Numerical Simulation on Zonal Disintegration in Deep Surrounding Rock Mass

Abstract

Zonal disintegration have been discovered in many underground tunnels with the increasing of embedded depth. The formation mechanism of such phenomenon is difficult to explain under the framework of traditional rock mechanics, and the fractured shape and forming conditions are unclear. The numerical simulation was carried out to research the generating condition and forming process of zonal disintegration. Via comparing the results with the geomechanical model test, the zonal disintegration phenomenon was confirmed and its mechanism is revealed. It is found to be the result of circular fracture which develops within surrounding rock mass under the high geostress. The fractured shape of zonal disintegration was determined, and the radii of the fractured zones were found to fulfill the relationship of geometric progression. The numerical results were in accordance with the model test findings. The mechanism of the zonal disintegration was revealed by theoretical analysis based on fracture mechanics. The fractured zones are reportedly circular and concentric to the cavern. Each fracture zone ruptured at the elastic-plastic boundary of the surrounding rocks and then coalesced into the circular form. The geometric progression ratio was found to be related to the mechanical parameters and the ground stress of the surrounding rocks.

Similar Material Simulation Study on Protection Effect of Steeply Inclined Upper Protective Layer Mining with Varying Interlayer Distances

“…At present, similarity criteria are based on elastic theory and dimensional analysis method. According to the pressure-relief mechanism of protective layer mining, the following similarity criteria should be satis ed in similar material simulation experiment [22][23][24]:…”

“…e type and proportion parameters of similar material determine whether experimental results obtained can represent mechanical responses of prototype. Similar material simulation experiments have been widely employed, but how to obtain accurate and optimum proportioning parameters is urgently needed to be investigated in coal mining [20][21][22][23][24][25][26]. In this section, the river sand, cement (containing gypsum and y ash), and water are used and mixed to manufacture a new similar material, which is used to represent various coal-rock strata around the protective layer in the coal mine.…”

“…e three in uencing factors (including sand-binder ratio, density and residual water content) are relaxed within speci c regions, and each factor is divided into four levels; then Poisson's ratio, compressive strength, and elastic modulus are determined. e orthogonal array L 16 (4 3 ) is applied to choose sixteen combinations to be tested [21][22][23]. e levels of orthogonal design for similar materials are shown in Table 2, and the sixteen combinations and corresponding mechanical parameters obtained are given in Table 3.…”

“…In short, protection effect of steeply inclined upper protective layer mining with varying interlayer distances is not fully understood and needs further investigation. Compared to site observation and numerical simulation, similar material simulation [20][21][22][23][24] in a laboratory can simulate real physical object (i.e., engineering prototype), with similar materials having mechanical properties similar to those of a prototype according to certain similarity criteria. As the similar material model has all or most of the major characteristics of the prototype, it can reflect failure or deformation process of prototype truly and visually.…”

Study on the Generation Mechanism and Development Law of the Zonal Disintegration in Deep Burial Tunnels

“…is is analogue to shallow tunnel loose, plastic, and elastic zones [4][5][6][7][8][9][10]. Understanding the rock mechanical behaviors in this environment prevents the impact pressure in the excavation and blasting process.…”