In order to improve the static mechanical properties and impact resistance of cement-based materials and to reduce the amount of cement for the purpose of less greenhouse gas emissions,mineral admixtures of silica fume(10%,wt.),steel fiber(2%,by volume) for functional components,matched with high efficiency water reducing agent(1.5%~2.0%,wt.) were used to prepare high-toughness cement composites in this study.The quasi-static and dynamic mechanical properties and microstructure evolution of the high toughness cement-based composites were investigated by the quasi-static compressive/flexural strength test,split hopkinson pressure bar test(SHPB),isothermal calorimeter and thermal gravimetric analyzer.The results showed that the typical failure process of cement-based composites under impact loading(impact rate of 0.5 MP/s) can be divided into three stages.Only limited amount of spalling or flying phenomenon of pastes occurred in high-toughness cement-based composite,while the control cement-based materials were significantly damaged until the whole samples were broken.The quasi-static mechanical properties(compressive strength and flexural strength reached 61.4 MPa and 23.9 MPa at 1 d) and dynamic compressive strength(to 123.3 MPa at 28 d) of cement-based composites were both improved with 10% silica fume addition.According to the microstructure evolution results,under the combined action of silica powder and water reducing agent,the main peak of heat release rate of slurry hydration was advanced,and the content of calcium hydroxide in the main hydration product phase was reduced,which reduced the orientation of calcium hydroxide distribution in slurry and helped to improve the microstructure of slurry.

In order to explore the influence law of damage accumulation effect on the surrounding rock of a large span chamber under multiple blasts,acoustic method and borehole imaging method were used in a large span chamber blasting project.The results show that the ultrasonic wave velocity decreases with the increase of blasting times.Besides,the damage value of surrounding rock increases,but the growth rate decreases and finally becomes stable.After several blasts,the radius of the broken rock zone in the surrounding rock of the chamber has gradually expanded from 2.8 m to 3.2 m,and the broken rock zone at the top of the chamber is larger than that at the side wall.Therefore,the stability of the surrounding rock at the top of the chamber must be taken into account in such cases.In addition,the influence of damage accumulation caused by multiple blasts on the radius change of the broken rock zone should be fully considered in surrounding rock support and safety protection.

In order to solve the problems of insufficient data utilization and large fluctuation of prediction accuracy in predicting rock blasting fragmentation using machine learning method under the condition of small samples,a LOO-XGboost model is built by Python 3.7,which combines the leave-one-out method(LOO) with the eXtreme Gradient Boosting(XGboost) algorithm.Firstly,31 sets of blasting data are selected for training and prediction.By calling different parameters,the optimal built-in parameters of the model are obtained as follows:tree model as solution method,the learning rate of 0.30,the number of decision trees of 50,the maximum iteration depth of the decision tree of 3,the minimum sample number of leaf nodes of 3,and the random sampling ratio of 0.8.Through comparing the prediction results with the support vector machine regression(SVR),BP neural network(BPNN),random forest(RF) model and XGboost model under 10 fold cross validation under the same conditions,the LOO-XGboost model has significantly higher prediction accuracy than the other four models.The correlation coefficient,root mean square error,and average absolute error are 0.9128,0.0587 and 0.0342,respectively.The results show that the LOO-XGboost model can not only guarantee the data utilization in the case of small samples,but also improve the prediction accuracy,and it is suitable for the prediction of rock blasting framentation.

For study the influence of macro-pore parameters on the damage evolution of concrete under static and impact loads,a physical model of random pore structure was generated by MATLAB program based on Monte Carlo method,and the stress-strain process of macro porous concrete under uniaxial compression was simulated by a self-programed peridynamic program.Furthermore,the accuracy of the calculation results was verified by uniaxial compression experiments of concrete specimens with macro porosity of 0%~40%.The concrete mortar specimens were prepared with polystyrene spheres which melt at high temperature into voids.Finally,the crack germination and expansion of the macro porous concrete under blasting impact loads were simulated.The results show that the porosity has a significant effect on the mechanical properties of macro porous concrete materials.With the increase of porosity,the density,compressive strength,elastic modulus and longitudinal wave velocity of samples continuously decreases,respectively.When the porosity reaches 30%,the effect of porosity on the axial compressive strength is weakened,and the stress before the peak has a drop phenomenon.The concrete samples with zero porosity have obvious compression shear failure mode under the impact load without confining pressure,while the existence of a large number of pores leads to tensile or shear failure of concrete skeleton.Under the same impact load,the failure of concrete with large porosity is more severe,which indicates that porosity plays an important role in energy dissipation of concrete under impact load.

In order to explore the applicability of particle blast method(PBM) in near-field blast problems,PBM and arbitrary Lagrange Eulerian algorithm(ALE & S-ALE) were used to simulate near-field blast tests of AL-6XN stainless steel plates.PBM was used to simulate the near-field blast of a steel plate with different distances to the explosion center.During this process,how the total number of particles and the particle number ratio influence the calculation accuracy of PBM was analyzed.Combined with the test results of T.B rvik,the calculation accuracy and operation efficiency of PBM,ALE and S-ALE methods were compared.By simulating the near-field blast of spherical C4 explosive 150 mm away from the explosion center the steel plate,the time proportion of different algorithms was also analyzed.The results show that under different conditions,the maximum error of steel plate deflection obtained by PBM is 20%,and the dispersion coefficient is 0.12,which is better than ALE and S-ALE algorithm.For the same mesh generation,the operation time of PBM algorithm is only one tenth of that of ALE or S-ALE algorithm.PBM has a higher accuracy and better simulation effect when the particle number ratio is closer to the particle mass ratio under certain total number of particles,or when the total number of particles is higher under certain particle number ratio.

In the numerical simulation of rock blasting,it is very important to accurately describe the work process of expanding detonation products and to determine the parameters of JWL equation of state(Eos) quickly and accurately.A parameter calibration method of industrial explosive material is proposed which is based on ANSYS/LS-DYNA finite element software by combining theoretical calculation with numerical simulation.Taking 2# rock emulsion explosive as an example,which is common in engineering,the unknown parameters of the JWL Equation of State(Eos) were calculated by a simple algorithm according to the density and detonation velocity explosive product manual.On this basis,the numerical simulation of lead column compression experiment and lead casting reaming experiment was carried out,and the accuracy of the calculation parameters was verified by two different experiments.The influence of the changes of four important parameters A,B,R1 and R2 in JWL equation of state(EOS) on the results of numerical simulation was studied by means of orthogonal tests.After the parameter correction,the error between numerical simulation results and field experiment results was less than 5%,indicating that the calibration method was feasible.

For improving rock blasting effect,a method of air deck stemming structure is presented in this paper.Through the finite element analysis software ANSYS/LS-DYNA,the models of continuous and air deck stemming structure are established,respectively.The calculation results show that the stress peak value is obviously weakened on the charge part of the hole wall.However,it has little effect for the peak value of rock stress at locations far from the hole center.Therefore,the structure is beneficial to control over-crushing in the center of explosion source and reduce the crushing area.Meanwhile,in the air stemming section,the stress peak value of the hole wall element decreases obviously,but the effective stress action time increases dramatically,which indicates that the structure has a promoting effect on improving the rock blasting effect at this position.In the cuttings stemming section,due to the influence of air decks,the stress of cuttings stemming unit attenuates basically according to an order of magnitude.Furthermore,at least 2 air decks should be designed in the stemming structure to achieve the desired effect.The feasibility of improving blasting effect of the stemming structure is proved by experiments of bench blasting.

In view of the complicated problem of determining the optimal parameters of cross-cut coal blasting cutting technology in coal-measure strata tunnels,taking the Guigala Tunnel of Tibet′s Laze Highway as the research object,theoretical analysis is used to determine that the cross-cut coal cutting section of the tunnel adopts hollow holes.Straight-cut,and analyzed the three kinds of hollow mechanical effects of the hollow holes;The numerical simulation test method is used to establish the calculation model of straight hole cut in stone gate tunnel,and different cut parameters were analyzed from the aspects of cut efficiency,cut depth and dynamic response of coal seam.The results show that with the increase of the key parameter of cutting a=24 cm to a=32 cm,the rock fragmentation degree of the trough cavity decreases,the coal body fragmentation degree is equivalent,and the thickness of the rock that is not penetrated between the blast hole and the hollow hole increases,which reduces the efficiency of cutting; When a=28 cm,the local coal uncovering depth is too large,which increases the risk of outburst; when a=32 cm,there is a loose zone in the deep part of the coal body,which reduces the stress intensity of the deep coal body.Different a has little influence on the dynamic action of the roof of the large section coal measure strata tunnel.The optimal value of the key parameters of the hollow-hole straight-hole cutting in the cross-cut coal blasting of the coal-measure formation tunnel was obtained.The recommended value of the distance between the blast hole and the empty hole is 24 cm,and the recommended value of the hole radius is 100 mm.Finally,the on-site blasting was completed.The test shows that the rock mass is uniformly broken after blasting,the cutting effect is good,and the coal uncovering depth is appropriate.The test results are close to the theoretical research results,which verify the reliability of the research results.

In coal mine roadway excavation,normal smoothing blasting technology has the phenomena of over-excavation,under-excavation and severe damage on the surrounding rock,which makes it difficult to support in the later stage and leads to high maintenance cost.Based on the mechanism analysis of directional fracture control blasting technology,we proposed a controlled blasting technology with slit charge in perimeter holes,and conducted comparison tests between blasts with slit charge and normal charge.The test results show that a good blasting effect can be achieved by a PVC pipe with outer diameter of 38 mm,inner diameter of 36 mm,slit width of 4 mm and slit length of 600 mm for directional fracture controlled blasting.This kind of controlled blasting technology improves the flatness of the roadway section,smooths the excavation contour and increases the half-hole rate with a maximum value of 90%.The average linear over-excavation was 0.171 m with a reduction of 0.238 m.Due to the increased hole spacing of the perimeter holes,the powder factor has been saved by 25%,which means about 20 kg less explosive per cycle of footage,and thus blasting vibration has also been reduced.Directional fracture control blasting effectively reduces the damage to the surrounding rock,increases its stability and achieves a more satisfactory blasting effect.

The crushing effect of roadway blasting determines whether the blasting parameters are reasonable or not,and its contour forming effect will also affect the stability of surrounding rock of underground mine roadway to a certain extent.Aiming at the problems of overbreak and surrounding rock breakage after blasting caused by excessive charge and dense arrangement of blast holes in roadway driving construction in Xifeng phosphate mine,Guizhou Province,theoretical analysis of rock fragmentation as well as reference to similar engineering experience were adopted to optimize hole spacing,burden and charge structure of tunneling blasting.As a result,six blast holes(two first-order cut holes,two roof holes and two auxiliary holes) were reduced by optimizing cutting method.At the same time,the total number of holes and explosive consumption were decreased by increasing hole spacing and air-deck charge.In addition,the finite element software LS-DYNA was used to analyze the optimized blasting scheme.The results show that the optimized blasting scheme reduces the peak stress and overbreak of roadway surrounding rock which stability is improved.Finally,through 15 groups of on-site practical experiments of tunnel excavation blasting,it is shown that,a good forming quality of tunnel excavation with no roof breakage or cut hole perforation can be achieved after optimizing the blasting parameters.The construction efficiency is improved,while the construction cost is reduced.Finally,it is considered that the blasting vibration can be effectively reduced and the forming quality of roadway can be ensured by properly increasing hole spacing and adopting air-decked charge,compared with the blasting without air decks.

In traditional smooth blasting construction,soft cracked surrounding rock is prone to a series problems,such as difficulty to control the amount of overcutting and undercutting,serious damage of surrounding rock,and low half-hole preservation rate.Based on the blasting construction of Xiaobaiyan tunnel in Guizhou Province,a casing pipe charge blasting design with double-layer perimeter holes was designed for soft fractured surrounding rock.In this study,starting from the causes of overbreak and underbreak,the perimeter hole layout,charge structure and blasting sequence were optimized.The charge structure of the outermost auxiliary holes was adjusted to the same uncoupled charge as that of the perimeter holes,and a protection casing pipe was added to the side of the reserved rock mass in each perimeter hole.The perimeter holes in were designed to initiate first and then followed by the inner layers of holes.Through numerical simulation and field tests,it is determined that the circumferential spacing of the double-layer perimeter holes is 500 mm,and the radial spacing is 650 mm.The initiation delay interval of the inner and outer layers is 50 ms.After applying the presented blasting design,the amount of over-excavation in the field test section has been reduced by 40% to 60% compared with conventional smooth blasting,and the half-hole preservation rate has increased to 89%.Finally,22 kg explosive consumption is saved per cycle advance and the economic benefit is significantly improved,which has a good popularization and application value.

Excavation of medium and small section extra-hard rock tunnels in water conservancy projects is often accompanied by difficulties in construction and low excavation efficiency.Based on the Fengdian-Pengdian reservoir connected emergency water diversion project,the drilling blasting scheme for the excavation of small-section extra-hard rock tunnel was studied.The field tests of different cutting blasting schemes were carried out and the technical scheme of combining multi-hole straight hole cutting blasting with air interval charging smooth blasting was proposed,and the specific drilling blasting parameters were determined.The field application results show that the combination of multi-hole straight hole cutting technology and air interval charge smooth blasting technology has good excavation forming effect,relatively flat excavation contour surface,basically no underbreak,and the maximum overbreak is about 20 cm,which realizes the safe and efficient excavation of the small section extra-hard rock diversion tunnel.

Due to complex geology of the Tanjiaba slope section of Enshi National Highway 209,fly rock was generated during blasting.According to the surrounding environment characteristics and the specific situation of cutting slope mountain section,a method to guide possible fly rock to a safe place was proposed combined with the advantage of the minimum burden principle,the multidirectional blasting action control principle and the group charge interaction principle.First of all,the short-hole and small bench height blasting was used to create a new lateral free surface for the main blasting of slope cutting,and then a deep-hole bench blasting method was carried out.The slope was descended sequentially in three small benches to reach the height of a deep-hole bench blasting.In the main blasting of deep hole slope cutting,a large-interval time delay hole-by-hole blasting method was adopted,and loose blasting with small explosive unit consumption,long packing,and inside-out sequential detonation were used.In order to reduce the generation of fly rock,some necessary measures were taken,such as the slope edge holes were independently designed according to the site conditions,the lateral minimum burden was obviously smaller than the slope minimum burden,and the detonation sequence and blasting parameters were flexibly adjusted according to the slope thickness.These measures greatly reduced the generation of fly rock,and effectively guaranteed the houses and factories safety in the villages below the slope.At the same time,the short-hole blasting also facilitates the addition of new working faces,which improves construction efficiency.It can provide a reference for similar projects.

Aiming at the blasting demolition project of a 120 m high reinforced concrete exhaust tower,the finite element software ANSYS/LS-DYNA was used to simulate the collapse process by a separate common node model.Compared with the video data,the movement state of the structural support part,the fracture part,and the top position of the instability failure process were analyzed.The results show that the cylinder structure with a large slenderness ratio was prone to fracture due to its large self-weight inertia and section mutation in the structure shape,and the interaction between impact failure and accelerated fall appeared in the process of sitting down.It was found that the blasting cut was formed at 0.2 s,and the stress concentration first appeared was at the top angle of the cut.After tipping at a certain angle,the back part was pulled and the stress concentration was transferred to the bottom angle of the cut.Furthermore,the initial stress redistribution time was at about 4.5 s,and there was a crack at 75 m of the structure at 9 s.Meanwhile,the cylinder was separated,the lower cylinder was slowly overturned around the plastic hinge,and the upper cylinder fell freely.The recorded video showed that the crack appeared at the position of the structure at about 70 m with a sudden mutation of the cross section at 8.5 s.The simulated collapse length was 104 m,the vibration velocity of cylinder collapse reached the maximum,the maximum velocity of the upper cylinder was 49 m/s,and the maximum velocity of the lower cylinder was 29 m/s.Besides,the simulated collapse time was about 12 s and the actual collapse time was 11.8 s,these two times were very close.

In a blasting demolition project of the bedrock cofferdam of a 300,000-ton dock,it was difficult to excavate shallow points and channels outside the cofferdam due to natural geographical conditions.So,it was necessary to increase the amount of cofferdam blasting to make the front of dock mouth form in one time.This lead to a 68 m long,43 m wide and 14.6~15.6 m deep wide-thick-type blasting demolition of bedrock cofferdam,which width was twice that of similar projects.In order to solve the problems of drilling accuracy,hazardous effects,and control of blasting effects,inclined main blast holes with parallel-fan pattern and vertical pre-split auxiliary holes were used to cover the entire cofferdam to be blasted.In addition,the strategy of dense holes and increased powder factor was adopted to achieve the desired effect of excavation and fragmentation.To control of harmful effects on the protected objects in the dock,high water level blasting supplemented by conventional safety protection was utilized.As for improving the reliability of blasting success and reduce the impact of blasting vibrations,the blast operation team decided to select customized explosive materials,increase the number of in-hole detonators,and connect the initiation network by a V-shape pattern with multiple branches.By summing up past experience,we presented the “super-deep and gently inclined hole drilling method”.Its circulating slag work platform and precise drilling control measures effectively guaranteed the quality,progress and safety of blasting construction.The blasting project was finally successful,and good blasting and excavation results were obtained,which accelerated the overall production schedule by about 2 months,and created nearly tens of millions of economic benefits for the shipyard.

The sub-way station in operation is extremely sensitive to blasting vibration.Existing regulations usually stipulate that blasting can only be carried out outside 50 m.The project requires accurate blasting decomposition of the concrete diaphragm wall in the area where the shield machine crosses only 2.8 m below the operating subway station.All blasting work should be completed within 5 hours when the subway stops running.Meanwhile,the normal use of operation,electrical and signal equipment and other equipment in the subway station should be ensured.The deviation of 28 m vertical deep hole is controlled within 5 through the bidirectional control of total station and level on the ground.Precise millisecond time delay blasting with 30 ms is used to form a presplitting fracture zone at the top.Layered charging millisecond time delay blasting is adopted and 72 blasting points are evenly arranged in the 50 m2 crossing area.The results of shield machine excavation after blasting show that the crushing particle size is less than 15 cm,and the station platform with the same structure as the blasting object is 3.4 cm/s on blasting vibration velocity at the station platform 5.6 m away from the explosion point,which achieves the dual purpose of ensuring the safety of the operating station and the crossing effect of the shield machine,and the subway station structure and electrical facilities operate safely after blasting.

In January 2021,the Anning River Bridge 1 was assessed as a class-4 dangerous bridge.In order to prevent the bridge from collapsing during the flood season,the local government planned to demolish the bridge by blasting.This Bridge was a double-curved arch bridge,with a length of 207.7 m and a width of 9.5 m.It was located in the downtown area of the city center and had a complex surrounding environment.The nearest distance to the existing Rainbow Bridge was 3 m.As the height of the bridge piers above the river bed was only 1.7~3 m,the collapse height of the bridge was insufficient.Therefore,the 3# bridge pier,which was far from the downtown on both sides of the bank,was selected for full blasting disintegration first.The powder factor of the 3# bridge pier,the upper cross wall of the pier and the upper cross wall of the arch was 1.5~2.13 kg/m3,which ensured the 3# pier could be fully broken and the space for the bridge to collapse could be created.Meanwhile,some stress components which affect the overall collapse of the bridge,such as arch ribs,piers,cover beams,transverse walls on piers,partial transverse walls on arches and connection beams,were destroyed locally,which resulted in the collapse of the bridge from the middle to both sides with powder factor of 1.44~1.96 kg/m3.A mixing initiation network of Nonel detonators and electronic detonators was adopted for different blast sections.In each section,equal interval short delay initiation was used according to the order of height and upstream to downstream,so that the initiation times of different sections of the bridge were different.For the same section,the difference of the initiation times and bridge collapse heights were made full use to realize the uneven settlement and full dislocated disintegration of the bridge under the low drop condition.In addition,multiple internal and external protection methods with rigidity and flexibility were utilized,including high-strength soft covering rubber,medium-strength covering geogrid plastic net,hard covering bamboo raft,soft covering straw mat and dense mesh safety net.Among them,the rigid and medium-high strength covering could control the large flying rocks,and the soft covering could play a buffering role to suppress the small flying rocks,which effectively protected the surrounding buildings(structures).

To dismantle a simply supported and then continuously prestressed reinforced concrete bridge,we adopted the blasting demolition scheme of split section in-situ collapse,based on the structural characteristics of the bridge and its distance to the surrounding buildings(structures).The short pier without a tethered beam had a diameter of 1.4 m and a height of 3 m,and the spacing between holes and rows were 30 cm and 50 cm,respectively.Meanwhile,the long pier with a tethered beam had diameter of 1.8 m and it was blasted by two sections separately.The blasting height of the section above the tie beam was 3 m and that of the lower section was 4m.The hole spacing was 40 cm,and the row spacing was 50 cm.Continuous charge was used in the hole,and electronic detonators were used for top detonation.The collapse-touch ground vibration was controlled by flexible collapse achieved by varying delay times.We adopted 4 layers of protective measures to strictly control flying stones.The blasting results showed that:the blasting network parameters were safe and reliable,and flexible collapse was achieved.The collapse vibration was reduced by controlling the flying stones so as to achieve a good blasting effect.

Blasting is the main excavation method of rock slope at present.In order to evaluate the effect of blasting damage on the stability of engineering slope,the weakening law of blasting damage is discussed based on the disturbance factor D in Hoek Brown strength criterion.Using the spatial variation of D characterized by change of longitudinal wave velocity in rock mass,the exponential type of D was obtained to reflect the spatial distribution of blasting damage degree.The impact on the factor of safety of the distribution rules as well as the influence area of the disturbance factor D were explored consequently.For the case in hand,the computed factor of safety is 1.14 when the value of D is gradually changed according to the law of exponential distribution,and the factor of safety increases to 1.39 and 1.47 respectively when it is gradually changed according to the law of linear and quadratic distribution.Considering the gradual change of exponential distributed D value in the blasting damage zone,the systematic bolts can effectively compensate the loss of the slope stability due to the rock mass mechanical properties weakened by blasting.The results show that considering gradual weakening of D can better reflect the actual effect of blasting damage on slope stability,the blasting damage can be effectively controlled by the system bolt,and the different distribution patterns and ranges of D have great influence on the factor of safety.

The bubble load caused by underwater explosion is the main reason for the overall damage of ship structure.Studying the dynamic characteristics of underwater explosion bubbles is crucial to the research of underwater weapon development and ship protection.Starting from the loading characteristics bubble pulsation in underwater explosion,the research progress of bubble dynamics theory,experiment and numerical simulation is reviewed.Meanwhile,the typical research results of the bubble non-spherical collapse process,bubble coupling with different structural surfaces and multi-bubble coupling in free field and the fragmentation of multiple bubbles in water after interaction are summarized.On the basis of the existing research results,it is suggested that the bubble motion mechanics model should be established considering the factors inside the bubble and different environmental factors in water,a more systematic experimental study should be carried out on the movement characteristics of bubbles in non-ideal explosive water,the research of multi-bubble coupling process under near-boundary conditions should be further strengthened.

Composite beams containing shear connectors are mostly used in bridge structures.Accidents may cause damage to the bridge structure due to vehicle explosion impact.At the same time,some abandoned bridges must be demolished by blasting.Based on this background,it is necessary to conduct an explosion analysis of a bridge structure containing shear connectors.First,ABAQUS was used to verify the rationality of the fluid-solid coupling model considering the high strain rate-related concrete constitutive and steel constitutive with reference to the explosion test in the existing literature.Then,the fluid-solid coupling numerical simulation was carried out for the composite beams with corrugated steel plates,perforated steel plates and bolted shear connectors under the action of explosion load,and the failure modes of the composite beams with three different shear connectors were studied.The results show that under the blast load of 2 kg spherical TNT,the concrete inside the composite beam connector is deleted,the concrete outside is spalling,and the concrete on the left and right sides near the explosion point has a large plastic damage.The damage of the steel plate connector is mainly concentrated at the joint of the round hole and tenon.During the explosion,the top of the stud connector is significantly impacted,and the bottom is sheared.For steel plate connectors,the addition of steel bars in the concrete tenon can effectively reduce the damage at the opening of the steel plate.The displacement of the bolted composite beam is the smallest.After the explosion peak,because the bolt is a flexible connector and interacts with concrete,the vibration speed is minimum and the energy absorption effect is good.The steel plate connector is a rigid connector with strong impact resistance and low peak vibration velocity.The research results can provide reference for anti-blasting and blasting demolition of bridge structures and other engineering structures.

The application of drilling and blasting technology in long urban cross-ridge tunnels can effectively improve construction efficiency and save the costs.However,due to the surrounding environment of urban tunnel,the harmful effects of blasting are becoming more and more prominent,especially the blasting vibration effects constraints the blasting excavation.According to the actual monitoring of the vibration on the surrounding buildings during the blasting excavation of the entrance and exit segments of the long urban cross-ridge tunnel in Dabanshan,the blasting seismic wave propagation attenuation law was analyzed.It is concluded that there is an inverse correlation between the integrity of the surrounding rock and the values of the key parameters K,α taken in the Sadovsky formula under the same rock type,the better the integrity of rock,the lower the values of the key parameters.The proposed values of K and α are 350 and 1.9 for the entrance section and 250 and 1.85 for the exit section,respectively.The blast vibration velocity propagation curves were plotted for three representative charge volume.Based on the plotted curves and the vibration velocity control requirements of the site building,the starting position of the tunnel blasting excavation from the tunnel entrance was determined.And it provides a reference for the actual tunnel excavation project with poor grade and integrity of surrounding rock and dense surrounding buildings.

In order to improve prediction accuracy of blasting vibration velocity,a model based on relevance vector machine(RVM) was proposed.The nonlinear mapping relationship between blasting vibration velocity and its influencing factors was established using the model.Three main factors affecting blasting vibration velocity(explosive charge,distance and elevation difference) were fitted for training by 36 sets of generated data based on which the remaining 5 samples were accurately predicted.The model was applied as an example and compared with the prediction results of BP neural network model and GA-BP neural network model.Under the same influence factor and data sample conditions,RVM model has higher prediction accuracy and lower dispersion.Compared to the actual values,the average relative errors of blasting vibration velocity predicted by RVM are obviously lower than those predicted by BP neural network and GA-BP neural network,which further verifies that the RVM model can improve the accuracy of the prediction accuracy and stability.