2)The effects of soil natural density,water content,and stress history on the load-settlement curve and deformation modulus were studied.The smaller the natural density,the greater the water content,and the greater the over consolidation ratio,the smaller the slope of the linear section of the load-settlement curve,and the greater the settlement amount of the foundation caused by unit pressure when loaded to the proportional limit pressure and ultimate load;When the water content and over consolidation ratio are the same,the deformation modulus increases with the increase of natural density.In the range of natural density increasing from 1.6 g/cm~3 to 1.8g/cm~3,the extent of the deformation modulus increasing with the increase of natural density decreases with the increase of water content and over consolidation ratio;When the natural density and over consolidation ratio are the same,the deformation modulus decreases with the increase of water content.Within the range of water content increasing from 37%to 49%,the extent of the reduction of soil deformation modulus with the increase of water content increases with the increase of natural density and the decrease of over consolidation ratio;When the natural density and water content are the same,the deformation modulus decreases rapidly and tends to stabilize with the increase of the over consolidation ratio.(3)Based on the analysis of the influence of the above factors on the deformation modulus,an empirical formula for the deformation modulus of clay in the Zhanjiang Formation is obtained by fitting,which comprehensively considers the effects of natural density,water content,and stress history.Based on the comprehensive structural potential theory,the empirical formula is modified by introducing soil sensitivity indicators,and the modified deformation modulus is replaced by the compression modulus in the current code recommended foundation settlement calculation method.A settlement calculation formula for Zhanjiang Formation clay ground is proposed that comprehensively considers the impact of multiple factors.Two engineering cases have verified the effectiveness of the calculation formula.