Abstract
To study the blasting and rock-breaking effects of stemming materials and their mechanisms, the friction force tests
on various stemming materials were conducted as well as field experiments involving blasting of concrete specimens under
different stemming conditions. The internal blasting stress and fragmentation of the specimens after blasting were analyzed, and
further discussions on rock blasting damage were conducted through numerical simulations. The results revealed that when
stemming materials were used, the internal blasting stress within the rock was higher, and the size of rock fragments after
blasting was smaller. Moreover, under stemming conditions, the distribution range of internal blasting stress widened, the stress
peak increased, and the extent of rock damage and fragmentation area increased. The sealing performance of stemming
materials was closely linked to their frictional resistance and sealing capability. Among the materials studied, polyurethane foam
material demonstrated superior stemming effectiveness and convenient usage, making it a promising choice for engineering
applications. These research findings provide valuable guidance for blasthole stemming in rock blasting scenarios.
Key Words
blasting stress; friction; numerical simulation; rock blasting; rock size; stemming material
Address
Nan Yao and Yufei Li: School of Resources and Environmental Engineering, Wuhan University of Science and Technology, Wuhan 430081, China;
Hubei Key Laboratory for Efficient Utilization and Agglomeration of Metallurgic Mineral Resource, Hubei, Wuhan 430081, China
Cheng Tan and Felix Oppong: School of Resources and Environmental Engineering, Wuhan University of Science and Technology, Wuhan 430081, China
Wei Jiang: Baosteel Resources Group Co, Shanghai 201800, China
Kunfeng Lin: Wuhan Safety and Environmental Protection Research Institute of Sinosteel Group Co, Wuhan 430081, China
Abstract
Existing theories for calculating the horizontal displacement of retaining structures do not simultaneously consider
the effects of dewatering and excavation. The dewatering leads to drawdown and the seepage force, the excavation leads to the
change of soil pressure. Under the combined effects of both factors, the distribution of water and soil pressure on both sides of
the retaining structure is reassigned, resulting in the occurrence of horizontal displacement. This paper simultaneously considers
the effects of dewatering and excavation, establishing a theoretical framework for predicting the drawdown and the horizontal
displacement of the retaining structure. Firstly, a new method is established to calculate the drawdown caused by dewatering,
deducing the numerical solution for the drawdown based on the unsteady seepage theory. Subsequently, a force balance equation
for the water body element is established, based on the Rankine earth pressure theory, to derive a water and soil pressure
calculation theory that takes into account seepage forces and drawdown. Meanwhile, this paper replaces the traditional Winkler
foundation model with the Pasternak foundation model, deriving the bending differential equation and employing the finite
difference method to calculate horizontal displacement. Compare the field monitoring data to verify the rationality of the theory.
Analyze the calculation errors caused by neglecting drawdown and seepage forces, as well as the selection of foundation model.
Additionally, further investigate the impacts of precipitation parameters and excavation parameters on the horizontal
displacement and drawdown.
Key Words
drawdown; excavation and dewatering; retaining structure; seepage force; soil-water pressure distribution;
unsteady-state seepage
Address
Kunpeng Li and Shihai Chen: College of Civil Engineering, Huaqiao University, Xiamen, Fujian, China
Weiyu Chen: Fujian Yongwang Construction Group Co., Ltd, Longyan, Fujian, China
Gangnan Ye: Fujian Mingtai Group Co., Ltd, Xiamen, Fujian, China
Abstract
High gangue emission has emerged as a significant issue impacting the ecological environment in mining areas.
Utilizing gangue as an aggregate material to prepare gangue slurry for filling caving zones has gained popularity as a solution.
However, due to the intricate nature of coal mine caving zones, the diffusion mechanism of gangue slurry is highly complex,
necessitating the elucidation of its diffusion laws to effectively guide mine-filling practices. In this paper, we conducted an
analysis of the impact of lithology, skeleton particle gradation, and axial stress on the distribution characteristics of the caving
zone, leveraging the internal void evolution test system of mining rock mass and the simulation approach for skeleton particles
of fractured rock mass. Furthermore, we established a fluid force balance model to investigate the diffusion characteristics of
gangue slurry within the void. As the lithology hardens, the coarse particle size within the skeleton particle grading increases.
Consequently, the void rate within the caving zone gradually expands, the void fractal dimension becomes increasingly
prominent, and the diffusion depth of gangue slurry gradually intensifies. Lithology serves as the primary factor influencing
gangue slurry diffusion. When the lithology hardens, the void ratio increases by 0.26, the void fractal dimension rises to 0.13,
and the gangue slurry diffusion depth expands by 208 meters. An industrial practice of gangue grouting has been implemented.
The results of on-site monitoring indicate that the diffusion range of gangue slurry aligns with the aforementioned findings,
thereby effectively addressing the challenges associated with gangue disposal.
Key Words
caving zone void ratio; diffusion law; gangue slurry; grout filling; lithology
Address
Jiaqi Wang, Rui Gao and Ming Chang: College of Mining Engineering, Taiyuan University of Technology, Shanxi 030024, China
Meng Li: State Key Laboratory of Coal Resources and Safe Mining, China University of Mining and Technology, Xuzhou, 221116, China
Abstract
This study considers terrestrial LiDAR to potentially capture undesirable displacements in mechanically stabilized
earth walls (MSEWs), over time. In the USA, MSEWs have been used for almost 50 years and are becoming ubiquitous in
bridge abutments. Time brings deterioration and the need to design and employ adequate inspection protocols for monitoring the
integrity and deterioration rate of these structures. In that regard, the authors are closely working with the Georgia Department of
Transportation (GDOT), USA. The current work aims to compare two scan-registration (scan-stitching) techniques to determine
their relative accuracy. They are the target-based (TB) and the visual-aligned (VA) approaches. The relative spatial accuracy of
their resulting virtual, 3D, point-cloud models, were compared against measurements completed in the field via a slow robotic
total-station (RTS) instrument, with one-second angular accuracy, serving as the benchmarking device. The main goal of this
study is to determine the minimum amplitudes of wall displacements that could be captured by the TB and VA approaches. The
resulting georeferenced models showed that both techniques, TB and VA, presented almost the same accuracy when modeling
MSEWs covering relatively small areas (0.23 and 0.38 ha). In a root-mean-square sense, the measurements obtained from the
first analyzed bridge could capture most wall displacements larger than ~24 mm. Similarly, for the second bridge, both
approaches could capture most wall displacements larger than ~11 mm. An additional multi-user analysis was completed to
estimate the variability of the results due to users having different levels of experience with these techniques.
Key Words
displacements; LiDAR; MSE walls; settlements; target-based and visual-aligned registrations
Address
Gustavo O. Maldonado, Marcel M. Maghiar,
Soonkie Nam, Md. Mehrab Hossain and Shakil Ahmed: Department or Civil Engineering & Construction, Georgia Southern University, Statesboro, GA 30460, USA
Abstract
When the installation of large diameter driven pile, the plugging effect is generally caused as the partially plugged
condition. In this condition, it is a key issue for design because the inner shaft friction between soil plugs caused by plugging
effect and pile's inside surface causes additional bearing capacity of driven piles. Thus, this study suggested a new method for
evaluating the inner shaft friction caused by partially plugged condition. The CEL (Coupled- Eulerian-Lagrangian) method was
used to simulate the driven pile installation process and proposed the trend of lateral earth pressure coefficient (Kplug) in soil
plugs and the normalized effective soil plug's height. In order to consider drieveability during the hammer driving, each driving
energy was separately calculated in each analysis case. Based on parameter studies, it was shown that the plugging effect
decreased with increasing the pile diameter, and increased with increasing the pile length, the elastic modulus of soil and the
driving energy. It was found that the trend of Kplug had almost uniform trends under the different parameters. A simple equation
for inner shaft friction at the pile inside was proposed by using the proposed Kplug.
Key Words
CEL method; driveability; large diameter open-ended driven pile; lateral earth pressure coefficient; plugging
effect; soil plug
Address
Sumin Song: Department of Civil Engineering, National Taiwan University, Taipei, Taiwan
Junyoung Ko : Department of Civil Engineering, Chungnam National University, Daejeon, Republic of Korea
Hyunsung Lim: Hanwha Ocean, Seoul, Republic of Korea
Abstract
Using a self-developed coal rock pressure water immersion test device, Brazilian splitting tests were performed on
five sets of coal samples under dry and 3, 6, 9, and 12 months pressure water immersion duration (immersion pressure of 5
MPa) to study the tensile properties of coal rock under pressure water immersion. The results indicated that with an increase in
the pressure water immersion duration, the average tensile strength of coal samples in Groups B to E decreased by 42.72%,
50.49%, 55.34%, and 60.19%, respectively, compared with those in Group A. The strain isopotential lines of the coal samples
became progressively denser and converged toward the deformation localized zone of the main macro-tensile cracks. The
increase in pressure water immersion duration intensified the water–coal rock interaction and disrupted the initial energy storage
structure of the coal samples, resulting in a gradual reduction in their pre-peak energy storage capacity. Compared with Group A,
the average energy storage capacity (U) of the coal samples in Groups B to E decreased by 50.26%, 68.91%, 76.68%, and
84.46%, respectively. With an increase in the pressure water immersion duration, compared with the A-1 coal samples, the
rupture fracture of the B-1, C-1, D-1, and E-1 coal samples exhibited more microcracks, more pores, larger cavities, and looser
particle arrangements. Additionally, their surfaces gradually became flocculent. The structure of the coal samples transformed
from dense to loose and porous, enhancing the deterioration effect on their tensile properties.
Key Words
deformation damage; deterioration mechanism; energy evolution; microstructure characterization of rupture
fracture; pressure water immersion duration
Address
Yizhen Zhang: Taiyuan Design Research Institute for Coal Industry, Taiyuan, China
Dawei Yin, Pengxiang Sun and Yisong Ding: College of Energy and Mining Engineering, Shandong University of Science and Technology, Qingdao, China
Shirui Zhang: Shanxi Pulongwan Coal Industry Co., Ltd., Datong 034400, China
