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The rock indentation tests by a conical pick were conducted to investigate the rock cuttability correlated to confining stress conditions and rock strength. Based on the test results, the regression analyses, support vector machine (SVM) and generalized regression neural network (GRNN) were used to find the relationship among rock cuttability, uniaxial confining stress applied to rock, uniaxial compressive strength (UCS) and tensile strength of rock material. It was found that the regression and SVM-based models can accurately reflect the variation law of rock cuttability, which presented decreases followed by increases with the increase in uniaxial confining stress and the negative correlation to UCS and tensile strength of rock material. Based on prediction models for revealing the optimal stress condition and determining the cutting parameters, the axial boom roadheader with many conical picks mounted was satisfactorily utilized to perform rock cutting in hard phosphate rock around pillar.

The goaf may face a series of deformation and settlement problems when the room-pillar mining method is used to excavate ore and pillars in the deep strata. To this end, a deep room-pillar model with two levels was made, and the pillar recovery was carried out. The instantaneous deformation responses during the pillars recovery and the long-term settlements after the pillar recovery were analyzed. During the pillar recovery, different regions of surrounding rocks suffer from different dynamic disturbances which can be divided into three types, including (I) the combined action of blasting disturbance and unloading disturbance, (II) the sequential action of blasting disturbance and unloading disturbance, and (III) the action of unloading disturbance. After the pillar recovery, the settlement above the first recovering pillar is the largest, which has a traction effect on the settlement in other areas. The settlement process can be divided into two stages, stable displacement stage and unstable displacement stage. When the pillar-room system undergoes the unstable displacement stage, rock spalling and further cascading collapse will occur.

Innovations of mining technologies were proposed by beneficial utilizations of unfavorable factors such as high geostress, high geotemperature and high mining depth to achieve green mining as mining depth increases inevitably. Cuttability of deep hard rock was investigated by experimental and regressed analyses to find the reasonable stress adjustment method to improve non-explosive mechanized fragmentation for hard ore-rock. A non-explosive mechanized and intellectualized mining method was proposed to continuously and precisely exploit phosphate underground, which promoted the high-recovery, low-waste and high-efficiency exploitation of phosphate with recovery rate over 90%, dilution rate near 5% and cutting efficiency about 107.7 t/h. A circular economy model and the backfill system were proposed to conduct resource utilizations of solid waste, by which the utilization amount of waste increased year after year. In 2018, the utilization amounts of phosphogypsum, yellow phosphorus slag and waste rock increased to 1853.6×103 t/a, 291.1×103 t/a and 1493.8×103 t/a, respectively.

Based on the stress redistribution analysis of rock mass during the deep underground excavation, the unloading process of pre-flawed rock material was simulated by distinct element method (DEM). The effects of unloading rate and flaw inclination angle on unloading strengths and cracking properties of pre-flawed rock specimens are numerically revealed. The results indicate that the unloading failure strength of pre-flawed specimen exhibits a power-function increase trend with the increase of unloading period. Moreover, combined with the stress state analysis on the flaws, it is found that the unloading failure strength increases with the increase of flaw inclination angle. The cracking distribution of pre-flawed specimens under the unloading condition closely depends on the flaw inclination angle, and three typical types of flaw coalescence are observed. Furthermore, at a faster unloading rate, the pre-flawed specimen experiences a sharper and quicker unloading failure process, resulting in more splitting cracks in the specimens.

High temperature treatment causes thermal damage to rocks in deep mining. To study the thermal effect on the energy dissipation of rocks during the dynamic cyclic loading, cyclic impact loading experiments of heat-treated rocks were carried out using the splitting Hopkinson pressure bar (SHPB) experimental system. The correlations among the energy dissipation, energy dissipation rate, impact times, accumulated absorbed energy per volume, failure mode and temperature were analyzed. The results show that the reflected energy under the first impact increases and finally exceeds the absorbed energy when the temperature increases; however, the total reflected energy decreases above 200 °C. The absorbed energy under the first impact and the total absorbed energy all decrease as the temperature increases, the rates of which decrease accordingly. And the same phenomenon appears for the transmitted energy and the rate of the transmitted energy. On the contrary, the rate of the reflected energy increases with the rising temperature. When the temperature increases, the fewer impact times are needed to destroy the sample. In addition, the failure modes are different when the rock is treated at different temperatures; that is, when the temperature is high, even though the absorbed energy is low, the sample breaks into powder after several impacts.

The outcome of the cutting blasting in a one-step shaft excavation is heavily related to the cutting parameters used for parallel cutting method. In this study, the relationships between the cutting parameters (such as the hole spacing L and the empty hole diameter D) and damage zones were investigated by numerical simulation. A damage state index γ was introduced and used to characterize the crushing and crack damage zones through a user-defined subroutine. Two indices, i.e., η1 and η2 that can reflect the cutting performance, were also introduced. The simulation results indicate that an optimal value of L can be obtained so that the η1 and η2 can reach their optimal states for the best cutting performance. A larger D results in better cutting performance when the L value maintains its best. In addition, the influences of the loading rate and the in-situ stress on the cutting performance were investigated. It is found that an explosive with a high loading rate is suit for cutting blasting. The propagation direction and the length of the tensile cracks are affected by the direction and the magnitude of the maximum principal stress.

In order to achieve the safe mining in Sanshandao Gold Mine, five schemes of secure pillar group are designed. Using the method of the renormalization group, the failure mechanism of the pillar group is explored, and the safety factor of the pillar system is also obtained. The displacement characteristics, stress–strain laws, distribution of plastic zone and damage range of different pillar group are analyzed using numerical calculation software FLAC3D. To determine a reasonable pillar group scheme, the pillar stability and roof deformation are utilized to evaluate the safety of the pillar group. In addition, the theory of fuzzy comprehensive evaluation is adopted to verify the optimal scheme. The pillar group with the lowest roof deformation value is chosen as the optimal plan, which renders a factor of safety of 2.06 for the pillar group. According to this scheme, pillars with the width of 10 m are set along the strike of undersea deposit with the interval of 50 m. Rib pillars of 15 m in width are set at the location of the exploration line of 127, 151 and 167. The analysis can be used to provide guidance for optimal design of pillar structures in undersea mining.

A laser technique based scanning system was employed to make a comprehensive scanning through borehole for unmapped cavity under open pit bench, then the three-dimensional data will be obtained, and these data were used for theoretical analysis and numerical simulation to analyze the stability of cap rock. Acoustic emission techniques were also adopted to carry out long term real time rupture monitoring in cap rock. Therefore, a complete safety evaluation system for the cap rock was established to ensure safe operation of subsequent blasting processes. The ideal way of eliminating collapse hazard of such cavity is cap rock caving through deep-hole blasting, thus, two deep-hole blasting schemes named as vertical deep-hole blasting scheme and one-time raise driving integrated with deep-hole bench blasting scheme were proposed. The vertical deep-hole blasting scheme has more explosive consumption, but the relatively simple blasting net work structure can greatly reduce workloads. However, the one-time raise driving integrated with deep-hole bench blasting scheme can obviously reduce explosive consumption, but the higher technical requirements on drilling, explosive charging and blasting network will increase workloads.

A new method, named relocation, was proposed to reduce the impact of sensor errors systematically, especially when available data of sensors are abundant. The procedure includes evaluating the reliability of every sensors datum, processing the initial location by the credible data, and selecting a set of equations with optimal noise tolerance according to the relative relationship between the initial location and sensors location, then calculating the final location by k-mean voting. The results obtained in this research include comparing traditional location method with the presented method in both simulation and field experiment. In the field experiment, the location error of relocation method reduced 41.8% compared with traditional location method. The results suggested that relocation method can improve the fault-tolerant performance significantly.

A coupled biharmonic spline and linear interpolation algorithm was proposed to create a three-dimensional smooth deposit model with minimal curvature containing grade and position data. To obtain the optimal technical parameters, such as cutting height and drum diameter, a virtual longwall mining procedure was modelled by simulating the actual fully mechanized longwall mining process. Based on the above work, a bauxite deposit in a longwall mining panel was modelled by scattered grade data from ores sampled on the entry wall. The deposit was then demarcated by industrial indexes and sliced according to the virtual longwall mining procedure. The results show that the proposed interpolation algorithm can depict the stratiform structure of bauxite deposits and that the uncovered bauxite deposit has high proportions of high-grade and rich ore. The ranges of optimal cutting height and drum diameters are 1.72–2.84 m and 1.42–1.72 m, respectively. Finally, an intellectualized longwall mining procedure was designed to guide the mining process with the lowest dilution and loss rates.

In order to get the dynamic mechanical properties of deep rock mass suffered both high temperature and high pressure, impact loading experiments on granite subjected to temperature and axial pressure were carried out. Furthermore, the internal structure characteristics of granite under different temperatures were observed by scanning electron microscopy (SEM). The results show that the longitudinal wave velocity assumes a downward trend which shows a rapid drop before falling slowly as the temperature increases. The uniaxial compressive strength of the specimen decreases significantly at temperatures of 25–100 °C compared to that at temperatures of 100–300 °C. The peak strain rises rapidly before the dividing point of 100 °C, but increases slowly after the dividing point. The internal structure of the rock changes substantially as the temperature increases, such as the extension and transfixion of primary and newborn cracks. In addition, the thermal damage under axial pressure is greater than that described by the longitudinal wave velocity and the phenomenon shows obviously when the temperature increases.

Static mechanical experiments were carried out on granite after and under different temperatures using an electro-hydraulic and servo-controlled material testing machine with a heating device. Variations in obvious form, stress-strain curve, peak strength, peak strain and elastic modulus with temperature were analyzed and the essence of rock failure modes was explored. The results indicate that, compared with granite after the high temperature treatment, the brittle-ductile transition critical temperature is lower, the densification stage is longer, the elastic modulus is smaller and the damage is larger under high temperature. In addition, the peak stress is lower and the peak strain is greater, but both of them change more obviously with the increase of temperature compared with that of granite after the high temperature treatment. Furthermore, the failure modes of granite after the high temperature treatment and under high temperature show a remarkable difference. Below 100 °C, the failure modes of granite under both conditions are the same, presenting splitting failure. However, after 100 °C, the failure modes of granite after the high temperature treatment and under high temperature present splitting failure and shear failure, respectively.

The strength of rock materials is largely affected by water and loading conditions, but there are few studies on mechanical properties of saturated rocks at high strain rates. Through compressive tests on dry and saturated sandstone specimens, it was found that the dynamic compressive strength of both dry and saturated sandstone specimens increased with the increase of strain rates. The saturated rock specimens showed stronger rate dependence than the dry ones. The water affecting factor (WAF), as the ratio of the strength under dry state to that under saturated state, was introduced to describe the influence of water on the compressive strength at different strain rates. The WAF under static load was close to 1.38, and decreased with the increase of strain rate. When the strain rate reached 190 s−1, the WAF reduced to 0.98. It indicates that the compressive strength of saturated specimens can be higher than that of dry ones when the strain rate is high enough. Furthermore, the dual effects of water and strain rate on the strength of rock were discussed based on sliding crack model, which provided a good explanation for the experimental results.

To find discriminating features in seismograms for the classification of mine seismic events, signal databases of blasts and microseismic events were established based on manual identification. Criteria including the repetition of waveforms, tail decreasing, dominant frequency and occurrence time of day were considered in the establishment of the databases. Signals from databases of different types were drawn into a unified coordinate system. It is noticed that the starting-up angles of the two types tend to be concentrated into two different intervals. However, it is difficult to calculate the starting-up angle directly due to the inaccuracy of the P-wave arrival's picking. The slope value of the starting-up trend line, which was obtained by linear regression, was proposed to substitute the angle. Two slope values associated with the coordinates of the first peak and the maximum peak were extracted as the characteristic parameters. A statistical model with correct discrimination rate of greater than 97.1% was established by applying the Fisher discriminant analysis.

The mechanical properties of red sandstone subjected to cyclic point loading were investigated. Tests were conducted using MTS servohydraulic landmark test system, under cyclic loadings with constant amplitudes and increasing multi-level amplitudes. The frequencies range from 0.1 to 5 Hz and lower limit load ratios range from 0 to 0.60. Laboratory investigations were performed to find the effect of the frequency and the lower limit load ratio on the fatigue life and hysteresis properties of sandstone. The results show that the fatigue life of sandstone decreases first and then increases with the increase of frequency and lower limit load ratio. Under the same cycle number, the spacing between hysteresis loops increases with rising frequency and decreasing lower limit load ratio. The existence of “training” and “memory” effects in red sandstone under cyclic point loading was proved.

Slabbing failure often occurs in the surround rock near a deep underground excavation. The mechanism of slabbing failure is still unclear. In order to reveal the influence of the intermediate principal stress (σ2) on slabbing failure, true triaxial unloading compressive test was carried out based on the stress path of the underground engineering excavation, i.e., unloading the minimum principal stress (σ3), keeping σ2, increasing the maximum principal stress (σ1). The initiation and the propagation of slabbing fracture in rock specimens were identified by examining the acoustic emission (AE) and the infrared radiation characterization. The test results show that the failure modes of the granite and red sandstone specimens are changed from shear to slabbing with the increase of σ2. The AE characteristic of rock specimen under low σ2 is swarm type which is the main shock type under high σ2. The infrared radiation properties of rock specimen under different σ2 are also different. The temperature change area is just along the shear fracture such as the uniaxial compression. With the increase of σ2, the temperature change area is planar of rock specimen which proofs that the failure mode of rock specimen turns into slabbing.

The method of Random Forest (RF) was used to classify whether rockburst will happen and the intensity of rockburst in the underground rock projects. Some main control factors of rockburst, such as the values of in-situ stresses, uniaxial compressive strength and tensile strength of rock, and the elastic energy index of rock, were selected in the analysis. The traditional indicators were summarized and divided into indexes I and II. Random Forest model and criterion were obtained through training 36 sets of rockburst samples which come from underground rock projects in domestic and abroad. Another 10 samples were tested and evaluated with the model. The evaluated results agree well with the practical records. Comparing the results of support vector machine (SVM) method, and artificial neural network (ANN) method with random forest method, the corresponding misjudgment ratios are 10%, 20%, and 0, respectively. The misjudgment ratio using index I is smaller than that using index II. It is suggested that using the index I and RF model can accurately classify rockburst grade.

To find the analytical solution of the acoustic emission/microseismic(AE/MS) source location coordinates, the sensor location coordinates were optimized and simplified. A cube monitoring network of sensor location was selected, and the AE/MS source localization equations were established. A location method with P-wave velocity by analytical solutions (P-VAS) was obtained with these equations. The virtual location tests show that the relocation results of analytical method are fully consistent with the actual coordinates for events both inside and outside the monitoring network; whereas the location error of traditional time difference method is between 0.01 and 0.03 m for events inside the sensor array, and the location errors are larger, which is up to 1080986 m for events outside the sensor array. The broken pencil location tests were carried out in the cross section of 100 mm×98 mm, 350 mm-length granite rock specimen using five AE sensors. Five AE sources were relocated with the conventional method and the P-VAS method. For the four events outside monitoring network, the positioning accuracy by P-VAS method is higher than that by the traditional method, and the location accuracy of the larger one can be increased by 17.61 mm. The results of both virtual and broken pencil location tests show that the proposed analytical solution is effective to improve the positioning accuracy. It can locate the coordinates of AE/MS source only using simple four arithmetic operations, without determining the fitting initial value and iterative calculation, which can be solved by a conventional calculator or Microsoft Excel.

A general analytical method to calculate the passive rigid retaining wall pressure was deduced considering all displacement modes. First, the general displacement mode function was setup, then the hypotheses were made that the lateral passive pressure is linear to the corresponding horizontal displacement and the soil behind retaining wall is composed of a set of springs and ideal rigid plasticity body, the general analytical method was proposed to calculate the passive rigid retaining wall pressure based on Coulomb theory. The analytical results show that the resultant forces of the passive earth pressure are equal to those of Coulomb's theory, but the distribution of the passive pressure and the position of the resultant force depend on the passive displacement mode parameter, and the former is a parabolic function of the soil depth. The analytical results are also in good agreement with the experimental ones.

Xinli district of Sanshandao Gold Mine is the first subsea metal mine in China. To achieve 6 kt/d production capacity under the premise of safe mining, high-intensity mining might destroy the in-situ stress filed and the stability of rockmass. According to sampling and testing of ore-rock and backfill and in-situ stress field measurement, safety factor method calculation model based on stress—strain strength reduction at arbitrary points and Mohr-Coulomb yield criterion was established and limit displacement subsidence values under the safety factor of different limit stoping steps were calculated. The results from three years in-situ mining and strata movement monitoring using multi-point displacements meter showed that the lower settlement frame stope hierarchical level filling mining method, mining sequence are reasonable and rockmass stability evaluation using safety factor method, in-situ real-time monitoring can provide the technical foundation for the safety of seabed mining.

A Bayes discriminant analysis method to identify the risky of complicated goaf in mines was presented. Nine factors influencing the stability of goaf risky, including uniaxial compressive strength of rock, elastic modulus of rock, rock quality designation (RQD), area ratio of pillar, ratio of width to height of pillar, depth of ore body, volume of goaf, dip of ore body and area of goaf, were selected as discriminant indexes in the stability analysis of goaf. The actual data of 40 goafs were used as training samples to establish a discriminant analysis model to identify the stability of goaf. The results show that this discriminant analysis model has high precision and misdiscriminant ratio is 0.025 in re-substitution process. The instability identification of a metal mine was distinguished by using this model and the identification result is identical with that of practical situation.

The failure characteristics under coupled static and dynamic loading were investigated by the improved split Hopkinson pressure bar (SHPB) with axial pre-pressure and confining pressure. The results show that the stress-strain curve of the rock under static-dynamic coupled loading is a typical class I curve when the dynamic load is comparatively high; With the decrease of the dynamic load, the stress-strain curve transforms to a typical class II curve. The dynamic failure process was recorded by high-speed photography. Analyses of fracture surface morphology show that the failure modes of specimens are tensile failure or combined shear failure when the impact load energy is low, but the failure modes of specimens become tensile failure when the impact load energy is high. The results of fractal dimension show that the elastic potential energy release leads to increase in the degree of crushing of samples when the energy of impact load is low under coupled static and dynamic loads with high stress.

The purpose of this study is to apply some statistical and soft computing methods such as Fisher discriminant analysis (FDA) and support vector machines (SVMs) methodology to the determination of pillar stability for underground mines selected from various coal and stone mines by using some index and mechanical properties, including the width, the height, the ratio of the pillar width to its height, the uniaxial compressive strength of the rock and pillar stress. The study includes four main stages: sampling, testing, modeling and assessment of the model performances. During the modeling stage, two pillar stability prediction models were investigated with FDA and SVMs methodology based on the statistical learning theory. After using 40 sets of measured data in various mines in the world for training and testing, the model was applied to other 6 data for validating the trained proposed models. The prediction results of SVMs were compared with those of FDA as well as the measured field values. The general performance of models developed in this study is close; however, the SVMs exhibit the best performance considering the performance index with the correct classification rate Prs by re-substitution method and Pcv by cross validation method. The results show that the SVMs approach has the potential to be a reliable and practical tool for determination of pillar stability for underground mines.

To quantitatively study the location errors induced by deviation of sonic speed, the line and plane location tests were carried out. A broken pencil was simulated as acoustic emission source in the rocks. The line and plane location tests were carried out in the granite rod using two sensors and the cube of marble using four sensors, respectively. To compare the position accuracy between line and plane positions, the line poison test was also carried out on the marble surface. The results show that for line positioning, the maximum error of absolute distance is about 0.8 cm. With the speed difference of 200 m/s, the average value of absolute difference from the position error is about 0.4 cm. For the plane positioning, in the case of the sensor array of 30 cm, the absolute positioning distance is up to 8.7 cm. It can be seen that the sonic speed seriously impacts on the plane positioning accuracy. The plane positioning error is lager than the line positioning error, which means that when the line position can satisfy the need in practical engineering, it is better to use the line position instead of the plane location. The plane positioning error with the diagonal speed is the minimum one.

Firstly, studies on propagation of one-dimensional normally incident wave in rock mass containing no joint, a single joint and two parallel joints were conducted by Three Dimensional Distinct Element Codes(3DEC). By comparison of the modeling results with the theoretical solutions, it has been found that a good agreement between them has been achieved. It is verified that the 3DEC is capable of modeling wave propagation in rock masses. Secondly, propagation of normally incident P-wave across two parallel joints was studied. The modeling results show that transmission coefficient increases with the increasing ratio of joint spacing to wavelength at first, then decreases with the increasing ratio of joint spacing to wavelength, lastly keeps constant. Finally, effect of interlayer on wave propagation is investigated. It is shown that interlayer results in marked attenuation and leading phase, and that attenuation increases with the increasing frequency and the increasing thickness of interlayer.

The importance of study on constitutive model of statically loaded rock experiencing dynamic load is set forth, and the studying methods on dynamic constitutive model are classified according to the current studying status. By way of combining statistic damage model and viscoelastic model, uni-axial and multi-axial constitutive models of statically loaded rock experiencing dynamic load (static-dynamic coupling constitutive model) under intermediate strain rate are established. The verification experiment on 2D constitutive model under different static stress and dynamic stress with different frequencies is designed and performed. It is found that there is a good agreement between the experimental stress-strain curves and the theoretical stress-strain curves.