The plastic limit is defined as the lowest moisture content of a soil that will permit a sample to be rolled into threads of 3 mm diameter without the threads breaking. The test procedure has remained, in principle, the same since 1932, when Casagrande proposed to define the various limits by relating the moisture content characteristics of soil under certain conditions. The apparatus required is simple yet effective.
|24-0430||Glass plate||info »|
|24-0811||Rod comparator||info »|
|81-0140||Spatula 200 mm||info »|
The condition of a soil can be altered by changing the moisture content. The liquid limit is the empirically established moisture content at which a soil passes from the plastic to the liquid state. A knowledge of the liquid limit allows the engineer to correlate several engineering properties with the soil. Two main types of test are used; the Casagrande type (Cup), which has been used for many years, and the cone penetrometer method, which is now the definitive method specified in BS 1377.
Particular design features of the instrument include a positive action horizontal lead screw, which is rapidly adjustable and rigidly fixes the height of cup in relation to the base during the test procedure. The cam mechanism and cup suspension assembly have been designed to withstand constant use with minimum readjustment
|24-0425||Grooving tool||Yes||-||-||info »|
|24-0434||Liquid limit device||-||Yes||Yes||info »|
|24-0410||Liquid limit device||Yes||-||-||info »|
|24-0453||Grooving tool||-||Yes||-||info »|
|24-0461||Grooving tool||-||-||Yes||info »|
|24-0417/01||Liquid limit device - motorised||Yes||-||-||info »|
|24-0430||Glass plate||Yes||-||-||info »|
•Reduces operator error
•Applicable to a wide range of soils
•Gives reproducible test results
•Provides direct measurement of penetration
The method is fundamentally more satisfactory than the Casagrande method as it is essentially a static test depending on the soil shear strength. The test is based on the relationship between moisture content and the penetration of a cone into the soil sample under controlled conditions.
Determines the moisture content at which clay soils pass from a plastic to a liquid state.
|24-0540||Cone Penetrometer||info »|
|24-0548||Penetration test cup||info »|
|24-0544||Test cone||info »|
|24-0546||Test gauge||info »|
When the water content of a fine-grained soil is reduced below the plastic limit, shrinkage of the soil mass continues until the shrinkage limit is reached. Shrinkage can be significant in clays but less so in silts and sands. The equipment listed enables the engineer to determine a number of important parameters, including shrinkage ratio, volumetric shrinkage and linear shrinkage.
Particle density or specific gravity is a measure of the actual particles which make up the soil mass and is defined as the ratio of the mass of the particles to the mass of the water they displace. A knowledge of the particle density is essential in relation to other soil tests. It is used when calculating porosity and voids ratio and is particularly important when compaction and consolidation properties are being investigated. The majority of apparatus used for the various tests is general laboratory equipment.