| Research of the stability of culvert buildings plays a significant role in engineering survey,design,construction and operation in dike engineering.Culvert buildings in Dongting Lake area are mostly built on soft soil foundation,which may easily lead to structural damages including uneven subsidence,crack and sliding.To deeply understand the damage mechanism of the Dongbao culvert buildings,based on the analysis of the e-p curve feature,method for the improvement of the evaluation of parameters(K,n,G,F)of the Duncan-Chang model on basis of compression experiments.The three-dimensional elasto-plastic finite difference method is used to analyze the influencing factors of the slippage deformation of Dongbao culvert buildings.Meanwhile,it also studies the anti-sliding stability of its culverts and octagonal wall structure.The main research results are as follows:1.Through the analysis of the correlation among compressive modulus,compression coefficient and initial porosity ratio,the relationship between porosity ratio and compressive stress is obtained.Moreover,with the obtained function relation,the calculation methos of soil initial elastic modulus is explored.Then,the estimation method of parameters K and n is obtained by the construction of 1g(Ei/Pa)-1g(σ3/Pa)relation.The Duncan-Chang tangent modulus and tangent Poisson’s ratio are introduced in the numerical simulation of consolidation compression experiment.The Mohr Coulomb elastic-plastic model is used to simulate the standard consolidation experiment.The relationship between compressive deformation and compressive stress is analyzed,and it is compared with the physical experiment,inversely deducing the parameters of K,n,G and F.2.The results show that the shear strength parameters of the backfill in the Dongbao culvert have a great influence on culvert deformation.The shear strength parameters of the backfill in design institute are reduced by 50%due to the continuous rainfall during backfill construction and the insufficient compaction degree.As results,the horizontal displacement grows by 0.3cm,an increase of 2.00%;the vertical displacement increases by 3cm with a growth of 1.67%;the third main tensile stress increases 33%to the maximum of 0.04MPa;and plastic area reaches to 15 m3 with an increase of 43%.These indicate that the reduction of the shear strength parameters of the backfill may lead to the slipping in the horizontal.3.The depth of the foundation cement pile and the lengthof culvert section have great influences on the uneven settlement and the stress distribution of culvert structure.When the lengths of cement injection piles are equal to each other,the maximum of the foundation soil settlement displacement calculated according to 18m-long cement injection piles increases by 3cm,12.8%less than that of 12m-long powder jet piles.If both sides of the pile group are not as long as the middle,the maximum settlement displacement in the central part is reduced by 1.1cm with the reduction of 4.7%,effectively reducing uneven settlement.Because the number of expansion joints increases,namely the culvert length growing,the third main compressive stress tends to focus on expansion joints.When section length increases from 8m to 12m,the third main compressive stress grows by 35%.4.Under normal circumstances,when Section Ⅷ of the culvert and the eight-wall are only influenced by the active earth pressure,the safety factor of the anti-sliding stability is 3.99.The base friction coefficient f under such conditions has the biggest influence on the anti-sliding stability,the extreme value of influence reaching to 1.1907.The backfill cohesion has the minimum effect on the anti-sliding stability,and the relative extreme value is 0.1232.When the backfill cohesion is 12kPa and the internal friction angle is 9°,the maximum sliding thrust is 840kN.At this time,the safety factor of sliding stability is the minimum of 1.04,and the anti-sliding stability of culvert structure is the smallest. |
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