Research On Method To Reduce Foudation Settlement And Strenghten Foudation Stiffness

Currently, machine tool manufacturing industry of our country is developing withmore modernization and lager-scale, and a great deal of large-scale manufacturingfactory buildings arise in economic development zones throughout our country.According to the requirement of machining process, forging hammer machine is the onekind of the essential processing equipments for single-storey industrial buildings. Thecyclic load caused by forging hammer is transferred through foundation to soil in theprocess of forging machine parts, then spreading in the form of waves, so the bearingstratum under bent frame column foundation of adjacent forging foundation not onlysupports the static load of upper structure, also settles with additional dynamic stresscaused by dynamic load. Based on engineering accidents of single-storey industrialbuildings, for instance, crack of wall and bent frame column, tilt of crane beam, andforge parts can not be lifted to right place, and what’s worse, forging production has tostop work; thus, in order to resolve all these engineering problems, the method tostrengthen foundation stiffness is proposed in the paper to thoroughly and completelysolve the state of production halting by means of finite element calculation,reinforcement design and construction techniques. The research has important practicalvalue in solving the above engineering problems.Firstly, on account of bent frame column reinforcement design of single-storeyindustrial building, a large number of domestic and foreign related literature and datawere obtained to summarize and analyze the most important influencing factors to crackof wall. The original design drawings of some single-storey industrial building withcracking wall and bent frame column were collected, as well as the recent settlementmonitoring data and engineering geological report. By field surgery and measuringacceleration of soil layer of bent frame column foundation and5t-forging foundation, itcan be obtained that the primary cause of the engineering accident is that theacceleration of dynamic machine foundation exceeds the allowed value of the code. Thestrengthening foundation stiffness method was proposed and the settlement deformationand the acceleration of foundation were successfully reduced.Foundation stiffness is the ratio of the unit force bore by soil to its lineardisplacement, so the only method to increase foundation stiffness is to decrease thelinear displacement when the load of foundation top is constant transferred from bentframe column and dynamic machines. On the basis of the soil of bent frame foundationmust be reinforced in the industrial building and the engineering geological conditions,the technology approach was proposed that high-pressure rotary jet grouting pile andthe original foundation bearing stratum will be applied to increase the foundation stiffness as one kind of composite foundation. Therefore, the finite element softwarePKPM was used to calculate the internal force of the bottom of bent frame column andthe settlement displacement. The length, diameter and layout of high-pressure rotary jetgrouting pile were designed to make the composite foundation provide enough bearingcapacity with static and dynamic loads, and the reliable joints between high-pressurerotary jet grouting pile and independent column foundation were also designed, and thestiffness of foundation bearing stratum before reinforcement will be compared andevaluated to that after reinforcement. According to the results of in-situ static load testand in-situ excavation measurement of high-pressure rotary jet grouting pile, thereliability of calculation and the levels of assurance of the pile lengths were verified, aswell as the rationality and the advancement of reinforcement engineering design.To resolve the engineering problem ultimately, the acceleration of soil layer causedby the dynamic loads form the dynamic machine foundation must be reduced, andaccording to Newton’s second, under the inertia force, the only approach to decrease theacceleration is to increase the mass of dynamic foundation and enhance the groundstiffness of resisting pressure. Thus, based on the situation that the acceleration and itsamplitude of dynamic machine foundation both exceeds the allowed values of the code,the technique method that the composite foundation wich consists of high pressuregrouting pile and massive dynamic foundation was creatively proposed in this paper,and it is proved that the new technique method of increasing the ground stiffness ofresisting pressure to reduce the foundation settlement displacement is correct,reasonable and reliable through the comparison of the stiffness of foundation bearingstratum before reinforcement and that after reinforcement.