浅覆土强透水砂卵石地层大直径泥水盾构干接收施工技术

为解决浅覆土强透水砂卵石地层大直径泥水盾构的接收难题，以常德沅江大直径泥水盾构隧道为依托，提出干接收施工技术，采用端头加固区RJP超高压旋喷加固、端头垂直冻结、塑性混凝土连续墙施作的联合加固手段，提高端头加固区整体结构的稳定性，为盾构接收创造条件。在盾构干接收过程中，通过控制各项施工参数、精确掌握施工时机要点，保证盾构顺利穿越既有管线及加固区，管线和地表最大沉降分别控制在6 mm和5 mm以内，确保盾构精确出洞。在洞门钢环内安装洞门刷防止盾构出洞时土体流失，同时增加盾构出洞过程中同步注浆量，并对管片进行槽钢连接固定，保证盾构出洞过程盾尾及支护安全。

Construction Technology of Large Diameter Slurry Shield in Strong Permeable Sand Pebble Stratum with Shallow Overburden Soil

In order to solve the problems of receiving large diameter slurry shield in strong permeable sand pebble stratum with shallow overburden, based on large diameter slurry shield tunnel of Yuanjiang in Changde City, dry receiving construction technology is proposed. The stability of the whole structure in end reinforcement area is improved and the conditions for shield acceptance are satisfied by using the joint reinforcement methods of RJP super high pressure jet grouting, vertical freezing and plastic concrete diaphragm wall in the end reinforcement area. In the process of shield dry receiving, by controlling various construction parameters and grasping the key points of construction timing accurately, shield machine smoothly passes through the existing pipeline and reinforcement area, and the maximum settlement of the pipeline and the surface is controlled within 6 mm and 5 mm respectively so as to ensure the accurate exit of the shield machine. In addition, portal brushes are installed in the steel ring of the portal to prevent soil loss when shield machine exits the tunnel. Meanwhile, synchronous grouting volume is increased and segments are connected and fixed with channel steel to ensure shield tail and support safety during the process of shield machine leaving the tunnel.