Study On Influence Of Soil Stress Path On Grouting Characteristics

With the increasing congestion of urban space,the construction environment of foundation engineering is becoming more and more complicated,which will inevitably affect adjacent existing tunnels,pipelines and above-ground buildings.As one of the commonly used deformation control measures,grouting technology has attracted more and more scholars' attention.However,the existing research does not consider the influence of soil unloading stress path in different regions caused by excavation.Based on this,the experimental study on the grouting characteristics of soil by stress path is carried out.Based on the existing true triaxial and plane strain instruments which can independently control the three-dimensional stress,a set of laboratory grouting model test device which can independently control the three-dimensional stress state and realize the visualization of the displacement field of soil is developed in this paper,and a series of laboratory grouting tests are carried out by using the test equipment.Based on the typical unloading stress path of soil in different areas caused by excavation of foundation,the test is divided into three parts,focusing on the influence of grouting amount,grouting pressure,sand compactness,grouting speed and grouting time interval on displacement field and grouting rate caused by soil grouting under six working conditions,as well as the change rule of grouting pressure or grouting amount with time under different grouting modes.The results showed that:The displacement amplitude of soil caused by grouting decreases with the increase of stress state and compactness of surrounding soil,and increases with the increase of grouting amount and grouting pressure,while the grouting speed and grouting time interval have little influence on soil displacement.The peak grouting pressure increases with the increase of grouting speed and decreases with the increase of grouting time interval.Constant volume mode grouting: after the grouting is completed,the grouting pressure will slowly approach the sum of the soil stress vectors.There is an upper limit of the grouting pressure in a certain stress state of the soil;before the grouting pressure reaches the upper limit of the grouting pressure under this stress state,it will increase with the increase of the amount of grouting,and reach After the limit is slightly reduced.Constant pressure mode grouting: after the grouting is completed,the grouting amount will slowly increase over time,but the rate of increase of the grouting amount is less than one thousandth of the normal grouting speed.Grouting rate: The grouting rate of the soil in all directions is not only affected by the stress state of the soil,but also related to the stress path before the soil.Under different grouting conditions,the slurry always preferentially diffuses in a direction with a small stress value and a direction with a large amount of unloading,which tends to return the stress state of the soil to the state before unloading.