No abstract

The dataset contains 1339 cone penetration tests (CPT, CPTu, SCPT, SCPTu) executed within Austria and Germany by the company Premstaller Geotechnik ZT GmbH. As a first processing step, core drillings, located within a maximum distance of approximately 50 m to the insitu tests, were assigned to these cone penetration tests, which allow an interpretation of the insitu measurements based on its grain size distribution. In a second step, the software Geologismiki was used to calculate various normalized measures, which can e.g. be used as input parameters for soil behaviour type charts. The present data can be utilized by researches for example to develop new approaches related to soil classification based on cone penetration test. Furthermore, it provides a framework for combining insitu measurements (q c , f s , R f , u 2 , V s ), normalized measures (i.e. Q t , B q , U 2 ) and soil classifications.

Piezocone penetration tests (CPTu tests) allow continuous measurements of the tip resistance, the sleeve friction and the pore water pressure over depth. Furthermore, they minimize the required time as well as costs for a soil characterization. Due to the difficulty related to undisturbed sample recovery of soils (i.e. of weak silty fine‐grained sediments) for laboratory testing, in situ investigations are becoming increasingly popular in geotechnical engineering. The article illustrates results of cone penetration tests, executed at three test sites in the city of Salzburg. It is shown that CPT‐based soil behaviour type charts according to Robertson lead to a realistic characterization of the underground conditions. The grain size distribution of the Salzburger Seeton varies between fine sand‐silt mixtures, which are found in the upper parts, to clayey silts in greater depths. According to CPT‐based soil behaviour type charts of Robertson clayey silts behave clay‐like contractive and are characterized by homogeneous properties with increasing depth. Qtn‐IG diagrams underline that the Salzburger Seeton with a high clay content presents a weak microstructure. On the other hand, the upper Seeton layers, which can be classified as silt‐sand mixtures and silty sands respectively, show a stronger bounding between the particles.

Cone penetration tests are a good option for in situ tests in case of soft, fine‐grained soils. Thus, they are often used for subsoil investigations in the Salzburger Becken, which mainly consists of silty, fine‐sandy sediments. Unfortunately, empirical correlations for the determination of soil parameters from cone penetration tests in case of silty, fine‐sandy soils are very rare in literature. This contribution should help to evaluate the known correlations and correlation factors for the determination of soil stiffness based on cone penetration tests regarding their applicability for the Salzburger Seeton. This is done by the comparison of cone penetration test results with results from laboratory tests.

Fine-grained sedimentary deposits can bear an increased risk for building settlements due to their moderate stiffness and strength properties, as well as high groundwater tables. However, some buildings, e.g., situated on shallow foundations in Alpine basins, show only relatively small settlements because the formation of carbonate cement can create bridging bonds between the detrital soil particles, leading to increased stiffness. These weak bonds can be damaged through dynamic loads and high static loads, causing a weakening of the soil’s microstructure and resulting in large settlements in several cases. However, the environmental controls and mechanistic processes underlying the formation versus damaging of microstructure in fine-grained, postglacial sediments are, to date, poorly understood. In the present study, fine-grained sediments are artificially cemented by calcium carbonates (CaCO3) to investigate (i) the influence of a mild and sustainable cementation process on the stress–strain behavior of silicate- and carbonate-rich soils and (ii) the possibilities and limitations of artificial microstructure development for soil stabilization. Incremental load oedometer testing (IL), bender element testing (BE), X-ray diffraction (XRD), scanning electron microscopy (SEM) and Brunauer–Emmett–Teller (BET) specific surface area (SSA) measurements are used to characterize the development of cementation and to elucidate the improvements in the soil mechanical properties. It is shown that cementation induced by CaCO3 mineralization (by 5–15% replacement) leads to an increased stiffness (factor ≈ 5–7) and shear wave velocity (factor ≈ 1.1), caused by the formation of nanocrystalline, particle-binding CaCO3 cements. The improvement of soil stiffness is dependent on the CaCO3 replacement level, reaction time and primary soil mineralogical composition.