Related Experiment Video
Updated: May 22, 2025

Mechanical Expansion of Steel Tubing as a Solution to Leaky Wellbores
Published on: November 20, 2014
Mechanism and control of floor heave in two entry retained roadways using dense boreholes
Qiang Xu1,2, Xue-Hua Li3,4, Ze Xia1,5
1School of Mines, China University of Mining and Technology, 1 Daxue Road, Xuzhou, 221116, Jiangsu Province, China.
Abstract:
This study addresses severe floor heave in retained entries of two-entry longwall faces through a case analysis of Chahasu Coal Mine, China. Surrounding rock deformation and failure in the 31,317 tail entry were characterized through field monitoring and laboratory tests, followed by analysis of geological and mining impacts on floor heave. Stress evolution in the coal pillar between entries during mining was examined through 3DEC numerical simulations, revealing floor heave mechanisms. Support strengthening and stress improvement measures were comparatively evaluated. A dense borehole roof-cutting technology (CRDBDCS) was developed for floor heave control, with key borehole parameters optimized. When implemented in the 31,315 head entry and adjacent roadways, an over 87% reduction in floor heave volume was achieved, enabling entry reuse. The effectiveness of CRDBDCS was thereby demonstrated, providing technical support for the safe and efficient operation of coal mine roadways.
Related Concept Videos
Design Example: Joints in Concrete Pavements
Contraction joints are typically formed by sawing a groove into the concrete shortly after it has hardened. This creates a weakened vertical plane, deliberately encouraging cracking at...
Design Example: Maintaining Level of an Embankment
Masonry Paving
Pumped Concrete
For direct-acting pumps, the concrete enters the pump via the inlet valve under the action of gravity and suction created by the movement of the piston. This concrete is then forced into the pipeline and out through the outlet valve by the forward movement...
Placing Concrete
While placing concrete, care is taken to ensure that the concrete is laid in uniform layers, and hand shoveling and moving concrete using poker vibrators is avoided. Also,...
Effects of Air-entrainment in Concrete

