Cement-based Materials Experimental Study On Application Of Splitting Grouting In Loess

As far as the western loess region is concerned,the grouting reinforcement technology of pure cement has been applied to engineering practice,but the effects are varies.The existing loess grouting is mostly based on pure cement slurry,the performance of which is difficult to meet the needs in engineering,and the poor configuration is more likely to lead the structural damage of loess and increase its collapse.More importantly,most of the existing loess grouting design reference conditions,but seldom from the loess research results obtained through the test has very important significance to meet the needs of the engineering practice of grouting parameters.This paper is based on the construction of Gansu province science and technology research project "large thickness characteristics of loess structure and foundation optimization research"(Project No.JK2014-34),to study the application of cement slurry on the loess area of split grouting in strengthening engineering.Combined with the laboratory tests of slurry performance,laboratory model tests,field tests and so on,the performance of cement-based slurry and its influence factors,the choice of optimal proportion,the corrosion resistance of stone and its mechanism,the form of slurry fracturing with different grouting parameters and its law,the effect of soil reinforcement are systematically elaborated.The main contents are as follows:(1)Experimental study on the basic properties of slurryBased on the tests of density,syneresis rate,stone rate,viscosity and stone strength of the pure cement slurry,the basic properties of pure slurry are obtained,which provides a reference range for the selection of component content of composite slurry.The conclusion is that the water cement ratio of loess grouting is from 0.6 to 1.2.(2)The analysis of composite slurry performance and the design of optimal proportionWhen analyze the factors of the admixture of cement-based slurry,the performances of cement-based materials were analyzed on the basis of the characteristics of admixture and orthogonal test with the method of range analysis,and the optimal proportion of loess grouting was chosen on the basis of orthogonal comprehensive analysis method.The durability test is designed aiming at the possibility that loess may erode grouting stone,and the corrosion mechanism is analyzed from the microcosmic angle.(3)Study on grouting by laboratory model testsIn order to study the relationship between the effect of loess fracturing grouting and the parameters of grouting process,characteristic parameters of formation and parameters of slurry,the laboratory model tests of grouting is carried out,and some laws of loess grouting are obtained according to three different laboratory tests.The conclusion is that the grouting pressure increases with the increase of time and does not exceed 0.5MPa.Under normal circumstances,homogeneous formations form only vertical single cracks.(4)Field grouting test and its application researchAccording to the laboratory test,the parameters of loess grouting and the design defects of the model are obtained.Combined with the practical engineering,the field test is designed.The interaction mechanism between the rheological morphology of loess fracturing grouting and the soil are analyzed by excavating soil on site.Combined with the geotechnical test,the improvement of the bearing capacity of foundation after grouting is summarized,the preliminary laws of the loess fracturing grouting are obtained and the feasibility of the loess fracturing grouting is verified.Some preliminary attempts has been made in practical engineering,which can effectively resolve some actual problems.These studies have contributed to the grouting reinforcement of foundation.