Research On Bearing Capacity Of Pile Foundation Influenced By Acid Rain

With the rapid development of China’s economy,fossil fuels such as coal and oil are widely used in industrial production.These substances produce a large number of SO2 and other gases after burning.Besides,because of the increasing number of cars,a lot of NOx exhaust emissions in the atmosphere through the vehicle.After the SO2 and NOx emissions into the atmosphere,oxidized and dissolved in rainwater,eventually form acid rain and fell to the ground.Acid rain will cause pollution to the soil,so that the pile in the soil will be contaminated.However,the study on the corrosion of acid rain on the pile foundation is still relatively few.In this paper,a series of experimental studies on the corrosion of pile foundation are carried out,and the corrosion mechanism is discussed.The model test of the pile foundation is carried out in two cases of neutral environment and simulated acid rain environment,the test process is divided into two parts,the test of loading and unloading on the pile cap and the simulation of the ground loading consolidation test are carried on.Mainly for the change of the surface the quality of the steel piles,the resistance,axial force and the change of the friction force of the piles before and after corrosion were analyzed.The research results show that in the soil of the simulated acid rain solution,model steel pile surface changes significantly,the phenomenon of uneven surface is very obvious,and a large number of red brown rust is appeared.With the different corrosion rate of pile,the rust off is in different degrees.Through the experimental data can be learned,the quality of the model steel piles decreases after corrosion,the pile and the corrosion rates vary.In the test of loading and unloading on the pile cap,with the increasing of loading level,the settlement of cap is gradually increasing.And because of the effect of group piles,under the same level load,the settlement of pile cap of pile group is more than that of single pile.After corroding,the pile tip settlement quantity and the change rate of settlement of single pile and group piles is basically the same.On the test of pile top loading and unloading,the pile tip resistance increased with the increasing of loading on pile top and the tip resistance of pile group basicly agreement.Pile tip resistance increases after corrosion,with the increasing of corrosion rate,the change of the resistance of the pile is gradually increasing.In the simulation of the ground load consolidation process,the settlement of each soil layer decreased gradually with the increasing of soil depth.And the settlement increases with the increasing of the consolidation time and the increasing rate is slow by fast,eventually stabilized.After corrosion,the settlement of soil around the pile is slightly reduced,but the change is not obvious.The change trend of soil settlement with the consolidation time is almost unchanged.In the process of the pile load consolidation test,the tip resistance of the pile is gradually increasing with the increasing of the consolidation time.And the pile tip resistance from big to small is corner pile,single pile and the center pile.After corrosion,tip resistance value of single pile and the pile in group decreased slightly and the higher the corrosion rate of foundation pile,the change rate of the pile tip resistance is more.With the increase of the consolidation time,the change rate of the pile tip resistance gradually decreased.In the process of the pile load consolidation test,the axial force of the pile from increasing to decreasing with the increasing of the pile depth.And the longer the consolidation time,the greater the axial force of the pile shaft,the range of increasing is rapidly first and then slowly.Axial force of pile shaft of the corner pile will be greater than central pile and the axial force of single pile is the smallest.The change rate of the axial force above neutral point is greater than below the neutral point.After acid environment corrosion,the pile shaft axial force decreased slightly,however,the axial force of the pile is increasing with the depth of the pile,compared with the neutral environment.In addition,the change rate of the axial force of the piles of different corrosion rates decreased with the increasing of the consolidation time,and then increased.In the process of simulating the ground load consolidation test,with the increasing of the consolidation time,the negative skin friction of the pile is gradually increasing.After simulated acid rain solution corrosion,the negative skin friction of the pile is also increased,and the position of neutral point of the model pile is moved down,and the higher the corrosion rate,the greater the negative friction of the pile.Combined with the basic theory of the corrosion of steel pipe piles,the action mechanism and development law of steel pipe piles are analyzed.And combined with the traditional,uniform corrosion model and local corrosion model,a mathematical model for the optimization of steel pipe piles is put forward.The theoretical value and the practical value are compared and analyzed by using the obtained steel tube pile corrosion model and the model has good accuracy.