Discing behavior and mechanism of cores extracted from Songke-2 well at depths below 4,500 m

The mechanism of microwave rock breaking and its potential application to rock-breaking technology in drilling

It has become an inevitable trend of human development to seek resources from the deep underground. However, rock encountered in deep underground engineering is usually in an anisotropic stress state (σ1>σ>σ3) due to the influences of geological structures and engineering disturbances. It is therefore essential to study the mechanical, seepage, and dynamic disaster behaviors of deep rock under true triaxial stress to ensure the safe operation of deep rock engineering and the efficient exploitation of deep resources. In recent years, experimental techniques and research on true triaxial rock mechanics have achieved fruitful results that have promoted the rapid development of deep rock mechanics; thus, it is necessary to systematically review and summarize these developments. This work first introduced several typical true triaxial testing apparatus and then reviewed the corresponding research progress on rock deformation, strength, failure mode, brittleness, and energy as well as the 3D volumetric fracturing (dynamic disaster) properties of deep rocks under true triaxial stress. Then, several commonly used true triaxial rock strength criteria and their applicability, the permeability characteristics and mathematical models of deep reservoir rocks, and the disaster-causing processes and mechanisms of disturbed volumetric fracturing (rockburst, compound dynamic disasters) in deep rock engineering were described. This work may provide an essential reference for addressing the true triaxial rock mechanics issues involved in deep rock engineering, especially regarding the stability of surrounding rock at depth, disaster prevention and control, and oil and gas exploitation. 

Experimental study on the mechanical and failure behaviors of deep rock subjected to true triaxial stress: A review

Laterally loaded piles are widely used in structural foundations under horizontal loads such as wave load, wind load, seismic load, and traffic load. Based on the complexity of pile-soil interaction, a test simulation of single pile through the indoor 1 g model test was conducted, in order to study the influence of different loading heights and relative stiffness of pile and soil on the bending moment, soil resistance, and horizontal displacement of pile. It is found that the shear modulus of soil from large to small is arranged as dry fine sand, dry coarse sand, saturated fine sand, and saturated coarse sand. The shear modulus of dry fine sand, dry coarse sand, and saturated fine sand are close under the same loading height and horizontal displacement of pile top, while the shear modulus of saturated coarse sand decreases sharply. Under the condition of water saturation, the particle size has a significant effect on the shear modulus of soil. The relative stiffness of pile soil is found to be the main influencing condition of pile horizontal displacement. Compared with the displacement and bending moment of the pile, the loading height has more influence on the soil resistance, and the main influence area is the soil resistance of the pile toe.

Effect of Pile-Soil Relative Stiffness on Deformation Characteristics of the Laterally Loaded Pile

Investigating the effect of water quenching cycles on mechanical behaviors for granites after conventional triaxial compression

During deep mining, the excavation disturbance stress path is the domination factor for the stability of the surrounding rock mass as well as the ground pressure. One of the important parameters of the stress path is the loading or unloading rate of the disturbed rock or coal, which depended on the mining rate. To achieve a well understanding of the mining rate and its effect on the coal behavior, a preliminary case investigation of the mechanical properties of the coal at the various mining rates in both the laboratory scale and field scale was performed. Based on the uniaxial compression test and the digital image correlation (DIC) method, the mechanical behavior of the coal samples, such as the evolution of the strength, surface deformation, crack propagation, and elastic strain energy of the coal under the various loading rates were analyzed. A threshold range of the loading rate has been observed. The uniaxial compressive strength (UCS) and releasable elastic strain energy (Ue) increase with increasing loading rate when the loading rate is below the threshold. Otherwise, the UCS and Ue may decrease with the loading rate. Under the low loading rate (≤0.05 mm/min), the tensile deformation of the original defects could result in crack coalescence, whereas failure of the coal matrix is the key contributor to the crack coalescence under the high loading rate (greater than0.05 mm/min). Afterwards, with the consideration of the bearing capacity (UCS) and energy release of the mining-disturbed coal mass (Ue), a power exponential relationship between the mining rate (MR) in the field and the critical loading rate (vc) in the laboratory was proposed. The application potential of the formulas was then validated against the field monitored data. Finally, based on the critical loading rate, the released strain energy, and the monitored pressure on the roof supports, a reasonable mining rate MR for the Ji15-31030 working face was determined to be approximately 3 m/d.

Mechanical behavior of coal under different mining rates: A case study from laboratory experiments to field testing

Research on in-situ condition preserved coring and testing systems

The invention discloses a test method for measuring rock wave velocity in a non-contact manner in a fidelity environment. The test method comprises the steps of selecting a cylindrical container, fixedly arranging a sound wave emission probe and a sound wave receiving probe in the cylindrical container through two fixing devices, selecting a sound wave test system provided with a waveform signal generator and a signal acquisition card, connecting the sound wave test system with the sound wave receiving probe and the sound wave emission probe, injecting a liquid sound wave transmission medium into the cylindrical container, and realizing the non-contact rock wave velocity measurement in the fidelity environment. The required equipment is simple, the manufacturing cost is low, and the measurement method is simple; the non-contact rock sound wave test can be realized by using a common acoustic emission test system; the rock sound wave test efficiency can be greatly improved, the support can be provided for the later-stage continuous rock physical property test integration work, and the method has important significance for deeply researching the mechanical property of the deep in-siturock.

Test method for measuring rock wave velocity in non-contact manner under fidelity environment

Disclosed is a testing method for non-contact measurement of the rock wave velocity in a fidelity environment. A cylindrical container (3) is selected; a sound wave emission probe (5) and a sound wave reception probe (6) are respectively and fixedly arranged inside the cylindrical container by means of two fixing devices (4); a sound wave testing system (1) provided with a waveform signal generator and a signal acquisition card is selected; the sound wave testing system is connected to the sound wave reception probe (6) and the sound wave emission probe (5); and a liquid sound-wave transmission medium (2) is injected into the cylindrical container (3). Non-contact measurement of the rock wave velocity can be achieved in the fidelity environment, and the required apparatuses are simple in structure, low in construction cost, and simple in measurement method. Non-contact rock sound wave testing can be achieved by using a conventional sound emission testing system, and the testing efficiency of rock sound waves can be greatly improved, support can also be provided for subsequent continuous integration work of rock petrophysical property testing, and an important significance is achieved for in-depth research into the mechanical properties of deep in situ rock masses.

Gao Yanan

Papers

Mechanical behavior of coal under different mining rates: A case study from laboratory experiments to field testing

Research on in-situ condition preserved coring and testing systems

Test method for measuring rock wave velocity in non-contact manner under fidelity environment

Testing method for non-contact measurement of rock wave velocity in fidelity environment