Rock burst roadway support design method based on comprehensive impact risk index evaluation
Technical Field
The invention relates to the technical field of roadway support. In particular to a design method suitable for underground coal mine rock burst roadway support.
Background
With the increase of the mining depth, the number of rock burst mines is gradually increased, and once rock burst occurs, the rock burst threatens the life of miners greatly and causes great loss to the mines. The rock burst is a dynamic phenomenon that the original mechanical balance of a roadway and a working face is destroyed due to mining influence in the coal mining process, and the elastic energy of the rock burst is rapidly released, and can affect ground buildings in severe cases. Therefore, the problem of rock burst becomes a great technical problem of coal mine tunneling and mining and threatens mine safety.
The occurrence frequency of rock burst is in a nonlinear growth relation with the increase of the coal seam mining depth, according to statistics, 85% of rock burst occurs in a roadway, the prevention and control of the rock burst of the roadway need to selectively support the rock burst roadway besides effective pressure relief, and the effectiveness of the rock burst roadway support technology directly determines whether the disaster of the rock burst can be effectively reduced. Particularly in serious rock burst mines, the disaster of rock burst cannot be eliminated despite various prevention and control technologies.
The geological conditions of coal mines in China are complex, particularly after the coal mines enter deep mining, the supporting difficulty of the roadway, particularly the supporting difficulty of rock burst roadway is increased. How to support the rock burst roadway is always a hotspot and difficulty for the study of scholars at home and abroad. With the development of anchor rod technology, a great deal of novel supporting materials are developed. The method improves the efficiency of roadway support, and researches and develops a high-strength energy-absorbing impact-proof anchor rod (cable) to solve the roadway disaster caused by rock burst. The rock burst roadway support must adopt full-section equal-strength support, and support members, support bodies and support bodies are mutually coupled to form a uniform support whole body.
The roadways with different impact risk levels adopt uniform support standards, and support is enhanced blindly, so that waste of support materials and reduction of support efficiency are caused. Different supporting modes and supporting methods are selected, so that the quantitative design of the roadways with different impact risk levels is realized, and the problems of supporting material waste and safety caused by excessive supporting and insufficient supporting of the roadways with different impact risk levels are effectively solved.
The roadway with different impact danger grades adopts different support design methods, is a new idea for preventing and controlling rock burst in coal mine tunneling, and is different from the traditional rock burst roadway support technology and method. The support design method for determining the rock burst roadway according to the rock burst risk level can realize effective support of different rock burst roadways, and has important significance for safe mining of rock burst mines, roadway support and rock burst prevention and control.
Disclosure of Invention
The technical problem is as follows: the invention aims to overcome the defects in the existing support design method and provide a roadway support design method for rock burst roadway evaluation based on impact danger comprehensive indexes.
The technical scheme is as follows: the invention relates to a rock burst roadway support design method based on comprehensive impact risk index evaluation, which comprises the following steps of:
a. determining rock burst roadway evaluation object
Acquiring data through roadway on-site investigation and a roadway support theory, and determining a rock burst roadway evaluation and support object according to rock burst roadway geological conditions and the position condition information;
b. coal rock impact tendency identification
Determining the impact tendency of the coal rock by measuring the uniaxial compressive strength, impact energy index, elastic energy index and dynamic failure time of the coal rock;
c. determining impact risk evaluation index applicable to evaluation target
Determining an impact risk evaluation index applicable to the rock burst roadway according to the geological conditions of the rock burst roadway, wherein the impact risk evaluation index is 'influence factor' and 'danger index score' and the corresponding relation of the influence factor and the danger index score; the influence factors comprise geological influence factors and mining influence factors;
d. determining impact risk index of geological influencing factors
Selecting a geological influence factor and a danger index score corresponding to a mining influence factor according to an impact risk index applicable to the rock burst roadway;
e. determining impact hazard index of mining-type influencing factors
Selecting mining influencing factors and danger index scores corresponding to the mining influencing factors according to impact danger indexes applicable to the rock burst roadway;
f. determination of impact comprehensive danger index WtAnd impact hazard class;
g. according to the coal rock impact tendency identification and impact risk evaluation results, calculating the roadway surrounding rock roof-side impact energy;
h. preliminarily designing a rock burst roadway support scheme and support parameters;
i. checking and calculating the impact resistance and the shock resistance of the supporting member, determining whether the impact resistance of the supporting member is greater than the impact energy or not, determining a supporting scheme and parameters, wherein the impact resistance of the supporting member is greater than the impact energy; and if the impact resistance of the supporting member is smaller than the impact energy, redesigning the supporting scheme and parameters.
j. And optimizing the determined rock burst supporting scheme to complete the rock burst roadway supporting design.
When impact comprehensive danger index Wt<0.25, the rock burst roadway belongs to the non-impact danger, and the maximum energy value of the microseismic monitoring roadway is 5 x 103J, the selected supporting technology is conventional anchor rod and anchor net supporting.
When impact comprehensive danger index of 0.25<Wt<0.5, the rock burst roadway belongs to weak impact danger, and the maximum energy value of the microseismic monitoring roadway is 3 x 104J, selecting a support technology of an anchor rod and an anchor net with high strength, high rigidity, high pretightening force and high anchoring points for support.
When impact comprehensive danger index of 0.5<Wt<0.75, the rock burst roadway belongs to medium impact danger, and the maximum energy value of the microseismic monitoring roadway is 3 x 105J, selecting a supporting technology to be one of anchor rods and anchor nets with high strength, high rigidity, high pretightening force and high anchoring points for supporting + O-shaped sheds, energy-absorbing unit frames or weak structures.
When impact comprehensive danger index of 0.75<Wt<0.95, the rock burst roadway belongs to the high impact danger, and the maximum energy value of the microseismic monitoring roadway is 3 x 106J, selecting two of anchor rods, anchor nets, O-shaped sheds, energy-absorbing unit frames or weak structures with high strength, high rigidity, high pretightening force and high anchoring points as supporting technologies.
When impact comprehensive danger index Wt>0.95, the rock burst roadway belongs to the unsafe rock burst roadway, and the maximum energy value of the microseismic monitoring roadway is less than 3 x 107J, selecting anchor rods and anchor nets with high strength, high rigidity, high pretightening force and high anchoring points as a supporting technology, an O-shaped shed, an energy absorption unit frame and a weak structure.
When impact comprehensive danger index Wt>0.95, the rock burst roadway belongs to the unsafe rock burst roadway, and the maximum energy value of the microseismic monitoring roadway is more than 3 x 107J, stopping production and removing people at the moment, and carrying out remote pressure relief treatment.
Has the advantages that: by adopting the technical scheme, the invention achieves the purposes of impact resistance and energy absorption by carrying out support design according to the energy check of the rock burst roadway, prevents and treats rock burst by utilizing the rock burst roadway support design of coal rock impact tendency identification and impact danger comprehensive indexes, and selects different support design methods by evaluating different impact danger comprehensive indexes of the rock burst roadway, thereby weakening the threat of impact energy to two sides and a top plate of the roadway and preventing the occurrence of rock burst. The method can be used for supporting the rock burst roadway more safely and effectively, and is also beneficial to reducing the production cost of the coal mine. Compared with the prior art, the main advantages are as follows:
1) the method comprises the steps of performing targeted support on the rock burst roadway, selecting a reasonable support design method according to coal rock impact tendency identification and impact risk level, determining a reasonable support technology, and achieving effective support on the rock burst roadway;
2) by selecting a reasonable support design method for the impact ground pressure roadway, quantitative checking of energy design of the roadways with different impact risk levels is realized, and the problems of support material waste and safety caused by excessive support and support lack of the roadways with different impact risk levels are effectively avoided;
3) the method effectively controls the damage of the rock burst roadway, realizes the reasonable design and support of the rock burst roadway, has important significance for preventing and controlling the rock burst, and is simple, safe, convenient, economic and practical.
Drawings
FIG. 1 is a flow chart of a rock burst roadway support method for rock burst roadway impact hazard comprehensive index assessment of the invention.
Detailed Description
An embodiment of the invention is further described below with reference to the accompanying drawings:
the invention relates to a rock burst roadway support design method based on comprehensive impact risk index evaluation, which comprises the following specific steps:
a. determining rock burst roadway evaluation object
Acquiring data through roadway on-site investigation and a roadway support theory, and determining a rock burst roadway evaluation and support object according to rock burst roadway geological conditions and the position condition information;
b. coal rock impact tendency identification
Determining the impact tendency of the coal rock by measuring the uniaxial compressive strength, the impact energy index, the elastic energy index and the dynamic failure time of the coal rock according to the geological and mining technical conditions on site;
c. determining impact risk evaluation index applicable to evaluation target
Determining an impact risk evaluation index applicable to the rock burst roadway according to the geological condition of the rock burst roadway, wherein the impact risk evaluation index is 'influence factors' and 'danger index score' and the corresponding relation of the 'influence factors' and the 'danger index score', and the 'influence factors' comprise 'geological influence factors' and 'mining influence factors';
d. determining impact risk index of geological influencing factors
Selecting a geological influence factor and a danger index score corresponding to the geological influence factor according to an impact risk index applicable to the rock burst roadway;
e. determining impact hazard index of mining-type influencing factors
Selecting mining influencing factors and danger index scores corresponding to the mining influencing factors according to impact danger indexes applicable to the rock burst roadway;
f. determination of impact comprehensive danger index WtAnd impact hazard class;
when impact comprehensive danger index Wt<0.25, the rock burst roadway belongs to the non-impact danger, and the maximum energy value of the microseismic monitoring roadway is 5 x 103J (Joule), the supporting technology is selected as the conventional simple anchor rod and anchor net supporting measure.
When impact comprehensive danger index of 0.25<Wt<0.5, the rock burst roadway belongs to weak impact danger, and the maximum energy value of the microseismic monitoring roadway is 3 x 104J, selecting a four-high anchor net support as a support technology, namely selecting an anchor rod and an anchor net support with high strength (tensile strength is more than or equal to 850MPa), high rigidity (yield strength is more than or equal to 700MPa), high pretightening force (pretightening force is more than or equal to 80kN) and high anchoring point (anchoring point is more than or equal to 2.4 m).
When impact comprehensive danger index of 0.5<Wt<0.75, the rock burst roadway belongs to medium impact danger, and the maximum energy value of the microseismic monitoring roadway is 3 x 105J, the selected supporting technology is four-high anchor net support +1, namely, one of an anchor rod and anchor net support with high strength, high rigidity, high pretightening force and high anchoring points, an O-shaped shed, an energy-absorbing unit frame or a weak structure is selectedAnd (4) seed preparation.
When impact comprehensive danger index of 0.75<Wt<0.95, the rock burst roadway belongs to the high impact danger, and the maximum energy value of the microseismic monitoring roadway is 3 x 106J, the selected supporting technology is four-high anchor net supporting +2, namely two of high-strength, high-rigidity, high-pretightening-force and high-anchoring-point anchor rods, anchor nets, an O-shaped shed, energy-absorbing unit frames or weak structures are selected.
When impact comprehensive danger index Wt>0.95, the rock burst roadway belongs to the unsafe rock burst roadway, and the maximum energy value of the microseismic monitoring roadway is less than 3 x 107J, selecting an anchor rod, an anchor net, an O-shaped shed, an energy absorption unit frame and a weak structure which are high in strength, rigidity and pretightening force and high in anchoring point.
When impact comprehensive danger index Wt>0.95, the rock burst roadway belongs to the unsafe rock burst roadway, and the maximum energy value of the microseismic monitoring roadway is more than 3 x 107J, stopping production and removing people at the moment, and carrying out remote pressure relief treatment.
g. According to the coal rock impact tendency identification and impact risk evaluation results, calculating the roadway surrounding rock roof-side impact energy;
h. preliminarily designing a rock burst roadway support scheme and support parameters;
i. checking and calculating the impact resistance and the shock resistance of the supporting member, determining whether the impact resistance of the supporting member is greater than the impact energy or not, determining a supporting scheme and parameters, wherein the impact resistance of the supporting member is greater than the impact energy; and if the impact resistance of the supporting member is smaller than the impact energy, redesigning the supporting scheme and parameters.
j. And optimizing the determined rock burst supporting scheme to complete the rock burst roadway supporting design.
Example (b): the mine is a rock burst mine, the geological structure of the mine is simple, the coal seam has impact danger, and when the most serious rock burst occurs in the mine, the microseismic energy monitored by the microseismic monitoring system is 1.3 multiplied by 106J, the supporting mode is as follows: (1) anchor bolt support: the top plate uses 5 phi 22 multiplied by 2800mm high prestress left-handed thread steel anchor rods, the eyelets at the two ends of the top plate are short anchor cables, and the row spacing is 0.8mAnchoring force is not less than 150 kN; (2) anchor rope supporting: 5 short anchor cables with the diameter of 21.8 multiplied by 6300mm are arranged on the top plate, the row spacing is 0.8m, and the anchoring force is not lower than 200 kN; 3 anchor cables with the length of phi 21.8 multiplied by 8300mm are arranged on the top plate, the row spacing is 0.8m, and the anchoring force is not lower than 250 kN; (3) supporting the energy-absorbing impact-resisting unit column: 1 energy-absorbing anti-impact unit column (2 columns) is arranged on the coal pillar side of the roadway. (4) And (4) weak structure supporting: the scour protection relief pressure hole sets up the weak structural drilling of tunnel surrounding rock, sends the coal rock body of splitting repeatedly and realizes that weak structure carries out pressure release.
The absorbing work of the roadway anchor rod cable support component is as follows:
in the formula: n isg,ns,ntThe number of anchor rods, anchor cables and other members, respectively, Eg,Es,EtThe absorption work of the anchor rod, the anchor cable and other components is respectively, B is the width of the roadway, and K is the support circulating row spacing.
The energy absorbed by the roof anchor cable and the anchor belt net under the combined action is as follows: (12 × 5+10 × 3)/(5.6 × 1.6) ═ 10.04J;
the energy absorbed by the upper anchor belt net is as follows: (8 × 5+8 × 3)/(3.7 × 1.6) ═ 10.81J;
energy-absorbing scour protection unit post: the energy absorption resistance of a single upright is 2000kN, the maximum energy absorption is 400kJ, and therefore, the maximum support resistance of three uprights is 6000kN, the maximum abdication displacement is 200mm, and the maximum energy absorption is 106J; can absorb 5 x 10 according to the energy absorption and impact prevention unit column5J
Energy absorption of the weak structure: the weak structure wave absorption energy is about 25-40% of the propagation energy of the impact vibration wave; the energy absorption of the weak structure for wave absorption is about 30 percent of the propagation energy of the impact shock wave.
The calculation is as follows: the microseismic energy monitored by the microseismic monitoring system is 1.3 multiplied by 106J, 30 percent of the energy transmitted by the shock wave is absorbed by the weak structure, and the residual energy is 9.1 multiplied by 105J, two energy-absorbing impact-proof unit columns can absorb 1 x 106J, the energy absorbed by the anchor rod cable is 20.85J. Impact resistance of a supporting memberThe capability is larger than the impact energy, and the supporting scheme and parameters are reasonable and implemented.