Gordian Technique Of Cement And Sodium Silicate Composite Grouting Reinforcement In Sand Gravel Strata

Abstract:At present, with the rapid development of economy, geotechnical engineering construction at the edge of the mountain and river become more and more. And different thickness sand pebble bed is common. The majority of the sand pebble bed is loose, poor cementation and strong instability. Therefore the process of the subway foundation pit excavation may lead to larger ground deformation, adverse impact, accident and casualties. So reinforcing sandy pebble stratum by grouting is frequently used to improve the bearing capacity and strengthen the engineering safety. But choosing grouting method, material selection and preparation mostly depends on the practical engineering experience and lack scientific theory to guide. And theoretical simulation research of the grouting reinforcement technique is difficult because of the complexity of grouted ground and the concealment of grouting engineering. So the study of sand gravel strata grouting technique is more urgent.In this paper, according to the characteristics of sandy pebble formation, the risk of its construction was analyzed and the corresponding safety management measures are put forward. Grouting method, material and theory are included. The grouting design plan of one station in Changsha subway and the relevant economic feasibility analysis are also contained. The following are the conclusions:(1) Small duct grouting, sleeve valve pipe grouting, pipe roof grouting, in deep hole fixed hole grouting and curtain grouting are frequently-used grouting methods in the sand gravel strata according to the construction works nearly a decade.The first four are commonly used in the underground engineering such as subway to reinforce sand pebble bed, while the curtain grouting is commonly used in dam of sand gravel dam foundation seepage control and water plugging. Cement, cement sodium silicate grout, cement clay grout and flyash cement grout are frequently-used grouting materials on site.The first two are more commonly.(2)In order to improve the performance of cement-sodium silicate, Contrast experiments were did when there were two kinds of admixtures. The experiments include gel time experiment, stone rate experiment, compressive strength experiment, lixivium pH experiment and durability test on the condition that the admixture and its mixing amount, water cement ratio were different. Then the cement-sodium silicate composite grouting material with better performance and its optimal proportion were got.(3) Grouting theory of sandy pebble was discussed. The theory of osmotic grouting, compaction grouting and filling grouting are suitable for sandy pebble stratum grouting. The formula of Bingham fluid seepage in sandy pebble stratum was constructed.(4) Grouting reinforcement design of foundation pit sandy pebble stratum in a Changsha subway station was did. The economic feasibility of composite slurries was proved according to the contrastive analysis of other common grout.