In-situ Subgrade Resilient Modulus Test System
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Solution Overview
Problem
Current in-situ test methods for subgrade dynamic resilient modulus do not accurately simulate the true force-bearing state of subgrades under repeated vehicle loads, leading to unreliable results due to the lack of consideration for the constraint effect of the pavement structure.
Innovation Solution
An in-situ test system comprising a loading module with a test vehicle, servo cylinder, and high-precision displacement sensors, which applies a stable and accurate cyclic load to simulate the effect of repeated vehicle loads and pavement structure constraints, allowing for inverse calculation of dynamic resilient modulus values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If FWD method applies impact load of 700 kPa to test subgrade resilient modulus, then dynamic resilient modulus can be obtained, but the load is much larger than actual vehicle load (21 kPa) and does not reflect true force bearing state
Solution Approach 1:
The patent changes the load magnitude parameter from 700 kPa (FWD method) to a much smaller load that closely simulates actual vehicle loads (21 kPa). This parameter change ensures that the test conditions match real-world operating conditions, thereby improving both measurement precision and reliability simultaneously.
Solution Approach 2:
The patent applies a dynamic cyclic loading process that simulates the repeated nature of vehicle loads. By using a loading-unloading cycle that mimics actual traffic conditions, the test dynamically captures the subgrade's resilient modulus under realistic force bearing states, resolving the contradiction between obtaining dynamic modulus and ensuring reliability.
2Productivity
If PFWD method applies lower level impact load to test dynamic resilient modulus, then test speed is improved, but the dynamic moduli obtained are all smaller than static moduli and differ from true subgrade dynamic resilient modulus under repeated vehicle load
Solution Approach 1:
The patent employs periodic cyclic loading that replicates the repeated application of vehicle loads. This periodic action allows the subgrade to undergo multiple loading-unloading cycles, enabling accurate measurement of dynamic resilient modulus under conditions that truly reflect repeated vehicle loading, thus improving measurement precision while maintaining test efficiency.
Solution Approach 2:
The patent adjusts the loading parameters to match actual vehicle load characteristics, including load magnitude, frequency, and duration. By changing these parameters to reflect real-world conditions, the test achieves both high productivity and accurate measurement of the true subgrade dynamic resilient modulus.
3Measurement precision
If bearing plate method applies level-by-level loading to test static resilient modulus, then detailed stress-strain relationship can be obtained, but many detection personnel are required and detection speed is slow
Solution Approach 1:
The patent uses automated cyclic loading that可以快速地完成多次加载卸载循环，从而在保持详细应力应变关系测量精度的同时，显著提高检测速度。通过周期性的自动加载，无需大量检测人员手动操作，解决了精度与效率的矛盾。
Solution Approach 2:
The patent replaces manual mechanical loading operations with an automated servo-controlled loading system. This substitution eliminates the need for many detection personnel while maintaining the ability to obtain detailed stress-strain relationships, thereby improving productivity without sacrificing measurement precision.
4Ease of operation
If FWD and PFWD methods apply impact loads without considering pavement structure constraint, then test operation is simplified, but the force bearing state does not match actual conditions and reliability is reduced
Solution Approach 1:
The patent places the loading plate within a rigid frame structure that simulates the constraint effect of the pavement structure. This nested configuration allows the test to incorporate complex structural constraints while maintaining ease of operation, as the constraint effect is built into the fixture design rather than requiring complex operational procedures.
Solution Approach 2:
The patent introduces a rigid frame structure as an intermediary element between the loading plate and the subgrade. This intermediary component provides the necessary constraint effect that mimics the pavement structure, thereby improving reliability of the force bearing state simulation without complicating the test operation.
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
The system provides more accurate and reliable dynamic resilient modulus measurements, closely reflecting the true force-bearing state of subgrades, thereby enhancing the design and inspection of highway and railway pavements.
Implementation Method 1
a servo cylinder 9 is mounted on the test vehicle 5, and a piston rod of the servo cylinder 9 is connected with a bearing plate 12 acting on a subgrade surface to simulate the half-sine cyclic dynamic load transmitted by the vehicle load
Implementation Method 2
a second high precision displacement sensor 34 and a plurality of first high precision displacement sensors 29... receive a resilient deformation displacement value tested by the second high precision displacement sensor and the first high precision displacement sensor
Implementation Method 3
an area of the subgrade surface acted by the bearing plate is consistent with an area of a pavement contacted by a vehicle wheel
Data Source
AI summary
A loading module includes a test vehicle, a servo cylinder is mounted on the test vehicle, a piston rod of the servo cylinder is connected with a bearing plate acting on a subgrade surface, an annular loading plate is disposed around the bearing plate, and the loading plate is connected, through a force transmission rod, with a bearing tray on which a counterweight block is placed; a data collecting module includes a second high precision displacement sensor and a plurality of first high precision displacement sensors; a data processing module includes a computer, the computer is connected with a signal input end of the servo cylinder, an output end of the first high precision displacement sensor and an output end of the second high precision displacement sensor respectively, and performs inverse calculation for a dynamic resilient modulus value of a subgrade using a software.