Square Sample Positioning for Low-Disturbance Rock-Shotcrete Coring
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Solution Overview
Problem
Conventional core sampling methods are inadequate for obtaining square samples from rock mass and shotcrete layers, especially in weak cementing structural planes, as they cause significant disturbance and low sampling success rates due to vibration and torsion loads applied during drilling.
Innovation Solution
An in-situ square sample acquisition device and method using a supporting shell, borehole positioning frames, and hollow adjusting bolts, which minimizes sample disturbance by allowing for precise positioning and drilling of square samples with reduced mechanical stress on the rock mass.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If core sampling method is used for sampling rock mass and shotcrete layer, then cylindrical samples can be obtained, but square samples cannot be obtained and sampling success rate is low
Solution Approach 1:
The device segments the sampling process into multiple stages: first creating a square hole outline through drilling, then removing material to obtain a complete square sample. This segmentation allows obtaining square samples from dual mediums (rock mass and shotcrete layer) that cannot be achieved by conventional core sampling methods.
2Productivity
If drill bit is used for sampling weak rock mass with weak cementing structural planes, then drilling can be performed, but vibration and torsion loads cause rock samples to break
Solution Approach 1:
The invention extracts the harmful vibration and torsion loads from the sampling process by avoiding the use of rotating drill bits with sawteeth. Instead, it uses a drilling method that creates square holes without applying cyclic mechanical stresses that would cause weak cementing structural planes to fail, thereby extracting only the beneficial drilling function while eliminating the harmful effects.
Solution Approach 2:
The device introduces an intermediary structure (the square hole positioning frame and supporting shell) that mediates between the drilling process and the rock mass. This intermediary guides the drilling process to create square holes while distributing stresses uniformly, preventing concentration of forces that would cause sample breakage at weak structural planes.
3Ease of operation
If conventional drilling method is applied to dual mediums, then drilling can proceed, but rock samples break at weak cementing structural planes resulting in low sampling rate
Solution Approach 1:
The device performs preliminary action by first positioning the square hole positioning frame and supporting shell to define the exact square sample boundaries before drilling begins. The positioning holes are pre-arranged in a staggered pattern to guide the drilling process, ensuring that the square sample is obtained完整地 without breaking during the drilling operation.
Data Source
AI summary
An in-situ square sample acquisition device and method for a bond contact test of a surrounding rock and a shotcrete layer are provided, the device includes a supporting shell, a fixing structure, hollow adjusting bolts and two borehole positioning frames, a guide hole is provided in a middle of the supporting shell, the frames are slidably fit in the guide hole, a plurality of positioning holes are provided in side walls of each of the frames, and the positioning holes in different frames are distributed in a staggered manner, four corners of the supporting shell are connected with four hollow adjusting bolts respectively, one end of each of the hollow adjusting bolts is fixedly provided with an adjusting nut, four fixing lugs are provided in four corners of each frame respectively, and the fixing structure includes four connecting bolts and four nuts.