Atterberg Limits Liquid Limit & Plastic Limit of Soils Topic N Topic N

Atterberg Limits Liquid Limit (LL) Plastic Limit (PL) Shrinkage Limit (SL) Moisture contents Used for classification, Comparisons, identification. Topic N

Figure 1: Soil States Solid Semi-Solid Plastic Liquid Plasticity Index Shrinkage Limit Moisture Content Low High

Plasticity Index (PI) Numerical difference between LL and PL PI = LL - PL Range of water content Figure 1 Topic N

Liquid Limit Test (Apparatus) Porcelain mixing dish Spatula Grooving tool Number 40 sieve Figure 2 & Table 1 Topic N

Figure 2: Liquid Limit Device Topic N

Table 1: Measurements (LL) Topic N

Adjustment of Device (LL) Cup drops freely when crank is turned? Measure cup drop 1.00 cm Topic N

Test Procedures (LL) Grind 100-200 grams of dried soil Sieve soil Mix in distilled water Place soil on device Make groove in soil (Figure 3) Record number of drops Scrape soil Topic N

Figure 3: Liquid Limit Test Topic N

Flow Curve (LL) Logarithm of the number of drops and water content Straight line Select point with 25 drops= LL Figure 4 Topic N

Figure 4: Flow Curve (LL) Log of number of drops LL Water Content Topic N

Plastic Limit Test (Apparatus) Hard flat surface Porcelain mixing dish Distilled water Number 40 sieve 1/8 inch welding rod Balance Drying oven Topic N

Test Procedure (PL) Grind 30-50 grams Sieve soil Mix distilled water Roll 10 grams out into a coil Cut into 6-8 pieces Knead soil Topic N

Calculation (PL) Average Water content from 3 trials. Topic N

Non-Plastic When LL or PL tests cannot be performed Non-Plastic (NP) PL=negative NP Topic N

Figure 5: Data Sheet Topic N