Study On The Impact Of Blasting Vibration On Tunnel Stability

Mineral resources play an important role in the development of national economy. With therapid pace of development of our country, there is a increasing demand for mineral resources. Themain technique used in mine production is blasting technique of which theshock effect may lead toroof collapse and instability of mine roadway. As a result, the quality of ore and the lives of minerswill be threatened, especially the more dangerous effect that accumulation of uninterrupted miningblasting operations generates. Therefore, it has a profound theoretical and practical significance forensuring the stability of the rock mass underground roadway and ensuring mine production safetyto conduct the study on the impact of underground mining blasting vibration effectson surroundingrock mining projects, especially the cumulative effect of blasting vibration. Then, controltechnologymeasureswillbe putforward to reducetheintensity oftheeffectof blastingvibration.Qianjaping vanadium ore adopted Level stage of deep-hole ore room method, using thetechnology of medium-length hole blasting. This kind of method has characteristics of intensivespacing burden and large amount of explosive payload. The blasting vibration effect resulted fromthis will have an impact on surrounding rock of extraction roadway. Particularly, more influenceswill be generated with more frequent cumulative effect of blasting vibration. Some sidewalls in theroadway have appeared cracks and collapse rocks on domes. If the mechanism of action of blastingvibration on the roadway can be fully understood, measures can be taken to effectively control theblasting vibration effects so as to effectively protect the roadway stability. For above reasons, basedon the mine site blasting vibration test data, this paper focuses on the theoretical and regressionanalysis and FLAC3D numerical simulation method to analyze the mechanism of medium-lengthhole blasting vibration effect on the roadway, combined with the actual situations, and proposesmeasures for controlling medium-length hole blasting vibration effects. The main contents andresultsofthispaperareas follows:1. Study on attenuation law of blasting vibration. Firstly, this paper conducted a siteinvestigation and conclusion on the effect of actual production blasting operations in the middle of995m Qianjiaping vanadium on mining roadway. Then, monitoring programs for blasting vibrationin mining roadway were designed and put into practice in order to obtain parameters like blastingvibration peak velocity, duration of shaking and blasting vibration frequency of test point.Regression analysis will be conducted based on the monitoring results and obtain the law of blasting seismic wave attenuation. Based on the sadov’s formula, prediction of blasting vibrationvelocity peak was made and also compared with the measured data. Attenuation law is morerealistic in line with actual results which can be used for prediction and provide the basis for thedesign of blasting parameters. Finally, based on HHT method, analysis on certain blastingvibration signals measured generated the relationship between the signal energy, frequency andtime. It can be seen that there is wide range of blasting seismic wave frequency, most of which iswithin50HZ and the energy is more concentrated here. It is similar to the natural frequencies ofgeneral buildings (structures) that have greater impact on the instability of buildings (structures),whichneedstobepaid sufficientattention.2. Numerical simulation of blasting vibration. Select a point on the middle of blastingoperations roadway as simulation study object, establish F1ac3D calculation model based onphysical and mechanical properties of the rock mass, use particle blasting vibration velocityactually monitored as input dynamic loads, simulate two situations like only in charge of self-weight and stress under dynamic loading respectively, which arrive at the situation changes in theroadway surrounding rock displacement, stress and plastic zone and other parameters. Resultsshowed that after the addition of the dynamic load applied, roadway surrounding rockdisplacement was relatively small, stress and plastic zone had increased slightly as well. Thisindicates that blasting vibration caused some damages to the mining roadway rocks. Damage zoneswere mainly located in the floor area and arch position of roadway. However, it will not damagethe roadway. It can be predicted that under frequent blasting operations in mine, the damage to themining roadway in stope will gradually worsen and eventually causing instability on roadway.Meanwhile, through comparative analysis the situation with shoring and another situation withoutshoring,betterstabilityoftheroadway canbefound with shoring.3. Roadway stability monitoring. After each blasting operations, roadway deformationconvergence intesting points were monitored and arriveat that convergence rateof roadway was atnormal levels, close to the results of numerical simulations. However, actually, after several deephole blasting operations, there was a certain degree of damage to the above area of roadway inoperating points which will be worsen due to further accumulation of this damage and eventuallylead to roadway damage. Therefore, after the completion roadway construction, there are needs forshoring in a timely manner. At the same time, adjusting the blasting parameters and reducing theintensityofblastingvibration should bedonetoweaken itsdamageto theminingroadway.