To facilitate data reduction, one deflection reading is taken for each load increment. Assuming that all of the tests are performed by the same laboratory technician, Gs for two separate tests of the same material should be within 0. However, for soils containing a significant amount of organic material or hydrous minerals such as gypsum, some of the water is bound by the soil solids, so excessive drying will effectively drive some of the soil solids away and produce erroneous results. If distilled water at room temperature is used for the test, and the room is kept at a constant temperature, a single water temperature reading should suffice. Laboratory-measured k may be several orders of magnitude less than actual large-scale field values. Since all of the grains in a mass of soil are not the same size, it is convenient to quantify grain size in terms of a gradation curve.
Measurement of Moisture Content 8 Min. If deformation is recorded using a deformation indicator that reads directly in units of length, d should be in units of length. One-Dimensional Consolidation Test 124 Soil Mechanics Laboratory Manual To record soil deformation during the test, a deformation indicator is positioned over the soil specimen. For stiffer clays, σ1f is defined as the peak of the σ1 — ε1 curve. For the constant head test, the length Lc is the distance between the manometer ports. Measure the length of the specimen Lf and the diameter of the specimen in the permeameter D. There is a linear relationship between deformation and applied load, so the deformation observed using the dial gauge can be converted to load using a calibration constant e.
You will need to scrub. The density of the fluid affects the buoyancy of the hydrometer. Strength Observation None Ball crumbles into powder when handled Low Ball crumbles into powder with some finger pressure Medium Ball breaks into pieces with considerable finger pressure High Must place ball between thumb and hard surface to break Very High Will not break between thumb and hard surface Table 7. Flocculation occurs because fine-grained soil particles are platy, and possess negative charges on their faces and positive charges on their edges. This soil will be used for the hydrometer analysis.
Modifying words are given in Table 7. Moisture in the soil is largely a function of whether the specimen was recovered from above or below the water table. This may result in erroneously classifying silty or clayey sands and gravels as clean sands and gravels. If more than 50% of the coarse fraction passes the 4 sieve, the soil is a sand. However, it is seldom used for testing cohesive soils, and its use is generally limited to cohesionless soils. Moisture content is also a measure of the shrink-swell and strength characteristics of cohesive soils as demonstrated in liquid limit and plastic limit testing.
Moisture categories are described in Table 7. If less than 5% of the soil passes the 200 sieve, it is a clean sand. Compacted specimens may be created using a Harvard compactor or other device. Count and record the number of cranks that are required to close the groove over a length of 0. During the test, σ1 is plotted versus ε1 to identify qu Fig. Many engineers use a Munsell color chart to classify soil.
This behavior is referred to as sidewall leakage, which leads to erroneously high values for k. To perform a hydrometer analysis, soil is mixed with water and sodium hexametaphosphate a dispersing agent to create a slurry of dispersed soil particles. To them, I express my utmost gratitude. When the hydrometer is placed in a fluid, it floats like a fishing bobber. Also measure the moist mass of the specimen M. One-Dimensional Consolidation Test of Cohesive Soil.
Measure and record its net mass M 40. In some areas where groundwater pumping has been extensive, large urban areas have undergone significant settlement due to an increase in effective stress. The compression and recompression indices are the slopes of the two portions of the curve. Connect the flask to the vacuum source with the hose and stopper and apply vacuum for 30 minutes, occasionally agitating the mixture. Open the influent valve and allow water to saturate the specimen.
Modifying words are given in Table 7. One goal of this laboratory is to teach students how to present experimental data in a professional manner. Laboratory exercises and data sheets for each test are included in the Soil Mechanics Lab Manual. The porous stones act as freely draining materials so that drainage in the soil specimen is two-way and the drainage distance is half the height of the specimen. Reading Number Time After Loading 1 6 sec.
If the base and cap are machined with grooves, make sure that the Orings are seated in the grooves. Each video describes the basic purpose of the test, lists the required materials, demonstrates the step-by-step procedure, and details methods for reducing the data. As a result, the soil undergoes a net decrease in volume as ΔV decreases. Vary the amount of head as described in Section 10. Soil particles from previous sieving activities may also become dislodged during sieving, leading to a final total mass that is greater than the initial total mass. To obtain two additional points, add either water or soil to the original mixture depending on w of the first point and repeat the procedure.