Study On Vibration Isolation And Vertical Bearing Capacity Of Foundation Under Dynamic Load

Most modern manufacturing facilities exhibit hammers or presses alongside precision cutting equipment in the form of production machinery.Foundations supporting hammers and presses experience immense dynamic effects that extend to the surroundings and may affect laborers,other sensitive machines within the facility,or neighboring residential areas.An installed wave barrier near the vibration source or in the area to be protected can attenuate the vibrations by reflecting or scattering the wave energy.Wave barriers,including sheet piles,and open or in-filled concrete,bentonite slurry or geofoam trench barriers,have been studied comprehensively.However,these studies mainly encompass the reduction of centrifugal and reciprocating machines vibrations,and are distinguished as harmonic,high-frequency and lowamplitude excitation machine vibrations.Besides,there exists an insufficient knowledge regarding the dynamic response of shallow and deep(pile)foundations under consecutive dynamic loads.Hence,this study aims to address a variety of issues characterized by a number of significant features.Firstly,the efficiency of the open trenches in case of transient or impact loads from shock generating machines(when the machine foundation is built as a shallow foundation)has not been thoroughly investigated in the past literature.In addition,it is important to mention that currently,only a few studies are available pertaining to the infilled(tire-derived aggregates(TDA)and rubber-sand mixtures(RSM))barriers.Also,not much effort has been done to evaluate performance of the trenches under transient loads on pile foundation,and no comparative analysis regarding the use of trenches for vibration reduction under harmonic and transient loading conditions is available till date.Secondly,power hammer machines induce harmful vibrations in different parts of the foundation which causes excessive dynamic settlement,alongside the ground vibration issues.The static load test(SLT)is generally performed in such foundations to obtain the ultimate capacity,however,it cannot predict the reliable response of the machine foundation.Although more power hammers have been utilized in manufacturing industries in recent past,the influence of multiple dynamic loads on machine foundations is scarcely studied.Therefore,it is the desideratum to analyze the behavior of the machine foundations by considering both the static and repetitive dynamic loads in order to achieve higher stability and serviceability of machine elements.Thirdly,piles often move horizontally during earthquakes.In case of superstructure interactions,accurate prediction of the pile response becomes more challenging due to vertical propagation of shear waves during the earthquake that sways the structure thereby causing a vertical axial movement.Most of the previous studies focused on lateral response of pile-soil systems while the axial response of piles subjected to dynamic loads was seldom studied.Thus,there is an urgent need to analyze the axial dynamic response of the piles in seismically active areas.Based on the above-mentioned limitations,this research study investigates the potential of using the open and infilled(TDA and RSM)barriers to reduce vibration caused by transient or pulse loads and to analyze the response of shallow and pile foundations subjected to dynamic loads.The main and innovative work of this paper is summarized as follows:1.The two-dimensional(2D)finite element modelling(FEM)was used to investigate the potential of open and filled(TDA and RSM)barrier applications to attenuate the vibration caused by transient or pulse loads(in shallow machine foundation).Parametric study was also conducted to evaluate different trench parameters,such as,depth,width and distance from source to the barrier upon shielding vibrations.Also,a multi-trench isolation system was simulated such that its comparative performance was evaluated.The obtained results would help designers and practitioners to effectively design and/or analyze the open trenches,TDA and RSM barriers under transient loads.2.The static and dynamic resistance of the power hammer machine foundation was examined by utilizing high-strain dynamic load test(DLT).The effect of variety of load test sequences and a repetitive dynamic load on the machine foundation capacity was investigated.Moreover,the static resistance,modulus of subgrade reaction,and stiffness of the machine foundation were also analyzed.And,the field test and axisymmetric FEM were performed to evaluate the stress settlement curve(SSC)by using nonlinear soil model.The significant findings from the experiments and numerical modeling would assist in developing a more robust foundation for power hammer machines.3.Performance of open trenches to mitigate the vibration caused by pile foundation subjected to transient or impact load was studied using FEM.The effect on the vibration reduction of different trench and pile parameters was evaluated.The efficacy of open trenches in reducing the unsafe distance of various structures has also been assessed using vibration sensitivity degree.The acquired results can help get a deeper understanding of trenches’ efficiency in vibration mitigation due to impact loading on pile foundation and serve guidance during the design and construction phases.4.A comparative study was then carried out on the trenching efficiency using harmonic and transient vibration when the pile foundation acts a vibration generator.The influence of pile length,radius,harmonic loading amplitude,and loading frequency on vibration mitigation were also studied.The obtained results can provide deeper insights into trenching performance under harmonics and transients vibrations.5.A series of large-scale 1-g model pile tests were performed to effectively design the pile foundation in sand and clay.The DLT and SLT were conducted on the fully instrumented piles to assess their stiffness and capacity.The characteristics of loading rate,loading test sequence,and cyclic effect were experimentally evaluated.Also,the axial force,skin friction distribution,and velocity response along the pile were examined.The conclusions drawn from the experimental study would contribute to the efficient,economical,and effective design of pile foundations in different soils under seismic loading.