Deformation Control Design Of Crossing-dyke Culverts

At present, dykes are constructed on a large scale in Pearl River Delta, where appears alot of construction problems of crossing-dyke culverts in soft soil. Reference shows that forcrossing-dyke culverts in water conservancy industry, due to the lack of the right cognition onthe foundation deformation under trapezoidal load and the computational theory of verticalsoil pressure on the top of culverts, there are many problems (e.g. uneven settlement, crack,etc.) in the culverts’ operation, which affects the culverts’ safety and normal use. Therefore,based on an actual engineering project, and combining with finite element numericalsimulation and theory analysis, this paper conducts preliminary research on foundationsettlement calculation of crossing-dyke culverts and vertical soil pressure on culverts. Mainresearch contents and conclusions are as follows:(1) Based on the characteristics of the reloading state of the soft soil after unloading, andaccording to the plate loading test of an engineering project, this paper analyzes how todetermine the deformation modulus under the reloading state of the soft soil after unloading.The results show that the reloading modulus is about1.83~2.04times of the compressionmodulus.(2) According to the actual engineering project, the unloading modulus is used to replacecompression modulus. The layer wise summation method and finite element method are usedto analyze the foundation deformation rule of the crossing-dyke culverts. The results illustratethat the settlement results by the layer wise summation method and finite element method areclose, and their maximum settlement difference is less than1cm; their settlement rules are thesame, which means that the deformation parameter is reasonable and the layer wisesummation method is feasible; due to the trapezoidal load on the culverts, whether thefoundation along the culverts is treated or not, the settlement is like to pot type; in realprojects, the pot-type settlement should be avoided in order not to pull the joints apart.(3) Through the finite element numerical simulation method, this paper analyzes atypical engineering. It is found that if the foundation under the culverts has been treated andunder the loads of the backfill, the settlement will be larger than that of the treated foundation,which will cause that the vertical soil pressure is higher than that by the specifications. Theincrement rules of the soil pressure on the top of the culverts under different boundaryconditions are studied as the plane problem, and the maximum vertical soil pressure can betwice as the gravity stress of the soil pillar, thus causing longitudinal cracks. As a result, thisproblem should be paid attention to in real engineering projects.