Relationship Between Physical and Mechanical Parameters of Coal Measures Rocks and Acoustic Wave Velocity

Meng, Zhaoping; Ji-chang, Zhang; Tiedemann, Joachim

doi:10.1002/cjg2.959

Cited by 25 publications

(11 citation statements)

References 9 publications

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“…The time cost by the pulse reflected back and forth 1 time in CA mortar specimens is 2l s /c s , where l s is the length of specimens, taken as 0.05 m, c s is the shearing wave velocity in the specimens and can be calculated by the following equation as [28]:…”

Section: Effectiveness Analysismentioning

confidence: 99%

Dynamic mechanical properties of cement and asphalt mortar based on SHPB test

Xie

Zheng

et al. 2014

Construction and Building Materials

102

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Section: Effectiveness Analysismentioning

confidence: 99%

Dynamic mechanical properties of cement and asphalt mortar based on SHPB test

Xie

Zheng

et al. 2014

Construction and Building Materials

102

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“…The low-velocity zone and high-velocity zone in the horizontal slices have clear boundaries and geometric features. The interpretation is based on the principle that the shear wave in the coal mined-out area presents low velocity and the shear wave in the security coal pillar offers high velocity, and also combined with the shear wave velocity range in the coal rock physics experiment (Meng et al 2006;Zhou 2012). The high-velocity zone with shear wave 22 velocity more than 1 100 m/s in the horizontal slice can be interpreted as the security coal pillar, and the low-velocity zone less than 1 100 m/s is the mined-out area, as shown by red solid line.…”

Section: Data Processingmentioning

confidence: 99%

Research on the Application of Surface Wave Method for the Precise Detection of Shallow Coal Seam Mined-Out Area and Overburden

Yang

Zou³

et al. 2022

Preprint

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To finely detect the boundary of a shallow coal mined-out area, as well as the extent of the overburden affected by the mined-out area, and to analyze the factors and interrelationships between the detection depth and lateral resolution of the multichannel analysis of surface waves (MASW) method, a low-frequency focusing factor is introduced into the phase-shift method, and a low-frequency focusing phase-shift method is proposed to improve the detection depth and lateral resolution of the MASW method. The method is applied to the processing and analysis of measured active-source surface waves. The results show that the low-frequency focused phase-shift method has the significant advantage of extracting the dispersion energy at low-frequency side from the short receiver spread. The receiver-spread length of the measured data used to calculate the dispersion energy is 35 m, which meets the 70 m detection depth of the target coal mined-out area. The measured data were processed to obtain high-precision horizontal slices of the shear wave velocity along the coal seam and in the overburden at different depths. The former clearly identify the boundaries of the coal mined-out areas and the locations and geometries of the security coal pillars and estimate the main coal mining direction to be approximately 23° NW, which is in general agreement with the actual direction of 21° NW of the back workings in the mining area of the study site. One mined-out area of approximately 30 m in width, one mined-out area greater than 50 m in width, and one roadway of approximately 10 m in width are inferred. The latter directly shows the extent of the overburden affected by the coal mined-out area gradually decreasing as the depth becomes shallower. The severe influence extent on the surface is delineated and mutually supported by the surface cracks in the village east of the research site. The effectiveness of the low-frequency focused phase-shift method in improving the depth and lateral resolution of the MASW method and the feasibility of the MASW method in precise detection of shallow coal mined-out area and overburden are confirmed.

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“…Once the drilled rock is exposed to the drilling mud, a chemical interaction may start and consequent changes occur for the drilled formation properties . The rock characteristics are influenced by the chemical interactions between the drilling fluid and rock mineralogical composition that leads to severe alterations in the pore system that show different behavior either due to the plugging mechanism that is attributed to the precipitation process and/or the opening mechanism that is attributed to the dissolution process. − Consequently, there will be alterations in the rock petrophysical characteristics such as formation porosity, flow characteristic in porous media, interior topography for rock, pore structure, and rock geomechanics. − …”

Section: Introductionmentioning

confidence: 99%

Role of Rock Saturation Condition on Rock–Mud Interaction: Sandstone Geomechanics Study

Gamal

Elkatatny

2022

ACS Omega

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The rock saturation condition affects the rock elastic and strength characteristics due to the role of fluid−rock interaction. However, the role of this parameter has not been studied well for mud−rock exposure during drilling operations. Hence, this study targets to assess the role of different rock saturation conditions on the rock geomechanics changes during the rock exposure for the drilling fluids. During the drilling operation, the mud filtrate invades the drilled formation pore system and replaces the saturating fluid and consequent alterations occur for the rock elastic moduli and failure properties. The current study employed Berea Buff sandstone rock type with different saturation conditions (brine-saturated, dry, and oil-saturated) to interact with drilling mud (water-based) through the filtration test to mimic the downhole rock−mud exposure under pressure, temperature, and time conditions. Extensive laboratory analysis was accomplished that covered the scratching test to get the strength of rock samples, acoustic data determination, elastic moduli evaluation, and scanning electron microscopy to assess the internal alterations of the rock pore system. The obtained results showed that the oil-saturated sample showed the least filtration characteristics for the rock−mud exposure and the best condition to maintain the rock strength from deterioration compared to the dry and brine-saturated samples. The rock strength showed a weakening behavior for the brinesaturated and dry samples by 5 and 18% respectively, while the oil-saturated sample showed only a 2% strength reduction after the mud exposure. Poisson's ratio showed a 21% increase for the brine-saturated sample and the dry sample showed a small increase from 0.2 to 0.22, while the oil-saturated sample maintains a stable Poisson's ratio at 0.24. Young's modulus showed an increase for the dry and brine-saturated rock samples by 10 and 7%, respectively, while a 25% reduction for the oil-saturated. The spectrometry analysis results showed the internal changes in the rock samples' pore system for the brine-saturated and dry samples, while the oilsaturated sample showed no internal changes that maintain the rock structure and strength after the mud exposure.

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Relationship Between Physical and Mechanical Parameters of Coal Measures Rocks and Acoustic Wave Velocity

Cited by 25 publications

References 9 publications

Dynamic mechanical properties of cement and asphalt mortar based on SHPB test

Dynamic mechanical properties of cement and asphalt mortar based on SHPB test

Research on the Application of Surface Wave Method for the Precise Detection of Shallow Coal Seam Mined-Out Area and Overburden

Role of Rock Saturation Condition on Rock–Mud Interaction: Sandstone Geomechanics Study

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