Deep Rock Roadway Research Articles

Numerical analysis for tunnelling-induced stress and plastic evolution causing instability of multilayered surrounding rock by varying three-dimensional in situ stresses

PurposeThe induction of geological disasters is predominantly influenced by the dynamic evolution of the stress and plastic zones of the multilayer rock formations surrounding deep-rock roadways, and the behaviours and mechanisms of high in situ stress are key scientific issues related to deep-resource exploitation. The stress environment of deep resources is more complex owing to the influence of several geological factors, such as tectonic movements and landforms. Therefore, in practical engineering, the in situ stress field is in a complex anisotropic three-dimensional state, which may change the deformation and failure law of the surrounding rock. The purpose of this study is to investigate the tunnelling-induced stress and plastic evolution causing instability of multilayered surrounding rock by varying three-dimensional in situ stresses.Design/methodology/approachBased on data from the Yangquan Coal Mine, China, a finite difference model was established, and the elastic-plastic constitutive model and element deletion technology designed in the study were analysed. Gradual tunnelling along the roof and floor of the coal seam was used in the model, which predicted the impact tendency, and compared the results with the impact tendency report to verify the validity of the model. The evolutions of the stress field and plastic zone of the coal roadway in different stress fields were studied by modifying the maximum horizontal in situ stress, minimum horizontal in situ stress and lateral pressure coefficient.FindingsThe results shown that the in situ stress influenced the stress distribution and plastic zone of the surrounding rock. With an increase in the minimum horizontal in situ stress, the vertical in situ stress release area of the roof surrounding rock slowly decreased; the area of vertical in situ stress concentration area of the deep surrounding rock on roadway sides decreased, increased and decreased by turn; the area of roof now-shear failure area first increased and then decreased. With an increase in the lateral pressure coefficient, the area of the horizontal in situ stress release area of the surrounding rock increased; the area of vertical in situ stress release area of the roof and floor surrounding rock first decreased and then increased; the area of deep stress concentration area of roadway sides decreased; and the plastic area of the surrounding rock and the area of now-shear failure first decreased and then increased.Originality/valueThe results obtained in this study are based on actual cases and reveal the evolution law of the disturbing stress and plastic zone of multilayer surrounding rock caused by three-dimensional in situ stress during the excavation of deep rock roadways, which can provide a practical reference for the extraction of deep resources.

Deformation and Failure Characteristics and Control Technology of Surrounding Rocks in Deep High-Horizontal Stress Rock Roadways in the Wanbei Mining Area

Taking the engineering conditions of the Zhujixi coal mine and Hengyuan coal mine in the Wanbei mining area as the background, based on the investigation of the deformation and failure status of the surrounding rock of the two mines, the deformation and failure characteristics of the surrounding rock of the deep rock roadway in the Wanbei mining area are systematically studied by using the comprehensive research methods of the surrounding rock mechanical parameter test, in situ stress measurements, and numerical simulation. The results show that the measured value of the intermediate principal stress is slightly less than the theoretical value, which is obviously affected by the tectonic stress. The lateral pressure coefficients of the two mines calculated according to the theory are between 1.06 and 1.24 and 1.18 and 1.24, respectively. The simulation shows that when the lateral pressure is higher than 1.5, the arrangement of drilling holes with a depth of 5–10 m and a diameter of 200–300 mm can effectively transfer the stress concentration, proposed using Ф22 L = 2800 mm anchor rods, row spacing 800 × 800 mm, specification Ф 22. For the anchor cable with a length of L = 6,300 mm, the row spacing between anchor cables is 1,600 ± 100 mm, and the coordinated support technology of the reinforcement support and grouting is added. The technology can fully mobilize the deep stable rock stratum when it is applied from the slope change point of 11 coal belt roadways in the east wing of the Zhujixi coal mine to the machine head chamber of 11 coal belt roadways in the west wing, and the field application is good.

Study on Monitoring Technology of Surrounding Rock in Deep Layered Roadway Based on Constant Resistance and Large Deformation Bolt

The stability monitoring of surrounding rock in layered roadway is an important method to ensure the safety of deep mining coal mine. In view of the actual situation of roadway stability monitoring, based on similarity theory, the deep roadway model is built and small-sized ordinary bolts and constant resistance and large deformation (CRLD) monitoring bolts are developed to detect the mechanical real-time information of surrounding rock in the model, the accurate measurement information of the displacement field and the force value of the bolts are obtained. According to the time series characteristics of the deformation field and the force curves of the monitoring bolts, the criterion of stability and instability pattern of surrounding rock in deep layered roadway are studied. The results show that the force monitoring method based on CRLD bolt is superior to displacement monitoring, the force monitoring curve of CRLD bolt can be divided into stable mode and instability mode, the characteristic of stable mode curve is rising slowly and the instability model with rapid rising and falling stages. The stability monitoring system of roadway with CRLD bolt is developed and applied in deep rock roadway, it has been proved by field practice that the early warning of surrounding rock instability of deep layered roadway is feasible.

Deformation control of asymmetric floor heave in a deep rock roadway: A case study

In order to control asymmetric floor heave in deep rock roadways and deformation around the surrounding rock mass after excavation, in this paper we discuss the failure mechanism and coupling control countermeasures using the finite difference method (FLAC3D) combined with comparative analysis and typical engineering application at Xingcun coal mine. It is indicated by the analysis that the simple symmetric support systems used in the past led to destruction of the deep rock roadway from the key zone and resulted in the deformation of asymmetric floor heave in the roadway. Suitable reinforced support countermeasures are proposed to reduce the deformation of the floor heave and the potential risk during mining. The application shows that the present support technology can be used to better environmental conditions. The countermeasures of asymmetric coupling support can not only effectively reduce the discrepancy deformation at the key area of the surrounding rock mass, but also effectively control floor heave, which helps realize the integration of support and maintain the stability of the deep rock roadways at Xingcun coal mine.

Simulation on THM Coupling Process of Deep Rock Roadway with Aquifer in Coalmine

THM coupling is an important process in engineering rock mass. In order to study the mechanism of THM coupling in surrounding rock of deep rock roadway in coalmine, the interactions between THM fields were analyzed, and the governing equations of THM coupling were given. Finally, a model of rock roadway with aquifer is simulated, and the distribution of pore pressure as well as the thermal and stress fields were obtained after some steps of calculation.

Support Effect and Application of High Convex Steel-Belt in Deep Roadway

The steel-belt has the ability to improve support effect of the whole system that coordinate the anchorage force of bolt or cable, improve the support effect of the anchor system and diffuse the fore acted on bolt or cable. During the progress of support in the roadway, there has appeared flat, W and M steel-belt, and all of them have played important roles in different stages of support in the roadway. However, steel-belt now is rarely used in the deep rock roadway. High convex steel-belt is a new product, but whether it can adapt or not to the deep roadway, it's well worth our attention. The structure of high convex steel-belt and the characteristics of deep roadway are introduced in this paper. Numerical test on four kinds of mine steel-belt is carried out by ANSYS, and the advantage of high convex steel-belt is comparatively analyzed in deep roadway. At last, an example is shown. Research indicates that the steel-belt bears mainly the point load or local load due to non smooth and even convex wall sides, and it lies in a state of inelastic and large deformation due to non uniformity deformation of surrounding rock in the deep rock roadway. The mechanical behavior of convex steel-belt has the performance of obvious advantages. It can adapt to the large deformation of deep roadway due to the convex structure. This result has been proved in the engineering practice.

Experimental Study on Anti-Shear Properties of Floor Heave Control Anchor of Deep Soft Rock

With the increase of Chinese mining depth, the deformation of deep soft rock is an increasingly serious problem, such as floor heave. The shear experiments of the different types of anchor were carried out. The results show that the anti-shear properties of the seamless anchor are higher than that of the seam anchor. It is significant for the anti-shear properties of anchor filled with different materials, like twisted steel, cement. The shear value of anchor inserted steel is the maximum, grouted one is the next and hollow one is the minimum. After steel installed, the anchor has better shear performance, it not only has greater anti-shear property, but has the secondary supported property because of the double-load peak during shear process. At the same time, the experiments also show that the anchor fixed into the floor in some angle, can effectively control the deformation of the floor heave of deep rock roadway. The studies can offer scientific basis for parameter design optimization of the anchor controlling the deformation of the floor heave.