Ning Jianguo

Notice of Retraction Creep model for Zonal disintegration of deep rock mass

Base on the Nishihara model ,change Euclid model with the Newton model , change the Newton model in Bingham model with Nonlinear viscous dampers (D model), and extend the number of the Visco-plastic model to n, so can obtain a strong rheology model, example analysis shows that this model can discribe strong rheology and obvious accelerated creep stage of deep rock, and can explain the obvious time effect of Zonal disintegration.

A constitutive model and numerical simulation for zonal disintegration of surrounding rock in deep roadway

In comparison to shallow roadway, disintegrative zone and un-disintegrative zone appear several times alternately in the surrounding rock of deep roadway, which is called Zonal Disintegration. Now, no agreement is established about the mechanism of zonal disintegration in deep roadway. First, based on traditional Nishihara model, the second power strong rheological model is constructed, which can describe full stage creep process of rock, and accelerated creep equation of rock mass is obtained. Second, according to evolution process on zonal disintegration of deep rock, maximum tensile stress criterion, shear failure criterion and the fourth strength criterion are determined as failure judgment criteria of deep rock mass with the priority level decreased. Against the background of mining and geological conditions of 4417 transport roadway, zonal disintegration simulation of surrounding rock is carried out in this roadway with FLAC-3D numerical simulation software, judgment criteria and constitutive equation got in this paper as accelerated creep equation of rock mass, and simulation results are the same as those of field tests.

The safety study of bolt and cable support in shallow roadway

At present, bolt-cable combined support system is still common in shallow roadway, and the design process of bolt-cable combined support system include four steps: initial design, implement design, pressure observation and modification of initial design. For modification of initial design, the rationality of support can be obtained from pressure observation that gives the prediction of deformation in roadway. However, as for whether the end of bolt and cable in surrounding rock have separated or damaged and whether the bolt and cable in surrounding rock have lost further effectiveness, it cannot help. So, evaluating the bolt-cable combined support system with new detect method has important value. This paper detects roof strata damage and working resistance of bolt (cable) in 20306 Lane Belt with Rock drilling Camera, Multi Displacement Meter and Bolt (Cable) dynamometer, analyses the development of damage (separation) in roof, and evaluates the safety of bolt or cable support system. The result shows: with the method of Rock drilling Camera, the detection of damage in surrounding rock is intuitive and true; in mining process, the number of separate zones in surrounding rock around peak pressure zones increased obviously, and cause failure of bolt and cable in this area.

Effect of weak structural layer on the zonal disintegration formation in the deep rock (The principle of the zonal disintegration formation)

Zonal disintegration has attracted the attention of many experts and scholars, also is the theoretical and practical issue to be solved in deep rock engineering. Based on the typically geological and mining conditions of Xinwen coal mine area, first, the compressive strength of rock samples which were taken from deep roadway was tested in the laboratory, and the layer thickness was identified according to compressive strength. Then, the failure characteristics were detected with strata exploring instrument. The result shows that zonal disintegration exists in surrounding rock of deep roadway, the location of fracture zone is almost the same with that of weak structural layer. When the initial stress is larger than the uniaxial compressive strength of rock in deep rock engineering, it is the external factor of zonal disintegration formation, at the same time, the weak structural layer is the internal factor.

Effects of Cement Contents on the Structure Formation of Stabilized Silt

Based on experimental investigation of the relationship between compression strength of cement stabilized silt and cement contents, a new model of structure formation of stabilized silt is proposed, in which the structure formation of stabilized silt consists of cementing silt particle together and filling pores by cement hydrates. According to this model a theoretical calculation formula is developed, with which the cement contents for both cementing silt particles and filling pores in stabilized silt can be calculated respectively. The result of this research revealed that filling pores in stabilized soil contributes great part of the strength of the stabilized soil.