A New Rock Brittleness Evaluation Method Based on the Complete Stress-Strain Curve

In order to understand the mechanical deformation characteristics of the permafrost layer and the stress-fracture-gas seepage law of the superimposed mining of the proximity coal seam group, a coupled gas-solid model of the proximity coal seam in the permafrost area was constructed based on the theoretical model of small deflection of thin plate and the deformation control equation, gas transport equation, porosity evolution equation and permeability evolution equation of the coal rock body, and the analysis of the dependent project. The analysis was carried out at the NMT coal mine. The results show that the multiyear permafrost seam in the NMT coal mine has a tendency to move to the left and will produce extensive pull damage near the right end. The initial and periodic collapse steps are 192.87 m and 43.24 m, respectively; the pore and fissure structural characteristics of the NMT coal seam are not conducive to gas transport, and the stress and fissure fields have a nonlinear increasing effect. The study also proposed the “protected seam mining and bottom extraction lane directional drilling group comining technology” to increase the daily production of working face by 25.8%. The results of the study can be used as a reference for similar projects.

Section: Theoretical Modelmentioning

confidence: 99%

Research on the Extraction Technology of Gas-Integrated Working-Face in Close Coal Seam Mining in Permafrost Area

Deng

2022

“…When the bridge is subjected to seismic force, the force will be dispersed to each pier, effectively reducing the influence of seismic force on the pier. Therefore, it is not necessary to establish a large-tonnage seismic bear in the construction process [22,23]. Moreover, the curvilinear bottom is used in the bridge box girder to reduce the size of the bridge structure and ensure the safe flood discharge with a large clearance height under the bridge.…”

Section: Types Of Pier Structure Of the Continuous Rigid-framementioning

confidence: 99%

The Influence of Buckling Mode and Buckling Stability Coefficient of Rigid-Frame Bridge during Construction in Cold Region

Zhang²,

Wang

2022

The study aims to further standardize the construction process, improve the construction quality, and ensure the stability of infrastructure construction. The continuous rigid-frame bridge is taken as the research object, the finite element model of the bridge body is established by using the beam element, and the overall stability of the rigid-frame bridge is analyzed in the construction and completion stages. Moreover, the stability coefficient and buckling mode are established under different working conditions in each stage, the linear stability variation law is summarized, and the geometric nonlinear stability analysis method is established through the specific data. The nonlinear stability safety factor and buckling mode are obtained, and the influence of wind load and initial defects on the stability of continuous rigid-frame bridge is further explored. The results show that with the increase of the bridge height, the overall stability factor of the bridge is decreasing, and the safety factor of the single-limb thin-walled hollow pier is relatively larger than that of the double-limb thin-walled hollow pier. During the construction, the asymmetric self-weight load caused by the asynchronous load and cantilever pouring has the greatest impact on the stability of the bridge. The stability safety factor of the geometric nonlinear stability analysis method constructed is 0.3% and 1.27% lower than the ideal state, respectively. The stability safety factor of the wind load and the initial defect is 12.65% lower than the ideal state, and the stability safety factor is greatly reduced. The results have important reference significance to ensure the construction safety and overall stability of the bridge.

“…Its main advantage is that it can directly observe the real characteristics of pores and then converts the image into quantitative data such as pore size distribution and porosity. Currently, domestic and foreign scholars have used the focused ion beam-helium ion microscopy (FIB-HIM) technique to analyze the particularities of organic matter derived pores in shale core samples [6] and the scanning electron microscopy (SEM) technique to qualitatively describe and to quantitatively characterize the microscopic pore structure of shales [7][8][9]. However, during the actual operation process, the image analysis method has several deficiencies.…”

Section: Introductionmentioning

confidence: 99%

Study on Pore Structure of Shale Reservoir by Low Temperature Nitrogen Adsorption Method

Guo

2022

Shale gas is one of the most actively explored unconventional sources of natural gas. There are several types of pores in the shale reservoir, and their structural characteristics are complex. Evaluating the characteristics of the shale pore structure is the basis for understanding the shale reservoir performance and the oil and gas migration mechanism. In this paper, the micro- and nanopores of shale samples from the Yanchang Formation, Hunan basin, are studied by applying the low-temperature nitrogen adsorption method. Several pore structure parameters such as the specific surface area, the pore volume, and the pore size distribution of the analyzed samples are calculated. The predominant characteristics of nanopores that influence hydrocarbon accumulation and control the development of pores are discussed. The results indicate that the shale reservoir rocks from the study area are mainly mesoporous with an average pore size distribution between 2 and 50 nm. A small number of micropores (less than 2 nm) and macropores (more than 50 nm) are also present in the pore network. The development of micropores and mesopores in the shale samples is associated with organic matter content, while the development of macropores is linked to clay minerals content. Total organic carbon (TOC) content is the key element to control the nanopore volume and the specific surface area of the reservoir rocks from the study area. At the same time, the organic matter-enriched pore network also provides extensive space for the accumulation of shale gas.