Influence of Compaction on the Properties of Remolded Cemented Sands

The properties and behaviour of compacted cemented sands in Kuwait were examined by laboratory and model tests. Upon excavation the cementation bonds are destroyed and the material, locally known as gatch, is transformed into clayey sands with fines content (<0.075 mm) ranging from 20% to 40%. Testing included basic properties, compaction, permeability, direct shear and consolidation tests. Model tests were also carried out on a circular plate loaded on compacted soils to failure. The test soil was compacted to a relative compaction of 85%, 90%, 95% and 100%. The results indicate a significant decrease in the ultimate bearing capacity and the shear strength parameters c, ϕ, and an increase in the compressibility parameters Cc, Cs and the permeability as the relative compaction decreases from 100% to 85%. The rate of variation of the various soil parameters with relative compaction is examined.

Appraisal of Bearing Capacity and Modulus of Subgrade Reaction of Refilled Soils

Soil is remoulded, replaced, or improved in place to meet the required engineering properties. Relative compaction is the measure of the resulting engineering improvement. But design engineers need the allowable bearing capacity while the modulus of subgrade reaction is the primary input of modern foundation design software. The current research appraised a correlation between Relative Compaction ( ), Moisture Content ( ), and allowable bearing capacity ( ) and another correlation between , RC, MC, and modulus of subgrade reaction ( ). The test samples were extracted from each trial of the standard proctor test using purpose-built extraction tubes. Allowable bearing capacity has been determined by performing unconfined compression tests on the extracted tubes. The relationships have been established employing statistical analysis. It was noticed that soil samples at the lower moisture content (6-9%) show brittle failure before reaching the allowable strain. The soil samples having a moisture content of 10-14% exhibited shear failure, nearly simultaneous to the allowable strain. The soil samples having higher moisture content undergone a strain of 15% without showing the shear failure. A simple equation has also been appraised to determined Ks involving the three-input variable, i.e., , , and . Moderate correlations have been found to exist between the studied parameters, owing to some other variables' influence. Recommendations for future studies have been drawn to quantify the effect of identified parameters. Doi: 10.28991/cej-2020-03091606 Full Text: PDF

Effect of Relative Compaction on Water Absorption and Gypsum Dissolution in Gypsum-Rich Clayey CBR Samples

A clayey gypsiferous soil of CL group according to the Unified Soil Classification System was studied for the effect of relative compaction on water absorption and gypsum dissolution during long-term soaking. The soil has a gypsum content of about 33%. Two sets of soil samples were prepared at optimum moisture content of 11.75% of the modified Proctor compaction test. The first set received 100%, while the second received about 93.5% relative compaction with respect to modified Proctor. These samples were soaked for 4, 7, 15, 30, and 120 days under 40 lbs (178 N) surcharge load. The moisture content was determined at top, quarter points, midpoint, and bottom of each soil sample. The test results revealed that for each compaction effort, the moisture content along each soaked soil sample is not uniform and increased with increasing soaking period. This increase in moisture content is greater for soil samples compacted at the lower compaction effort. The moisture content at top of each soil sample is greater than at the bottom, and the least moisture content took place at the middle of the sample. The dissolution of gypsum, at the top of soil samples, was greater than that at the middle. A multiple regression equation was developed relating strongly the decrease in gypsum content along the clayey CBR samples, with compaction effort and increase in average moisture content along the samples due to soaking. Similarly, strong correlation was obtained from the multiple regression developed between absorbed water, soaking period, and compaction effort. The paper shows that the water absorption and gypsum dissolution decrease with increasing relative compaction as the soil becomes denser.

Evaluation of the Volume Measurement Optical Method Suitability for Determining the Relative Compaction of Soils

The goal of this paper is evaluation of the volume measurement optical method suitability for determining relative compaction of soils. The Structure for Motion technique was utilized in order to achieve the goal by making the three-dimensional models (with Bentley ContextCapture software). Created models were used in volume measurement of the pit-holes. The results were compared with the basic methods: the sand cone test and the water method. The laboratory tests were carried out in two stages. In the first stage, the optical method was tested in similar to operating conditions. Ten holes were made in the soil and the volumes were measured with three different methods. The results were compared and submitted for statistical analysis. Statistical analysis showed the potential of optical method. The second laboratory test focused on repeatability and accuracy of measurement. The volume of the vessel imitating a pit-hole was obtained. The results of the second stage showed that the optical method has better accuracy and lower statistical dispersion compared with sand method. On this basis it can be concluded that optical method of volume measurement has great potential in soil compaction testing.