1 Introduction
2 Model design scheme
2.1 Model scale design
Physical index | Similarity constant | Value |
---|---|---|
Geometry (l) | \(C_{l}\) | 2 |
Dynamic stress (σ) | \(C_{\sigma }\) | 1 |
Linear load (q) | \(C_{q}\) | 1/2 |
Strain (ε) | \(C_{\varepsilon }\) | 2 |
Concentrated load (F) | \(C_{F}\) | 22 |
Vibration frequency (ω) | \(C_{\omega }\) | 2–1/2 |
Linear displacement (δ) | \(C_{\delta }\) | 2 |
Acceleration (a) | \(C_{a}\) | 1 |
2.2 Model construction
2.2.1 Test model box production
2.2.2 Rail-bearing beam and subgrade construction
Structure name | Material | Parameters |
---|---|---|
Door-shaped block | C40-reinforced concrete | Geometry: 650 mm × 245 mm × 100 mm |
Base plate | C40-reinforced concrete | Geometry: 5790 mm × 1000 mm × 200 mm |
Dowel steel | Q235 steel | Diameter: 50 mm; length: 700 mm; spacing: 150 mm |
Concrete cushion | C25 plain concrete | Geometry: 11,800 mm × 1500 mm × 50 mm |
Backfill | Cement-treated soil | Thickness: 150 mm |
Upper roadbed | Group A-fill | Evd: 46 MPa |
Lower roadbed | Group B-fill | Evd: 40 MPa |
Subgrade body | Cement-treated soil | Evd: 40 MPa |
2.3 Layout monitoring equipment and data collection
Test items | Sensor element | Type | Main technical parameter | Quantity | Symbol | No. |
---|---|---|---|---|---|---|
Dynamic stress | Earth pressure cell | BW | Range: 100 kPa; precision: ± 0.1 kPa | 15 | T | T1–T15 |
Acceleration | Accelerometer | TST120A1000 | Range: 50 m/s2; sensitivity: 100 mV/(m·s2) | 8 | J | J1–J8 |
Cumulative deformation | Displacement sensor | JMDL-5105Y | Range: 100 mm; sensitivity: 100 mV/mm | 2 | S | S1–S2 |
3 Model loading scheme
3.1 Load scheme
3.1.1 Load frequency
3.1.2 Load amplitude
Parameter | g (m·s−2) | v (m·s−1) | α (°) | β (°) | Rh (m) | Rv (m) |
---|---|---|---|---|---|---|
Value | 9.8 | 55.56 | 6 | 3.4 | 730 | ∞ |
Parameter | Ps (kN) | Fmin (kN) | μ | Pd (kN) | Fmax (kN) | f (Hz) |
---|---|---|---|---|---|---|
Value | 54 | 13.5 | 1.193 | 369.4 | 105.9 | 1.20 |
3.1.3 Load waveform
3.2 Service environment simulation and testing process
3.2.1 Loading devices and rainfall equipment
3.2.2 Testing process
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Step 1 Before formal loading, the test model is preloaded 1000 times.
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Step 2 The testing model successfully performs 210,000 cyclic loadings, and the data are recorded from the model test.
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Step 3 Cyclic loading is stopped and rainfall begins. The values for the rain speed and rainfall are 12 mm/h and 4.17 m3, respectively, which are based on the largest rainfall in history in Changsha, China.
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Step 4 The rainfall is stopped, 210,000 cyclic loadings are continued, and the data are recorded from the model test.
4 Test results and analysis
4.1 Typical time history curve of dynamic stress and acceleration
4.2 Variation curve of the moisture of the subgrade
4.3 Dynamic stress analysis
4.3.1 Dynamic stress distribution along the depth direction of the subgrade
4.3.2 Longitudinal distribution of the dynamic stress
Loading condition | \({(3} \times {\text{T1)}}/{\text{(T2 + T3 + T4)}}\) | \({(3} \times {\text{T5)}}/{\text{(T2 + T3 + T4)}}\) |
---|---|---|
Nature | 1.07 | 0.80 |
Rainfall | 1.03 | 0.83 |
Parameter | E (GPa) | I (m4) | b (m) | L (m) | K30 (MPa/m) |
---|---|---|---|---|---|
Value | 28 | 1.56 × 10–5 | 1.5 | 5.79 | 156.9 |
4.4 Acceleration analysis
4.5 Long-term dynamic stability analysis
4.5.1 Long-term dynamic stability analysis based on critical dynamic stress
Subgrade depth (m) | Subgrade dynamic stress σ (kPa) | Filling critical dynamic stress σ1 (kPa) | σ/σ1 | Evaluation result | |
---|---|---|---|---|---|
0–0.15 | Natural | 11.69 | 154 | 0.38/5 | Stabilization |
Rainfall | 12.03 | 118 | 0.51/5 | Stabilization | |
0.15–0.75 | Natural | 8.96 | 99 | 0.46/5 | Stabilization |
Rainfall | 10.64 | 59 | 0.90/5 | Stabilization |