3
deformations (Su 2016, 2017 Su et al. 2018, 2019 Zhang
and Su 2021 Zhang et al., 2023 Tulu et al., 2024).
The modelling approach uses FLAC3D to simulate
the mining-induced stress and deformations. The extrac-
tion of longwall panels 26 Right to 31 Right (R26 to R31)
were simulated according to the operational parameters
provided by the mine operator. The overburden strata are
modeled by ubiquitous joint material from surface to below
the mining horizon. The geology at the site is interpreted
from the core hole data, and surface contours provided by
the mine operator are used to generate overburden topogra-
phy. The simulations were performed in 2D slice instead of
a full 3D model. Figure 3 shows the cross-sectional view of
the FLAC3D mode and the overburden geology.
Recommended overburden rock strata and weak inter-
face properties were published by Zhang et al. (2019 and
2023) and Tulu et al. (2017). Zhang et al. (2019) estimated
these field scale mechanical properties from analysis of the
laboratory tests and back analysis of the subsidence and
mining-induced stress distributions from different field
measurement case studies. Table 1 summarizes the field
scale mechanical properties used in the simulation of the
overburden strata.
To predict the response of overburden strata and gas
emission zone, it is important to model the gob response
realistically. Tulu et al. (2017) used a strain hardening
model to simulate the gob compaction. The hyperbolic
function, derived by Salamon (1990), used to simulate the
strain hardening stress-strain relationship. In this model-
ling approach, it is assumed that gob forms under an initial
bulking factor of 1.5, based on the observation of caving
height in boreholes discussed by Su (1991), representing a
maximum vertical strain of 33% and a caving height equal
to three times the mining height. The details of this model
can be found in Tulu et al. (2017) and Tulu et al. (2024).
CFD Model Development
Computational fluid dynamics (CFD) modeling has been
used to understand the airflow and contaminant (gas and
particulates) distribution in underground and open pit
mines for quite some time (Raj et al., 2015, Raj et al.,
2013, Morla et al., 2021, Mohamed et al., 2024, Raj and
Gangrade, 2023). More specific to the current research on
airflow and gas distribution in the gob area of the longwall,
researchers in the past have conducted several CFD stud-
ies to understand gas flow (Wang et al., 2023, Guo et al.,
Figure 2. Stratigraphy in vicinity of study site. A. Generalized stratigraphy for lower Pennsylvanian strata in region (Gilland et
al., 2013). B. Localized stratigraphy at mine near Pocahontas No. 3 mined seam
deformations (Su 2016, 2017 Su et al. 2018, 2019 Zhang
and Su 2021 Zhang et al., 2023 Tulu et al., 2024).
The modelling approach uses FLAC3D to simulate
the mining-induced stress and deformations. The extrac-
tion of longwall panels 26 Right to 31 Right (R26 to R31)
were simulated according to the operational parameters
provided by the mine operator. The overburden strata are
modeled by ubiquitous joint material from surface to below
the mining horizon. The geology at the site is interpreted
from the core hole data, and surface contours provided by
the mine operator are used to generate overburden topogra-
phy. The simulations were performed in 2D slice instead of
a full 3D model. Figure 3 shows the cross-sectional view of
the FLAC3D mode and the overburden geology.
Recommended overburden rock strata and weak inter-
face properties were published by Zhang et al. (2019 and
2023) and Tulu et al. (2017). Zhang et al. (2019) estimated
these field scale mechanical properties from analysis of the
laboratory tests and back analysis of the subsidence and
mining-induced stress distributions from different field
measurement case studies. Table 1 summarizes the field
scale mechanical properties used in the simulation of the
overburden strata.
To predict the response of overburden strata and gas
emission zone, it is important to model the gob response
realistically. Tulu et al. (2017) used a strain hardening
model to simulate the gob compaction. The hyperbolic
function, derived by Salamon (1990), used to simulate the
strain hardening stress-strain relationship. In this model-
ling approach, it is assumed that gob forms under an initial
bulking factor of 1.5, based on the observation of caving
height in boreholes discussed by Su (1991), representing a
maximum vertical strain of 33% and a caving height equal
to three times the mining height. The details of this model
can be found in Tulu et al. (2017) and Tulu et al. (2024).
CFD Model Development
Computational fluid dynamics (CFD) modeling has been
used to understand the airflow and contaminant (gas and
particulates) distribution in underground and open pit
mines for quite some time (Raj et al., 2015, Raj et al.,
2013, Morla et al., 2021, Mohamed et al., 2024, Raj and
Gangrade, 2023). More specific to the current research on
airflow and gas distribution in the gob area of the longwall,
researchers in the past have conducted several CFD stud-
ies to understand gas flow (Wang et al., 2023, Guo et al.,
Figure 2. Stratigraphy in vicinity of study site. A. Generalized stratigraphy for lower Pennsylvanian strata in region (Gilland et
al., 2013). B. Localized stratigraphy at mine near Pocahontas No. 3 mined seam