Study On Failure Mode And Reliability Analysis Of Cement Concrete Pavement In Permafrost Regions

Cement concrete pavement has been widely used for its high strength, good stability,great durability, constructed easily and little work in conventionality maintenance. With thedepth of the construction of country western and northeastern regions and the continuousimprovement of the permafrost region road network density, early destruction of pavementunder complexity of the climate and environment conditions and adverse geological Lot hasbecome increasingly prominent. It directly affects the use of the highway performance andincreases highway maintenance workload. Deeply carrying out the theoretical studies ofpermafrost regions pavement has really been an extremely urgent subject. This paper mainlyanalysis stress and failure mode of cement concrete pavement slab in permafrost regionsunder climate and geological characteristics of the environment. It has great significance toimprove design theory and performance and reduce maintenance costs of cement concretepavement.Based on finite element analysis software ANSYS, research was conducted atfollowing aspects: establishing the cement concrete pavement structure heat exchangermathematical model of the northeast permafrost region and analyzing the maximumtemperature gradient of the concrete pavement in this region. In consideration of theinfluence to the stress of the concrete pavement structure caused by external climaticconditions, using finite element to calculate and analyze the maximum tensile stress anddeformation of four free edges concrete slab and set dowel concrete pavement undermaximum negative temperature gradient conditions. This paper also simulated and analyzedthe impact on pavement structure temperature gradient and early stress under differentconstruction seasons and casting time. The combined effects on pavement performance bythe traffic load and maximum temperature gradient also were calculated. In addition, theinfluence to maximum tensile stress and deformation caused by load location and designparameters was analyzed and proposed the design life and failure mode of the cementconcrete pavement in this region. In the end, the theory of structural reliability andstochastic finite element were combined and applied to cement concrete pavement design.Main results obtained through numerical simulation of cement concrete pavement are as follows: the finite element analysis of pavement temperature field by the cement concretepavement structure heat exchanger mathematical model is feasible. The reason andrecommended values of making the maximum negative temperature gradient as the standardvalue of the concrete pavement design were given. Setting dowel in joint can effectivelyimprove pavement roughness and decrease dislocation phenomenon by reducing thedeformation of concrete slab, but at a certain extent the maximum tensile stress would beincrease caused by temperature load. In order to decrease the built-in curling stress inconcrete pavement structure, it should try to avoid pouring concrete in the hot summernoon.A certain insulation measures should be used to prevent the concrete pavement surfaceto early cracking at the lower temperatures of autumn and winter construction. At the sametime, the outside air temperature change suddenly results in larger stress in pavement. Thecement concrete pavement is prone to a top-down cracking damage under the combinedeffect of negative temperature gradient and vehicle load, the maximum tensile stressobtained from the analysis was used to predict the design life of the pavement around4years.A large additional stress caused by uneven ground thaw will reduce the service life ofpavement. The methods combinated of stochastic finite element and structural reliabilitytheory can effectively address the various uncertainties in the pavement design.Finally,reducing the variability of the thickness of the cement board and improve primary stabilityin construction can effectively improve the service life of concrete pavement.