The long-term safety of a deeply buried soft rock tunnel lining under inside-to-outside seepage conditions

et al. 2020

Sustainability

The roadway instability in deep underground conditions has attracted constant concerns in recent years, as it seriously affects the efficiency of coal mining and the safety of personnel. The large rheological deformations normally occur in deep roadway with soft coal mass. However, the failure mechanism of such roadways is still not clear. In this study, based on a typical soft coal roadway in the field, the in-situ measurements and rock mass properties were obtained. The rheological deformation of that roadway was revealed. Then a time-dependent 3D numerical model was established and verified. Based on the verified model, the deformation properties and evolutionary failure mechanism of deep coal roadway were investigated in detail. The results showed that the deformation of the soft coal roadway demonstrated rheological behavior and the applied support structures failed completely. After roadway excavation, the maximum and minimum stresses around the roadway deteriorated gradually with the increase of time. The failure zones in soft coal mass expanded increasingly over time, which had a negative effect on roadway stability in the long-term. According to the findings, helpful suggestions were further presented to control the rheological deformation in the roadway. This research systematically reveals the instability mechanism of the deep coal roadway and provides some strategies for maintaining roadway stability, which can significantly promote the sustainability of mining in deep underground coal mines.

Section: Discussion and Suggestionsmentioning

confidence: 92%

Failure Mechanisms of Rheological Coal Roadway

et al. 2020

Sustainability

“…In this study, the burger‐creep viscoplastic model (CVISC) is used for simulating the time‐dependent property of coal according to recommendation . Rheological parameters are critical for analyzing the deformation behavior of coal mass.…”

Section: Numerical Modelingmentioning

confidence: 99%

Investigation on jet grouting support strategy for controlling time‐dependent deformation in the roadway

Energy Science & Engineering

2020

The efficiency of coal mining is seriously affected by roadway stability, as large time‐dependent deformation of roadway frequently occurs and needs to be maintained several times during its service life. Such rheological deformation was common in soft coal mass at Huaibei coalfield in China. To address this issue, in this study, the time‐dependent deformation of the soft coal roadway was analyzed and a new Jet Grouting (JG) technique was presented for controlling deformation. The time‐dependent deformation of the soft coal roadway was numerically simulated and validated. Based on the field test results and the verified model, a JG support model was established to examine its effect on roadway deformation. The JG support system can reduce the horizontal and vertical displacement of the roadway effectively and constrain the time‐dependent deformation of coal mass. The deformation rate and stabilization time of roadway decreased significantly by comparison with conventional support. This work presented a promising JG support scheme for controlling the time‐dependent deformation in the roadway in deep underground mine, which can greatly promote the JG design and application.

“…One of the objectives of this study is to reveal the rheological behavior of the soft coal mass around the roadway. To simulate the time-dependent behavior of the soft coal mass, the Burger-creep viscoplastic model (CVISC) was adopted to model the coal mass, which was effective at reflecting the rheological properties of the rock or coal mass, and was confirmed in the literature [3,7,14,15]. In CVISC, the rheological parameters η M , G M , η K and G K represent the time-dependent behavior of the unit element corresponding to a Burgers model (visco-elastic constitutive law), while C, ϕ, and E denote the elastic-plastic behavior of the unit element, corresponding to a Mohr-Coulomb (M-C) model [28].…”

Section: Burger-creep Viscoplastic Model (Cvisc)mentioning

confidence: 99%

“…This value in the coal mass was close to the initial stress (19.2 MPa), demonstrating that a lower stress concentration accumulated in the coal mass, and therefore JG support optimized the stress conditions around the roadway effectively. In addition, a monitoring line (shown by a red dashed line in Figure 13a) was set in the middle of the roadway to obtain the changes in maximum principal stress with time (1,3,7,15,30,60,150, 300 days). The monitoring results are shown in Figure 14.…”

Section: The Stress States Around the Roadway By Jg Supportmentioning

confidence: 99%

“…The efficiency and sustainability of coal mining are greatly affected by the stability of the roadway (a transportation corridor) in underground mines [1]. Ensuring the long-term stability of the roadway is a quite challenging task in deep coal mines, although recent advances in support systems have been presented and utilized [2][3][4][5]. Experience and engineering practice have proven that roadway stability is closely related to the time-dependent behavior of the surrounding rock mass [6][7][8].…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Stability Control for the Rheological Roadway by a Novel High-Efficiency Jet Grouting Technique in Deep Underground Coal Mines

et al. 2019

Sustainability

In maintaining the efficiency of coal mining, the stability of roadway plays a significant role, as it is closely related to the production of coal and the safety of personnel. In deep underground coal mines, the rheological deformation of roadway normally occurs, which affects its service life. To address this problem, in this paper, a novel high-efficiency Jet Grouting (JG) technique was presented, and its control effect on roadway stability was investigated. A creep test of a coal specimen in a laboratory scale was performed, and its creep behavior was revealed. The rheology of the coal mass surrounding the roadway was further analyzed according to the field-monitoring results of roadway deformation. A time-dependent numerical model with a Burger-creep visco-plastic model (CVISC) was established and validated by comparing the calculated displacement with in-situ measurement. The JG technique was tested in the field, and its applicability and practicability were confirmed. According to the validated model and field test results of JG, a numerical model with CVISC by JG support was established to analyze the effect of JG on the roadway. The results showed that the JG support can effectively reduce roadway deformation, optimize stress conditions, and reduce the extent of the plastic zone around the roadway. The rheological properties of the soft coal roadway were constrained and long-term stability was ensured. This pioneering work can guide the application of JG for the stability control of roadways and promote the sustainability of coal mining efficiently.