Law and mechanics of thermal cracking of rock by laser irradiation

The influence of the process parameters of thermal cracking of rock by laser on the mechanical properties of rocks was analyzed to improve the efficiency of thermal cracking of rock by laser. The orthogonal experimental studies of thermal cracking of rock by laser were carried out. The influence of laser power.irradiation time and irradiation distance on the temperature change of thermal cracking of rock by laser and the morphological damage of rock were analyzed. Based on X-ray diffraction (XRD).the composition and content of different regions of the rock were analyzed. The influence trend of laser power.irradiation time and irradiation distance on the change of phase content in the laser irradiation area was discussed. The degree of weakening of the rock intensity by laser power.irradiation time and irradiation distance was studied. The results show that with the increase of laser power and irradiation time and the decrease of irradiation distance.the temperature of the rock reaction zone becomes larger.the number of thermal cracks increases.the crack depth becomes larger.and the thermal fracture reaction of the rock is enhanced. The proportion of quartz and calcium feldspar containing high brittleness.low intensity.low thermal conductivity.and low coefficient of thermal expansion in the rock sample after laser high-temperature irradiation increases. With the increase of laser power and irradiation time and the decrease of irradiation distance.the composition of quartz and calcium feldspar contained in the rock-like cauterization hole increases. The main components of condensed sediments in the lithoid cauterization holes after laser irradiation are quartz and albite. Some of the crystals in the condensed sediment are transformed into amorphous structures under laser irradiation. Laser irradiation time has the greatest impact on the degree of weakening of rock strength. Laser irradiation distance is secondary. The laser power has the least impact on the weakening of rock strength. With the increase of laser power and irradiation time and the decrease of irradiation distance.the compressive strength of the rock is significantly reduced from 83.89 MPa to 36.13 MPa. The axial extrusion deformation variable of the rock becomes larger.the crushing effect is enhanced.and the rock strength weakens to a greater extent. The results show that laser irradiation of rocks can effectively reduce rock strength.thereby improving the efficiency of laser irradiation hot cracking rock breaking.