深埋风积沙隧道施工工法及围岩变形特征研究

风积沙作为一种抗剪能力弱、黏聚力低、自稳能力差的土体,隧道开挖时围岩变形难以控制,研究风积沙隧道的围岩变形特征及其适用的施工工法则显得尤为重要。依托蒙华铁路王家湾隧道穿越风积沙段,通过室内试验得到相关参数,采用有限差分法进行数值模拟,对比分析有无水平旋喷桩加固两种工况的围岩变形和塑性区发展,从而得出三台阶法、三台阶临时仰拱法、三台阶七步法、CD法以及双侧壁导坑法5种工法的变形特征和水平旋喷桩的加固效果。研究结果表明,(1)在无水平旋喷桩加固围岩的情况下,双侧壁导坑法最适用于大断面深埋风积沙隧道,但其控制效果仍然不能满足变形要求;(2)采用水平旋喷桩加固后,三台阶加临时仰拱法最适合于大断面深埋风积沙隧道;(3)水平旋喷桩与三台阶加临时仰拱法结合能够有效控制围岩变形;(4)水平旋喷桩能够显著控制上半部分围岩变形大小,并减缓全环围岩变形速率,但对下半部分围岩变形大小控制不明显。

Study on Construction Method and Deformation Characteristics of Surrounding Rock in Deep Aeolian Sand Tunnel

With aeolian sand as a kind of soil with low shear strength, low cohesion and poor self-stability, it is difficult to control the surrounding rock deformation of the tunnel in aeolian sand. It is particularly important to study the surrounding rock deformation characteristics of the aeolian sand tunnel and its applicable construction method. Relying on the Wangjiawan Tunnel of Menghua Railway, this paper obtains relevant parameters through laboratory tests, uses finite difference method to conduct numerical simulation, and compares and analyzes the surrounding rock deformation and plastic zone development with or without horizontal jet grouting pile reinforcement. Thus, the deformation characteristics of the three-step method, the three-step temporary inverted arch method, the three-step seven-step method, the CD method and the double-wall guide pit method, and the reinforcement effect of the horizontal jet grouting pile are obtained. The research results show that: 1) In the case of no surrounding horizontal jet grouting pile reinforcement, the double-wall guide pit method is most suitable for large-section deep-buried aeolian sand tunnel, but its control effect still can not meet the deformation requirements; 2) With horizontal jet grouting pile, the three-step plus temporary inverted arch method is most suitable for the large-section deep-buried aeolian sand tunnel; 3) The horizontal jet grouting pile combined with the three-step plus temporary inverting arch method can effectively control the surrounding rock deformation of the tunnel. 4) The horizontal jet grouting pile can significantly control the deformation of the surrounding rock in the upper part and slow down the deformation rate of the surrounding rock. However, the control of surrounding rock deformation in the lower part is not obvious.