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Liu X.,Tongji University | Wang X.,Tongji University | Lin L.,Chongqing Construction Science Research Institute
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering | Year: 2013

The paper conducts the research on the force-deformation mechanism under the effects of stick-slip dislocation of the normal fault with 75° obliquity by making use of 1:50 model experiment. And the strata pressure of the tunnel vault and bottom, axial strain and hoop strain are monitored. Result shows that with the normal fault rupture propagating in the overburden layer, the tunnel structure which is orthogonal to the normal fault will undergo relatively big shear displacement. The strata permanent deformation and the interaction between the strata and the tunnel structure causes the formation pressure changes significantly, of which the pressure on the vault in the hanging wall zone increases significantly, followed by the pressure on the vault in the foot wall zone. The pressure on the tunnel bottom in the hanging wall zone decreases, while greatly increases in the foot wall zone. That leads the tunnel being possibly separated from the wall rock so as to accommodate the shear displacement of the fault. The longitudinal bending moment in the hanging wall zone is positive and negative in the foot wall zone. By judging the lining failure from the cement prototype under compression, the maximum allowed fault displacement of the prototype structure D = 1.25 m is determined. Theoretically, the value is overestimated.


Liu X.,Tongji University | Lin L.,Chongqing Construction Science Research Institute | Wang X.,Tongji University | Li X.,Chongqing Construction Science Research Institute
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering | Year: 2013

Based on the project of the tunnel crossing the normal active fault whose dip angle is 60°, the length of segment is 0.5D(D is the diameter of tunnel) and flexible connection between two segments design is adopted in articulated tunnel. Through a model experiment, the deformation characteristics of tunnel with flexible joints are discussed. The experiment results show that the longitudinal strain and transverse strain of articulated tunnel change greatly in the range of 1D near the fracture plane. The tunnel failure mode is the combined rotation and slab staggering, the rotation angle is 33° and 28°, and the deformation range is 2.5D. Compared the tunnel where the anti-breaking measures are taken with the flexible tunnel, under the same experiment condition, the result indicats that the longitudinal strain of tunnel with flexible joints is smaller than the complete tunnel's, and the deformation range of the flexible tunnel is smaller than that of the complete tunnel.


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.


Liu X.,Tongji University | Wang X.,Tongji University | Lin L.,Chongqing Construction Science Research Institute
Tumu Gongcheng Xuebao/China Civil Engineering Journal | Year: 2014

The force-deformation mechanism and failure process under the effects of stick-slip dislocation of the normal fault with 60° obliquity is studied by a 1:50 model experiment. The strata pressure of the tunnel vault and bottom, axial strain and hoop strain were monitored. The result show that with the normal fault rupture propagating in the overburden layer, the tunnel structure orthogonal to the normal fault emerge relatively big shear displacement. The strata permanent deformation and the interaction between the strata and the tunnel structure cause the formation pressure changes significantly. The pressure on the vault in the hanging wall and the shear zone increases significantly, followed by the pressure on the vault in the foot wall. The pressure on the tunnel bottom in the hanging wall and the shear zone decreases, while the pressure in the foot wall increases. The tunnel may possibly separate from the wall rock to accommodate the shear displacement of the fault. The longitudinal bending moment is positive in the hanging wall and the shear zone and negative in the foot wall zone due to the eccentric pressure in tunnel. By evaluating the lining failure from the cement prototype under compression, the maximum allowed fault displacement of the prototype structure is determined as D=0.3 m, which is overestimated in theory. Tunnel lining fracture length is 0.75 and 1.5 times the width of the tunnel in the shear zone and foot wall zone respectively.


Liu X.,Tongji University | Li X.,Tongji University | Sang Y.,Shanghai Tong Yan Civil Engineering Ltd. | Lin L.,Chongqing Construction Science Research Institute
Tunnelling and Underground Space Technology | Year: 2015

Understanding earthquake fault rupture propagation is important in building and lifeline engineering, especially in the construction of mountain tunnels. Thus, studying rupture propagation in strata and tunnel failure with fault displacement is significant. For this purpose, an experiment has been designed to simulate normal fault displacements with different dip angles. The influence of normal faults on tunnels has been observed by examining the rupture and strata deformation and analyzing the shear zone, tunnel stain, position, and forms of tunnel cracks. The results show that more than one strata rupture appears when the normal fault moves, and at least one rupture reaches the ground surface as the vertical fault dislocation is approximately 4.4% of the covering depth. In general, those ruptures form an inverted triangle zone in which strata deform significantly. The range of the rupture shear zone increases as the fault dip angle decreases. Strata-tunnel -fault can be considered as a beam on an elastic foundation. The lining of the tunnel in the hanging wall and shear zones is subjected to sagging, and that in the foot wall zone is subjected to hogging. Failure modes appear to change with fault dip angle. The lining damage form is flexure failure occurring mainly in the foot wall with the circumferential cracks, when the dip angle is 75°. When the dip angle is 60° and 45°, the failures are caused by a combination of flexure and shear both in the shear and foot wall zones with a lot of circumferential and diagonal cracks. Furthermore, to guide design work reasonably, the calculation method in determining the weak parts of the tunnel and feasible reinforcement measures are discussed. © 2015.


Chen Z.,Chongqing University | Tan D.,Chongqing University | Zeng Y.,Chongqing University | Lin W.,Chongqing Construction Science Research Institute
Chongqing Daxue Xuebao/Journal of Chongqing University | Year: 2016

The environment-induced corrosion of steel bars in concrete results in deterioration of reinforcement-concrete bond properties, and causes the damage of concrete structures. The accelerated corrosion of reinforced concrete specimens and also the pull-out test of the corroded specimens were carried out to study the deterioration of corroded reinforced-concrete bond strength. We used industrial computed tomography (ICT) scanning to exam the cracking of the concrete cover of the specimens caused by corrosion. According to the pullout tests, the ultimate shear capacity and the corresponding displacement of the corroded specimens are degraded with the corrosion extent, and the bond stiffness is depressed. The analysis based on the experimental results shows that the thickness of corrosion products, other than the corrosion ration of steel bars, influences the corroded expansion force and the degradation of bond strength more directly. By introducing the factors of the thickness of corrosion, the ratio of thickness of concrete coat to the steel bar's diameter, and the tension strength of concrete, a bond strength model of corrosion reinforced-concrete is proposed. The practicability of the suggested model is proved by experimental data. © 2016, Chongqing Medical University. All right reserved.


Lin J.,Chongqing University | Lin J.,Chongqing Jiaotong University | Zhang C.,Chongqing Jiaotong University | Liu X.,Chongqing Construction Science Research Institute
Electronic Journal of Geotechnical Engineering | Year: 2014

A processing technology of ultrasonic signal of concrete is developed in this study, and a tentative experiment has been conducted on polymer modified cement concrete which is widely used. By filtering through 297 kinds of traces of polymer modified cement concrete samples tentatively mixed, we acquire a proper mix proportion, according to which, a total of 75 groups of 225 polymer modified cement concrete specimens are produced. After further selective preference of these specimens, ultrasonic test is done on the selected ones under different loading conditions. Afterwards, signal processing is accomplished by using the developed processing technology of ultrasonic signal of concrete and we preliminarily find a kind of acousto-elastic sensitive concrete material which is comparatively sensitive to stress. This kind of material is produced by mixing epoxy resin, styrene-acrylic emulsion, acrylic emulsion, auxiliaries and iron powder together into cement concrete. The sensitivity of ultrasound and stress of this kind of modified concrete behaves preferably well as follows: at the low stress stage, not only the correlativity curve of ultrasound velocity and stress but also the correlation curve of weighted spectrum area and stress arise apparent. If this kind of material can be applied to the practical engineering successfully, the acousto-elastic test accuracy of the concrete service stress will be greatly improved. © 2014, EJGE.


Li W.,Chongqing University of Science and Technology | Liao X.,Chongqing Construction Science Research Institute | Miao G.,Chongqing University of Science and Technology | Zhou X.,Chongqing University of Science and Technology
Advanced Materials Research | Year: 2012

To identify current situation of built environment in underground shopping malls, the study based on both field test and questionnaire investigation was carried out in underground shopping mall A and B in Chongqing in P.R. China. It analyzed the current situation of indoor thermal environment, light environment, sound environment as well as air quality. It found that the most prominent issue was indoor ventilation, and then air quality, thermal comfort and noise sequentially. Light and moisture problem was easy to be overlooked. Based on the current issues, it puts forward several measures to improve the built environment of underground shopping malls in this study. © (2012) Trans Tech Publications, Switzerland.


Chen Y.,Chongqing Jiaotong University | Zhou J.-T.,Chongqing Jiaotong University | Zhang H.,Chongqing Jiaotong University | Shen P.-W.,Chongqing Construction Science Research Institute
Wuhan Ligong Daxue Xuebao/Journal of Wuhan University of Technology | Year: 2014

Under repeated dynamic loads, fatigue conditions of the reinforced concrete bridge arouse more and more people's attention recently. The real-time fatigue state assessment method of existing bridge was proposed, based on the failure criterion of concrete in compression zone. Firstly, according to the rule that the fatigue damage maximum total strain under repeated cyclic loads equals to the strain corresponding to the softening period maximum stress under monotonic loads, the failure criterion of concrete in the compression zone was clearly illustrated. Secondly, with the aid of the MATLAB programming and based on the setting threshold, the statistics and the acquisition of probability density function of real-time monitoring data were realized. At last, based on the method proposed, the fatigue state of Bridge Gaoligong mount was evaluated. According to 966180 measuring points, the fatigue failure probability was put forward when a particular strain is produced.


Dong Q.,Chongqing University of Science and Technology | Wan H.,Chongqing University of Science and Technology | Kong F.,Chongqing construction science research institute | Zhao B.,Chongqing University of Science and Technology
Applied Mechanics and Materials | Year: 2013

Three-dimensional finite element model of tunnel-soil-structures interaction was set up to analyze the causes of settlement and structural cracking when tunnel crossing complex gravelly soil area. It simulated the real tunnel excavation process of Chongqing Metro Line 3. Based on analysis and monitoring results, improved technical measures were used to control settlement, such as advance strengthening, excavation speed control and so on. The latest monitoring results indicate that vault and ground settlement are controlled, and convergence value is reduced significantly. The 3D numerical simulation analysis method provides reference for similar projects, and improvement of technical measures is conducive to settlement control. © (2013) Trans Tech Publications, Switzerland.

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