The paper presents a concept of determination of pre-compression stress. It assumes that the stress value is close to the unit pressure value which is indispensable to increase the initial degree of soil compaction. Thus, an attempt was made to develop an empirical model for predicting the value of stress at which the initial compaction of a soil sample increases by a determined value. Samples with the so-called intact structure (NS) and soil material in the form of loose mass were collected from subsoil, and they were used to form model samples. Both types of samples were uniaxially compressed. For the study, data on moisture and dry bulk density of model samples were used, as well as determined ratios (conversion factors) that present relations between the results of compaction of model samples and samples with the intact structure. It was reported that the pressure necessary for the increase of the initial compaction of the model samples with the value of +0.05 or +0.10 g∙cm−3 were higher than the formation pressure respectively by 1.03-1.11 and 1.42-1.93 times. It was proved that for determination of the pre-compression stress of the NS samples models of linear regression for prediction the pressure needed to increase the initial compaction of the model sample by the value of +0.05 g∙cm−3, combined with a coefficient calculated for the present state of the soil properties, can be applied.
The objective of the research was to evaluate soil compaction with selected indexes and to determine the relation between them including results obtained with Proctor’s method. Measurements of penetration resistance and shear vane, dry density of soil particles (ρd) and their moisture were made in layers in the following depths: 25-30, 35-40, 45-50 and 55-60 cm. Moreover, the maximum volumetric density of soil particles, particles size distribution, content of calcium carbonate and humus, density of solid particles, reaction, plastic and liquid limit were determined with Proctor's method (ρds). Also, packing density and natural density were measured. It was found out that the investigated soils may be generally included to excessively compacted and susceptible to compaction to an average and small degree. It was shown that soil may be recognized as excessively compacted when the quotient ρd/ρds exceeds the value of 0.87.
The objective of this paper was to compare the results of soil material compaction carried out with the use of the Proctor and uniaxial compression tests in order to find relations between these methods. Soil material in the form of loose mass was collected from the layer deposited at the depth from 35 to 60 cm in order to determine its typical properties (textural group, density of solid particles, humus content, reaction, plastic and liquid limits) and in order to compact it in the Proctor apparatus and in the uniaxial compression test. Results of both tests were used for construction of regression models reflecting the course of the unit stress (Pρdp), necessary to generate compaction equal to the dry density of solid particles obtained in the Proctor apparatus (ρdp) in relation to the sample moisture (ws). It was stated that the stress value Pρdp on the soil sample in the uniaxial compression test depends significantly on ws. It was proved that for the purpose of comparing the results of both tests, the uniaxial stress of samples must be performed in conditions of their lateral expansion. It was also proved that the use of the uniaxial test with possible lateral expansion of soil with a model sample, a diameter of which is 100 and the height is 30 mm, one may determine the obtained compaction with the use of the plate movement value.
The objective of the research was to construct an empirical model for prediction of a unit pressure indispensable for generation of a specific compaction of soil samples. Soil material in the form of loose mass was collected from the soil layer deposited in the depth from 35 to 40 cm and then its typical properties were determined (textural group, density of solid particles, humus content, reaction, plastic and liquid limits) and in order to compact it in Proctor apparatus and in the uniaxial compression test. Results of both tests were used for construction of regression models reflecting the course of the unit strength (Pρd) necessary to generate compaction (ρdj) equal to the dry bulk density obtained in Proctor apparatus (ρdp), in relation to the sample moisture (ρdm). Searching for relations was restricted to the scope of moisure between an optimal one acc. to Proctor and the soil plastic limit. It was stated that the pressure value Pρdp made on the soil sample in the uniaxial compression test depends significantly on ws and ρdm, and for description of this relation the use of multiple regression is sufficient. It was found out that for model samples with a textural group of silt loam and loam, differences in dry bulk density obtained in Proctor apparatus are approximately up to 0.15 g⋅cm−3.