BS 1377 : 1990 – 2 Determination of moisture content – xác định độ ẩm
3.1 General
Water is present in most naturally occurring soils. The amount of water, expressed as a proportion by
mass of the dry solid particles, known as the moisture content, has a profound effect on soil behaviour. In this context a soil is dry when no further water can be removed at a temperature not exceeding 110 °C.
Moisture content is required as a guide to classification of natural soils and as a control criterion in recompacted soils and is measured on samples used for most field and laboratory tests. The oven-drying method is the definitive procedure used in standard laboratory practice.
BS 1377 : 1990 -2 Determination of moisture content – xác định độ ẩm của đất
3.2 Oven-drying method
3.2.1 General.
This method covers the determination of the moisture content of a specimen of soil as a percentage of its dry mass. The requirements of Part 1 of this standard, where appropriate, shall apply to this test method.
3.2.2 Apparatus
3.2.2.1 A drying oven, capable of maintaining a temperature of 105 °C to 110 °C.
3.2.2.2 For fine-grained soils
3.2.2.2.1 A glass weighing bottle, fitted with a ground glass stopper or cap, or a suitable airtight corrosion-resistant metal container.
3.2.2.2.2 A balance readable to 0.01 g.
3.2.2.2.3 A desiccator containing anhydrous silicagel.
3.2.2.2 For fine-grained soils
3.2.2.2.1 A glass weighing bottle, fitted with a
ground glass stopper or cap, or a suitable airtight
corrosion-resistant metal container.
3.2.2.2.2 A balance readable to 0.01 g.
3.2.2.2.3 A desiccator containing anhydrous silicagel.
3.2.3 Procedure
3.2.3.1 For fine-grained soils
3.2.3.1.1 Clean and dry the weighing bottle or metal container and weigh it to the nearest 0.01 g (m1).
Take a sample of at least 30 g of soil, crumble and place loosely in the container or weighing bottle, and
replace the lid or stopper. Then weigh the container or bottle and contents to the nearest 0.01 g (m2).
3.2.3.1.2 Remove the lid or stopper, and place the container or bottle with its lid and contents in the
oven and dry at 105 °C to 110 °C. The period required for drying will vary with the type of soil and the size of sample but the sample shall be deemed to be dry when the differences in successive weighings of the cooled sample (see 3.2.3.1.3 and 3.2.3.1.4) at intervals of 4 h do not exceed 0.1 % of the original mass of the sample. Do not replace the lid or stopper while the sample is in the oven.
3.2.3.1.3 After drying, remove the container or bottle and contents from the oven and place the
whole in the desiccator to cool.
3.2.3.1.4 Replace the lid and then weigh the container or bottle and contents to the nearest 0.01 g (m3).
3.2.3.2 For medium-grained soils
3.2.3.2.1 Clean and dry the container and weigh it to the nearest 0.1 g (m1). Take a sample of at least 300 g of soil, crumble and place loosely in the container, and replace the lid. Then weigh the container and contents to the nearest 0.1 g (m2)
3.2.3.2.2 Remove the lid and place the container and contents in the oven and dry at 105 °C to 110 °C (see note 1 to 3.2.3.1.2). The period required for drying will vary with the type of soil, the size of sample and the number of samples in the oven but the sample shall be deemed to be dry when the differences in successive weighings of the cooled sample (see 3.2.3.2.3 and 3.2.3.2.4) at intervals of 4 h do not exceed 0.1 % of the original mass of the soil (see note 2 to 3.2.3.1.2). Do not replace the lid while the sample is in the oven.
3.2.3.2.3 After drying, replace the lid and allow the whole to cool.
3.2.3.2.4 Weigh the container and contents to the nearest 0.1 g (m3).
3.2.3.3 For coarse-grained soils
3.2.3.3.1 Clean and dry the container and weigh it to the nearest 1 g (m1). Take a sample of at least 3 kg of soil, place loosely in the container and replace the lid. Weigh the container and contents to the nearest 1 g (m2).
3.2.3.3.2 Remove the lid and place the container and contents in the oven and dry at 105 °C to 110 °C
3.2.3.3.3 After drying, replace the lid and allow the whole to cool.
3.2.3.3.4 Weigh the container and contents to the nearest 1 g (m3).
BS 1377 : 1990 -2 Determination of moisture content – xác định độ ẩm
3.2.4 Calculations and expression of results
3.2.5 Test report.
The test report shall affirm that the test was carried out in accordance with BS 1377-2:1990 and shall contain the following information:
- a) the method of test used;
- b) the moisture content;
- c) the temperature at which the soil was dried, if less than 105 °C;
- d) the comparison with Atterberg limits, if required (see note 1 to 3.2.4);
- e) the fluid content, if appropriate (see note 2 to 3.2.4);
- f) the information required by clause 9 of BS 1377-1:1990;
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