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Meng G.,HydroChina Itasca Research and Development Center | Meng G.,Hydrochina Huadong Engineering Corporation | Fang D.,Hydrochina Huadong Engineering Corporation | Li L.,Hydrochina Huadong Engineering Corporation | And 2 more authors.
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering | Year: 2013

Preferred discontinuity derived from diagenesis and tectonics reworking always results in the anisotropic characteristics of engineering rock mass. Large-scale engineering rock masses with intermittent joints set have anisotropic strength characteristic, which is influenced by the rock bridge either. So the test results of intermittent joints can not be directly used for ubiquitous joint model, while the equivalent continuum persistent joint parameters should be adopted. When the macroscopic anisotropy simulated by FLAC3D ubiquitous joint model coincides by 3DEC model, the equivalent continuum persistent joint parameters can be defined by inversion analysis. Then, indirectly equivalent continuum method has equal function with discontinuum method in describing anisotropic mechanical behavior of rock mass. In summary, numerical experiment has become a more effective way than analytical method to estimate the macroscopic parameters with random intermittent jointed rock mass. Result shows that the equivalent strength of the equivalent continuum persistent joint parameters by the combined effects of intermittent joints and the rock bridge is higher than that of the real intermittent joints. In addition, in order to keep the definition of the set of directions where the strength of the equivalent discontinuities is equal to the strength of the intermittent discontinuities containing rock bridges, the most likely apparent dip direction of the ubiquitous joint model should have (φj-φj)/2 separation angle with the real dip direction of the intermittent joints.


Fang D.,Hydrochina Huadong Engineering Corporation | Liu N.,Hydrochina Huadong Engineering Corporation | Zhang C.,CAS Wuhan Institute of Rock and Soil Mechanics | Chu W.,HydroChina Itasca Research and Development Center | Chen X.,Hydrochina Huadong Engineering Corporation
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering | Year: 2013

Water diversion tunnels #1 and #3of Jinping II hydropower station are bored by tunnel boring machine(TBM). The rockburst risk is high in the middle alignment. For the purpose of establishing reasonable boring scheme and rockburst control measurement, based on previous researches, different numerical methods are used to evaluate different pilot boring schemes' effects on reducing the rockburst risk, combining with actual situation. All these three pilot boring schemes can obviously reduce the rockburst risk. The selection of pilot boring schemes depends on the equipment and economic benefit factors. So, rockburst risk control measurements for large diameter TBM boring in high stress region are proposed. During TBM boring, the measurements of pilot, stress relieving blasting, assisting timely, systemic and high quality support are applied to reduce rockburst risk and ensure construction and structure safety.


Zhang C.,Hydrochina Huadong Engineering Corporation | Liu N.,Hydrochina Huadong Engineering Corporation | Zhu H.,HydroChina Itasca Research and Development Center | Chu W.,HydroChina Itasca Research and Development Center | Wu J.,HydroChina Itasca Research and Development Center
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering | Year: 2013

The marble of Jinping II hydropower station diversion tunnel shows a phenomenon of crack propagation with time under high geostress, which impacts significantly the run-time safety of diversion tunnel. The lag fracture after excavation, monitoring results by bolt stress meter and sound wave test all reflect the characteristic of crack propagation with time. The laboratory test and numerical analysis are adopted to prove that the fracture is the main response way of marble after excavation, which indicates that a bolt stress meter and sound wave test have better applicability, and multipoint displacement meter sensitivity is worse. The behavior of GSI decreasing exponentially with time is used to stand for marble strength decreasing with time, and further behalf on tunnel excavation damage zone increasing with time. Based on the theory, the stress corrosion(SC) model is set up. The obtained field monitoring and testing data are used to check the related parameters of SC model. The long-term mechanical response of marble, anchor stress state and lining structure security are analyzed in detail;and these characteristics consist well with the actual excavation response.


Cui Z.,Hydrochina Huadong Engineering Corporation | Cui Z.,HydroChina Itasca Research and Development Center | Cui Z.,Tianjin University | Hou J.,Hydrochina Huadong Engineering Corporation | And 4 more authors.
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering | Year: 2014

The time-dependent propagation of cracks was observed from the failure of field surrounding rock and the monitored data of the water diversion tunnels in Jinping and became the dominating factor of the long-term stability of the tunnel. A long-term loading test was conducted on the marble from Jinping leading to the establishment of a fitted formula for the time-dependent behavior and a threshold ratio of driving stresses. A numerical specimen based on CPM model was set up considering the transitional characteristics from brittle-ductile-plastic and a numerical test of long-term loading was performed. A full scale PFC-based model was constructed for the water diversion tunnel and the long-term stability of the tunnel with various depths and rock types was assessed. It was found that in the test the failure time varied with the loading level exponentially. The subcritical crack began to expand if only a threshold of stress level, termed as the critical ratio of driving stresses, was reached. The ratio is 0.492 for Jinping marbles. The CPM-based numerical specimen reproduced nicely the triaxial behavior and the effect of confining pressure. The growth trend of the crack numbers was notable under the lower confining stress, but less noticeable under the higher confining stress. The number of the tensile cracks remained unchanged under the higher confining stress. During the numerical test of long-term loading, the axial strain and the growth of the number of cracks were in accordance with the three stage curve of creep. As the ratios of the driving stresses decreased, the strains due to creep increased. The development of the cracks due to the stress corrosion was also in accordance with the three stage curve of creep. A smaller ratio of driving stress led to a linear growth of the number of cracks of stress-corrosion but an exponentially decreased rate of growth of it. The results of the full scale PFC simulation suggested that after 100 years, the fracture zone of the tunnel would be with the range of 2.1-3.1 m for the class II marble and 3.3-4.5 m for the class III marble. It was thus confirmed that the long-term stability of the water diversion tunnel could be guaranteed.


Liu N.,Hydrochina Huadong Engineering Corporation | Zhang C.,CAS Wuhan Institute of Rock and Soil Mechanics | Chu W.,HydroChina Itasca Research and Development Center | Zhu H.,HydroChina Itasca Research and Development Center | And 2 more authors.
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering | Year: 2013

According to the characteristics of chlorite schist in Jinping II hydropower station, in the same section, multiple monitoring means including the deformation, stress and borehole TV were adopted to analyze the internal mechanical state of surrounding rock. In order to understand the engineering mechanical properties of chlorite schist and its impact on the deformation failure mechanism, uniaxial and triaxial compression tests, grouting penetration test and triaxial rheological test were carried out. And the test results revealed many factors of deformation, instability and destruction of chlorite schist, and provided reference for determination of supporting measures. The stability of chlorite schist depends mainly on whether the lining structure can resist the squeezing effects caused by rheology and water softening. By introducing softening coefficient and Burgers rheological model, the surrounding rock stability from the viewpoint of the force of the lining structure was evaluated. The results of numerical calculation show that the lining structure is in high safety redundancy.

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