Through a theoretical analysis of the spalling characteristics of rocks under the impact loading of the half-sine wave incident，the location and thickness of rock spalling fracture are obtained. In the laboratory，the improved Split Hopkinson pressure bar device which produces the incident half-sine wave is applied to measure the spall characteristics of the granite specimens. The complete experimental process is recorded by a high-speed camera. Test results show that the rock specimens under the impact loading of the half-sine incident wave only produce one spalling layer initially，which is completely in accord with the theoretical analysis；and the rock specimens produce several spalling fractures with time. The analyses of both pictures from the high-speed camera and waveform recorded by dynamic strain gauges indicate that the reason of following small spalling fractures is the damages of rock specimens caused by the initial loading. For a damaged rock specimen，a very weak residual reflected wave spreading along the specimen will make it produce small spalling fractures. Hence, the investigation on the spalling characteristics of rock or other brittle materials should not only consider the dynamic tensile fracture caused by the interaction of incident and reflected waves，but also should take the influence of material damage into account. The research methodology of this paper based on the waveform theoretical analysis of the spalling characteristics and the experimental technique with high-speed camera will be helpful for the area of understanding the rock spalling process or other relevant characteristics.

The transient release of excavation load is accompanied by the development of cracks，the outburst of detonation gases and the formation of new free surface during the rock fragmentation by blasting. For the case of full face excavation of deep tunnel，divisional excavation loads corresponding to milli-second delay blasting are decided first；and a mathematical description of the load boundary condition during the release of excavation loads is presented through analyzing the mode and duration of transient release of excavation loads. Considering the complex stress stale and change of continuity state of rock mass around blast hole caused by rock fragmentation by blasting，an equivalent numerical method is proposed to simulate the coupling of blasting load and excavation load for multi-hole blasting in accordance with the spatial distribution characteristics of blast-induced damage zone and the equivalent elastic boundary. Comparison between simulation results and monitoring data indicates that the proposed equivalent simulation method is applicable to predicting the dynamic response of surrounding rock during the blasting excavation of deep tunnel.

Different stress paths of surrounding rock corresponding to different excavation methods，such as blasting or tunnel boring machine(TBM)，have important influence on the formation of excavation damage zone during construction of deep tunnel. However，the influence has not yet attracted enough attention. Based on the excavation in deep tunnel group of Jinping II hydropower station，the characters and formation factors of damage zones under different excavation methods are discussed by field detecting test；and extents of damage zone induced by in-situ stress transient or quasi-static adjusting are calculated by using numerical simulation method；and the basic mechanical characters of Jinping marble and in-situ stress transient adjusting effect are considered in the calculation. The test results show that the depth of inner damage zone(severely damaged zone) in blasting excavation tunnel accounts for more than 50% of the total damage zone depths；and the rock in this area have been damaged seriously and lost its bearing capacity. The distribution of inner damage zone in the tunnel section is seriously influenced by redistribution stress field，which can be regarded as the evidence of that the in-situ stress transient adjusting effect is one of the direct causes of damage zone formation. In the tunnels excavated by TBM method，the inner damage zone only accounts for 30% of the total damage zone depths；and the formation of this area could be mostly attributed to the time effect of the strength of Jinping marble. It is the result of improvement of stress relaxation at tunnel surface. After considering the mechanical characters of brittle-extension-plastic of marble and transient adjusting effect of in-situ stress，the extents of excavation damage zones under different excavation stress paths can be estimated objectively using numerical simulation method. The conclusion of this paper has important significance for the selection of excavation method and support measures of deep tunnel.

Full-digital hydraulic pressure and high temperature fatigue testing system with scanning electron microscope(SEM) is used to real-time observe and study thermal cracking of Beishan granite under different temperatures. Experimental results indicate that the threshold temperatures of thermal cracking of Beishan granite is 68 ℃–88 ℃. At the lower temperatures，intergranular thermal cracking is the main thermal cracking for Beishan granite. However，at the higher temperatures，transgranular cracking and coupling of intergranular and transgranular thermal cracking are the main cracking for Beishan granite. Beishan granite thermal cracking is not only effected by thermal expansion mismatch and thermal expansion anisotropy of minerals，but also effected by the physico-mechanical and thermal properties of mineral grains and mineral particle shape structures. Fluid inclusions within the granite may also effect the thermal cracking of Beishan granite，which is a new effect mechanism for thermal cracking. At microscopic and mesoscopic levels，thermal cracking has been classified；and different mechanisms for intergranular and transgranular thermal crackings can be quantitatively interpreted using the fractal models. When the temperature rises above 250 ℃，there is thermal melting effect in Beishan granite，which leads to a decrease in thermal cracking amount. The relationship between temperature and its corresponding thermal cracking amount fits Gauss curve well.

Based on the failure behavior of deep hard rock and group works，a rock mass local deterioration model(RLDM) is developed to reflect the evolution of deformation and strength parameters of rocks with plastic variables under polyaxial stress conditions. The model is integrated into a self-developed three dimensional elastoplastic cellular automaton(EPCA). The cellular automaton technique，which is based on the localization theory，is convenient to perform the dynamic updating of local mechanical parameters. The EPCA code with RLDM is used to study the influence of polyaxial stress on failure behavior of rock specimens in laboratory and in-situ deep diversion tunnel of Jinping II hydropower station. The modeled complete stress-strain curves of rocks under triaxial compression can well reflect the transition from brittle failure to ductile failure of rocks；the curves are agreement with experimental phenomenon. The modeled failure mode of Jinping II diversion tunnel well reflects the actual failure mechanism. Based on the calibrations of the model and numerical method，it is used to simulate the failure behaviors of deep hard rock tunnels by considering different lateral stress coefficients and different intermediate principal stresses and their directions. Influence of polyaxial stress on fracture of deep hard rock is analyzed；and causes of complex failure modes of deep hard rock tunnels are also explained. It is concluded that，the increase of minor principal stress increases the stability of the tunnel. The stability of deep tunnel shows the phenomenon of intermediate principal stress effect and interval characteristics.

Based on summarizing the main results and theoretical methods of rockburst vulnerability evaluation，the development process and basic framework of a new rockburst vulnerability evaluation method for deep tunnels are put forward. The 62 rockburst cases which occurred in deep tunnels of Jinping II hydropower station are analyzed；and the characteristics and main controlling factors of rockburst are revealed. New empirical assessing index—rockburst vulnerability index(RVI) and its established methods are both proposed；while the principle of selecting controlling factors is confirmed. RVI is constituted by four controlling factors，namely stress control factor Fs，rock petrophysical factor Fr，rockmass system stiffness factor Fm and geologic structure factor Fg，which respectively reflect different contributions of rockburst controlling factors to rockburst vulnerability. It is found that there is a significant correlation between the failure depth of rockburst and RVI. An empirical equation is established and its determination coefficient is more than 80%. The empirical equation can be used for evaluating the rockburt vulnerability and its damage level. The applicability of RVI method is verified through the analysis of representative rockburst cases which occurred in deep tunnels of Jinping II hydropower station.

According to the code for design of concrete structure and scientific research achievements of plastic concrete materials，and based on the experimental results of mechanical characteristics of plastic concrete materials，complete stress-strain relationships for plastic concrete materials under compression and tension are proposed respectively. Accordingly，damage definitions of plastic concrete have been put forward on the basis of energy equivalence theory；and damage development process is also analyzed. As a case study，a velocity-based controlling method for plastic concrete damage due to blasting vibration propagated from surrounding rock blasting at a project of rockfill cofferdam in Hongyanhe Nuclear Power Plant(HNPP)，Liaoning，China，is described. The relationship between the damage area at cut-off wall section and the peak vibration velocity at the top of cut-off wall，which is constructed with plastic concrete and lies in the inner part of rockfill cofferdam，has been studied in detail. Then，a blasting vibration velocity control standard is set up for plastic concrete material in HNPP. It?s shown that blasting vibration will not result in damage to plastic concrete when the peak velocity at the top of cut-off wall is less than 3.0 cm/s. The damage area increases linearly with peak velocity when the peak velocity at the top of cut-off wall is in the range of 3.0–7.5 cm/s. When the peak velocity goes beyond the value of 7.5 cm/s，the damage area will increase dramatically and the cut-off wall begin to lose its function.

According to the calculation for the lining structures of deep tunnel，the hypotheses that the activated rock caused by the blasting wave is rigid body and the lining is built with reinforced concrete are put forward. By using the incompressible rigid-plastic model and the upper limit analysis theory，the impact force component of the lining on the rock blocks can be obtained by establishing the kinematical admissible velocity field. Considering the effects of longitudinal reinforcements on spalling and penetration，the approximate calculation formulae for critical thickness of spalling and penetration of reinforced concrete structure featuring with physical basis are obtained based on the characteristics of resistance curves. The reliability and practicality of the method are verified by comparing with the empirical formulae.

Based on the experiment results，a surface blasting model of rock with pre-existing defects，including voids，pores and small open joints under blasting loads is established. The defects are randomly distributed，and are empty or saturated with water. A shock equation of state (EOS)，obtained from the existing test results，is employed for the granite near the explosive charge；and for the granite far from the charge，a linear EOS is applied. A modified principal stress failure criterion is applied to determining the granite statuses. The granite dynamic strengths，which increase with the strain rate，are calculated from the existing test results. The simulation results show that：under blasting，as rock contains water，its dynamic strength decreases；the larger the defect density is，the smaller the damage range is. A blasting near a tunnel induces spalling cracks near tunnel free surface easily；and combining with the radial cracks caused during tunnel blasting excavation，the surrounding rock near the tunnel free surface would be cut into a group of blocks which may fall down and may result in rock burst.

In the mine under large-scale mining，the complex seismicity induced by extensively mining are familiar；and under the conditions of high stress and hard rock，the areal hazardous seismicity and rockbursts are probable. The seismic apparent stress and deformation are important hypocenter parameters to study the seismic mechanism and prediction. According to the Dongguashan Copper Mine，the characteristics of seismic apparent stress and displacement in the mining process are investigated；and we find that the seismicity shows the areal distribution characteristics which have greatly corresponding relation to the mining activity and distribution of pillars in this mining area. Based on the results，combining with the geological structure and in-situ stress，the areal seismic mechanism in this mining area is studied. It is pointed out that the seismic nucleation mechanism can be explained with the knaggy theory of complex hypocenters of natural earthquakes；and a conceptual model of seismic nucleation in the mine is proposed. Simultaneously，a method to identify the location of potential hazardous seismic areas is discussed in accordance with the seismicity characteristics. Aiming at the areal rock failures，the characteristics of time series of apparent stress and apparent volume are analyzed；and the prediction and assessment of rock failure behavior and seismic risk in the potential seismic nucleation zone are discussed. The research result is applied to the project.

Based on the scientific understanding of deep rock under high crustal stress and dynamic excavating perturbation，the dynamic failure characteristics of sandstone subjected to three-dimensional(3D) coupled static and dynamic loads are experimentally studied preliminarily with a modified 3D split Hopkinson pressure bar(SHPB) apparatus. Three levels of confining pressures(0，5 and 10 MPa) and three typical levels of axial compressions(60，80 and 100 MPa)，are designed；and the 3D coupled loads tests are carried out under different strain rates. The results show that，when the confining pressure is constant，the impact compressive strength will decrease when the ratio of axial compressive stress to axial compressive ultimate capacity increases from 0.52 to 0.87. Compared with the influence of confining pressure 10 MPa，the impact compressive strength changes a little under confining pressure 5 MPa. The results also show that the axial pressure will induce the internal cracks in rock，weaken the carrying capacity of microelement and reduce the secant modulus of rock；While the confining pressure will inhibit the initiation and propagation of cracks，consolidate the carrying capacity of microelement and enhance the secant modulus of rock. When the confining pressure is constant，the results also show that the release energy per unit volume will decrease when the ratio of axial compressive stress to axial compressive ultimate capacity increases and change into absorbing energy state at the ratio of axial compressive stress to axial compressive ultimate capacity of 0.6–0.7. The rock will show a single-cone compression-shear failure model under 3D coupled static and dynamic loads.

Based on large amounts of wave velocity-depth curves of surrounding rocks in underground powerhouses of Jingping I and Xiluodu hydropower stations，the acoustic velocity-depth curves are analyzed and classified into 5 types. With the least square method，acoustic velocity-depth curves are fitted with 3 different functions. By substituting the acoustic velocity in classical wave velocity-elastic modulus formula with the fitting functions，the relationship between elastic modulus and depth of surrounding rock in underground powerhouse is established. Thus the relaxation phenomenon of elastic modulus of rock mass near the cave wall and decreasing law of elastic modulus after excavation are evaluated；and the fitting formula in wall rock loosing zone is proposed. The newly proposed formula is applied to back analysis and deformation advanced forecasting in underground powerhouse. The analytical results fit practical deformation law of surrounding rock much better than classical elastoplastic analysis results. The study results provide a new theoretical foundation for stability calculation and feedback analysis of surrounding rocks.

The uniaxial compression tests of plate-shape granite samples containing two prefabricated holes on each side，prepared from Iddefjord granite blocks in Norway，are carried out by Instron hydraulic servo control testing machine in laboratory. The axial stress，axial and lateral strain，acoustic emission(AE) counts and failure modes of the samples are monitored during the tests. The splitting cracks occur near the holes′ vertical surface and parallel to the loading direction when the loading stress increases to a certain value. Some characteristics of rockburst phenomena such as rock block ejection and slabbing failure can be observed around the prefabricated holes under high compressive stress. The failure modes of samples always initiate from the splitting fractures around the holes under uniaxial compression. By observing the AE counts rate curve，it is shown that more jumping mutation points appear in the curve than that of intact rock samples. Based on the experimental studies，numerical models are validated by FLAC3D(3 dimensions fast lagrangian analysis of continua). The principal stresses distributions in the samples are obtained by the elastic model analysis，while the failure process is studied by the Mohr-Coulomb strain softening model. The modes of failure zones are monitored and characterized by the AE count events. Most failure zones are failed in tension and connected together to form as splitting fractures parallel to the vertical boundary of the holes. The numerical results are almost the same as the laboratory tests. The research results，to some degree，reveal the formation mechanism of slabbing fractures，which are usually parallel to the excavation boundary surrounding underground openings in hard rocks under high in-situ stresses.

For the interface of the weak structural plane and the rock mass，the shear strength is an important parameter to affect the fissured rocks stability. The two-material mechanical model and direct shear test are employed to study the fissured rocks? mechanical properties of the interface. According to the famous Barton?s rough description method (JRC value)，five different JRC curves are chosen to make a series of two-material mechanical model specimens. Each specimen is casted with the mortar and concrete on the both sides of the interface. Besides，the interface is rough along one direction(shear direction)，but un-rough along another. The rough degree of interface is also described with the modified fractal index Rd and shape factor λ. The Rd-λ description system can not only describe the roughness of the interface，but also explain the experimental phenomenon that the same rough surface shows different mechanical behaviors if the shear stress direction on the surface is changed. Through the direct shear tests，the failure patterns of the interface in fissured rock mass and their shear stress-shear displacement curves are obtained. The main influence factors，such as the material strength ratio k，the surface appearance，the normal stress σ and the cohesional strength C，are determined and analyzed. Based on the analysis，a shear strength formula，in which the main influence factors are included and the rough interface appearance is expressed with Rd-? system is proposed. Finally，the formula calculating result is compared with test results provided by other researcher and its validity is testified.

In-situ observation has been carried out to investigate the surface subsidence law of high-intensity full-mechanized mining in Wangzhuang coal mine in recent years. Through the hole observation，the distribution laws of caving zone and fractured zone have been obtained based on these in-situ observation data；and the maximum subsidence value has also been monitored. Discontinuous deformation analysis(DDA) has been used to simulate the movement and failure of rock strata；and the surface subsidence model is established. Especially，effects of multiple faults on rock strata movement and surface subsidence have been considered in the numerical model. The maximum subsidence value is about 4.5 m based on DDA，which is less than in-situ measurement value of 4.9 m. The main reason is that the effects of four larger faults around the working face have been only considered in the numerical models. However，there are many small faults and other small geologic structures in the actual area. The actual geological conditions are far more complex than that considered in the proposed numerical model. Finally，the surface subsidence laws of working face with and without faults effects which have the similar geological conditions are compared. The laws of fracture and movement of the overlying rock strata with and without faults have been investigated，respectively；and the discrepancy between them has been discussed in detail.

According to tunnel boring machine(TBM) advance rate，surrounding rockmass is classified into 4 grades，i. e. good，comparatively good，comparatively bad and bad in working condition. Based on fuzzy mathematics method，two indices of uniaxial compressive strength UCS and rock mass integrity index KV are adopted；and their membership functions of the 4-grade classification of rock mass about TBM construction are established. Meanwhile，Sigmoid function is adopted to depict the weight of UCS and KV rather than a constant as QTBM and traditional fuzzy mathematics method. Based on the maximum membership degree criterion of fuzzy mathematics，the rockmass quality of TBM construction could be classified. Applications of three construction cases show that the prediction results coincide well with the TBM construction advance rate reality. The classification method is simple and feasible；and it can be put into practice.

The mortar is used to simulated the rock material to study its microcracks evolution laws. The distribution properties and statistical characteristics of density in rock materials are investigated by means of CT scanning during the failure process under uniaxial compression；and the activities of microcracks are reflected by the density varieties of same location in mortar. The evolution behavior of microcracks is studied through the statistical characteristics of density changes and the fractal index Rd. The research results show that：(1) The changes of amplitude and shape of grey frequency statistical curve reflect the different microcracks evolution effects. When load level is at 0%–50%，the curve is a sine curve，its wave peak rises and the amplitude increases evidently. When load level is at 50%–70%，the wave peak declines，the frequency amplitude increases，and the curve has a deviation from sinusoid. When load level is at 70%–90%，the curve shape，wave peak location and frequency amplitude do not change basically，and only a few gray interval?s frequencies change. When load level is greater than 90%，the wave peak rises largely and the curve becomes sinusoid again. Meanwhile，the movement of wave trough is opposite to the wave peak. The change laws of the amplitude and curve shape indicate that the dominant evolution action of microcracks is initiation in prophase，metaphase closing and propagation in anaphase during the failure process. (2) Through the gray transformation of CT images and its fractal index description，the relationship between Rd and load presents three-stage increment，which is related to the interaction of generating effect and closing effect of microcracks in compression process. In prophase，Rd increases with microcracks initiation remarkably. At middle stage，because the microcracks initiation becomes slow and its propagation develops slowly as well，the microcracks closing effect is dominant. So，Rd decreases tardily. In anaphase，the microcracks propagation and influx speed up and Rd is increasing rapidly. (3) The proposed fractal index Rd of microcracks volume fraction can characterize the evolution behavior of the microcracks in the compression fracture process.

Based on the views of random point process theory and stereological interpretation，the first criterion is proposed to check that the trace midpoint in sampling window is the scope of structural homogeneity zone，which is simulated by the Poisson disc joint model and trace information revealed by sampling window. To check the validity of the first criterion，two examples are simulated by Monte Carlo method and their results are checked by statistical tests. Based on the characteristics of two dimensional Poisson process，the second criterion for the relationship between measuring scale of grid and Poisson point number covered by square grid is derived，which shows fractal characteristics in a specific scale range. Joint distribution density and joint orientation are both considered in the derivation of the formula. The Lyman formula is tested for accuracy by theoretical equations. The detailed implementation steps of the two criteria mentioned above are suggested. To check the validity of the detailed implementation steps，two examples are simulated by Monte Carlo method and their results are checked by statistical tests. Geological survey data of the experimental adit #3 in Jinping hydropower station are used to verify the existence of relationship between measuring scale of grid and Poisson point number；and it is shown that the two criterion is very convenient for engineering applications.

A discontinuous elastoplastic model for plane strain was presented to depict rock shear strain localization phenomenon；and the classical slip line field theory is used as a frame in the model. The discontinuities of displacement field on slip lines are described with an assemblage of continuous functions；and control equations in the model are deduced from physical law in local orthogonal curvilinear coordinates. The deformation process is divided into three phases：elastic，plastic and post-peak shear localization phases. The materials on slip lines obey the Coulomb criterion and break on slip lines appeared after peak strength，while initial cohesion decreases linearly and finally disappears. The model is dispersed with finite element method(FEM) and solved with the Newmark method，which is actualized with Fortran code. A simple case is given to validate the model by comparing with the analytical solutions of traditional continuous model. Both strain and stress tensors of materials are asymmetric in the model；and plastic behavior and energy dissipation of materials depend on deformation motion at discontinuous interface. The discontinuous model can profoundly describe the post-peak shear localization phenomenon of deep rock mass.

The variable-compliance-type constitutive equation is employed in this study. The constitutive equation can express the failure process of rock，which has been well proved heretofore. In the constitutive equation，it is assumed that the rock fails at a rate which depends on stress severity. The concept of stress severity Sv is expanded to the stress state where Sv take negative value and the healing parameter Hp= –Sv is introduced. The constitutive equation is also modified assuming that fractured rock is gradually compacted or healed at a rate which depends on the healing parameter. According to the results in this study，it can be said as follows. (1) The equation expresses the behaviors of the fractured rock when the compliance becomes smaller in the compaction test. (2) Though further discussions are essential in the future definitely，it can be said that the modified variable-compliance-type constitutive equation shows much potential for simulating the behaviors of fractured rock in compaction test and interpreting strength recovery of rock in loosening zone or excavation damaged zone around an underground structure.

For studying the characteristics and influence factors of restitution coefficient of rockfall collision，the  field tests are carried out. By using the FASTCAM SA1.1 high-speed camera and the Motion Plus software，the velocities of rockfall before and after impact are obtained；and the normal restitution coefficient and tangential restitution coefficient are calculated. Meanwhile，the ANSYS/LS-DYNA software is adopted to simulate the test process；and the simulation results and test results are anastomotic well. The results show that：(1) While the ground material changes from fragment，accumulation layer to loose gravelly soil，the corresponding normal restitution coefficient decreases gradually；but the tangential restitution coefficient increases gradually. (2) The normal restitution coefficient is almost independent of the side length of rock block，incidence velocity and incidence angle；and it just affected by the physico-mechanical properties of ground material. (3) The tangential restitution coefficient is independent of the side length of rock block，but it increases with the incidence velocity and decreases with the incidence angle increase.

In order to carry out the in-situ rotary penetration test for determining the mechanical parameters of soft rock quickly and accurately，the intrinsic relationship between mechanical parameters of soft rock and load parameters of rotary penetration test should be known. The soft rock with uniaxial compression strength less than 15 MPa is simulated by the building block，gypsum A，gypsum B and mould gypsum samples. The uniaxial  compressive test，shear test and rotary penetrometer test with two kinds of probes with the same diameter of pore-forming are carried out under the same experimental conditions. The axial force and torque of the probe，and the compression strength，Young?s modulus and shear strength of the sample are obtained. In the light of the similarity between cutter?s loading mode in rotary penetrometer test and plate?s loading modes in uniaxial compressive test and shear test，the mathematical model of load parameters in rotary penetration test and mechanical parameters in uniaxial compressive test is established theoretically，which is the intrinsic relationship of the two kinds of parameters. When the sample is at the stage of local volume damage during penetration test， the axial force and torque are not only related to the compression strength，cohesion and internal friction angle，except Young?s modulus，but also linearly increasing with the compression strength and cohesion. When the sample is at the stage of grinding damage，the axial force and torque are related to the Young?s modulus，cohesion and internal friction angle except the compression strength.

According to Xin′an coal mine，the mechanism of coal and gas outburst in “three-soft”coal seam under the condition of rockburst is discussed by means of investigation，test，laboratory test，theoretical calculation and analogy. The results show that：(1) Because of the in-situ rock stress and mining-induced stress，the high elastic modulus sandstone strata of roadway floor bends to the upward，which makes the ordinary gas ventages close. The generating cracks in coal make the adsorptive gas desorb as dissociative gas，which provides the external preparation conditions of coal and gas outburst. (2) The impact of the floor strata with large Young′s modulus opens the gas′s channel，which provides the external trigger conditions. (3) The rockburst energy near the heading face is more than 105 J. The inoculation and generation processes of rockburst make the coal wall close and fracture. For the coal seam with the initial expansion energy contained in 1 m3 coal less than 1.3×106 J (the gas pressure less than 0.74 MPa)，the gas outburst or unusual gas emission would be induced；and for the other coal seam，the coal and gas outburst would be induced. In order to prevent the risks mentioned above，it is suggested that the drilling or blasting measurements should be used for the high elastic modulus strata.

Pores and fractures are two main flow channels in fractured porous media. Under low and ultra-low permeability conditions，whether seepage occurs in media or not is decided by whether pores and fractures can form a penetrated channel or not. A dual-percolation model coupled the pore percolation theory and the fracture percolation theory is presented to study the conductivity of the low and ultra-low fractured porous media. Based on the presented dual-percolation model，two parameters   and D are presented to reflect and compare the conductivities of fractured porous media；and the physical meaning of these two parameters is quantitatively discussed. The connectivity of low and ultra-low permeability fractured porous media is investigated based on these two parameters. It is shown that the low and ultra-low permeability fractured porous media can be generally divided into three types by taking   as the critical value，i.e. dispersion type，critical type，and directional type. Media are self-sealing when  and they can be named as directional type. However，with the enhancements of randomnesses of porous connectivity and fracture directions，the self-sealing tendency will be destroyed and the conductivity will increase，which causes the media tending to become dissipation type. A few long fractures can play a great role on the connectivity of media.