In-Situ Vane Shear Measurement for Soil Rheology
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Solution Overview
Problem
Current methods for measuring the mechanical and rheological properties of soils, such as undrained shear strength and viscosity, are prone to sample disturbance and alteration, require costly and time-consuming laboratory testing, and do not allow for real-time decision-making due to sample handling and transportation issues, leading to inaccurate and environmentally unsustainable results.
Innovation Solution
A method and apparatus using a vane blade with a variable rate motor and sensors to measure torque and rotational speed in situ, allowing for accurate determination of geotechnical and rheological properties by varying the rotational speed of the vane blade and recording torque and speed relationships.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional laboratory rheometer with concentric cylinder geometry is used to measure viscosity and yield stress, then measurement precision can be achieved, but sample disturbance and handling cause irreversible changes to shear history and wall slip effects lead to artificially low viscosity measurements
Solution Approach 1:
The patent replaces the conventional concentric cylinder mechanical rheometer system with an in-situ vane shear apparatus that measures torque and rotational speed directly in the tailings pond. This substitution eliminates the need for sample collection, transportation, and laboratory preparation, thereby preventing sample disturbance and preserving the original shear history of the flocculated structure. The vane blade rotates within the tailings material in its natural environment, avoiding wall slip effects that occur in laboratory containers.
2Measurement precision
If laboratory sampling and testing procedures are implemented, then geotechnical and rheological properties can be measured, but sampling equipment and crew requirements increase cost and complexity, and transportation implies higher costs and greenhouse gas emissions
Solution Approach 1:
The in-situ vane shear apparatus is designed to be deployed directly in the tailings pond without requiring complex sampling equipment or laboratory facilities. The device performs self-contained measurements by rotating the vane blade within the tailings material and measuring torque and rotational speed in place. This eliminates the need for separate sampling, transportation, and laboratory testing operations, significantly reducing equipment requirements, operational complexity, and environmental impact.
3Measurement precision
If standard field vane shear test with constant rotation rate is used, then undrained shear strength can be measured, but drainage effects during testing at standardized rates influence measurement accuracy in silty soils
Solution Approach 1:
The patent implements a variable rotation rate system that dynamically adjusts the rotational speed of the vane blade during testing. Unlike standardized field vane shear tests that use constant rotation rates, this system can vary the rotation speed to achieve undrained conditions in silty soils by controlling the rate of shearing. The ability to adjust rotation rate allows the apparatus to adapt to different soil types and drainage conditions, eliminating drainage effects that plague standardized testing methods.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables reliable, cost-effective, and environmentally friendly in-situ measurement of soil properties, minimizing sample disturbance and providing precise rheological data for improved handling and treatment operations, such as dredging and tailings management.
Implementation Method 1
a torque sensor configured to measure a torque exerted on the vane blade
Implementation Method 2
a speed sensor configured to measure a cumulative rotation of the vane blade and a lapsed time and to calculate a rotational speed of the vane blade
Implementation Method 3
a variable rate motor configured to rotate the vane blade around an axis
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
A method for measuring mechanical (undrained shear strength, residual shear strength, remolded shear strength, sensitivity, brittleness) and rheological (viscosity, yield stress, thixotropic) properties of soil, the method comprising: providing a measuring apparatus comprising a rotatable vane blade; inserting the vane blade into the soil at a first depth; during a first period of time, accelerating the rotational speed of the vane blade; during a second period of time, decelerating the vane blade while measuring the torque applied to the vane blade and the rotational speed of the vane blade; determining a relationship between the torque and the rotational speed; and determining rheological properties of the soil at the first depth based on the relationship between the torque and the rotational speed.