Research On Mechanism Of Sonic Vibration Drilling Grouting In The Silty Fine Sand Formation

Silty fine sand formation is soft and weak,which is usually founded in urban underground integrated corrider,subway,foundation,dam,reservoir,tunel and other construction engineering.This kind of formation has loose structure,poor self-stability,and is easy to burst that leads to accidents.The reinforcement and seepage prevention treatment of this stratum has always been a hot spot in engineering research.Sound frequency vibration grouting technique is a new type of grouting method,which uses a pair of reverse eccentric axis of rotation to produce the excitation force of 50²00Hz to liquefy the fine sand formation.In the meanwhile,the slurry was injected into the stratum for seepage prevention and reinforcement,which can effectively improve the quality of the diffusion area and the consolidation body of the slurry.In this paper the technique of sound frequency vibration drilling grouting in fine sand strata is studied.After the establishment of the mathematical model and the experiment method,the strengthening mechanism of the vibration liquefaction characteristics and the law of the slurry diffusion are studied.A slurry diffusion model including vibration parameters,slurry parameters and soil parameters was established,which was verified by laboratory test.Further study was carried out on the optimization of the sound frequency grouting process that is helpful for the guidance of grouting reinforcement for seepage prevention project.The main contents and conclusions of this paper are as follows:?1?The soil characteristics under vibration are studied by FLAC^3D.The variation of pore water pressure at different depth of nodes is obtained.There is a sharp change area for the pore-water pressure after the vibration begins.It rises sharply and then drops sharply near the drill pipe,which is opposite in other area.The variations of node displacements in different depth are:at about 0.018 second,the velocity of dissipation of pore-water pressure has been slowed down,and the soil has basically stabilized with almost no displacement.?2?To achieve the purpose of solving flow resistance under different vibration conditions?amplitude,frequency and duration?,the Fluent software was used to get the flow resistance coefficient and flow resistance.The working conditions were calculated with the parameters:the physical diameter of the soil particles is 0.08mm,the size of the slurry is 1400,the amplitude is 0.3mm,the frequency is 80Hz,and the vibration time is 1 second.It is concluded that the flow resistance changes periodically with time,and the maximum flow resistance is 3.4×10^-7 N,vibration reduces the flow resistance and increases the slurry diffusion distance.?3?The prediction model of the effect of vibration grouting is put forward and the diffusion distance of the slurry in the formation is calculated based on the theory and the related computational method by Fluent.The UDF mathematical model is programmed by the C language using the vibration parameters,the pressure parameters,the slurry and soil parameters.The relationship between these three aspects and the law of grouting diffusion is established.It is reasonable to optimize the interval of the grouting hole to be 40mm according to the simulation results.?4?To ensure the successful conduct of the vibration grouting experiment,the volume ratio of eerous silica fluoric acid,water glass?35 degrees Bé?and water is1:8:4.The maximum allowable grouting pressure of the slurry is determined to5.75×10⁴Pa by the static pressure grouting experiment.The experimental results show that the diffusion radius of slurry increases with the increase of amplitude,frequency and vibration holding time.The change of axial diffusion distance of slurry is not significant after reaching a certain value.Because the flow resistance of sandy soil is less than that of cohesive soil,the diffusion radius and the axial diffusion distance of fine sand is larger than that of cohesive soil.?5?The results of laboratory experiments and numerical simulation show a consistent trend:the maximum relative error of the different frequencies and amplitudes is 13.5%,while the maximum relative error for different vibration holding time is 24.3%.All the results by laboratory experiment validate the prediction model of vibration grouting.