A New Non-Destructive TDR System Combined with a Piezoelectric Stack for Measuring Properties of Geomaterials
Abstract
:1. Introduction
2. Measuring Methods
2.1. Measuring Water Content and Dry Density
2.1.1. Sand Cone Test
2.1.2. TDR Technique
- (1)
- TDR Instrument
- (2)
- Measuring Water Content and Dry Density of Soil by Using the TDR System
2.2. Measuring Modulus of Elasticity
2.2.1. SASW Method (Spectral Analysis of Surface Waves Method)
2.2.2. RPLT (Repetitive Plate Load Test)
2.2.3. LFWD (Light Falling Weight Deflectometer)
3. Development of a New TDR System
3.1. Development of Flat Type Probe
3.2. Combining Flat Type Probe with Piezoelectric Stack
4. Discussions of the Test Results
4.1. Results of Water Contents and Dry Density
4.2. Results of Modulus of Elasticity
5. Conclusions
- A new non-destructive TDR system, capable of measuring the dry density, water content, and elastic modulus has been developed. While the conventional TDR system requires inserting a probe into the ground to measure the soil’s dry density and the water content, the new non-destructive TDR system developed in this study can measure these parameters on the surface of the compacted soil. Based on the test results on standard sand in Korea, the dry density and water content measured by the new TDR system with a flat type probe are in good agreement with those measured by the standard test. This indicates that the new TDR system is feasible and can lead to time and cost savings in measuring dry density and water content.
- Based on the test results on different types of materials such as asphalt, concrete, and soil, a clear difference in the elastic moduli for the tested materials was observed. This implies that the new TDR system can be used as a tool to measure the stiffness of soil. A further study on developing the correlation between the moduli measured by the new TDR and those by LFWD will be useful.
- This new non-destructive TDR system is an innovative TDR system that can enable the measurement of moisture content and dry density as well as elastic modulus on the surface of compacted soil. This system will be useful for advancing the compaction quality of soil after it is reinforced with numerous test data on a variety of types of soils. This can be accomplished in further study.
Acknowledgments
Author Contributions
Conflicts of Interest
References
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Campbell Scientific Pulse Generator/Sampler | |
---|---|
Input signal type | Step rise |
System rise time | <250 ps |
Time resolution | 12.2 ps |
Bandwidth | 1.7 GHz |
Output impedance | 50 ± 1 ohms |
Noise filtering | 1 to 128 average |
Temperature range | −40 to 55 °C |
Dimension | 236 mm × 126 mm × 59 mm |
Piezoelectric Stack | |
---|---|
Compressive Strength | 8.8 × 108 N/m2 |
Tensile Strength | 4.4 × 106 N/m2 |
Young’s Modulus | 4.4 × 1010 N/m2 |
Poisson’s Ration | 0.34 |
Density | 7900 Kg/m3 |
Wires | Red positive, Black negative |
Thermal Operation Range | −20 to 80 °C |
Thermal Storage Range | −30 to 85 °C |
Humidity | <50% |
Soil | Classification | Sand (%) | Silt (%) | Clay (%) | Gs | P < No. 200 (%) | Liquid Limit (%) | Plastic Index |
---|---|---|---|---|---|---|---|---|
Jumunjin Sand | SP | 100 | 0 | 0 | 2.65 | 0 | - | - |
Wonju Soil | SM | 80 | 17 | 3 | 2.58 | 20 | - | - |
Seomjingang Soil | SP | 95 | 4 | 1 | 2.64 | 5 | - | - |
Okgwa Soil | SM | 78 | 16 | 2 | 2.60 | 18 | - | - |
Asphalt | |||||
Wave Type | Distance (cm) | Signal Start (us) | Signal Arrival (us) | Wave Speed (m/s) | Modulus of Elasticity (MPa) |
Compression Wave | 6.5 | 0 | 53.01 | 1226.2 | 3758.92 |
Shear Wave | 6.5 | 0 | 102.02 | 637.1 | 1014.74 |
Concrete | |||||
Wave Type | Distance (cm) | Signal Start (us) | Signal Arrival (us) | Wave Speed (m/s) | Modulus of Elasticity (MPa) |
Compression Wave | 10 | 0 | 48.02 | 2082.5 | 8673.61 |
Shear Wave | 10 | 0 | 128.6 | 777.6 | 1209.32 |
Soil | |||||
Wave Type | Distance (cm) | Signal Start (us) | Signal Arrival (us) | Wave Speed (m/s) | Modulus of Elasticity (MPa) |
Compression Wave | 15 | 0 | 283 | 530.03 | 421.40 |
Shear Wave | 15 | 0 | 886 | 169.30 | 42.99 |
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Choi, C.; Song, M.; Kim, D.; Yu, X. A New Non-Destructive TDR System Combined with a Piezoelectric Stack for Measuring Properties of Geomaterials. Materials 2016, 9, 439. https://doi.org/10.3390/ma9060439
Choi C, Song M, Kim D, Yu X. A New Non-Destructive TDR System Combined with a Piezoelectric Stack for Measuring Properties of Geomaterials. Materials. 2016; 9(6):439. https://doi.org/10.3390/ma9060439
Chicago/Turabian StyleChoi, Chanyong, Minwoo Song, Daehyeon Kim, and Xiong Yu. 2016. "A New Non-Destructive TDR System Combined with a Piezoelectric Stack for Measuring Properties of Geomaterials" Materials 9, no. 6: 439. https://doi.org/10.3390/ma9060439