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Liu X.,Tongji University | Liu W.,Shanghai Tongyan Civil Engineering Technology Co. | Liu W.,Tongji University | Suo C.,Tongji University
Modern Tunnelling Technology | Year: 2014

Based on an indoor gypsum model test, this paper discusses the span and height, as well as the area of collapsed arches of surrounding rock with joint spacings of 0.5 m; dip angles of 0°, 30°, 45°, 60°, 90°; and without support. Compared with the values of the Platts theory, there is a nonlinear relationship between the joint dip angle and the collapse height, width, and area, with the minimum values occurring with angles of 45°~60°. The test results are consistent with the calculated ones according to a 2D numerical analysis of the above conditions with UEDC software. Based on a comprehensive analysis of numerical calculations and indoor test results, a calculation method for collapsed arch heights under different joint dip angles is obtained. ©, 2014, Editorial Office of "Modern Tunnelling Technology". All right reserved. Source

Yu W.,Changsha University of Science and Technology | Yu W.,Jiangxi Highway Investment Group Co. | Sang Y.,Shanghai Tongyan Civil Engineering Technology Co.
Modern Tunnelling Technology | Year: 2014

Based on the similarity ratio of 1:10, a tunnel secondary lining model was made in which the depth of a single longitudinal crown crack was one-third of the original lining thickness. With the ground resistance simulated as the spring, the radial load test of the tunnel secondary lining model was carried out, which was reinforced by the new cover arch separated with the original lining by additional waterproof broad, and the deformation law and failure mode of cracked lining after reinforced by separated cover arch were achieved. The results show that under the action of loosening pressure, the loading process of separated cover arch reinforced structure can be divided into three phases: initial loading-radial penetration of the prefabricated crack-radial penetration of the cover arch crown crack-failure of the specimen; the failure load is governed by the haunch section of original lining, and the overall failure property acts as the brittle failure with a failure sequence of key parts as crown cracking-haunch fracture-crown failure. Source

Zhou D.-H.,TU Munich | Cao L.-Q.,China Railway Siyuan Survey and Design Group Co. | Wang X.-X.,Shanghai Tongyan Civil Engineering Technology Co. | Fang S.-T.,China Railway Eryuan Engineering Group Co.
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2010

In order to ensure the security of the construction of a double-arch tunnel with shallow large section and span, which has large span, shallow depth, poor rock stability and complicated geological condition, the extensive measurements of the tunnel are essential. Based on a double-arch tunnel project, the contents, techniques and methods of stress monitoring of the support system are described. The stress characteristics of the tunnel during different excavation stages are monitored and analyzed. Some conclusions are drawn as follows: 1) The construction of the upper stage in the left and right holes, which changes the stress distribution in the support system greatly, is the main point for controlling the stability of the support system; 2) The construction of the upper and lower stages in the right hole is the main point for controlling the stability of the middle wall due to great change of the stress distribution in the middle wall; 3) The longitudinal incidence of the excavation of the upper stage of right and left tunnels are about 1/3 and 1/2 times the tunnel span; 4) The secondary support structure and the enclosing of the lining must be established in time to improve the performance of the lining. The experience and conclusions presented can be referred to in the design, construction and in-situ monitoring of similar tunnels. Source

Liu X.,Tongji University | Liu W.,Tongji University | Sang Y.,Shanghai Tongyan Civil Engineering Technology Co. | Kong F.,Chongqing Construction Science Research Institute
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering | Year: 2015

Based on laboratory model test with 1:10 geometric similarity factor, stacked inner lining has been taken to reinforce the structure with axial cracks on the top lining. With test data, we conclude the failure mechanism of reinforced lining under loose pressure, by analyzing its lateral deformation, development of main cracks, short-term stiffness of lining apex and final failure mode. In addition, we also quantitively study the influence of crack depth on the ultimate bearing capacity. It is important to note that the cracked tunnel works under loose load and the rock resistance coefficient is 10 MPa/m. The results show as follows: (1) the process of failure can be divided into three stages, namely, specimen crack stage, "arch crack-penetrated arch crack", penetrated arch crack-specimen fail. (2) The main cracks in on the vault and haunch, the overall failure mode is brittle failure. (3) There exist linear relationship between existed crack depth and crack moment, short term stiffness, ultimate load. ©, 2015, Academia Sinica. All right reserved. Source

Liu X.-Z.,Tongji University | Ye K.,Shanghai Tongyan Civil Engineering Technology Co.
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2011

The relationships among span, depth, rock grades and vertical surrounding rock pressure are discussed based on the monitoring data of a large number of highway tunnels. A comparative analysis is made for obtaining the relationship between the measured and calculated values of the surrounding rock pressure. And the distribution regularities of lateral pressure, lateral pressure coefficients and secondary lining pressure are statistically analyzed under the conditions of every rock grade. The lateral rock pressure increases slowly with the growth of the depth and rock grade. The lateral pressure coefficient increases with the growth of rock grade and is larger than code value. The load sharing ratio of the secondary lining is consistent with the code. Source

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