Abstract:With the further clarification and deepening of planning, social and economic development, and the improvement of people's living standards, the phased implementation and expansion and reconstruction of underground space development are very common. The structural extension of the joint points and the waterproofing of the seams are an unavoidable technical challenge. For underground structures of different types and scales, the joint treatment has certain commonalities as well as distinct characteristics, and the targeted research is needed. Based on an actual deep-buried excavated tunnel, the construction procedures and requirements for the removal of the retaining isolation wall and the connection of the structure in the first phase of the tunnel extension project, as well as the waterproofing treatment of the joints are introduced in detail. By setting up the reinforced concrete supports, purlins and temporary vertical steel structure columns under the isolation wall, the isolation wall removed in sequence is ensured. The structural interfaces shall be treated as construction joints. In the early stage of construction, the upper part of the structural plain concrete is retained, the lower part is crushed and rebar is planted and effectively connected. On the new and old junction surface, the cement crystalline waterproof coating is applied, and the water-swelling waterstop strips and waterproof mortar are used. By integrating measures such as pressing in high-elasticity sealing strips and large-width water collection boxes, the structure is ensured to be safe and continuous, and the probability of leakage is minimized and the efficient drainage is achieved. It can be seen that the above-mentioned scheme will not cause additional engineering volume or excessive demolition volume, which is in line with the overall development concept of green and low-carbon. The on-site implementation effect is good, which can be used as a reference for similar projects.
