Experimental Investigation on the Mechanical Properties of Vault Void Lining in Highway Tunnels and Steel Plate Strengthening

In the present study, large-scale specimens based on the tunnel prototype were prepared and static load tests were carried out to investigate the damage caused by lining voids. Based on the strengthening scheme of the tunnel, the strengthened specimens were prepared to explore the strengthening effect on the strengthening structure. The strengthening structure is made of a steel plate fixed with chemical anchor bolts and two-component epoxy adhesive. By analyzing the failure mode, structural deformation, and the relationship between load and strain, the damage caused by vault void with various void heights was analyzed and the obtained results were verified through the experiment. Moreover, the enhancement of the bearing capacity and stiffness of the structure strengthened by surface bonding steel was studied. The obtained results show that the damage caused by the lining void mainly occurs at the void boundary. The damage appears as multiple longitudinal cracks. The crack starts from the lower surface and develops radially. Using chemical anchor bolts and two-component epoxy adhesive to bond the steel plate on the lining surface, the damage can be reduced, and the bearing capacity of the structure can be improved effectively when the void height is a quarter of the second lining thickness, the number of cracks is reduced from 14 to 5 after steel plate strengthening, and the length of the longest crack is reduced from 13.2 cm to 8.3 cm, reduced by 37.12%. The steel plate strengthening also reduces the strain of the lower steel bar at the void boundary from 1130.58 mu epsilon to 555.12 mu epsilon, and the strain decreases by 50.89%. The experimental results show that the position where the void has the greatest impact on the lining is at the void boundary. Therefore, when steel plates are used to strengthen the void lining, the void boundary should be emphasized, which makes the strengthening more accurate and saves the cost of treatment.

在本研究中，制备了基于隧道原型的大尺寸试件，并进行了静载试验，以研究衬砌空洞造成的损伤。根据隧道的加固方案，制备了加固试件，以探究对加固结构的加固效果。加固结构由化学锚栓和双组份环氧胶粘剂固定的钢板组成。通过分析破坏模式、结构变形以及荷载与应变的关系，分析了不同空洞高度的拱顶空洞造成的损伤，并通过实验验证了所得结果。此外，还研究了表面粘贴钢板加固结构的承载力和刚度的提高情况。所得结果表明，衬砌空洞造成的损伤主要发生在空洞边界处。损伤表现为多条纵向裂缝，裂缝从下表面开始并呈放射状发展。采用化学锚栓和双组份环氧胶粘剂将钢板粘贴在衬砌表面，当空洞高度为二次衬砌厚度的四分之一时，能够减少损伤，有效提高结构的承载力，钢板加固后裂缝数量从14条减少到5条，最长裂缝长度从13.2厘米减少到8.3厘米，减少了37.12%。钢板加固还使空洞边界处下层钢筋的应变从1130.58微应变减少到555.12微应变，应变降低了50.89%。实验结果表明，空洞对衬砌影响最大的位置在空洞边界处。因此，当使用钢板加固空洞衬砌时，应着重考虑空洞边界，这样能使加固更精准，节约处理成本。