Cylindrical Shear Box for Undisturbed Soil Testing
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Solution Overview
Problem
Existing large-scale direct shear apparatuses are limited to testing remolded soil samples due to their square shear boxes, which are not suitable for cylindrical undisturbed soil samples, leading to inaccurate measurement of soil mechanical parameters.
Innovation Solution
A large-scale direct shear apparatus designed for multi-size cylindrical undisturbed soil samples, featuring a sample shear box with upper and lower square shear boxes and a cylindrical shear box, along with a horizontal and vertical loading device, and a control system for automated testing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If square shear boxes are used in large-scale direct shear apparatus, then the apparatus can test remolded soil samples, but it cannot accommodate cylindrical undisturbed soil samples
Solution Approach 1:
The shear box is divided into separate upper and lower boxes that can be assembled and disassembled. The lower shear box contains a removable cylindrical insert that can be exchanged for different sizes, allowing the same apparatus to accommodate various cylindrical undisturbed soil sample dimensions while maintaining structural integrity.
Solution Approach 2:
A cylindrical insert is nested within the lower shear box, which itself is part of the larger square shear box assembly. This nested structure allows the cylindrical sample holder to be positioned precisely within the square frame, enabling compatibility with cylindrical undisturbed samples while maintaining the overall square apparatus structure.
2Device complexity
If square samples are used in shear testing, then the apparatus structure is simplified, but stress concentration occurs at corners leading to uneven force distribution
Solution Approach 1:
The sample geometry is changed from square to cylindrical, eliminating the sharp corners that cause stress concentration. The curved surface of the cylindrical sample distributes shear stress more uniformly across the sample perimeter, improving force distribution uniformity while the square outer frame maintains structural simplicity.
3Device complexity
If remolded soil samples are tested instead of undisturbed samples, then the apparatus can be simpler, but the mechanical properties do not accurately represent actual working conditions
Solution Approach 1:
Undisturbed soil samples are collected and prepared in advance using field drilling equipment before being transported to the laboratory. The samples are carefully handled and installed in the cylindrical shear box inserts without disturbance to their natural structure, preserving their in-situ mechanical properties for accurate testing.
Data Source
AI summary
A large-scale direct shear apparatus for direct shear test of multi-size cylindrical undisturbed soil samples, comprising an external framework, a sample shear box, a horizontal loading device, a vertical loading device, and a control system. The sample shear box is disposed within the external framework and includes an upper shear box, a lower shear box, and a base. The horizontal loading device includes a horizontal drive motor equipped with a load sensor, a horizontal mechanical loading mechanism, and an upper shear box connection structure. The horizontal drive motor is installed on one inner side of the external framework and contacts the lower shear box via the horizontal mechanical loading mechanism. The upper shear box connection structure is fixed to the other inner side of the external framework and contacts the upper shear box. The vertical loading device includes a vertical drive motor and a vertical mechanical loading mechanism.