Mobile Soil Stiffness Test System with Confining Stress Control
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Solution Overview
Problem
Conventional methods for determining in situ stress and deflection-dependent stiffness and bearing capacity of soils and geo-materials are limited by their inability to provide measurements under static conditions, reliance on flat or ring loads, sensor system limitations, lack of confining stress control, and inability to perform strain or deflection-controlled testing.
Innovation Solution
A mobile test system that applies controlled static or cyclic loading to bearing plates of various geometries, with optional ground confining stress conditions, to determine stress and deflection-dependent stiffness and bearing capacity, using a trailer equipped with a hydraulic piston and derrick assembly, plow assembly, and confining plate assembly to prepare and stabilize the testing area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional deflectometer methods are used to determine in situ stiffness, then measurements can be obtained quickly, but the measurements cannot be taken under static conditions and are limited to dynamic loading only
Solution Approach 1:
The testing system is divided into separate functional modules: a mobile platform for transport, a loading system with hydraulic actuators for applying static and cyclic loads, a confining stress control system with independent actuators, and a sensor system. This segmentation allows each module to be optimized for its specific function while enabling static condition testing that conventional integrated deflectometers cannot achieve.
2Adaptability or versatility
If flat plate or ring loading is used for in situ testing, then the testing procedure is simple, but the results are only suitable for selected material conditions and lack versatility
Solution Approach 1:
The loading system is designed with multiple bearing plate geometries (flat plates, curved plates, rings) that can be interchanged on the same application point. The system can apply both static and cyclic loads, and independently control confining stress, making it universally applicable to various material conditions including soils, aggregates, and stabilized materials, rather than being limited to specific material types.
Solution Approach 2:
The system transitions from static geometric configurations to dynamic, adjustable configurations. Bearing plates with different geometries can be selected based on material conditions, and the loading regime can be dynamically changed between static and cyclic applications. The confining stress can also be dynamically adjusted during testing to simulate different field conditions.
3Measurement precision
If conventional sensor systems are used, then the equipment is simpler, but measurements cannot be taken under controlled confining stress conditions
Solution Approach 1:
A confining plate assembly acts as an intermediary between the mobile platform and the bearing plate. This confining plate can be pressed against the ground with independently controlled hydraulic actuators to apply controlled confining stress around the bearing plate perimeter. The sensor system measures both the bearing plate deflection and the confining stress, enabling precise measurement of stiffness and bearing capacity under controlled confining conditions that conventional systems cannot achieve.
4Measurement precision
If indirect measurement methods like CBR or density testing are used, then the testing process is simpler and faster, but the measurements do not directly characterize stress and deflection dependent stiffness and bearing capacity
Solution Approach 1:
The system replaces indirect mechanical measurement methods (CBR, density testing) with direct mechanical measurement of stress-deflection relationships. Instead of measuring surrogate properties like density or CBR value and calculating stiffness indirectly, the system directly applies controlled loads to bearing plates, measures the resulting deflections with precision sensors, and directly calculates stress-dependent stiffness and bearing capacity from the measured stress-deflection curves, providing direct characterization of the engineering properties needed for design.
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 real-time measurement and calculation of in situ stress-dependent stiffness and bearing capacity, facilitating quality control and assurance in construction processes by simulating final stress conditions and providing accurate data for a wide range of materials and conditions.
Implementation Method 1
a mobile test system that applies controlled static or cyclic loading to bearing plates of various geometries, with optional ground confining stress conditions
Implementation Method 2
plow assembly, and confining plate assembly to prepare and stabilize the testing area
Implementation Method 3
with optional ground confining stress conditions
Data Source
Figure 1
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Figure 3(a)
AI summary
An integrated mobile test system and methods for characterizing in situ stress or strain/deflection - dependent stiffness and bearing capacity enables the testing of engineering properties of natural, compacted, stabilized, and reinforced soils and geo-materials. The mobile test system and associated methods (1) prepare the ground for testing and (2) apply static or cyclic loading to one or more bearing plates of various geometries positioned at the ground surface or below the ground surface to determine both stress and deflection dependent stiffness relationships and the bearing capacity of the soil or geo-material. Optionally, the mobile test system and associated methods (3) apply ground confining stress conditions independent of the bearing plate loading.