# Predictive Models for Correlation of Compaction Characteristics of Weakly Cohesive Soils
## 3 Methodology and Model Parameters  
The experimental setup for evaluating compaction in weakly cohesive soil has already been described in a previous paper of the authors [13]. The proposed objectives of the practical investigations carried out at the Movilita site (located on DN 2 Bucharest-Urziceni, km 43 + 500, Romania) consisted of:  
* checking the characteristic parameters and the working regime of the compactor. * monitoring the settlement achieved in the compaction process through determinations of topometric and geotechnical levels. * measuring the increase in soil strength and stiffness by different in situ tests. To assess the behavior of soil under load, tests were conducted on an experimental site using an ABG DD16 roller (Volvo Construction Equipment, Eskilstuna, Sweden) operating in vibration modes and an VV170 (Stavostroj, Nove Mesto, Czech Republic) operating in static mode. The test sections were constructed as channels measuring 50 m in length, 2.5 m in width, and with 1 m in depth of the deposited layer. The measuring points (noted F, G, H, I in Figure 1) have different depths from 24.5 cm up to 29.5 cm. In this way, the measurement points F through I represent different terrain variants. While the soil type and characteristic geotechnical parameters, such as maxim dry density (\(\varrho_{\text{dmax}}\)) and compaction time (t\({}_{\text{c}}\)), remained constant, the initial geotechnical parameters initial dry density (\(\varrho_{\text{d}}\)), static longitudinal modulus (E\({}_{\text{st}}\)), and moisture content (w) varied across these points. Thus, these parameters distinguish four different variants of the same terrain undergoing compaction. Additionally, the initial thickness of the deposited soil layer, considered a factor in the applied technology, also establishes a unique initial state for the compaction process. The data processing of the soil samples entailed determining the average value derived from two separate in situ measurements, both conducted under identical field and environmental conditions to ensure consistency and accuracy. The analysis of the granulometric composition (according to STAS 1913/5: Foundation land. Determination of granularity) of the soil brought from the quarry indicates 40% clay, 36% silt, and 24% sand. The plasticity tests (according to STAS 1913/4: Foundation land. Determination of plasticity limits) indicate the results: plasticity index, \(\mathrm{I_{P}}\) = 20.04%; natural humidity, \(\mathrm{w}\) = 11.5%; consistency index, \(\mathrm{I_{c}}\) = 1.055. The compressibility and consolidation characteristics of the soil based on oedometric tests (according to STAS 8942/1: Foundation land. Determination of the compressibility of soils by the oedometer test and STAS 8942/3-90: Foundation land. Determination of the linear deformation modulus by field tests with the plate) show the following results: maximum density in the dry state, \(\mathrm{\rho_{dmax}}\) = 1980 kg/m\({}^{3}\); optimal compaction moisture, \(\mathrm{w_{opt}}\) = 18.54%; consolidation time, \(\mathrm{t_{P}}\) = 2 h; static longitudinal modulus, \(\mathrm{E}\) = 139.4e\({}^{5}\) N/m\({}^{2}\)[6; 13]. The experimental tests for verifying the parameters of the vibratory working regime of the compact consisted in the signals acquisition of time variation of the drum vibration amplitude, by processing the acceleration signals acquired with acceleration transducers located directly on the jacket of the vibratory roller, in the vertical direction, around its contact with the ground and on the upper chassis of the machine, for both drums. The identification of the working regimes with vibrations consisted in checking the operation at nominal and maximum speeds of both the front drum vibrator and simultaneously (with both rollers active), as well as the maintenance of the frequency and amplitude of the roller vibrations at stable values over time to ensure a stable technological working regime.