Compressive Behavior of Oil Shale with Calcareous Concretion: Parametric Study

The non-uniformly distributed calcareous concretion among the oil shale in the Junggar basin of China has led to the difficulty in achieving the slope stability. This paper presents the numerical simulation of the behavior of oil shale with calcareous concretion via the Particle Flow Code (PFC2D) program based on the trial experimental test results. The critical parameters investigated in this research covered the size, distribution, strength, and number of the calcareous concretion. The following conclusions can be drawn based on the discussions and analysis: (1) the hard concretion always results in the high compressive strength of the specimen compared with that without concretion; (2) when the radius of the concretion size raised from 2.5 mm to 20 mm, the peak strength of tested specimens is approximately 50 MPa, whereas, the specimen with large concretion is much more ductile under compression; (3) the compressive behavior of tested specimens is similar even when the position of the concretion is variable; and (4) different from the specimens with only one concretion, these specimens contained two concretions featured with the double “X” failure mode. Meanwhile, the peak strength of the specimens with two hard concretions is about 2.5 times that of its counterparts with two soft concretions. The numerical simulation results are meaningful in guiding the design and analysis of the oil shale slope with the concretion.

Experimental Study on Strength Influencing Factors of Calcareous Nodule Soil in Northern Jiangsu

The physical and mechanical properties of calcareous concretion soil depend largely on the shape, size and distribution of calcareous concretion soil besides the impact of soil layer. Due to the long time required for clay saturation, consolidation, and shearing, as well as the tedious sample preparation, larger triaxial tests of calcareous nodules have not been carried out. In this chapter, based on the medium triaxial test of calcareous nodules, the strength characteristics of remolded soil samples under different confining pressures are studied. By controlling parameters such as calcareous nodules particle size and water content, the impact of different test conditions on the strength of calcareous nodules is analysed, and the variation rule is analysed. It is concluded that the impact of nodular particle size on soil strength is not obvious at 20% nodular content. The impact of different water content on the strength of soil is more regular, showing hardening characteristics, in line with the natural law.

U–Pb dating of calcite in ancient carbonates for age estimates of syn- to post-depositional processes: a case study from the upper Ediacaran strata of Finnmark, Arctic Norway

Results of in situ U–Pb dating of calcite spherulites, cone-in-cone (CIC) calcite and calcite fibres from a calcareous concretion of the upper Ediacaran of Finnmark, Arctic Norway, are reported. Calcite spherulites from the innermost layers of the concretion yielded a lower intercept age of 563 ± 70 Ma, which, although imprecise, is within uncertainty of the age of sedimentation based on fossil assemblages. Non-deformed CIC calcite from the bottom part of the concretion yielded an age of 475 ± 25 Ma, which is interpreted as the age of CIC calcite formation during a period of fluid overpressure induced during burial of the sediments. Deformed CIC calcite from the top part of the concretion yielded an age of 418 ± 23 Ma, which overlaps with a known Caledonian tectono-metamorphic event, and indicates a potential post-depositional overprint at this time. Calcite fibres that grew in small fissures along spherulite rims, which are interpreted as a recrystallization feature during deformation and formation of a cleavage, gave an imprecise age of 486 ± 161 Ma. Our results show that U–Pb dating of calcite can provide age constraints for ancient carbonates and syn- to post-depositional processes that operated during burial and metamorphic overprinting.

Exploration of Determining the Bearing Capacity of Calcareous Concretion Soil with Static Cone Penetration

Cohesive soil containing calcareous nodule in Huaibei plain is a kind of regional special soil, which has a unique material composition and structure. The paper discusses the types and distribution of calcareous concretion in soil, and the influence on the strength of soil and the engineering property. Through a lot of the load test and the corresponding static cone penetration test, analyzing the correlation between them.Then linear regression equation between and is established. Finally, it is show that linear regression effect is remarkable, and the equation can be reference for the local practical engineering