Study On The Mechanism Of Ground Emprovement With Surcharge Beside The Frame Bridge In Subsidence Area

The Ji Rever Railway Bridge of Xieqiao Mine of Huainan Mining Group is affected bycoal mining. The surface subsidence of the bridge foundation is enormous. The subsidence invertical direction alone is more than10meters. The bridge has experienced ground treatmentof high-pressure rotary jet grouting pile. This paper proposes the method of loading lateralreinforcement bridge foundations and studies the mechanism of natural foundation andexisting composite foundation loading lateral reinforcement in the context that conventionalexisting building (structure) foundation reinforcement methods are difficult to apply. FLAC3Dnumerical calculation was used to analyze the loading parameters’ influence on ultimatebearing capacity. This paper puts forward the basic relationship between surface overload andfoundation bearing capacity incremental according to sliding surface law theory. Foundationbearing capacity incremental formula was obtained which provide a theoretical basis toloading design.The variation of ground bearing capacity of natural foundation and reinforced existingcomposite foundation was analyzed by numerical model test. The influence rule and actioneffect between the height, top width, slope and the distance of load carrier and the groundbearing capacity is obtained by changing size and location of the load carrier. The main factoraffecting the foundation reinforcement effect is the height of load carrier. The additional stressunder foundation and the anti-slide torque increase along with the increase of the height ofload carrier. However, when the height reaches6meters, load carrier has less influence onground bearing capacity. According to results of the calculation which changes the physicaland mechanical parameters such as cohesion, internal friction angel and gravity density，gravity density has more significant impact on the foundation bearing capacity. Gravitydensity has directly impact on overload. The increase of ultimate bearing capacity isapproximately proportional to the incremental of gravity density. According to research ofnature foundation, among the studies of existing composite foundation loading, approximaterelationship between surface load and foundation bearing capacity was obtained whichconsidered only two variables: gravity density and height.Assumed sliding surface method was used to derive the formula of foundation bearingcapacity when loading was considered. The results in chapter III were verified at the sametime. According to Prandtl bearing capacity theory and Prandtl-Reissner formula, surfaceoverload can significantly improve the bearing capacity. Natural foundation bearing capacityand incremental of foundation bearing capacity can be ascertained according to normativeformula. The height can be modified as well, which is less than or equal to6meters. It is complicated to ascertain the composite foundation bearing capacity, when lateral loading istaken into account.In this case, the basic expression of incremental of foundation bearingcapacity under the lateral loading is derived in this paper according to composite doublelayered foundation theory. According to the results of numerical simulation, the height of theexpression is limited to6meters and it will be calculated as6meters when over6meters.Finally, based on the above research results, the side surcharge method is successfullyapplied to the Ji River Bridge reinforcement design in Huainan Mining area. The foundationbearing capacity of the reinforced area is increased nearly5.4%, and the foundation bearingcapacity of substratum is increased nearly14.9%, The surcharge reinforcement effect isremarkable.