Study On Secondary Consolidation Property And Forecasting Model For Marine Sedimental Clay

The material composition and structural characteristics of marine soft soil are very complex and affected by the external conditions in a great degree.The main feature of marine soft soil is that the void ratio,natural moisture content,organic matter content are high and rheology,compressibility are obviously.The secondary consolidation property of marine soft soil causes many technical difficulties for near sea construction,for example the stability of deformation,non-uniform settlement,large-strain consolidation,settlement prediction of treated foundation,etc.In order to study the secondary consolidation property of marine soft soil,we chose the undisturbed mucky marine soft in 10 meters depth underground of Yili Road and Qinghai Road project at Tianjin Binhai Dongjiang area.Through staged loading one-dimensional consolidation tests and preconsolidated staged loading one-dimensional consolidation tests,we analyze the test results and get some rules and summary of the secondary consolidation property.We also make some conclusions and suggestions for soft soil foundation engineering construction and foundation preload.The research includes:(1)The prophase consolidation pressure of test sample is about 87 kPa.The time of demarcation point for primary-secondary consolidation is 90~100min.The change of load ratio will cause peak migration of C_a-p curve.The after-peak secondary consolidation coefficient C_a will increase or decrease with the increase and decrease of load ratio.As the increasing of consolidation pressure p,C_a first increase to a peak and then decrease.The position of the peak is near the prophase consolidation pressure p_c.(2)For preconsolidated samples,the C_a-p curve is no peak.As the increasing of consolidation pressure p,C_a increase to a constant value finally and that value is proportional to the magnitude of the preloading load.The greater the preloading load,the greater the value of the stability C_a.(3)For unconsolidated samples The ratio of secondary consolidation coefficient C_a and compression index C_c is scattered,the value of C_a/C_c is between 0.011 0.027.For preconsolidated samples,the ratio has good linear relationship,the value of C_a/C_c is between 0.023 0.034.In addition,the author also analyzes the influence of the secondary consolidation of soft soil on the practical engineering and introduces the related engineering cases.Author also makes clear the necessity of the research on the model of secondary consolidation for soft clay.Starting from the Buisuman model which is currently used in engineering,this paper analyzes the problem it existed.From Buisuman's improved model,hyperbolic model,and structural soil consolidation model,author introduces new models of some scholars and analyzes its applicability and rationality.