DLY-1 coarse-grained soil vertical permeability deformation instrument - Database & Sql Blog Articles

STD-CSR-1
HT7550-1
Probe domestic double-head probe 038-BB-5.7L The shape of the two ends of the needle is outside the pointed needle

DLY-1

Coarse Grain Vertical Permeability Analyzer

This test follows the standard DL/T5356-2006, which outlines the procedure for testing coarse-grained soil in hydropower and water conservancy projects. The method involves osmotic water flow from the bottom to the top, making it ideal for analyzing permeability in coarse-grained soils. It helps determine key parameters such as the permeability coefficient, dry density, porosity, osmotic gradient, and seepage flow rate.

Technical Specifications

  1. Test tube diameter: φ300 mm
  2. Test tube height: 340 mm
  3. Water supply tank size: φ510 mm x 500 mm
  4. Measuring cylinder: 1000 mL
  5. Measuring cylinder: 100 mL
  6. Total weight: Not specified

Instructions for Use

  1. Connect the lower water inlet to the water supply pipe and fill the instrument with water. Check all components for blockages or leaks. After inspection, lower the water supply tank so that the water level inside the device aligns with the bottom edge of the lower permeable plate.
  2. Remove the top cover, place a filter on the lower permeable plate, and apply a sealing material around the gap between the barrel wall and the filter.
  3. Open all pressure taps to release air.
  4. Divide the sample into 3–5 layers, ensuring each layer has the same gradation. For sand soil, the thickness should be 2–3 cm; for gravel, the thickness should be 1.5–2 times the sample size. If needed, mix in 1%–2% water by weight to ensure even distribution.
  5. Place each weighed sample into the measuring cylinder, compact it using a hammer, and reach the required height. Vibration compaction may be used for weathered stone slag or crushed earth materials.
  6. Saturate the sample using the capillary saturation method. Adjust the water supply tank so that its water level is slightly above the sample’s bottom surface, then slowly raise it by 1 cm and keep it stable for 10 minutes. As the water level rises, open the corresponding pressure tubes until the sample is fully saturated and water overflows from the outlet. At this point, the water levels in all pressure tubes should match the outlet level.
  7. Based on the fine particle content, estimate the failure mode of the sample. If it's a piping failure, start with an initial slope of 0.02–0.03, increasing gradually by 0.05, 0.10, 0.15, 0.20, 0.30, 0.40, 0.50, 0.70, 1.00, 1.50, 2.00. When nearing the critical slope, reduce the increment accordingly. For fluid failure, increase the slope as needed.
  8. Raise the water head step by step according to the guidelines. After each increase, allow the outflow to stabilize for 30–60 minutes. Measure the pressure tube levels and collect seepage volume using the measuring cylinder. Take at least three readings per water head level, spaced 10–20 minutes apart. Record the temperature of the inflow and outflow. When the readings are stable, proceed to the next level. Average the closest three readings as the final result.
  9. Observe and document phenomena during the test, such as turbidity of the effluent, bubbles, fine particles moving or being carried away, soil suspension, seepage flow, and changes in pressure tube levels. Adjust the slope increment if a critical condition or precursor to failure occurs.
  10. End the test when the sample is damaged or the water head can no longer be increased. For tests only requiring permeability coefficient determination, continue after reaching the critical slope for one or two more levels before stopping.
  11. After the test, close the nozzle, remove any remaining water, observe the sample, and measure its height. Unload the sample and check for rebound. Remove the top cover, absorb residual water, and take off the upper permeable plate. Drain the remaining water from the device and extract the sample. Perform particle grading analysis if necessary.
  12. Plot the relationship between osmotic gradient and seepage velocity on a double logarithmic graph, with the osmotic slope on the y-axis and seepage velocity on the x-axis. If needed, also plot seepage velocity against time. Adjust the duration and head difference based on the curve trend.

The test results must conform to DL/T5356-2006 standards. Clean the equipment thoroughly for future use.

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