| The shield section of Datang station from Kecun to Datang, No. 3 line of Guangzhou subway is two separated single line tunnels. Depth of burying for profile of the tunnels is from 9.6 m to 31.3m, of which total tunneling length being 2967m. Interval of two lines is from 15.2m to 11.2m. It has totally four plane curve sections, radius of the curve is 1000m. Total length of the curve sections accounts for 54% of whole alignment. Maximum gradient of the section line is 3.0 %, while minimum gradient is 0.8%, and maximum length of the slope is 365m. The alignment is concentrated with architectures and more in allocated underground pipelines.The tunnels pass through mainly strong weathering zone (stratum No.7), medium weathering zone (stratum No. 8), light weathering zone (stratum No.9 ) and partially plastic or light dense residual soil (stratum No.5-1), hard plastic or medium dense residual soil (stratum No.5-2 ), rock fully weathering zone (stratum No. 6 ), siltstone and sandrock appear in it. Head part of the tunnel is mainly medium and strong weathering stratum and eluvium.Out diameter of circle to the tunnel within the shield section is 6.0m,while inner diameter is 5.4m. Thickness of segment is 300mm, of whichwidth being 1.5m. It has six separated blocks in total. Space between thecircles is built with break joint assembly method and C50 S12 concrete isused for the segments.One set shield has been adopted for the construction. It has been proposed to start the work from the right line, go down the tunnel excavated with mine tunneling method, via middle air shaft, and make turn within the retrace line in the undercutting section, then make the left line construction, again go down the tunnel excavated with mine tunneling method, via middle air shaft. It will be disintegrated and removed from the shield shaftof the left line.Having studied and made comparison to the geological condition of the works, compound earth-pressure balancing shield has been determined to be used in the works. Tool pan of the shield is designed to have soft and hard styles, which can ensure earth-pressure ballance, half open and open three tunneling models, with synchronous pouring system. Total thrust of the shield is 3421t, torque 450t.m (Max. torque 530t.m). The shield can make tunneling 10m, with 10000 hours longevity to main shaft bearing. The tool is designed to be replaceable and can be removed and installed at back. One over break tool is fitted on the tool pan for monitoring posture during curves construction and direction rectification. All the tool pan, sealed barricade and conveying worm have been designed with foam and bentonite injection pipes and screw of the conveying worm can expand and contract, which can deal with the problem of blocking to the conveying worm. Monitoring system of the shield adopts PLC, which can control the three models effectively. Data gathering and teletransmission system can be office managing tunneling, it's fitted with automatic synchronous pouring system of confirmed pressure and SLS-T APD automatic measuring and guiding system, which can control posture of the shield and assembly accuracy of segments. Style of middle wringing is used for the purpose of adapting to the propelling turn of small radius curves. Propelling jack can control the expanding and contracting activity in group or independently, with 2000mm stroke, which can meet the assembly requirements of 1500mm segments and works of monitoring tunneling direction and deviation rectification can be done well with the fitted over break tool. |
PDF Full Text Request