Deformation and Failure Mechanism of Surrounding Rock in Mining-Influenced Roadway and the Control Technology

Aiming at the problem of surrounding rock deformation and failure of mining roadway and its control, a mechanical model of the circular roadway under the mining environment is established, and the implicit equation of the plastic zone boundary is derived. By analyzing the morphologic evolution law of the surrounding rock plastic zone in the mining roadway, the key factors affecting the morphologic change of the plastic zone are obtained, that is, the magnitude and direction of principal stress. .e influence law of the magnitude and direction of principal stress on the plastic zone of the mining roadway is analyzed by using numerical simulation software, and the deformation and failure mechanism of surrounding rock of the mining roadway is revealed. .e results showed that the size and morphology of the plastic zone were closely related to the confining pressure ratio (η). Taking the boundary of η valuing 1, the larger or smaller η value was, the more serious the deformation and failure of surrounding rock would be; the morphology of the plastic zone changed with the deflection of the principal stress, with the location of the maximum plastic zone influenced by the principal stress direction. For the surrounding rock control in the mining-influenced roadway, it is advised to take the following methods: firstly, it is necessary to consider how to reduce or remove the influence of mining on surrounding rock, improve the stress environment of surrounding rock, and reduce the failure depth of the plastic zone, so as to better maintain the roadway. Secondly, in view of the deformation and failure characteristics of the mining roadway, the fractional support method of “yielding first and then resisting” should be adopted, which applies the cable supplement support after mining instead of the one-off high-strength support during roadway excavation, so as to control the malignant expansion of the surrounding rock plastic zone and prevent roof falling accidents.


Introduction
e mining-influenced roadway is an important part of underground coal mining, which directly serves the working face [1][2][3][4]. Affected by one or more mining operations, the surrounding rock of the roadway is deformed, the supporting body fails, and even the roof collapses, which makes the roadway maintenance extremely difficult [5][6][7]. erefore, it is of great significance to study the deformation and failure mechanism of the mining-influenced roadway and its control technology [8][9][10].
A lot of research studies have been carried out by many experts and scholars in the deformation of mining-influenced roadway surrounding rock and the damage control.
Zhao et al. [11,12] analyzed the influence of the nonuniform stress field on the morphology and size of the tunnel plastic zone under the influence of mining and put forward the theory of butterfly-shaped plastic zone. e stability control technology of the surrounding rock with a long bolt is studied and applied in the face of the butterfly failure roadway. Considering the stress environment of surrounding rock of the deep mining roadway, Ma et al. [13,14] proposed the mechanical mechanism of the formation of the plastic zone in surrounding rock under nonisobaric conditions and its morphological and discussed the influencing factors of roof stability. Yuan et al. [15,16] clarified the mechanical conditions for the formation of class I and class II butterfly-shaped plastic zones by further studying the morphological evolution law of plastic zones in the deep dynamic pressure roadway and defined the malignant expansion and criticality of plastic zones. He et al. [17,18] analyzed the root cause and process of the failure and instability of the coal roadway which was affected by the intense mining in the large adjacent fully mechanized caving face and proposed anchor cable truss and grouting supporting technologies. Chen et al. [7,19] studied the mechanical mechanism of complex deformation of the deep dynamic pressure roadway, and they believed that the size and direction of the surrounding rock stress field changed due to mining disturbance, which was the main factor causing the asymmetric deformation of the roadway. erefore, an asymmetric multimode coupling control strategy is proposed. Hui et al. [20] explored the deformation evolution law of surrounding rock in a gob-side roadway subjected to dynamic pressure through physical simulation and pointed out that intense mining obstructs the control of surrounding rock. e above research results play an important role in the control of surrounding rock in the mining roadway.
Because of the complexity and difference of geological environment and mining conditions of the coal seam, the deformation and failure mechanism of surrounding rock of the mining roadway are different. e problem of surrounding rock stability control has not been completely solved.
erefore, further research is still needed. In this paper, based on elastic-plastic theory, a mechanical model of the circular roadway under the mining environment was established, and the plastic zone boundary implicit equation was inferred. Based on the numerical simulation with the implicit equation applied, this paper analyzed the morphological evolution law of the roadway plastic zone, revealed the deformation failure mechanism of the mininginfluenced roadway, and introduced roadway surrounding rock control methods.

Deformation and Failure Characteristics of
Surrounding Rock in the Mining-Influenced Roadway e mining roadway should not only bear the influence of driving disturbance but also bear the intense influence of the mining of the working face and its adjacent working face from opening to scrapping [21]. e stress field of surrounding rock in the mining-influenced roadway is complex, which is the combination of the initial stress field, excavation stress field, and mining stress field. erefore, the deformation and failure of the mining roadway are closely related to the complex stress field around it. e interaction between the stress environment and the mechanical properties of surrounding rock results in the severe deformation and failure of most mining roadways [22]. e statistical data show the relationship between the buried depth of the roadway and the stability of surrounding rock [23]. e surrounding rock deformation and failure are not obvious after the excavation of the roadway with a buried depth of 200 m∼400 m, and the surrounding rock deformation and failure are not obvious until it is affected by the intense mining. Surrounding rock deformation and failure will occur in the tunnel with a buried depth greater than 400 m during tunneling, and severe deformation and failure will occur in the surrounding rock under the influence of mining [24]. A large number of investigation data have summarized the deformation and failure characteristics of the mining roadway, as shown in Figure 1.
(1) e severe roof sag can reach 200∼1000 mm, as shown in Figure 1(a). In the stage of strong mining influence, even the local roof caving appears. (2) e coal body at the side was seriously damaged, with the phenomenon of "net pocket" and "net breaking" appearing, and the bulging volume at the side could reach 200∼1000 mm, as shown in Figure 1(b). (3) e floor heave of the roadway leads to concrete cracking damage, which makes it difficult for pedestrians and traffic. e floor deformation can reach 200∼1500 mm, as shown in Figure 1(c). (4) In the complex mining stress and heterogeneous rock mass environment, the surrounding rock exhibits nonuniform deformation, such as roof step subsidence and different deformation and failure locations of the surrounding rock surface, as shown in Figures 1(d) and 1(e). (5) e bolt fails because its length is less than the range of damaged surrounding rock, and the cable fails because its elongation is too small to resist the large deformation of surrounding rock, as shown in Figure 1(f ). Roof collapse is easy to occur when the support body is damaged seriously without timely supplement of anchor bolts and cables.

Fundamental eory.
Referring to the previous research results [25,26], this paper continues to discuss the change rule of the plastic zone of the circular roadway under the mining environment. e basic assumptions of the mechanical model are as follows (Figures 2 and 3).
(1) Level the roadway with infinite length, circular-cut face with a radius of R 0 , and orebody depth (H) ≥ 20 times radius. (2) Surrounding rock mass is an isotropic homogeneous medium with plastic and incompressible properties. (3) Extremely complex inhomogeneous high-stress field is formed by the superposition of initial stress and intense mining stress. Generally, there is an angle α between the stress direction and the vertical direction, as shown in Figure 2(a). To simplify the calculation, the direction of the model is changed into 2 Shock and Vibration vertical by contrarotating the angle α, as shown in Figure 2(b). ere is an assumption that P 1 is the maximum principal stress and P 3 is the minimum principal stress. (4) Two parameters related to the coefficient of mining influence are introduced, which are the mining influence coefficient of maximum principal stress D ζ1 and the mining influence coefficient of minimum principal stress D ζ3 . e stress model of surrounding rock under a certain loading condition is shown in Figure 3. In this model, surrounding rock can be divided into the plastic zone (radius R p ) and elastic zone from the center to edge.
According to the stress environment of surrounding rock of the mining roadway and the theory of elasticity, we can get the stress state of a certain point of surrounding rock of the circular roadway under the bidirectional nonisobaric condition:     Shock and Vibration where σ r is radial stress, σ θ is circumferential stress, τ rθ is shear stress (MPa), and r and θ are the polar coordinates of any point. e equation of the Mohr-Coulomb criterion is expressed in the form of stress in polar coordinates, and the equation is In equation (2), x � (D ζ1 P 1 + D ζ3 P 3 )/2, y � (D ζ1 P 1 − D ζ3 P 3 )/2, z � R 0 2 /r 2 , and t � cos 2|θ − α|; substitute equation (1) into equation (2), then the binary implicit function (with two variables r and θ) is In this equation, C is the internal cohesion of surrounding rock (MPa) and φ (°) is the internal friction angle. e above equation shows that r is related to the parameters P 1 , D ζ1 , P 3 , D ζ3 , α, R 0 , C, and R 0 , in which the first five parameters represent the stress of surrounding rock, R 0 is the radius of the roadway, and C and φ represent the mechanical properties of surrounding rock. erefore, the plastic zone is mainly determined by the surrounding rock stress, when the roadway excavation size and surrounding rock parameters are determined. is paper focuses on the study of the influence law of the mining stress environment on the plastic zone.

Analysis of the Surrounding Rock Plastic Zone in Mining-Influenced Roadway.
According to the boundary equation of the surrounding rock plastic zone in the mining-influenced roadway, the morphology of the plastic zone and its evolution are analyzed, and the internal relationship between the development, morphology distribution, and principal stress of the surrounding rock plastic zone is discussed. Calculation conditions: a circular roadway with a radius of 2.5 m is selected, which is in the homogeneous extrathick coal seam, where coal cohesion is measured as 3 MPa and internal friction angle is 25°; two initial stress conditions of P 1 � 6 MPa and P 3 � 5 MPa and P 1 � 18 MPa and P 3 � 15 MPa (respectively, representing conditions of the static pressure roadway with orebody depths of 200 m and  600 m, in which the side pressure coefficient is 1.2) are selected, and the confining pressure ratio (η) is defined as D ζ1 P 1 /D ζ3 P 3 . Figure 2(a) shows the morphology distribution of the plastic zone under the influence of minimum principal stress in the mining-influenced roadway with the orebody depth of 200 m, where D ζ1 is 1.0 and D ζ3 is 1.0, 2.0, 3.0, or 4.0. When D ζ3 is 1.0, the shape of the plastic zone in the roadway is similar to a vertical ellipse, and its maximum size is 0.22 m; when D ζ3 is 2.0, the shape of the plastic zone changes into a horizontal ellipse, and its maximum size is 0.59 m; when D ζ3 is 3.0, the shape of the plastic zone is like a butterfly shape with the maximum size of 1.59 m; when D ζ3 is 4.0, the butterfly-shaped plastic zone appears with the maximum size of 3.84 m. Figure 2(b) shows the morphology distribution of the plastic zone under the influence of minimum principal stress in the mining roadway with the orebody depth of 600 m, in which D ζ1 is 1.0 and D ζ3 is 1.0, 2.0, 3.0, or 3.3. When D ζ3 is 1.0, the shape of the plastic zone is similar to a vertical ellipse, and its maximum size is 0.86 m; when D ζ3 is 2.0, the shape of the plastic zone is similar to a rectangle, and its maximum size is 1.38 m; when D ζ3 is 3.0, the butterflyshaped plastic zone appears with the maximum size of 5.64 m; when D ζ3 is 3.3, the shape of the plastic zone does not change with its maximum size of 11.2 m. Figure 4(a) shows the morphology distribution of the plastic zone under the influence of maximum principal stress in the mining-influenced roadway with the orebody depth of 200 m, where D ζ3 is 1.0 and D ζ1 is 1.0, 2.0, 3.0, or 4.0. When D ζ3 is 1.0, the shape of the plastic zone is like a vertical ellipse, and its maximum size is 0.22 m; when D ζ3 is 2.0, the shape of the plastic zone is like a butterfly shape, and its maximum size is 0.88 m; when D ζ3 is 3.0, the shape of the plastic zone changes into a butterfly with the maximum size of 5.86 m; when D ζ3 is 3.3, the butterfly-shaped plastic zone appears with the maximum size of 10.97 m. Figure 4(b) shows the morphology distribution of the plastic zone under the influence of maximum principal stress in the mining roadway with the orebody depth of 600 m, in which D ζ1 is1.0 and D ζ3 is 1.0, 2.0, 2.2, and 2.4. When D ζ3 is 1.0, the shape of the plastic zone is like a vertical ellipse, and its maximum size is 0.86 m; when D ζ3 is 2.0, the shape of the plastic zone changes into a butterfly, and its maximum size is 4.02 m; when D ζ3 is 2.2, the butterfly-shaped plastic zone remains with the maximum size of 5.83 m; when D ζ3 is 2.4, the maximum size of the butterfly-shaped plastic zone expands into 12.27 m.
In conclusion, it can be seen from Figures 4 and 5 that mining activities have a significant influence on the morphology distribution of the surrounding rock plastic zone. e shape and size of the plastic zone change with the mining coefficient decided by the maximum and minimum principal stresses of surrounding rock. Under the influence of mining, the maximum and minimum principal stresses vary. e boundary confining pressure ratio (η) value is 1. e larger or smaller value of η is, the more serious the deformation and failure of the surrounding rock plastic zone will be and the more severe the malignant expansion of the plastic zone will be. Figure 5 shows the morphology distribution of the plastic zone in roadways influenced by the change of the principal stress direction. When the direction of principal stress is the vertical direction (α � 0°), the largest plastic zone is located in the roadway shoulder; when the principal stress deflects clockwise 45°(α � 45°), the largest plastic zone is located on roadway roof, floor, and two sidewalls, and the plastic zone also rotates 45°; when the principal stress deflects clockwise 90°(α � 90°), the largest plastic zone lies on the top shoulder of the roadway, and plastic zones also rotate 90°. It can be seen that, under the condition of homogeneous surrounding rock, when the direction of principal stress changes, the size of the plastic zone will not change, but the plastic zone direction will deflect. Under the influence of mining, the direction of principal stress will change. When α is 45°, the sizes of the surrounding rock plastic zone on roof, floor, and two sidewalls represent larger. As a result, roof collapse, rib spalling, and floor heave easily occur, obstructing the maintenance of the roadway.

Deformation and Failure Mechanism of Surrounding Rock in the Mining-Influenced Roadway
e field measurement shows that the intense mining influence not only changes the magnitude of the surrounding rock stress field but also changes the direction of the stress field to some extent. is can be reflected in some coal mine pressure phenomena, such as large deformation of the roadway and nonuniform failure of the surrounding rock. erefore, a study on the distribution characteristics of the surrounding rock plastic zone in the roadway through researching of the complex stress field contributes to further revealing of the deformation and failure mechanism of the surrounding rock. In the following analysis, the FLAC 3D finite differential method is applied to conduct a numerical study on the morphology characteristics of the surrounding rock plastic zone in the mining-influenced roadway [27,28].

Numerical Calculation Model and Parameters.
e size of the model is 50 m × 50 m × 1 m (width × height × thickness), and the roadway size is 5 m × 3.5 m. e grid is divided into hexahedral units. e model boundaries are all subject to displacement constraints. e Mohr-Coulomb strength model is used for rock material simulation, and the material mechanical parameters are shown in Table 1.
To verify the morphological distribution of the plastic zone of roadway surrounding rock under the influence of mining, we designed a simulation scheme under different mining environments. e mining coefficient and deflection angle are mainly considered in the scheme. In the scheme, P 1 is 18 MPa, P 3 is 15 MPa, and the lateral pressure coefficient is 1.2. e first scheme fixed the mining coefficient and changed the deflection angle, as shown in Table 2. e second scheme fixed the deflection angle and changed the mining coefficient, as shown in Table 3.

Deformation and Failure Mechanism of Surrounding Rock
in the Mining-Influenced Roadway. Figure 6 shows the morphology of the surrounding rock plastic zone under different mining stress conditions. When the impact of mining is not considered (η �1.2), the shape of the surrounding rock plastic zone is similar to the butterfly shape, the size of the maximum plastic zone of surrounding rock above the roof is 1.6 m, and the maximum plastic zone sizes of the floor and the side surrounding rock are both 1.4 m. When P 1 remains unchanged and P 3 increases by 2 times (η � 0.6), the shape of the surrounding rock plastic zone around the roadway is similar to a horizontal ellipse, the maximum size of the plastic zone above the roof is reduced to 0.8 m, the maximum size of the plastic zone at the sidewall increases to 2.4 m, and the size of the plastic zone on the floor is reduced to 0.6 m. When P 1 is unchanged and P 3   e change law of the plastic zone of surrounding rock after the change of principal stress is basically consistent with the theoretical calculation results. When the vertical principal stress is large, the plastic failure mainly occurs at the side, and when the horizontal principal stress is large, the plastic failure mainly occurs at the roof and floor. When the confining pressure ratio is high to a certain extent or low to a certain extent, the plastic zone of surrounding rock is severely damaged. is is the main reason of roof subsidence, side bulge, and floor heave in the mining roadway. Figure 7 shows the different morphologies of the surrounding rock plastic zone when the magnitude of principal stress is unchanged and the direction of the stress deflects with the angle ranging from 0°to 90°. When the principal stress does not deflect, the plastic zone is basically arch shaped with the roof plastic zone's size of 0.8 m, the side plastic zone's size of 2.6 m, the floor zone's size of 0.4 m, and the plastic zone size of 2.6 m at the bottom corners, which can be seen from Figure 7(a); when the principal stress deflects by 15°, the morphology of the surrounding rock plastic zone changes; the depth of the roof plastic zone increases, and the shape of the roof plastic zone varies, and the roof plastic failure near the left sidewall is more serious with the maximum failure depth of 2 m, the plastic zone on the sidewall hardly changes, and floor plastic failure near the right sidewall is more severe with the maximum failure depth of 2.2 m, which is shown in Figure 7(b); when the principal stress deviates by 30°, the roof plastic zone continues to expand, the maximum damaged area approaches from the roof's left side to the roof's center, with a maximum size of 2.6 m, the depth of plastic failure at sides increases, with the maximum size of 3.2 m, a sharp corner appears in the plastic zone, the area of the floor plastic zone increases, and the maximum failure area approaches from the floor's right side to the center, with a maximum size of 2.8 m, as shown in Figure 7(c); when the principal stress deviates by 45°, the plastic zone of the surrounding rock also deflects; the maximum failure zone on the roof reaches the middle of the roof with the maximum size of 2.8 m, the roof plastic zone continues to expand with the maximum failure zone approaching from the left to the middle on the roof, with the maximum size of 2.6 m, the sharp corner of the side plastic zone reaches the center of the side with the maximum size of 3 m, and the maximum floor failure zone reaches the floor's middle, with the maximum size of 2.8 m, as shown in Figure 7(d); when the principal stress deviates by 60°, the maximum failure depth of the roof plastic zone is 3 m, the area of the side plastic zone slightly reduced with the maximum size of 2.8 m, the sharp corner approaches to the roof, and the maximum failure depth of the floor plastic zone is 2.8 m, as shown in Figure 7(e); when the principal stress deviates by 75°, the maximum failure depth of the roof plastic zone is 2.8 m, the area of the sidewall plastic zone continues to reduce with the maximum size of 2.4 m, the sharp corner continues to approach to the roof, and the  Shock and Vibration 7 maximum failure depth of the floor plastic zone is 2.8 m, as shown in Figure 7(f ); when the principal stress deviates by 90°, the maximum failure depth of the roof plastic zone is 2.8 m, and the sidewall plastic zone decreases with the maximum of 2.0 m, the side plastic zone transfers to the roof and floor, and the maximum failure depth of the floor plastic zone is 2.8 m, as shown in Figure 7(g). In summary, the plastic zone morphology also changes when the principal stress angle changes from 0°to 90°. e plastic zone of the side transfers to the top and bottom plate. e plastic zone of the side shows a decreasing trend, and the plastic zone of the roof shows an increasing trend. However, the maximum value of the plastic zone is stable within a certain range. It can be seen that when the principal stress continues to deflect, the overall shape of the plastic zone will transfer from the top and bottom to the two sides. e change of the principal stress direction causes the change of plastic zone morphology of surrounding rock.

Discussion
e deformation and failure of surrounding rock in the mining roadway are mainly caused by the change of the surrounding rock stress field. erefore, the surrounding rock of the mining roadway can be controlled by adjusting the mining stress field to improve the plastic zone. e plastic zone size of surrounding rock can be reduced after stress adjustment. Finally, the stability of the broken rock mass in the plastic zone is maintained employing a roadway support. e support can prevent the broken rock from falling and instability in the plastic zone of surrounding rock. With existing technology, we can optimize the production layout. e methods of optimizing mining layout include mining sequence of the coal seam, reasonable selection of roadway position, and adjustment of coal pillar size. In this way, the stress environment of the roadway can be improved to achieve the stability of reducing the size of the plastic zone of the roadway.
Currently, several supporting means are applied to protect the mining-influenced roadway, such as anchor bolts (cable) support, grouting reinforcement, and frame support. And, the anchor bolt (cable) support method is most widely applied to increase support resistance and to reduce the roof subsidence amount. In practice, when the method of anchor bolt (cable) support is applied, more anchor cables are used. e increasing cost does not bring a significant control Figure 6: Morphology distributions of the surrounding rock plastic zone in the roadway influenced by stresses with different magnitudes. effect, and roof falling accidents happen sometimes. e roof reason why the control effect of the anchor bolt (cable) support method is not satisfying is that the performance of conventional anchor bolts and cables do not match the deformation and failure characteristics of the mininginfluenced roadway. Although the elongation of conventional bolts is higher than 15%, the bolts with a limited length cannot reach the stable rock bed outside the plastic zone. Being a kind of supporting material with great bearing capacity but weak resistance to deformation, conventional cables with lower elongation (<3.5%) cannot adapt to the large deformation of the roadway and break [11,29,30]. erefore, given the deformation and failure characteristics of the mining-influenced roadway, especially the large deformation roadway, the fractional support method of "yielding first and then resisting" should be adopted, which allows the multiple high-strength supporting activities during roadway excavation and high-strength reinforcement support with anchor cables after mining to control the malignant development of the plastic zone and prevent the roof falling accidents. First, in the process of the roadway's excavation, based on the characteristics of the plastic zone, an appropriate number of anchor bolts and cables are selected to ensure the safety of the roadway and the speed of roadway completion. In the process of mining, according to the characteristics of the plastic zone and its deformation, anchor cables are used to reinforce support. e safety management of the roof and sides is strengthened. If broken anchor bolts and cables are found, new bolts and cables should be re-installed in time preventing the malignant expansion of the plastic zone.

Engineering Application
6.1. Engineering Overview. Buertai coal mine 42,106 return air roadway is serving the 42,106 working face for ventilation, pedestrians, and transport roadway. e dip length of the 42,106 working face is 309 m, the strike length is 5073.8 m, and the goaf of the 42,105 working face is in the northeast, as shown in Figure 8. e average thickness of the 0° deflection ere is almost no deformation and failure in the 42,106 return air roadway in the process of excavation. However, after the mining of the 42,105 working face, the 42,106 return air roadway was located in the area behind the working face, and severe deformation and failure occurred under the influence of the mining of this working face, as shown in Figure 9. e roof of the advanced support section of the roadway has significant sag, with the maximum sag up to 300 mm∼500 mm, as shown in Figure 9(a). e maximum deformation of the side under the influence of mining can reach 1800 mm, resulting in the collapse of the anchor cable and the failure of support, as shown in Figure 9(b). e floor also suffered severe deformation, which seriously affected the normal production, as shown in Figure 9(c).

Deformation and Failure Mechanism of the Return Air
Roadway. Based on the above analysis of the failure form and characteristics of the surrounding rock in the 42,106 return air roadway, it is believed that mechanical stress environment is the main factor affecting the deformation of the roadway. Two mining activities (mining in the 42,105 working face and mining in the 42,106 working face) make the stress environment worse and more complex. e irregular-shaped plastic zone is generated in the roadway affected by the high-deviatoric stress field. Due to the change of the principal stress direction, the maximum plastic zone is unevenly distributed, causing the nonuniform deformation of the roadway. As shown in above analysis, the deformation of surrounding rock in the 42,106 return air roadway is one of the most typical kind of mining-influenced roadway deformation. e mechanism of roadway's deformation and failure can be summarized as follows: affected by the mining deviatoric stress, the confining pressure ratio becomes larger or smaller, the malignant development happens in the surrounding rock plastic zone with the changed morphology of the plastic zone and increased size, deflection of the surrounding plastic zone is caused by the different directions of the principal stress, and the nonuniform distribution of roadway surrounding rock occurs; affected by the secondary mining activity, the plastic zone further expands to the deep rock mass, leading the serious deformation and failure of surrounding rock, such as roof falling, sidewall collapse, floor heave, and severe shrinkage of the cross section ( Figure 10).

Support Parameters of the Return Air Roadway
(1) Roof support: the method of "left-hand twist threaded steel bars without the longitudinal rib for rock-anchor bolt + steel net + anchor cable + Π-type steel stripe" is applied. e size of left-hand twist threaded steel bars without the longitudinal rib for rock-anchor bolts is Φ22 × 2200 mm, 6 sets of bolts are posited in each row in rectangular arrangement and row spacing between bolts is 1100 × 1000 mm; the size of steel nets is Φ6.     (3) Negative side support: the method of "rebar bolt + wood plate + rhombic net" is adopted. e parameters of equipment used in this support are as follows: the size of rebar bolts is Φ18 × 2100 mm, five sets of bolts are posited in a row in rectangular arrangement, and the row spacing of bolts is 800 × 1000 mm; the size of steel plates is 150 × 150 × 10 mm, the size of wood plates is 500 × 200 × 50 mm, the rhombic nets are 1200 × 4200 mm, and the size of meshes is 45 × 45 mm.
After the primary mining, the supplement support with anchor cables is carried out. e parameters of equipment used in this support are as follows: the size of anchor cables is Φ15.24 × 5000 mm, the size of anchor cable steel plates is 200 × 140 × 10 mm, and the sizes of two kinds of Π-type steel stripes are 4500 × 140 × 10 mm and 2400 × 140 × 10 mm; three sets of equipment packages are posited in a row in rectangular arrangement, with the row spacing of 1000 × 2000 mm, and the anchor cables are arranged on the Π-type steel stripe, as shown in Figures 10(a) and 10(d).
e method of fractional stress yielding support can reduce the pressure to prevent a large number of fracture of anchor cables, which effectively stops the malignant expansion of the surrounding rock plastic zone, controls the broken rock falling, and eliminates the risk of roof collapse.

Conclusion
(1) e influence of mining on the distribution of plastic zone morphology of roadway surrounding rock is obtained by theoretical calculation. e shape and size of the plastic zone change with the change of stress. e critical value of the confining pressure ratio η is 1. e extreme increase or decrease of η will lead to the sharp instability of surrounding rock.
When the principal stress direction changes, the plastic zone morphology will be deflected. (2) e deformation and failure mechanism of surrounding rock of the mining roadway are revealed. When the vertical principal stress is greater, the plastic zone is mainly at the side, and when the horizontal principal stress is greater, the plastic zone is at the top and bottom plate. When the confining pressure ratio is high or low to a certain extent, the plastic failure of surrounding rock is extremely serious. When the principal stress direction changes, the maximum plastic failure area of surrounding rock also changes. is explains why the mining roadway appears to have asymmetrical deformation and failure.
(3) e fractional support method of "yielding first and then resisting" is put forward. e method applies cable supplement support after mining instead of the one-off high strength support during roadway excavation, to control the malignant expansion of the surrounding rock plastic zone and prevent roof falling accidents. (4) Based on the analysis of the failure modes and characteristics of 42,106 return air roadway surrounding rock in the Buertai mine, it is determined that the failure of surrounding rock in the 42,106 return air roadway is a typical deformation mode of surrounding rock in the mining-influenced roadway. e fractional stress yielding support is adopted to hobble the continuous malignant expansion of the surrounding rock plastic zone, which effectively eliminates the risk of roof falling.

Data Availability
e data used to support the findings of this study are available from the corresponding author upon request.   Shock and Vibration