Study On Engineering Properties And Strength Increasing Rule Of Tianjin Marine Soft Soil

Tianjin port is a typical soft clay foundation area. To built constructions of whichstability is the controlling condition like breakwaters、reclamation dams and docks onthis kind of foundation, stability analysis is a key part in engineering design and shearstrength indices are decisive factors in stability analysis. Soft soil strength increaseswith drainage consolidation under the action of external loads. This is very importantfor soft foundation with low bearing capacity. Mastering the strength increasing rulehas important guiding significance to make reasonable construction schemes andcorrectly evaluate stability of structures.This paper first expounds the measuring methods and selection principles ofshear strength indices in stability analysis in current engineering practice, summarizesthe achievement about shear strength increasing rule home and abroad. Then takeTianjin soft soil as research object, on the basis of collection and collation of a largenumber of laboratory test data and the least square principle, study the distributionand the regression equation for physical and mechanical indices and make a χ2test ofthe probability distribution model of soil indices.Then, calculate effective consolidation pressure of every soil sample by means offinite element software ABAQUS, analysis the change law of shear strength indicesυ、c with the effective consolidation pressure and find that when pressure increases,υ、c also increases linearly. Fit the empirical equation between υ、c and effectiveconsolidation pressure based on the least square principle.Apply the empirical equation to the stability computation of north breakwaters inTianjin south port in normal work condition and make a comparative analysis with theresult using consolidated quick shear index and vane shear strength. Comparisonresult shows that safety factor is relatively low by using quick shear indices. Thereason is that the inevitable disturbance in sampling and experiment causes the quickshear indices are lower than actual strength value. Checking result adopting vaneshear strength is close to1.0, showing that vane shear strength can reflect the actualstrength more exactly.Finally, study the impact of the change of slope ratio and the width of berme andoptimize the section of breakwaters based on the study result.