In-situ-testing

THERMAL RESISTIVITY TEST


The thermal properties of soil are a component of soil physics that has found important uses in engineering. These properties influence how energy is partitioned in the soil profile. While related to soil temperature, it is more accurately associated with the transfer of energy (mostly in the form of heat) throughout the soil, by radiation, conduction and convection.


Soil thermal properties are strongly influenced by the soil volumetric water content, volume fraction of solids and volume fraction of air. Air is a poor thermal conductor and reduces the effectiveness of the solid and liquid phases to conduct heat. While the solid phase has the highest conductivity it is the variability of soil moisture that largely determines thermal conductivity. As such soil moisture properties and soil thermal properties are very closely linked and are often measured and reported together. Temperature variations are most extreme at the surface of the soil and these variations are transferred to sub surface layers but at reduced rates as depth increases.

Thermal resistivity measurement - In Situ Test
About GOSCO
GOSCO provide the soil thermal resistivity measurement service with competitive costs according to ASTM D 5334-08 (Standard Test Method for Determination of Thermal Conductivity of Soil and Soft Rock by Thermal Needle Probe Procedure).

Steps to perform the SPT test:

– Step 1: Drill to the test depth, cleaning & dredged muck from bottom of the borehole, and install equipment according to standards.

– Step 2: Mark 3 equal intervals (15cm) on the drliing rod.

– Step 3: Release the donut hammer in free fall and count the total number of hammers through the marked segments.

– Step 4: Take the hammer number of the last 2 segments as SPT index

– Step 5: Uninstaling SPT inquipment and remove SPT sample, repeat the steps when performing the experiment at the next times.

Thí nghiệm xuyên tiêu chuẩn - Standard penetration test (SPT)

Figure 1:Standard Penetration Test

 

Thermal resistivity measurement - In Situ TestFigure 1:Standard Penetration TestTools for Standard Penetration Test:
1. Standard Split Spoon Sampler
2. Drop Hammer weighing 63.5kg
3. Guiding rod
4. Drilling Rig.
5. Driving head (anvil).

 

The main purpose of the test is to provide an indication of the relative density of granular deposits, such as sands and gravels from which it is virtually impossible to obtain undisturbed samples. The great merit of the test, and the main reason for its widespread use is that it is simple and inexpensive.
The usefulness of SPT results depends on the soil type, with fine-grained sands giving the most useful results, with coarser sands and silty sands giving reasonably useful results, and clay and gravelly soils yielding results which may be very poorly representative of the true soil conditions.

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