Experimental study on mix proportion optimization of anti-calcium dissolution shotcrete for tunnels based on response surface methodology  

作　　者：Chongming Tian Yueping Tong Junyuan Zhang Fei Ye Guifeng Song Yin Jiang Meng Zhao 

机构地区：[1]School of Highway,Chang’an University,Xi’an 710064,China [2]Yunnan Laman Expressway Co.,Ltd.,Yunnan Xishuangbanna 666300,China [3]Hebei Traffic Planning Design Institute,Shijiazhuang 050035,China

出　　处：《Underground Space》2024年第2期203-220,共18页地下空间（英文）

基　　金：funding provided by the Project of Yunnan Provincial Department of Transportation(Grant No.yjkjb[2019]No.59);the Fundamental Research Funds for the Central Universities,CHD(Grant No.300102212706).

摘　　要：Aiming at the issue of crystallization and blockage of drainage system due to the massive calcium loss from the tunnel shotcrete,a selfdesigned tunnel seepage crystallization modelling system was developed.This system was produced in conjunction with the initial tunnel support shotcrete construction and drainage pipe installation,and is capable of simulating both the seepage process of groundwater in the shotcrete and the process of crystallization in the drainage pipe.Based on three different mechanisms of anti-crystallization,which include absorbing free calcium,reducing the porosity and increasing hydrophobicity,antialkali agent,nano-calcium carbonate,and silane were selected to test,respectively.Firstly,the suitable dosing ranges of these three external admixtures for resisting calcium loss in shotcrete were determined by single factor tests,which were 7%–11%,4%–8%,and 0.3%–0.5%,respectively.Thereafter,the response surface method was employed to evaluate the interaction of antialkali agent,nano-calcium carbonate and silane on calcium loss in shotcrete,and to establish the relationship between them,and thus to determine the admixture ratio that can effectively reduce calcium loss crystallization in shotcrete,with the optimal admixture amounts of antialkali agent being 9.242%,nano-calcium carbonate 4.889%and silane 0.366%.Lastly,the reliability of the model test results was verified by the microscopic analysis,and the results showed that the total amount of calcium dissolution in the optimized group could be reduced by 75%compared with the blank control group,and was basically consistent with that derived from the response surface regression model,validating the high accuracy of the buildup response surface regression model.The present study can provide some ideas and references for reducing the seepage crystallization behavior of groundwater in the initial tunnel support shotcrete.

关 键 词：Tunnel engineering Calcium loss Crystallization blockage Model test Response surface methodology Interaction effect 

分 类 号：U45[建筑科学—桥梁与隧道工程]