Project Overview

      The Beijing East Sixth Ring Road Reconstruction Project starts from the Jingha Expressway in the south and extends to Luyuan North Street in the north, with a total length of 16 km. Among them, the tunnel has a total length of 9.16 km, an outer diameter of 15.4 m and an inner diameter of 14.1 m, making it the largest-diameter shield tunnel project in northern China to date.

      The project presents extremely complex construction conditions and technical challenges, including large burial depth of the passage, water-rich strata, high confined water head, large segment thickness and high hole-forming accuracy requirements. During tunnel boring, surface risk sources are dense, the underground space environment is complex, and there are many factors controlling the boring.

Construction Highlights

In this project, horizontal MJS high-pressure jet grouting reinforcement is adopted to reinforce the pedestrian cross passage in advance. The reinforcement piles have a diameter of 2.4 m, with a designed minimum pile interlock of 40 cm and a maximum of 100 cm, forming a fully enveloping support structure to ensure excavation safety.

(1) The cross passage has a large burial depth and lies in water-rich sand layers, so water and sand inrush are highly likely to occur when openings are cut in the segments; therefore, blowout prevention and control during opening cutting are extremely important. The crown burial depth is 63 m, and the maximum water and earth pressure reaches about 0.7 MPa.

(2) The interior space of the box culvert is small, so construction of the lower MJS piles is restricted by the working space. Therefore, work inside the box culvert places higher demands on the coordination and cooperation of personnel.

(3) For the power head device and drilling accuracy control, since the east and west lines are spaced relatively far apart with an average length of about 20 m, it is necessary to repeatedly confirm whether the power head is installed at the center of the drill hole. High drilling accuracy is required during pilot hole drilling, and deviation correction by inclination surveying must be carried out multiple times; on-site inclination surveyors must be proficient in the use of gyroscopes.

(4) For the firmness of the blowout prevention device installation, on-site construction personnel are required to follow the embedment depths of the chemical anchors and the orifice pipe. The chemical anchors must be driven to a depth of not less than 20 cm, and the orifice pipe must be embedded to a depth of not less than 38 cm.

Tunnel Lifting Platform 

JS-5000-5‍

      Shanghai Jiuzhuo has deployed multiple sets of equipment to participate in the MJS horizontal reinforcement construction. At the same time, based on its "horizontal MJS reinforcement construction technology," it has launched the Tunnel Lifting Platform. This platform is specially designed for tunnel reinforcement work and offers a wide reach. It is the ** equipment for medium- to heavy-load lifting and working coverage, providing strong technical support for project construction.

Specifications

Maximum lifting capacity:5000 Kg (net weight)

Working pressure:13 MPa

Maximum working stroke:5 m

Total power:11 kW

Applicable tunnel height:7.5 m

Equipment weight:10000 kg

Dimensions (L x W x H):7400 x 6200 x 7150 mm‍

      The Tunnel Lifting Platform JS-5000-5 is mainly used for the placement and positioning of MJS construction equipment, solving the problem that MJS horizontal reinforcement process equipment must be continuously raised as the pile positions change, and has had a hugely relevant impact on the progress of the entire project construction.