Research On The Seepage Characteristics Of Slurry Through Coarse-Grained Soil And Impervious Characteristics Of Slurry Cake

In the foundation engineering, bored concrete pile and cutoff wall's excavation depth become bigger and bigger, geology condition become more and more complex, along with our country infrastructure construction scale magnification and function expansion. How to ensure engineering quality and engineering go on wheels while drilling hole(such as bored concrete pile) and excavating deep trench(such as cutoff wall) in such coarse-grained soil bad ground as sand soil, a key link is favorably and safely boring hole and excavating trench, ensuring hole and trench's wall stabilized. As a result of the underground condition complexity as well as the underground construction hiding, it is difficult to detailedly understand the underground situation, specially difficult to detailedly understand slurry seepage process and slurry retaining wall mechanism in slurry retaining wall, therefore it's necessary to reveal slurry seepage mechanism in stratum through experiment, provides the theory basis for slurry retaining wall measure and trench stability analysis.This article is based on this point, firstly designed an apparatus that can really simulates slurry seepage in stratum during the actual drilling hole, and proposed a new parameter---biggest transfusion single grain of hole that can reflect sand soil gradation and void ratio, completed such three kinds of experiments as slurry completely seeping specimen not to form the slurry cake, completely seeping specimen to form the slurry cake and incompletely seeping specimen to form slurry cake under the test condition, obtained the permeability curve of slurry seepage in coarse-grained soil, and slurry seepage process is divide into three stages on the basis of mostly reflecting the actual situation ---incompletely seeping specimen to form slurry cake.Secondly, this article discussed the influence of biggest transfusion single grain of hole, slurry viscosity, differential pressure, sand content and the seepage time to slurry seepage, discovered the influence of single grain most seeping hole and whether containing sand to slurry seepage in a big way, and the influence of sand content number, differential pressure andslurry viscosity and so on to slurry seepage influence is not too big, when Biggest transfusion single grain of hole is bigger, the influence of differential pressure to slurry seepage is also bigger. Meanwhile obtained the terminal conditions of such four kinds of experiments as slurry completely seeping specimen not to form the slurry cake, completely seeping specimen to form the slurry cake, incompletely seeping specimen to form slurry cake and nearly no-seeping to form the slurry cake under the test condition.Finally, this article studied the impermeability of slurry cake through the experiment, discovered that the water seepage in slurry cake does not conform to the Darcy's law, but in order to study the impermeability of slurry cake, still used the Darcy's law to roughly estimate permeability coefficient of slurry cake, discovered its permeability coefficient reaching 10-8cm/s under seepage differential pressure of 75kPa when the slurry cake forming differential pressure is 70kPa, is same with the permeability coefficient of concrete, only its thickness is thinner, the intensity is smaller, and easily is destroyed. Generally speaking, slurry cake formed in the wall construction process has important compensation to reduction of impermeability owing to the flaw of cutoff wall.