The Interpretation of CPTu, PMT, SPT and Cross-Hole Tests in Stiff Clay

Abstract

Abstract. The paper presents the comparison of results of CPTu, PMT, SPT and CH (crosshole) tests performed in stiff, heavily overconsolidated clay at a test location in Zagreb. This clay exhibits very high pore pressures generated during CPTu penetrations despite significant overconsolidation and relatively high values of shear strength and stiffness in its undisturbed, natural state. The clay is classified using the CPTu and CH test results in recently published soil classification charts based on the soil behaviour in (S)CPTu penetrations. The results of classifications indicate that the tested clay probably has a pronounced microstructure that is likely a consequence of the geological processes of cementation and aging. Effects of cementation and aging are manifested on very high shear wave velocities, as measured in cross-hole seismic tests, and consequently very high values of the small-strain modulus. The collapse of the soil structure at higher shear displacements is resulting in volume contractions and softening behaviour after reaching the peak shear strength. The study shows a relatively good agreement between CPTu, PMT and SPT parameters and adequate correlations have been established between the cone resistance (CPTu), limit pressure (PMT) and number of blows (SPT). The in situ state and parameters of strength, stiffness and compressibility of the clay tested are estimated based on the in situ test parameters as well as comparative laboratory test results obtained on undisturbed soil samples. Existing empirical correlations developed for the interpretation of CPTu test results are mainly from young and uncemented soils without microstructure and therefore, the results shown here are important for better understanding of the structured soil behaviour characteristics (stiffness, strength, and compressibility).

Efficiency of biomass and solid waste energy processing based on the cogeneration plant with plasma heat source

“…Comparative analysis shows a slight discrepancy between the data, but the general nature of the formation of gas mixture components is similar for all [27][28][29][30][31][32]. It can also be noted that at an average process temperature of 1200°C, the calculation shows a greater amount of combustible components in the gas mixture.…”

CPT—DMT Correlations on Regional Soils from Croatia

“…Highly micro-structured soils could also be recognized in the interpretations and cemented aged or fissured clays. These materials can be recognized by a parameter called modified normalized small-strain rigidity index 𝐾𝐾 𝑔𝑔 * [30,31]. Examples of vertical profiles of the comparison between the CPT evaluated M′ and measured M′DMT 1D constrained modulus for two of the study sites are shown in Figure 17.…”

Interpretation of CPTu and SPT data about sandy soils in the Plovdiv region

“…(2) K* g = (G o /q t -s n )´(Q tn ) 0.75 (Kavur et al, 2019), където: Q tn е нормализирано съпротивление на конуса с отчитане на налягането в порите (MPa). Песъчливите почви, установени в изследваната площадка, попадат в интервала 100 < K g < 330, т.е.…”