Caving mechanisms of loose top-coal in longwall top-coal caving mining based on stochastic medium theory

2018 ◽  
Vol 11 (20) ◽  
Author(s):  
Dijie Zhu ◽  
Zhonghui Chen ◽  
Weisheng Du ◽  
Lingfan Zhang ◽  
Zihan Zhou
Keyword(s):  
Stochastic Medium ◽  
Medium Theory ◽  
Longwall Top Coal Caving

scholarly journals Ground Movement Analysis Based on Stochastic Medium Theory

2014 ◽  
Vol 2014 ◽  
pp. 1-6
Author(s):  
Meng Fei ◽  
Wu Li-chun ◽  
Zhang Jia-sheng ◽  
Deng Guo-dong ◽  
Ni Zhi-hui
Keyword(s):  
Distribution Function ◽  
Back Analysis ◽  
Movement Analysis ◽  
Measured Data ◽  
Ground Movement ◽  
Pile Driving ◽  
Normal Distribution Function ◽  
Stochastic Medium ◽  
Medium Theory ◽  
Vertical Ground

In order to calculate the ground movement induced by displacement piles driven into horizontal layered strata, an axisymmetric model was built and then the vertical and horizontal ground movement functions were deduced using stochastic medium theory. Results show that the vertical ground movement obeys normal distribution function, while the horizontal ground movement is an exponential function. Utilizing field measured data, parameters of these functions can be obtained by back analysis, and an example was employed to verify this model. Result shows that stochastic medium theory is suitable for calculating the ground movement in pile driving, and there is no need to consider the constitutive model of soil or contact between pile and soil. This method is applicable in practice.

scholarly journals A New Modified Peck Formula for Predicting the Surface Settlement Based on Stochastic Medium Theory

2019 ◽  
Vol 2019 ◽  
pp. 1-14 ◽  
Author(s):  
Zhanping Song ◽  
Xiaoxu Tian ◽  
Yuwei Zhang
Keyword(s):  
Friction Angle ◽  
Surface Settlement ◽  
Calculation Error ◽  
Stochastic Medium ◽  
Medium Theory ◽  
Comparison Results ◽  
Calculation Process ◽  
The Difference ◽  
Shallow Buried Tunnel ◽  
Prediction Approach

Peck method and stochastic medium method are the two most commonly used methods to estimate surface settlement caused by tunnel excavation. However, the Peck method was not suitable for a shallow-buried tunnel, and the calculation process of the stochastic medium theory was complicated. To solve this problem, in this paper, a simple and accurate prediction approach for surface settlement was obtained by improving the Peck method based on the basic idea of stochastic medium theory. In detail, the over-excavation area of the tunnel was divided into n independent units, and the surface settlement caused by the collapse of each unit was calculated, respectively. Then, the total surface settlement can be obtained by superimposing surface settlement induced by each unit. Taking the shallow-buried section of Mulingguan tunnel entrance as a case, the surface settlement calculated by the modified Peck formula and original Peck formula was compared with the observed data, respectively. The comparison results indicated that the surface settlement calculated by the modified Peck formula is closer to the observed data than that calculated by the original Peck formula in the calculation process of surface settlement of shallow-buried tunnel. The table of recommendation for the number of units can be obtained by a discussion of reasonable n values. Finally, the difference between the original Peck formula and the modified Peck formula was analysed, and the results showed that the change rule of the surface settlement is consistent under the tunnel depth, internal friction angle, and ground loss of the tunnel. However, the calculation error of the surface settlements calculated by the original Peck formula is more significant than that calculated by modified Peck formula under the tunnel diameter ratio being less than 1.75. The modified Peck formula is more suitable for calculating the surface settlement under internal angle friction being less than 20° or greater than 40°. The research results expand the scope of application of the original Peck formula and enrich the calculation approach of surface settlement induced by underground excavation in tunnel construction.

Influence Mechanism of Isolation Layer to Granular Media Flow

2012 ◽  
Vol 256-259 ◽  
pp. 2514-2518
Author(s):  
Yun Xiang Liu ◽  
Qing Fa Chen ◽  
Hong Qi Chen
Keyword(s):  
Granular Media ◽  
Working Condition ◽  
Underground Mining ◽  
Particle Flow Code ◽  
Radius Of Curvature ◽  
Stochastic Medium ◽  
Medium Theory ◽  
Isolation Layer ◽  
Influence Mechanism ◽  
Shrinkage Method

By using particle flow code (PFC2D), influence mechanism of isolation layer to granular media flow was studied by simulating two ore-drawing modes of filling mining method (working condition Ⅰ) and synchronous filling shrinkage method(working condition Ⅱ). After analyzed simulation results, some laws were gotten: (1) by the fitting process conducted on released volume and height, it is found that the relationship of released volume and height was power equation, which is same as the stochastic medium theory for ore-drawing; (2) The released volume, the size in most width of loosing body and the location of working condition Ⅱ was both bigger than those of working condition Ⅰ; (3) the radius of curvature of drawn-funnel of working conditionⅡ was bigger than those of working conditionⅠ, but the volume of residual ore was opposite. Analysis shows that the isolation layer reduced the contact force in ore drawing regional, made the porosity bigger, so as to improve liquidity. The results provide a theoretical reference for the changes in underground mining techniques and ore-drawing control.

Analysis of Ground Movement in Pile Driving Based on Stochastic Medium Theory

2013 ◽  
Vol 438-439 ◽  
pp. 1404-1408 ◽  
Author(s):  
Fei Meng ◽  
Jia Sheng Zhang ◽  
Hui Ying Liu
Keyword(s):  
Axisymmetric Problem ◽  
Back Analysis ◽  
Measured Data ◽  
Ground Movement ◽  
Pile Driving ◽  
Normal Distribution Function ◽  
Stochastic Medium ◽  
Medium Theory ◽  
Vertical Ground ◽  
Soil Interface

In order to calculate the ground movement induced by displacement piles driven into horizontal layered soil, it is simplified to an axisymmetric problem. Then the vertical and horizontal ground movement functions were deduced based on stochastic medium theory. The vertical ground movement is a normal distribution function, while the horizontal ground movement is an exponential function. Utilizing field measured data, parameters of these functions can be obtained by back analysis. The example indicates that the stochastic medium theory is suitable for calculating the ground movement in pile driving, and there is no need to consider the constitutive model of soil or contact model of pile-soil interface in calculation. This method is fairly applicable in practice, and can provide a reference for related research.

scholarly journals Method of Calculating the Vertical Displacement and Additional Stress of Existing Tunnels under the Influence of Grouting Rings of New Tunnels

Symmetry ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 1623
Author(s):  
Yongjie Qi ◽  
Gang Wei ◽  
Yu Xie
Keyword(s):  
Calculation Method ◽  
Mechanical Model ◽  
Volume Expansion ◽  
Vertical Displacement ◽  
Additional Stress ◽  
Stochastic Medium ◽  
Medium Theory ◽  
Volumetric Expansion ◽  
Engineering Data ◽  
Good Agreement

In order to reduce the disturbance to adjacent tunnels caused by tunnel crossing, the existing tunnels are often reinforced by setting grouting rings along the pipe piece ring. In this context, the volume expansion of the grouted soil has to be taken into account, and a mechanical model of the volume expansion of the grouting rings is proposed here to study the effect of the grouting rings of new tunnels on the additional stress on the existing tunnels as well as their vertical displacement. The additional stresses on and the vertical displacement of the axis of the existing tunnels caused by the expansion of the grouting rings were deduced based on the stochastic medium theory. The influences of various volumetric expansion rates (Q) of the grouting rings, different lengths of the grouting rings, and different tunnel crossing angles on the settlement of and the additional stress on the existing tunnels were studied. The results demonstrate that the grouting rings can effectively reduce the impacts of the additional stress and the settlement deformation on the existing tunnels. The results of the tunnel settlement obtained from the calculation method proposed in this paper are in good agreement with the measured engineering data.

Prediction of the Ground Settlements Induced by Shallow-Buried Subway Tunneling in the Loess Region

2011 ◽  
Vol 368-373 ◽  
pp. 1259-1263
Author(s):  
Dong Han ◽  
San Qing Su ◽  
Yu Yang
Keyword(s):  
Engineering Practice ◽  
Stochastic Medium ◽  
Medium Theory ◽  
Loess Region ◽  
Ground Settlements

Stochastic medium theory is applied in the research of the ground settlements Induced by subway tunneling lately. There are a lot of simplification and many difference between the predict results and the engineering practice in the prediction process in irregular tunneling. This paper gives expression of the ground settlements Induced by any section tunneling using standard transform principle on the base of the correctional stochastic medium theory. On the basis of above discussion, proving this method is effective and reliable by the verification.

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