| The seasonal frozen areas of China are widely distributed,with seasonal changes,the rock mass of the slope in the frozen area is continuously damaged and deteriorated under repeated freeze-thawing,resulting in the reduction of slope stability.With the development of the national economy,more and more mining projects are being built in seasonal frozen areas,and the strength of the rock mass on the slope of open-pit mines is reduced after freeze-thawing,which may bring geological disasters such as collapse and landslide.Therefore,it is of great guiding significance to study the mechanism of freeze-thaw damage deterioration of rock mass on open-pit slope,analyze the stability of open-pit slope,and reveal the potential instability mode of open-pit slope.Based on the background of the Du mu mining area of Gongchangling open-pit mine in Liaoyang City,Liaoning Province,firstly,ascertains the properties of rock mass and the development degree of joint fractures on the slope through on-site investigation and investigation.Secondly,the tests on the physical and mechanical properties of petrophysics under different freeze-thaw cycles were carried out to reveal the mechanism of freeze-thaw deterioration of open-pit rock mass.Finally,combined with the test results and the design of open-pit mining,a numerical simulation model for the stability analysis of the slope of open-pit mine is established,and the slope stability study after freeze-thaw cycle is simulated and analyzed,which provides theoretical and technical support for the safe mining of open-pit mine.The main findings of this thesis include the following:(1)Combined with on-site investigation and analysis of the geological environment of freeze-thaw weathering area,through statistical structural surface characteristics,it is concluded that the Beibang structural surface is mainly IV and structural surface,joint fracture development,rock mass fragmentation.By calculating the joint number and integrity index of the rock mass,it is concluded that the integrity of the Beibang rock mass is poor,and the basic data is provided for the reduction of the mechanical parameters of the rock mass.(2)Through the freeze-thaw cycle test of saturated rock samples,the mass and wave velocity of rock samples under different freeze-thaw times were obtained.With the increase of freeze-thaw times,Some rock samples appear local rock block falling phenomenon.The mass of rock samples increased with the increase of freeze-thaw times,the total mass was increased by 0.25%,and the mass of 25 freeze-thaw times increased significantly.The wave velocity of saturated rock samples gradually decreases with the increase of freeze-thaw times.Through uniaxial compression test,it is found that the peak compressive strength of saturated rock samples decreases exponentially with the increase of freeze-thaw times,the elastic modulus of the rock sample decreased by 33.3%,which decreased significantly.(3)According to the actual project,the freeze-thaw cycle test and uniaxial compression test were conducted on natural water-bearing rock samples.The test results show that the wave velocity changes of natural water-bearing rock samples and saturated rock samples have similar laws,showing a downward trend;The quality change is different from that of saturated rock samples.With the increase of freezing and thawing times,the quality tends to decline.There are two main reasons.One is the macroscopic damage of rock samples,and the other is caused by the lack of water.The peak compressive strength and elastic modulus of rock samples have a downward trend.With the increase of freezing and thawing frequency,the high frequency band of the acoustic emission signal gradually increased,the low frequency band gradually decreased,and the compression section of the stress-strain curve also increased,indicating that the freezing and thawing causes the internal structural damage of rock samples.(4)On the basis of structural plane investigation and basic mechanical experiments,the H-B strength criterion is applied to estimate the mechanical parameters of slope rock mass,and the results of deterioration of rock physical and mechanical parameters with freezing and thawing are applied to the numerical simulation analysis of slope rock mass.The numerical simulation results showed that the slope displacement increased significantly between freezing and thaw 0 and 40 times,the slope foot and shoulder were greatly affected,and the displacement increment increased to 3.56 mm and 7.01 mm respectively;From the distribution of the plastic zone of the slope,it is mainly the shear yield of the shallow surface of the slope,and the yield range gradually expands and extends with the increase of the number of freeze-thaw cycles;According to the strength reduction method,the safety factor of the slope decreases with the freeze-thaw cycle,the freezing and thawing effect reduces the stability of the slope,which may lead to local collapse of the slope,and eventually lead to the overall instability damage of the slope. |
PDF Full Text Request