全断面开挖隧道喷射混凝土早期力学强度与抗渗性能试验

Early Mechanical Strength and Water Penetration Resistance Test of Tunnel Shotcrete Based on Full-Section Construction Method

针对全断面施工方法下喷射混凝土早期力学强度与抗水渗性能的高性能化需求问题,选取郑万高铁宜兴联络线某隧道斜井全断面开挖工况,采用混凝土材料性能测试、实体施工验证以及水化微观分析等方法研究喷射混凝土设计强度等级与全断面隧道施工方式的适应性。试验结果表明:1)与模筑混凝土相比,喷射混凝土的早龄期小时强度发展更快,随设计强度等级从C25提高至C40,喷射混凝土8 h抗压强度从3.2 MPa提升至7.0 MPa;2)喷射混凝土的抗水渗性能与其28 d抗压强度遵循良好的线性正相关性;3)与C25喷射混凝土相比,C35喷射混凝土内部的层状C-S-H凝胶数量及致密性明显增加,并充分填充了速凝产物钙矾石形成的骨架孔隙,进而促进了喷射混凝土力学强度及抗水渗性能的提高;4)在全断面施工工况下C35高性能喷射混凝土施工后,采用实体射钉法测试8 h力学强度达到6.0 MPa以上,有效降低了初期支护的早期位移变形及累计变形量。

To investigate the early mechanical strength and water penetration resistance of tunnel shotcrete under fullsection construction method,a case study is conducted on an inclined shaft of the Zhengzhou-Wanzhou railway constructed by full-section method.Then,the adaptation between designed strength grade of shotcrete and full-section construction method is analyzed via concrete performance test,actual construction verification,and hydration microscopic analysis.The test results reveal the following:(1)The early age mechanical strength of shotcrete per hour develops faster than molded concrete.The eight-hour compressive strength of shotcrete increases from 3.2 to 7.0 MPa when increasing the designed strength grade from C25 to C40.(2)The water penetration resistance of shotcrete is positively and linearly related to 28-day compressive strength.(3)The magnitude and compactness of plate-like C-S-H in the C35 shotcrete perform better than C25 shotcrete,which can reduce the porosity of hydration microstructure induced by rod-like ettringite crystal,thus increasing 28-day compressive strength and enhancing water penetration resistance.(4)The eight-hour mechanical strength of primary support structure after applying C35 high-performance shotcrete reaches 6.0 MPa,effectively reducing the early and accumulated displacement deformation of primary support.