CN104794315A - Coal seam floor damaged zone depth determination method based on improved rupture mechanical model - Google Patents

Abstract

The invention provides a coal seam floor damaged zone depth determination method based on an improved rupture mechanical model and belongs to the technical fields of three under-one above mining and gas extraction. The coal seam floor damaged zone depth determination method is provided on the basis of accurately-measured data of national mines so that the limitation of regions is overcome; the coal seam floor damaged zone depth determination method can completely consider factors which are well-known and influence the damaged zone depth, and consider the influences on the damaged zone depth of a floor by a coal seam inclined angle for the first time, so that the precision and stability of a calculation model are effectively improved.

Description

Based on the Seam Floor Failure band depth determination method improving fracture mechanics model

Technical field

The invention belongs to " three next on " exploitation and gas pumping technical field, be specifically related to a kind of Seam Floor Failure band depth determination method based on improvement fracture mechanics model.

Background technology

Along with the development of China's mining technique and scientific and technological level, overlength workplace, the quantity of large mining depth workplace increases year after year, and the base plate water damage problem occurred in China also constantly increases, and obtains concern and the attention of numerous experts and scholars in the industry; In base plate water damage prediction, achieve great successes through numerous experts and scholars effort for many years with the base plate water damage research of research China; Wuqiang County professor applies vulnerable index and generalized information system etc., propose " the two prediction of three figure " method, Jiang Zhenquan professor and Duan Hong such as to fly at the evaluation method proposing mining under safe waterpressure of aquifer Water Inrush, and Wang Lianguo teaches and Sun Jian etc. conducts in-depth research inclined seam coal seam floor failure feature and mechanism of water inrush.Coal seam floor failure causes water damage most important reason, particularly important to the prediction of plate destructing depth; Miao assists emerging professor, Jiang Yaodong professor and Liu Shucai etc. to conduct in-depth research adopting coal seam floor failure rule, Shi Longqing professor and Yu Xiaoge etc. have carried out multiplicity to plate destructing depth, establish multifactor plate destructing depth computation model, Guo Wenbing etc. establish the plate destructing depth Prediction Model based on BP neural network;

Above experts and scholars acquire a great achievement in destruction band depth determination method, but also have a lot of things to do on the research road determining the coal seam floor failure degree of depth, the computational accuracy improving coal seam floor failure remains the direction that we update pursuit;

Original coal seam floor failure degree of depth mechanics model:

Rear coal seam floor failure and stress distribution are adopted in analytical work face, the ANALYSIS OF CALCULATING of general application structure mechanics, adopt rear base sheet stresses distribution and damage envelope model as shown in Figure 1;

The base plate of workplace, due to mining influence, makes stress redistribute, and stress concentrates on rib both sides, rib place support pressure is increased, forms a stress-relaxed area in goaf; Tu1Zhong① district is active principle stress district, and 2. district is zone of transition, and 3. district is passive stressed zone; The collapse dept formed due to support pressure impact increases, and the collapse dept in rib both sides will much larger than work centre position, and the maximum destruction band degree of depth generally all concentrates in zone of transition;

Application fracturing mechanics sets up coal seam floor failure depth calculation model:

$h=\frac{1.57{\mathrm{\γ}}^2{H}^{2}L}{4R_c^2}---\left(4\right)$

In formula: h is for destroying the band degree of depth, m; H is base plate buried depth, m; L is stope width, m; γ is floor rock volume-weighted average, MN/m ³; R _cfor the compressive strength (0.15 times that generally gets rock uniaxiality strength) of floor rock, MPa.

Can find out from formula (4) destroy the band degree of depth and buried depth square, the quadratic sum stope width of floor rock volume-weighted average is directly proportional, with square being inversely proportional to of the compressive strength of floor rock; Think in fracturing mechanics that the destruction band degree of depth of seam inclination on base plate does not affect, but in the production of reality, find that the existence of seam inclination is clearly on the impact of coal seam floor failure really.

Summary of the invention

For the deficiencies in the prior art, the present invention proposes the Seam Floor Failure band depth determination method based on improving fracture mechanics model, to reach the object improving coal seam floor failure degree of depth determination precision and stability.

Based on the Seam Floor Failure band depth determination method improving fracture mechanics model, comprise the following steps:

Step 1, structure Seam Floor Failure band degree of depth test model, wherein, maintenance is adopted deeply, stope width, roof and floor lithologic, mining height and boundary condition are constant, changes the value of seam inclination, obtains the Seam Floor Failure band depth value of correspondence;

Step 2, according to obtained often group seam inclination and its corresponding Seam Floor Failure band degree of depth, adopt the funtcional relationship between least square fitting coal output layer inclination angle and the Seam Floor Failure band degree of depth;

Step 3, fracture mechanics model to be combined with the funtcional relationship between seam inclination and the Seam Floor Failure band degree of depth, obtain the coal seam floor failure depth model based on fracturing mechanics after improving;

Step 4, according to obtain improvement after the coal seam floor failure depth model based on fracturing mechanics, the compressive strength of the seam inclination in Practical Project, base plate buried depth, stope width, floor rock volume-weighted average and floor rock is substituted into above-mentioned model, obtains the coal seam floor failure degree of depth of target coal seam.

Seam inclination variation range described in step 1 is 0 ° ~ 30 °.

Structure Seam Floor Failure band degree of depth test model described in step 1, adopts UDEC numerical simulation software.

Seam inclination described in step 2 and the funtcional relationship between the Seam Floor Failure band degree of depth, formula is as follows:

h＝aα ³+bα ²+cα+d (1)

Wherein, h represents the Seam Floor Failure band degree of depth, m; α represents seam inclination, and a, b, c, d all represent undetermined coefficient.

Fracture mechanics model is combined with the funtcional relationship between seam inclination and the Seam Floor Failure band degree of depth described in step 3, according to the principle of similitude, specific as follows:

$\frac{h}{\frac{1.57{\mathrm{\γ}}^2{H}^{2}L}{4R_c^2}}=\frac{{\mathrm{a\α}}^3+{\mathrm{b\α}}^2+\mathrm{c\α}+d}{d}---\left(2\right)$

Wherein, h represents the Seam Floor Failure band degree of depth, m; H represents base plate buried depth, m; L represents stope width, m; γ represents floor rock volume-weighted average, MN/m ³; R _crepresent the compressive strength of floor rock, Mpa; α represents seam inclination;

According to the principle of similitude, a α on the right of equal sign left side h and equal sign in formula (2) ³+ b α ²+ c α+d all considers seam inclination, equal sign left side fracture mechanics model in formula (2) all seam inclination is not considered, i.e. α=0 ° with d on the right of equal sign;

Arrange the coal seam floor failure depth model of formula (2) acquisition based on fracturing mechanics:

$h=(\frac{a{\mathrm{\α}}^3+{\mathrm{b\α}}^2+\mathrm{c\α}}{d}+1)\frac{1.57{\mathrm{\γ}}^2{H}^{2}L}{4R_c^2}---\left(3\right)$

Advantage of the present invention:

The present invention proposes a kind of based on improving the Seam Floor Failure band depth determination method of fracture mechanics model, and gained on the measured data basis of collecting national mine, therefore overcomes the limitation of region; It is thorough that the present invention considers the factor affecting the zone of fracture degree of depth that we know, but also consider the impact of seam inclination on the coal seam floor failure degree of depth first, therefore, effectively improves the precision and stability of computation model.

Accompanying drawing explanation

Fig. 1 is base sheet stresses distribution and damage envelope schematic diagram;

Fig. 2 is the projective water point location map of an embodiment of the present invention;

Fig. 3 is that the measured data seam inclination of an embodiment of the present invention is to destruction band effect of depth curve map;

Fig. 4 is the Seam Floor Failure band depth determination method process flow diagram based on improvement fracture mechanics model of an embodiment of the present invention;

Fig. 5 is that the numerical experiments seam inclination of an embodiment of the present invention is with degree of depth matched curve figure with destruction.

Embodiment

Below in conjunction with accompanying drawing, an embodiment of the present invention is described further.

In the embodiment of the present invention, the statistics of the projective water point position in each mining area of China is analyzed;

Although the upper-lower position of inclined cut also exists elevation difference, because buried depth is more much bigger than elevation difference, and earth's surface absolute altitude also also exists difference, so the initial stress of apparent dip workplace upper-lower position is equal; In the embodiment of the present invention, the statistics of the projective water point and seam inclination that have collected nationwide is analyzed, because the length of workplace is different, analyze according to projective water point " proportional positions ", 0 is the foot of inclined cut, and 1 is the topmost of inclined cut, and 0 ~ 0.3 is considered as workplace bottom, 0.3 ~ 0.7 is considered as in the middle part of workplace, 0.7 ~ 1 is considered as workplace top, in table 1, analyzes data preparation and lists in Fig. 2, horizontal ordinate is the position of projective water point, and ordinate is seam inclination.The projective water point position 72% of water inrush accident concentrates on the bottom of workplace, and when seam inclination be greater than 10 ° be less than 30 ° time projective water point position 79% projective water point concentrate on lower position.Illustrate that the band degree of depth is destroyed in bottom comparatively large, can show that the existence due to inclination angle destroys band degree of depth maximum position in the bottom of workplace, inclination angle becomes more obvious on the impact destroying the band degree of depth greatly.

Table 1 seam inclination and projective water point position statistical form

In the embodiment of the present invention, analyze the seam inclination of collection and destroy the data being with the degree of depth.

43 groups that collect national each mining area are destroyed the statistics being with the degree of depth and seam inclination, in table 2, destroy the variation relation of the band degree of depth along with seam inclination, as shown in Figure 3.As can be seen from the figure when the variation range of seam inclination is 0 ° ~ 30 ° along with the change of seam inclination is large, the degree of depth destroying band presents the rule increased progressively.

The band degree of depth and seam inclination statistics are destroyed in the national each mining area of table 2

In the embodiment of the present invention, based on the Seam Floor Failure band depth determination method improving fracture mechanics model, method flow diagram as shown in Figure 4, comprises the following steps:

Step 1, structure Seam Floor Failure band degree of depth test model, wherein, maintenance is adopted deeply, stope width, roof and floor lithologic, mining height and boundary condition are constant, changes the value of seam inclination, obtains the Seam Floor Failure band depth value of correspondence; Described seam inclination variation range is 0 ° ~ 30 °.

In the embodiment of the present invention, for accurately reflecting that seam inclination is on the impact destroying the band degree of depth, sets up Utopian test model, UDEC numerical simulation software is adopted to carry out analysis of experiments;

In the embodiment of the present invention, the moulded dimension set up is the square model of 300 × 200, for eliminating boundary effect, the border of 50m is all at least left at right boundary, roof and floor lithologic is all hard rock in selecting, for comparatively accurate analog bottom collapse dept, floor undulation distance model lower limits 80m; It is all 200m that the lower limits of model is adopted deeply, and stope width is 100m, and mining height is 2m.

Step 2, according to obtained often group seam inclination and its corresponding Seam Floor Failure band degree of depth, adopt the funtcional relationship between least square fitting coal output layer inclination angle and the Seam Floor Failure band degree of depth;

In the embodiment of the present invention, numerical simulation change of seam inclination and the coal seam floor failure degree of depth when seam inclination is 0 ° ~ 30 °, in table 3, data are 6 group models simulation seam inclinations and destroy the result being with the degree of depth.

Table 3 numerical experiments destroys band depth data

For drawing the incidence relation destroying the band degree of depth and seam inclination, in the embodiment of the present invention, according to 6 groups of test figure (x _i, y _i), (i=1 ..., 6), ask approximate function y=S (x); In fitting function problem, when determining function parameter in engineering, the most frequently used method is least square method, and the ultimate principle of the method is the sum of square of deviations minimized between match value and actual value.

In the embodiment of the present invention, using seam inclination as independent variable, destroy the band degree of depth as dependent variable, set up cubic fit function, simulate seam inclination and be with depth function curve with destruction:

h＝0.0001α ³+0.001α ²+0.1α+10.0 (5)

Wherein, h is for destroying the band degree of depth, and α is seam inclination.The function curve simulated as shown in Figure 5.

As can be seen from Figure 5, when seam inclination is within the scope of 0 ° ~ 30 °, destroy band and increase along with the increase of seam inclination.But destroying the band degree of depth within the scope of change of pitch angle is not remain linear pattern to increase progressively, when 0 ° ~ 12 ° of scopes, rate of curve is 0.13, destroy the band degree of depth less along with changing when seam inclination changes, when 12 ° ~ 30 ° of scopes, rate of curve is 0.28, changes greatly when destroying the change of being with the degree of depth along with seam inclination.

Step 3, fracture mechanics model to be combined with the funtcional relationship between seam inclination and the Seam Floor Failure band degree of depth, obtain the coal seam floor failure depth model based on fracturing mechanics;

In the embodiment of the present invention, according to the principle of similitude, the destruction band degree of depth of application fracture mechanics model and foundation and the functional relation of seam inclination, establish a kind of novel destruction band degree of depth Im-FM computation model;

The principle of similitude can be applied to and solve according to Theory Solution in engineering, and ask and generally separate, well-known theory function f (x) sum functions ratio of similitude k, then general function S (x)=kf (x), wherein, k value solves according to special similitude; Similar function principle in applied mathematical model sets up the coal seam floor failure fracturing mechanics computation model considering seam inclination impact:

$h=(\frac{0.0001{\mathrm{\α}}^3+0.001{\mathrm{\α}}^2+0.1\mathrm{\α}}{10}+1)\frac{1.57{\mathrm{\γ}}^2{H}^{2}L}{4R_c^2}---\left(6\right)$

Step 4, according to obtain improvement after the coal seam floor failure depth model based on fracturing mechanics, the compressive strength of the seam inclination in Practical Project, base plate buried depth, stope width, floor rock volume-weighted average and floor rock is substituted into above-mentioned model, obtains the coal seam floor failure degree of depth of target coal seam.

In the embodiment of the present invention, the coal seam floor failure depth model based on fracturing mechanics is tested, show that this model computational accuracy and stability all increase, can be applied among engineering reality.

Collect the coal seam collapse dept measured data in the whole nation, and the data of collecting conscientiously are selected, the data selected are all without tomography impact, affect and affect without repeated mining without initial fissure, and seam inclination is all the measured data within the scope of 0 ° ~ 30 °, totally 10 groups of sample datas, in table 4.

Table 4 sample data affecting parameters is with deep statistical table with destruction

Application Im-FM (fracturing mechanics of improvement) computation model and the fracture mechanics model parameter respectively in application table 2 calculates, and analyze the error of calculation of two models, result of calculation is in table 5.

Table 5 Im-FM model and fracture mechanics model error contrast table

As can be seen from the comparing result of table 5, except the 4th and the 8th group of result of calculation fracture mechanics model error is less, the error of other eight groups of data Im-FM computation models is all less than the relative error of fracture mechanics model.The square error of Im-FM computation model is 7.75, and the square error of fracturing mechanics computation model is 15.70, illustrates that the algorithm of Im-FM computation model is more stable.

Claims (5)

1., based on the Seam Floor Failure band depth determination method improving fracture mechanics model, it is characterized in that, comprise the following steps:

Step 1, structure Seam Floor Failure band degree of depth test model, wherein, maintenance is adopted deeply, stope width, roof and floor lithologic, mining height and boundary condition are constant, changes the value of seam inclination, obtains the Seam Floor Failure band depth value of correspondence;

Step 2, according to obtained often group seam inclination and its corresponding Seam Floor Failure band degree of depth, adopt the funtcional relationship between least square fitting coal output layer inclination angle and the Seam Floor Failure band degree of depth;

Step 3, fracture mechanics model to be combined with the funtcional relationship between seam inclination and the Seam Floor Failure band degree of depth, obtain the coal seam floor failure depth model based on fracturing mechanics after improving;

Step 4, according to obtain improvement after the coal seam floor failure depth model based on fracturing mechanics, the compressive strength of the seam inclination in Practical Project, base plate buried depth, stope width, floor rock volume-weighted average and floor rock is substituted into above-mentioned model, obtains the coal seam floor failure degree of depth of target coal seam.

2. the Seam Floor Failure band depth determination method based on improving fracture mechanics model according to claim 1, it is characterized in that, the seam inclination variation range described in step 1 is 0 ° ~ 30 °.

3. the Seam Floor Failure band depth determination method based on improving fracture mechanics model according to claim 1, is characterized in that, the structure Seam Floor Failure band degree of depth test model described in step 1, adopts UDEC numerical simulation software.

4. the Seam Floor Failure band depth determination method based on improving fracture mechanics model according to claim 1, it is characterized in that, the seam inclination described in step 2 and the funtcional relationship between the Seam Floor Failure band degree of depth, formula is as follows:

h＝aα ³+bα ²+cα+d (1)

Wherein, h represents the Seam Floor Failure band degree of depth, m; α represents seam inclination, and a, b, c, d all represent undetermined coefficient.

5. the Seam Floor Failure band depth determination method based on improving fracture mechanics model according to claim 1, it is characterized in that, fracture mechanics model is combined with the funtcional relationship between seam inclination and the Seam Floor Failure band degree of depth described in step 3, according to the principle of similitude, specific as follows:

$\frac{h}{\frac{1.57{\mathrm{\γ}}^2{H}^{2}L}{4R_c^2}}=\frac{a{\mathrm{\α}}^3+b{\mathrm{\α}}^2+\mathrm{c\α}+d}{d}---\left(2\right)$

Wherein, h represents the Seam Floor Failure band degree of depth, m; H represents base plate buried depth, m; L represents stope width, m; γ represents floor rock volume-weighted average, MN/m ³; R _crepresent the compressive strength of floor rock, Mpa; α represents seam inclination;

According to the principle of similitude, a α on the right of equal sign left side h and equal sign in formula (2) ³+ b α ²+ c α+d all considers seam inclination, equal sign left side fracture mechanics model in formula (2) all seam inclination is not considered, i.e. α=0 ° with d on the right of equal sign;

Arrange the coal seam floor failure depth model of formula (2) acquisition based on fracturing mechanics:

$h=(\frac{a{\mathrm{\α}}^3+b{\mathrm{\α}}^2+\mathrm{c\α}}{d}+1)\frac{1.57{\mathrm{\γ}}^2{H}^{2}L}{4R_c^2}---\left(3\right).$