BS 1377 : 1990 Determination of the liquid limit, giới hạn chảy

BS 1377 : 1990 – 2 Determination of the liquid limit, Xác định giới hạn chảy

4.1 General

The liquid limit is the empirically established moisture content at which a soil passes from the liquid state to the plastic state. It provides a means of classifying a soil, especially when the plastic limit (see clause 5) is also known.

Two main types of test are specified. The first is the cone penetrometer method, which is fundamentally more satisfactory than the alternative because it is essentially a static test depending on soil shear strength. It is also easier to perform and gives more reproducible results. The second is the much earlier Casagrande type of test which has been used for many years as a basis for soil classification and correlation of engineering properties. This test introduces dynamic effects and is more susceptible to discrepancies between operators.

For both types of test an alternative rapid §one-point¨ procedure is given, which may give less

accurate results. The method of sample preparation is the same for all of these tests.

BS 1377 : 1990 – 2 Determination of the liquid limit, Xác định giới hạn chảy của đất trong phòng thí nghiệm

4.2 Sample preparation

4.2.1 General.

Wherever possible the test shall be carried out on soil in its natural state. With many clay soils it is practicable and shall be permissible to remove by hand any coarse particles present, i.e. particles retained on a 425 µm test sieve. Otherwise these particles shall be removed by wet sieving as specified in 4.2.4.

In the definitive method the soil shall not be allowed to become dry before testing. Where air drying is required the method used shall be stated. Drying and breaking down procedures shall comply with 7.3.4, 7.3.5 and 7.4.3 of BS 1377-1:1990. The requirements of Part 1 of this standard, where appropriate, shall apply to this test method.

4.2.2 Apparatus

4.2.2.1 Test sieves, of sizes 425 µm and 2 mm, with receiver.

4.2.2.2 Apparatus for determination of moisture content, as specified in 3.2.2.

4.2.2.3 A sharp knife.

4.2.2.4 An implement for shredding cohesive soil.

4.2.2.5 Two palette knives.

4.2.2.6 A corrosion-resistant airtight container, large enough to take 200 g to 300 g of wet soil.

4.2.2.7 A flat, glass plate, a convenient size being 10 mm thick and about 500 mm square.

4.2.2.8 A wash bottle containing distilled water complying with 5.1 of BS 1377-1:1990

4.2.2.9 A corrosion-resistant container of 600 mL or 1 000 mL capacity.

4.2.2.10 A glass stirring rod.

4.2.3 Specimen from natural soil

4.2.4 Sieved specimen

BS 1377 : 1990 – 2 Determination of the liquid limit, Xác định giới hạn chảy của đất

4.3 Cone penetrometer method (definitive method)

4.3.1 General.

This method covers the determination of the liquid limit of a sample of soil in its natural state, or of a sample of soil from which material retained on a 425 µm test sieve has been removed

4.3.2 Apparatus
4.3.3 Procedure
4.3.4 Calculations and expression of results
4.3.5 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:

  1. a) the method of test used;
  2. b) the liquid limit;
  3. c) the percentage of material retained on the 425 µm test sieve;
  4. d) the history of the material, e.g. whether tested in the natural state, or after wet sieving or after any other process;
  5. e) the information required by clause 9 of BS 1377-1:1990.

BS 1377 : 1990 – 2 Determination of the liquid limit, Xác định giới hạn chảy của đất

4.4 One-point cone penetrometer method

4.4.1 General.

This method enables the liquid limit of a soil sample to be determined from only one measurement of moisture content. This method enables a result to be obtained when only a small amount of soil is available.

4.4.2 Apparatus
4.4.3 Procedure
4.4.4 Calculations and expression of results
4.4.5 Test report

BS 1377 : 1990 – 2 Determination of the liquid limit, Xác định giới hạn chảy của đất – Phương pháp casagrande

4.5 Casagrande apparatus method

4.5.1 General.
4.5.2 Apparatus
4.5.3 Adjustment of apparatus.
4.5.4 Procedure

Tải BS 1377 : 1990 – 2 file pdf – Determination of the liquid limit, Xác định giới hạn chảy của đất theo link bên dưới – nguồn xaydung360

BS 1377 1990 – 2 Determination of the liquid limit

 

Call Now Button
Contact Me on Zalo