Steel Tube Concrete Pier Column Technology for Goaf Roadway Preservation

Literature Overview

The paper by Shen Yusan, Wu Kai, Zhang Tao, Huang Wanpeng, Wang Jun, Dong Qinkai, and Xia Zhicun (2019), published in Coal Mine Safety, Vol. 50, No. 2, presents a novel goaf roadway preservation technology using steel tube concrete pier columns in the context of the Luxi Coal Mine's 3-under A02 working face. This research addresses the critical challenge of maintaining roadway integrity in high-stress mining environments where mining succession is under severe time pressure.

Technical Background and Problem Statement

In underground coal mining, goaf roadway preservation (YKL) is essential for minimizing excavation costs and improving mining efficiency. However, under high stress conditions, conventional preservation methods often fail due to excessive convergence and roof failure. The Luxi Coal Mine faced a particularly challenging scenario where the stress environment around the working face exceeded the design limits of traditional support systems.

Novel Technical Scheme

The proposed technical scheme integrates five key components:

Component	Function	Key Parameters
Steel tube concrete pier columns	Primary load-bearing support	Column spacing, diameter, wall thickness, concrete grade
Flexible cushion layer	Stress distribution and accommodation	Cushion material type, thickness, compressibility
Controlled roof anchor cables	Roof stability control	Anchor cable length, spacing, preload
In-roadway reinforced support	Secondary support system	Steel arch spacing, bolt pattern
Wind prevention measures	Airflow management	Sealing material, barrier design

Construction Process Analysis

The construction process is the critical differentiator of this technology. The key technical steps include:

Pier column erection: Steel tubes are fabricated to precise dimensions and erected at calculated intervals along the roadway side adjacent to the goaf.
Concrete pouring: The steel tubes are filled with concrete to create the composite pier columns. The pouring sequence and timing are critical to ensure proper bonding between steel and concrete.
Auxiliary reinforcement support: Additional support measures are installed to ensure stability during the construction phase and subsequent mining operations.
Sequential installation: The columns are installed progressively as the working face advances, maintaining a continuous support system.

FMEA Analysis of Critical Construction Steps

Process Step	Potential Failure Mode	Severity	Occurrence	Detection	Countermeasure
Column erection	Misalignment, insufficient verticality	8	3	5	Laser alignment, plumb bob verification
Concrete pouring	Segregation, insufficient compaction	7	4	4	Pump placement, vibrator use, slump control
Cushion installation	Uneven thickness, material degradation	6	5	3	Standardized thickness control, quality inspection
Anchor cable installation	Insufficient anchorage, premature failure	9	3	4	Pull-out testing, grouting quality control

Industrial Trial Results

The industrial trial at Luxi Coal Mine demonstrated that:

The preserved roadway maintained structural integrity throughout the mining period.
Surrounding rock stability was effectively controlled with acceptable deformation limits.
The construction process was simplified compared to conventional methods, enabling faster deployment.
The combined approach achieved both high strength and high efficiency objectives.

Engineering Practice Integration

From a steel pipe manufacturing perspective, this application highlights several important considerations:

Pipe specifications: The steel tubes used as pier columns must meet specific requirements for wall thickness uniformity, dimensional accuracy, and mechanical properties. Typical specifications include seamless or ERW steel tubes with wall thickness of 6-12 mm and outer diameters of 219-325 mm.
Quality control: The steel tubes must undergo hydrostatic testing, dimensional inspection, and visual examination before deployment. Any weld defects or wall thickness deviations could compromise the structural integrity of the pier columns.
Concrete-steel interaction: The bonding quality between the steel tube and concrete is critical for the composite action. Surface preparation of the inner tube wall, including roughening or application of bonding agents, is recommended to enhance the interface strength.

Key Technical Parameters

Based on the study and industry practice, the following parameters are critical for the design of steel tube concrete pier columns in goaf roadway preservation:

Column spacing: typically 2.0-3.0 m depending on roof conditions
Steel tube diameter: 219-325 mm
Wall thickness: 6-12 mm
Concrete grade: C30-C50
Column height: matching the roadway height (typically 2.5-3.5 m)
Cushion layer thickness: 50-100 mm

Study Insights and Implications

This research demonstrates the practical viability of steel tube concrete pier columns as a primary support element in underground mining applications. The integration of multiple support measures into a comprehensive system reflects modern engineering philosophy where redundancy and multi-layered protection are preferred over single-element solutions.

The success of this technology in a high-stress mining environment validates the structural performance of steel tube concrete composite members under severe loading conditions. For pipe manufacturers, this application represents a growing market segment where the demand for high-quality, dimensionally accurate steel tubes is increasing. The study also highlights the importance of construction methodology and process control in achieving the designed structural performance.

The flexibility of the system, allowing for progressive installation as the working face advances, makes it particularly suitable for mining operations where time constraints and changing ground conditions require adaptable support solutions. This represents a significant advancement over rigid, pre-installed support systems that cannot accommodate dynamic loading scenarios.