Study on the effect of rock stratum structure on the stability of weakly cemented layered floor and the floor control measures: A case study of Meihuajing Mine

Given the deformation and instability of the layered floor of weakly cemented soft rock roadway, taking the mining roadway of Meihuajing Mine as the engineering background, the deformation and instability mechanism of the floor and the control measures of the surrounding rock under different stratum combination conditions are studied by using the methods of field investigation, numerical calculation and field test. The results show that: (1) the layered characteristics of surrounding rock in weakly cemented soft rock roadways are significant, and the combination structure of floor rock strata is complex and changeable. Under the influence of engineering disturbance, the roadway has a tendency of large deformation, especially floor heave. (2) The buckling instability of the layered floor is caused by the layered weakening effect, and the unstable zone, the substable zone and the stable zone are formed successively from the shallow to the deep. With the increase of the layer thickness, the integrity of the layered floor is improved, the layered weakening effect is reduced, and the overall stability of the layered floor is improved. (3) The existence of weak interlayer further degrades the integrity of layered floor, and the progressive failure of floor rock mass layer by layer is more significant under the influence of layered weakening effect. (4) The relatively hard rock stratum in the composite structure plays an important role in controlling the deformation and failure of the floor, playing the role of “local key stratum.” (5) Based on the cooperative control countermeasure of roof–rib–floor surrounding rock, the support technology of roof and ribs supported by blots mesh beam cable + floor supported by bolts grouting hardening + full section shotcrete is proposed. The results of numerical calculation and field test show that the support scheme greatly improves the stability of layered floor.


| INTRODUCTION
With the transformation of the national macroeconomic structure and the adjustment of the energy structure, China's coal mining has gradually shifted to the west area. The generation age of the coal seams in the western mining areas is relatively late Jurassic and Cretaceous. The roof and floor strata of the coal seam are significantly different from those in the central and eastern regions, which are called weak cementation strata. 1,2 Weakly cemented soft rock is mainly characterized by its obvious layered characteristics, poor cementation performance, low strength, easy disintegration, and argillization in case of water. 3,4 Under this condition, the roadway surrounding rock has a tendency to produce large deformation.
For a long time, the safe and efficient mining of coal resources in weakly cemented strata has been a difficult problem focused on by professional technicians and scientific researchers in the coal industry.
In view of the deformation and failure mechanism and control measures of the floor, scholars have carried out a series of research work and achieved fruitful research results. Lu et al. [5][6][7][8] carried out a series of research work on the layered floor, built a mechanical analysis model, and obtained the stress distribution law and the analytical expression of the floor failure depth. Wen et al. 9,10 took the soft floor affected by mining as the research object, established a mechanical model, deduced the analytical expression of floor load, revealed the floor control mechanism, and proposed a new inverted arch to control floor heave. Hua et al. [11][12][13] studied the crack dynamic evolutionary characteristics and deformation law of the gob side entry by means of theoretical analysis, numerical calculation and field test, and systematically evaluated the stability of the floor. Song et al. [14][15][16] established the stress model of the floor based on the elastic theory, and obtained the stress distribution and failure form of the floor through theoretical derivation and calculation. Li et al. [17][18][19] focused on the failure behavior of floors influenced by coal mining in deep mines. According to the theory of unloading mechanics and damage mechanics, the compression shear failure and unloading failure mechanical behavior of floor under mining disturbance is studied, and the partition of floor disturbance failure is divided. In addition, Luo et al. [20][21][22] have also explored the control measures of the floor and formed representative achievements. The above results have laid a good foundation for the research on the deformation and failure mechanism and control measures of weakly cemented soft floor. In most of the above studies, the floor is simplified as an isotropic medium. However, weakly cemented soft rock has an obvious layered property, and the floor presents obvious progressive failure layer by layer in the process of instability. Therefore, in the weakly cemented soft rock roadway, the application of the above research results has certain limitations.
Focused on the stability of the mining roadway in Meihuajing Mine, the paper obtained the layered characteristics of the roof and floor rock mass through field investigation, analyzed the microlayered attribute and mineral composition of weakly cemented soft rock through laboratory tests, realized the numerical characterization of the layered floor using FLAC3D, and analyzed the impact of different rock structure on the stability of the floor. On this basis, the coordinated surrounding rock control strategy of roof-rib-floor is proposed to effectively control the deformation and failure of weakly cemented layered floor.

| Working face overview
Meihuajing Mine mainly exploits the coal bearing strata of the Jurassic Yan'an Formation in Ningdong Coalfield. Influenced by sedimentary environment and diagenetic time, the roof and floor of coal bearing strata mainly consists of weakly cemented soft rocks such as mudstone, sandy mudstone, siltstone and fine sandstone. The rock has low diagenetic degrees, poor cementation performance, and its mechanical property deteriorates significantly after encountering water. At present, the coal mine mainly mines No. 2 coal, with an average buried depth of 630 m and more than 700 m in some areas. Taking a borehole in 232204 working face as an example, as shown in Figure 1, the average thickness of the coal seam is 5.5 m, which is nearly horizontal. The immediate roof is siltstone with an average thickness of 5.0 m. The bedding of the rock stratum is developed, and mudstone interlayers appear in local areas. The basic roof is coarse sandstone with an average thickness of 9.0 m. The rock stratum structure is loose, containing gravel particles. The immediate floor is a fine sandstone with an average thickness of 4.0 m. The horizontal bedding of the rock stratum is developed, and there are siltstone interlayers in some areas. The bearing capacity of the coal seam and the roof and floor rock mass is generally low, and the surrounding rock of roadways has an internal incentive for large deformation.

| Engineering geological characteristics
Based on the field investigation of several working faces and the results of laboratory tests, it is concluded that the ZHU ET AL.

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weakly cemented soft rock roadway in Meihuajing Mine has the following special engineering geological characteristics: (1) The content of clay minerals in the roof and floor rock is relatively high. As shown in Figure 2, the content of clay minerals in siltstone is 44.3%, and that in mudstone is 58.4%. The rock has strong hydrophilicity. The strength of the roadway surrounding rock is significantly affected by the weakening effect of water. After the dry-wet cycle test, the rock is disintegrated and broken.
(2) The weakly cemented soft rock formed the original sedimentary bedding in the process of sedimentation. The microfissures of rock are developed. The fissure is filled with organic matter, with poor cementation performance. The rock forms a microdiscontinuous layered structure. The exposed roof and floor rock mass has an obvious layered property, forming a macrodiscontinuous structure. The layer thickness of rock mass is generally 0.1-0.5 m, with poor interlayer bonding, and the roof and floor show significant progressive failure layer by layer. Soft interlayer is developed in the roof and floor rock stratum, with the interlayer thickness less than 0.5 m, and the lithology is mainly mudstone and carbonaceous mudstone. The structural characteristics of rock stratum are shown in Figure 3.
(3) The data of eight boreholes in five working faces were collected through field investigation, and the lithological changes of coal seam roof and floor were summarized. As shown in Figure 4, the lithology and thickness of the roof and floor have significant regional differences. In the horizontal direction, the rock stratum is thickened, thinned or even pinched out, forming a horizontal discontinuity; In the vertical direction, the lithology of the rock stratum changes alternately, with typical layered structure, forming a longitudinal discontinuity. The lithology of the rock stratum within 10 m of the floor mainly includes siltstone, fine sandstone, coarse sandstone, mudstone and No. 3 coal seam. The lithology of the floor is diverse, the thickness of the rock stratum varies, and the influence of geological structure will make the rock stratum combination of the floor more complex, which will bring greater difficulty to the floor control.
(4) The sandstone aquifer exists in the roof rock of the working face, causing the water rich environment of the roadway. The weakening effect of roof water on surrounding rocks is significant. Primary fractures of weakly cemented soft rocks in the roof are developed. Under the influence of engineering excavation disturbance, primary fractures expand and secondary fractures sprout, forming a natural water diversion channel, and the roadway is seriously affected by water disasters.

| STABILITY ANALYSIS OF LAYERED FLOOR
Layered structure is formed in coal bearing strata during sedimentation. The difference in sedimentary environment results in the diversity of floor layer thickness and composite structure. When the stress of the surface floor reaches its ultimate bearing value, the floor will be damaged. Without effective support measures, the layered floor will be damaged layer by layer, and then cause serious floor deformation. The structural characteristics of the layered floor determine its deformation and failure characteristics, and the deformation and failure characteristics dominate the design of roadway support parameters. The Interface element in FLAC3D is used to construct the bedding plane, realize the numerical characterization of layered rock mass, and obtain the influence of floor rock structure on its stability.  Table 1.
After the roadway is excavated, the surrounding rock stress is redistributed. Under the action of local concentrated stress, the layered floor becomes unstable, and the exposed floor of the roadway provides a free surface for the release of stress and deformation. The results of long-term field investigation show that the normal function of the roadway will not be affected if the floor deformation is within 200 mm. When the deformation of the floor exceeds 200 mm, corresponding measures must be taken to ensure the normal use of the roadway. Thus, the part of the floor deformation exceeding 200 mm is divided into unstable zones, and the part not exceeding 200 mm is divided into substable zone. The layered floor forms an unstable zone in the shallow part, and the rock mass in this zone basically loses its bearing capacity. It is the main source of large deformation of the floor and the key part of surrounding rock control. The rock stratum below the unstable zone forms a substable zone, and the rock mass in this zone forms a slightly curved structure with a certain bearing capacity. The rock stratum in the substable zone can not only bear the load, but also block the load transfer from the deep rock stratum to the unstable zone, which has a macrocontrol effect on the deformation of the layered floor. The relative size of this zone is a key index to measure the stability of the floor. The rock stratum outside the substable zone is little affected by the engineering disturbance, forming a stable zone, which is the main bearing structure of the layered floor.
As shown in Figure 6, when the layer thickness is 0.2 m, the rock mass is severely divided by the bedding plane, and the integrity of the floor is greatly weakened. Driven by the surrounding rock stress, the surface floor is destroyed first, and the plastic zone expands downward layer by layer, forming a large range of unstable zones. With the increase of layer thickness, the integrity of layered floor is improved, and the bearing capacity of single layer and the overall floor is improved. The expansion of the unstable zone is restrained, the influence range of the substable zone is enlarged, and the overall stability of the layered floor is improved.
The displacement information at different depths of the layered floor shows that the floor deformation reaches the peak value at the middle line of the roadway, and the rock stratum deformation in the unstable area is more than 200 mm, which is the main source of the roadway floor deformation. The layer thickness has a remarkable regulating effect on the deformation of the floor. With the increase of the layer thickness from 0.2 to 0.5 m, the maximum floor heave of the floor decreases There are naturally weak surfaces with poor mechanical properties between the layers. Under the influence of these weak surfaces, the layers are deformed asynchronously under the action of external forces, and the layered floor produces discontinuous separation zones. The appearance of layer separation further weakens the integrity of the floor and is a potential inducement for large deformation of the floor. After the instability of the layered floor, the unstable zone formed in the shallow part of the floor is the main source of the large deformation, and also the key part of the floor treatment. The goal of floor heave prevention and control is to realize the transformation from unstable state to stable state in this zone.

| Influence effect of weak interlayer
The interlayer is the weak part of the surrounding rock, which plays an important role in the stability of the roadway floor, even a control role. The existence of weak interlayer further weakens the integrity of the layered floor, which is an important factor to induce strong floor heave. The results of geological data and field investigation show that the weak interlayers at the roof and floor are mainly coal line and mudstone, and the thickness of the weak interlayers is mainly 0.1-0.4 m. In the simulation, the thickness of the weak interlayer is taken as 0.4 m, and the weak interlayer is set at 1, 2, and 3 m below the roadway floor.
As shown in Figure 7, due to the disturbance of engineering excavation, the plastic zone appears to expand significantly along the weak interlayer. By comparing the two cases in Figure 7A,B, it can be seen that the weak interlayer weakens the overall strength of the floor, and the existence of the weak interlayer causes the maximum deformation of the floor to increase from 626.2 to 719.6 mm. As the naturally weak plane in the floor bearing system, the weak interlayer has worse bearing capacity than the upper and lower rock masses. In the process of surrounding rock instability, the weak interlayer acts as a "free surface." The deformation of the floor at the weak interlayer increases significantly. With the increase of depth, the clamping effect of surrounding rock increases, and the "free surface" effect of weak interlayer decreases.
With the increase of the number of weak interlayers, the integrity of layered floor is further weakened, and the plastic zone of floor is further expanded. By comparing the deformation curves of the floor in Figure 7B,E, it can be seen that with the number of weak interlayer increasing from 1 to 2, the maximum deformation of the floor at 0 m below the roadway is increased from 719.6 to 813.8 mm, and the maximum deformation of the floor at 1.8 m below the roadway is increased from 107.1 to 259.5 mm. That is to say, with the increase of the number of weak interlayers under the roadway, the deformation of the floor increases generally.
Because of its low bearing capacity, the weak interlayer is easily disturbed by the engineering excavation. The existence of weak interlayers further degrades the integrity of the layered floor, and under its influence, | 2243 the progressive failure of floor rock mass is more significant. As a weak link in the floor bearing system, the weak interlayer provides a "free surface" for the deformation and failure of surrounding rock. The rock mass structure within its influence area is activated, the deformation is significantly increased, and the plastic zone is significantly extended along the weak interlayer.

| Influence of floor lithology
The complexity of sedimentary environments has resulted in the diversity of coal measure stratum structure, and the lithologic combination mode and layer thickness of layered floors will have various changes. The key to controlling this kind of roadway is to master the deformation and failure characteristics of layered floor and propose targeted control measures. According to its composite type, the layered floor can be mainly divided into the following four types of typical structures, namely: I uniform type, including soft type and hard type; II soft-hard type, including upper hard lower soft type and upper soft lower hard type; Ⅲ progressive type, including gradually soft type and gradually hard type; Ⅳ sandwich type, including hard-soft-hard type and soft-hard-soft type. The lithological combination form and layer thickness of each type are shown in Figure 8. As shown in Figure 9, when the floor is soft type or upper soft lower hard type, the surface of the floor is thick soft mudstone. Due to the influence of the structural plane, the bearing capacity of the surface floor is low and it is easy to be damaged. After the surface floor is damaged, the stress of surrounding rock transfers to the deep rock, and the plastic zone also develops downward layer by layer. The relatively hard sandstone in progressive type and sandwich type has higher bearing capacity and can form bearing structure locally. However, due to the thin thickness of sandstone, the floor integrity is still poor, which has limited inhibition on the expansion of plastic zone of the floor. The hard and thick sandstone in the upper part of the hard type or upper hard lower soft type has strong bearing capacity, forming a stable structure in the shallow part of the floor, and the load strength borne by the lower soft rock layer is low, effectively restraining the expansion of the plastic zone of the floor to the deep rock. Due to the different composite structures of the layered floor, its deformation laws also show some differences. When the layered floor is uniform type with good integrity, the floor heave of the roadway mainly depends on the lithology. Compared with the soft floor, the hard floor has stronger bearing capacity and deformation resistance, and the deformation of the floor is greatly reduced. When the layered floor is soft-hard type, the strength of upper rock becomes the key factor to control the floor deformation. If the upper rock of the floor is soft mudstone, the surface floor can easily reach its bearing limit and be damaged. By hardening the surface floor of the roadway, strengthening the bearing capacity of the shallow floor can significantly reduce the overall deformation of the floor. When the layered floor is progressive type and sandwich type, the relatively hard rock stratum in the composite structure plays an important role in controlling the deformation and failure of the floor, that is, the role of "local key stratum." "Local key stratum" has strong bearing capacity. When it is located in the upper layer, the lower weak floor will bear low load, and the floor heave is limited. With the downward movement of the "local key stratum," the overall bearing capacity of the shallow floor decreases. When the load reaches the critical value, the failure first occurs in the shallow rock stratum, and then expands downward layer by layer until it reaches the "local key stratum." Based on the above analysis, the rock stratum combination structure of the floor has a significant impact on the stress distribution law and deformation and failure characteristics of the layered floor. By hardening the surface floor, a "local key stratum" is built in the shallow rock mass of the floor to realize the active control of the floor rock mass combination structure, improve the stability of the shallow rock strata, and thus significantly reduce the deformation of the layered floor.

| Control countermeasures
In the surrounding rock bearing system of weakly cemented soft rock roadway, the performance of roof and rib is directly related to the stability of floor. The treatment of layered floor must consider the influence of roof and rib. The support and reinforcement measures aim to form a coordinated and integrated bearing system of roof-rib-floor.
(1) Improve the rib strength and build a stable bearing foundation in the roof-rib-floor bearing system.
The influence of the bearing capacity of the rib on the stability of the floor is mainly reflected in the following two aspects. On the one hand, the deformation and failure characteristics of the rib directly affect the span of the floor beam. Under the influence of engineering excavation disturbance, the surrounding rock stress is redistributed. The concentrated stress causes the coal body at the lower corner of the roadway to be damaged, and the support point of the floor rock beam moves to the deep rock mass. The increase of the real span of the roadway results in the exponential growth of the floor deformation. 23 On the other hand, as the medium of the load transfers from the overlying strata to the floor, the bearing capacity of the rib determines the floor load and has an important impact on the overall stability of the roadway. As shown in Figure 10, compared with weak rib condition, under strong rib condition, the stability of the roadway is improved as a whole, the range of surrounding rock plastic zone is greatly reduced, and the depth of floor failure is also reduced. As the stability of the roadway rib is improved, the lateral compression on the floor is weakened after the deformation of the rib, and the strength of the horizontal load acting on the floor rock beam is reduced, thus reducing the deformation of the floor.
(2) High performance bolts and cables enhance the stability of the roof and limit the transfer of overburden load from the rib to the floor.
High performance bolts and cables are selected to reinforce the roof as a whole, so as to improve the overall strength and stiffness of the surrounding rock bearing system. While ensuring sufficient stability of the roof, it blocks the transmission path of overburden load to the floor and weakens the stress strength of the floor from the source. The bolts and cables components exert axial restraint on the layered roof rock mass, increase the friction between the broken rock blocks, improve the antislip performance between the roof layers, restore the bearing capacity of the surrounding rock in the broken area, and keep it in a three-dimensional stress state, as shown in Figure 11. The bolts form a continuous bearing arch in the plastic zone through its active force on the surrounding rock. The strength of the rock mass in the bearing arch is improved, and the bearing capacity of the surrounding rock can be fully exerted. At the same time, it can bear the external rock mass load and limit the deformation of surrounding rock. The stable rock stratum in the deep elastic zone is anchored as a whole with the unstable rock stratum in the shallow plastic zone through the cables, forming a cooperative bearing structure.
(3) Through support and reinforcement, the layered floor is transformed from the superimposed beam structure to the composite beam structure to improve the overall stability of the layered floor. The floor anchoring and grouting technology is adopted to improve the mechanical properties of weak planes between layers, enhance the integrity of rock strata in unstable areas, and finally transform the layered floor from a superimposed beam bearing structure to a composite beam bearing structure, thus greatly improving the anti-deformation capacity of the layered floor. At the same time, the concrete floor is laid to isolate water hazards, improve the stiffness of the surface floor, and actively adjust the composite structure of the layered floor. (4) The surrounding rock shall be timely sealed with full section shotcrete to prevent water from degrading the strength of weakly cemented soft rock.
The roadway is located in a water rich environment. The strength of weakly cemented soft rock is seriously reduced after immersion, and the stability of surrounding rock of the roadway is reduced, which brings great difficulty to the maintenance of the roadway. The full section shotcrete mortar can seal the surrounding rock, fill the cracks on the surface of the surrounding rock, block the seepage channel, and prevent the weathering and expansion of the surrounding rock. At the same time, the shotcrete layer will bond the surrounding rock and the supporting components into a unified supporting structure, which can give full play to the bearing capacity of the surrounding rock.

| Control technology
Based on the cooperative control countermeasure of roof-rib-floor surrounding rock, the support technology of roof and ribs supported by blots mesh beam cable + floor supported by bolts grouting hardening + full section shotcrete is proposed. The roadway support section is shown in Figure 12, and the specific support parameters are as follows: (1) Roof and floor collaborative control technology. As the source and transfer medium of load, the stability of roof and rib is very important to the stability of layered floor. The key to realize the stability of the roof and floor is to select high-performance bolts and cables, apply sufficient pretightening force and timely support.
To improve the overall stability of the roof, bolts are used to intensively support the surrounding rock in the arch. The type of roof bolt is ϕ 20 mm × L2500 mm. The anchoring length of each bolt is 1207 mm, and the spacing is 800 mm × 800 mm. The bolts of each row are connected with each other by Φ 16 mm steel strips. The type of roof cable is ϕ 21.6 mm × L 7300 mm. The anchoring length of each bolt is 1970 mm, and the spacing is 1500 mm × 1600 mm.
The two bolts at the upper part of the rib are of the same type as those at the roof, with a spacing of 600 mm × 800 mm. The bolt at the lower corner is lengthened, with a length of 3000 mm and a downward deflection angle of 15°. shotcrete. The roadway is located in a humid and hot engineering environment, and the surrounding rock is easy to be weathered and broken. The surrounding rock can be sealed and the surface cracks can be filled by shotcrete to improve its integrity. C20 concrete with a thickness of 100 mm is sprayed on the roof and rib.

| Evaluated by numerical calculation
A single bolt or cable can form a certain range of support stress fields in its anchoring area. By reasonably controlling the spacing of support components, the support stress fields of each bolt and cable can be superposed to form a certain range of pre-stressed extrusion zone in the surrounding rock (as shown in Figure 13A). The rock mass properties in this area can be improved, so that the bearing capacity of surrounding rock can be enhanced. As shown in Figures 13B,C, the bolts and cables improve the mechanical properties of the weak structural plane and enhance the antislip ability between layers. The layered floor changes from the superimposed beam structure to the composite beam structure, and the layer by layer failure phenomenon of the floor disappears. The supporting components reach the stable rock mass, and form a roof-rib-floor cooperative bearing system by coupling with the surrounding rock. The overall stability of the roadway has been greatly improved, the damage range of the surrounding rock has been reduced, and the deformation of the floor has been limited, thus preventing the occurrence of a large range of floor heave.

| Evaluated by engineering application effect
The roadway was timely supported after being excavated, and the rock pressure measuring station was set up to evaluate the surrounding rock control effect ( Figure 14A). Dynamometers are used to monitor the stress of bolts and cables in its working process, and laser rangefinder and steel tape are used to monitor roadway surface displacement. The displacement curve of the surrounding rock on the roadway surface is shown in Figure 14B. After the roadway is excavated, the surrounding rock enters a period of severe deformation, and the deformation of the surrounding rock increases rapidly. With the supporting components and surrounding rock forming a cooperative bearing structure, the surrounding rock enters a stable deformation period, and the deformation speed tends to be stable. Then the surrounding rock enters the stable period, and the deformation of the surrounding rock basically does not increase. The cumulative deformation of the roof, floor and rib is 53, 73, and 135 mm, respectively, and the deformation of surrounding rock is small, indicating that the overall stability of the roadway is good. The stress variation trend of bolts and cables is shown in Figure 14C,D. During the monitoring period, the stress of bolts and cables increases synchronously, and there is no phenomenon that the stress returns to zero after the component fails, which indicates that the bolts and cables have reached the cooperative bearing state with the surrounding rock. After the roadway is excavated, the internal structure of roof and rib is detected through borehole television. As shown in Figure 15, the support technology effectively controls the evolution of surrounding rock fractures. The fractures are not interconnected to form a fracture zone, and only a small number of fractures appear in the shallow local area, indicating that the overall stability of the roadway is good.

| CONCLUSION
(1) The surrounding rock of weakly cemented soft rock roadway in Meihuajing Mine is rich in clay minerals, with obvious layered characteristics, and the rock stratum combination structure of the floor is complex and changeable. Under the influence of engineering disturbance, the roadway has a tendency of large deformation, especially floor heave. (2) The Interface element in FLAC3D is used to construct the bedding plane to realize the numerical representation of layered rock mass. The layered floor is unstable due to the influence of layered weakening effect, and the floor successively forms an unstable zone, a sub stable zone and a stable zone from the shallow to the deep. With the increase of layer thickness, the integrity of layered floor is improved, and the bearing capacity of single layer and the overall floor is improved. The expansion of the unstable zone is restrained, the influence range of the substable zone is enlarged, and the overall stability of the layered floor is improved. (3) The existence of weak interlayer further degrades the integrity of the layered floor, and under its influence, the progressive failure of floor rock mass is more significant. As a weak link in the floor bearing system, the weak interlayer provides a "free surface" for the deformation and failure of surrounding rock. The rock mass structure within its influence area is activated, the deformation is significantly increased, and the plastic zone is significantly extended along the weak interlayer. (4) The relatively hard rock stratum in the composite structure plays an important role in controlling the deformation and failure of the floor, that is, the role of "local key stratum." By hardening the surface floor, a "local key stratum" is built in the shallow rock mass of the floor to realize the active control of the floor rock mass combination structure, improve the stability of the shallow rock strata, and thus significantly reduce the deformation of the layered floor. (5) Based on the surrounding rock cooperative control countermeasure of roof-rib-floor, the support technology of roof and ribs supported by blots mesh beam cable + floor supported by bolts grouting hardening + full section shotcrete is proposed. The results of numerical calculation and field test show that the support scheme effectively restrains the deformation and failure of weakly cemented soft surrounding rock, and greatly improves the stability of layered floor.