Weathering of soft rocks is usually considered as an important factor in various fields such as geology, engineering geology, mineralogy, soil and rock mechanics, and geomorphology. The problem of ...stability over time should be considered for slopes excavated in soft rocks, in case they are not protected against weathering processes. In addition to disintegration of material on slope surface, the weathering also results in shear strength reduction in the interior of the slope. Principal processes in association with weatherinz are discussed with the examnles of marl hosted on flvsch formations near Solit. Croatia.
Steep slopes in soft rock are characterized by their susceptibility to instability (rockfall, rockslide) due to weathering and erosion of the slope surface. This article deals with the problem of ...adapting to the increasing height of the scree slope. The construction of a retaining wall in a scree slope in front of a slope of soft rock with a steep face, where a very rapid weathering and erosion process of weathered material takes place, and the simultaneous deposition of material in front of the steep slope is a common solution. Changes in the geometry of the slope and the front scree are taken into account, and at the same time, sufficient safety against rockfall must be ensured. The analysis is shown on a specific example of a steep flysch slope near Split, Dalmatia. The retaining wall solutions are compared in terms of function, cost and sustainability. The construction of a single colossal, reinforced concrete retaining wall shows that this solution is not feasible due to the high construction costs and CO2 emissions of the retaining wall. A model was therefore developed to determine the height of the retaining walls for different construction time intervals and distances from the original rock face. The critical failure modes were investigated for various retaining wall solutions with regard to the highest degree of utilization of the resistance, which also allows the cost-optimized solutions to be determined. By building two or more successive retaining walls at suitable intervals and at an appropriate distance from the original rock face, construction costs and CO2 emissions can be significantly reduced.
Soft rocks in various forms of marly materials have an important role in the geological structure of Dalmatia (Croatia) and Budapest region (Hungary). These materials can cause serious problems in ...design and construction, due to their complex behavior under atmospheric conditions. For the purpose of better understanding soft rocks behavior and their properties, a database with approximately 600 samples collected throughout Dalmatia was made and collated along with 260 samples from the Budapest area. Based on the collected data, 30 regression analyses were performed among 14 material properties, and eight different types of linear and non-linear correlations with high coefficients of determination were selected, which connect the important mechanical properties (uniaxial compressive strength and Young’s modulus) with physical properties of marls (porosity, dry unit weight, and ultrasonic pulse wave velocity). Most of the determined relations show symmetry between the marls from the Dalmatian region and the Budapest region, and the relation between dry unit weight and uniaxial compressive strength asymmetry can be observed between the marls with different origins. Obtained correlations may be used in cases where little or no information on geotechnical parameters is available, or where results need to be verified due to the problems present in soft rock testing.
Embankments made from crushed soft rock grains can be susceptible to additional settlement caused by a deterioration of the grains inside the embankment. This additional settlement is not caused by ...the change of the stress state inside the embankment and cannot be predicted by standard calculating methods using the embankment modulus of deformability measured after compaction of the embankment. The deterioration of the grains is mainly caused by the weathering process, which, in soft rocks such as marl, is mainly induced by the wetting and drying processes. If marl grains in an embankment are subjected to the wetting and drying process, the result is breakage of the grains, as well as decomposition into soil material. Disintegrated material then fills the macro-pores of the embankment grain structure and gradually causes additional settlement. This process in soft rock material lasts from a few months to a few years. We propose a calculation procedure to estimate the possible value of the additional settlement, based on measured settlements gained from examples of laboratory-weathered samples. The samples were made of crushed marl in laboratory conditions. A test was conducted with a modified oedometer apparatus. In the proposed model, the deformation is calculated based on possible volume changes due to the deterioration of the grains and transport of the detached material into the macro-pores; this is done with the intention of estimating the settlement without measuring the deformation modulus change caused by the weathering.
The mechanical weathering of marl in the form of disintegration of intact material caused by repeated drying and wetting, also known as “slaking”, is an important factor affecting the durability and ...stability of cuts in soft rocks and Eocene flysch formations (Dalmatia, Croatia). It is often valued and used in rock classification as a slake durability index (SDI), an index property recommended by the International Society for Rock Mechanics and American Society for Testing and Materials. It was observed that the results of conventional laboratory tests on marl samples using two slaking cycles are not always in accordance with the appearance of the samples after testing (highly fragmented rock material, in spite of the high resistance/durability result based on the retained sample mass). Depending on factors such as porosity, hydraulic conductivity, and mineralogical composition, the effects of weathering might sometimes not be obvious within two cycles, which suggested that durability classification is not suitable for all soft rock types. In order to determine the additional criteria that would reduce the uncertainty of standardised durability testing in soft rocks, both the standard and modified tests of durability as well as a series of additional index tests (carbonate content, dry density, water absorption, porosity, and point load strength index) were conducted on 70 samples of marl. Several variants of the SDI were analysed with various numbers of cycles, cycle times, and combinations thereof. To emphasise the differences between various types of marl, a variant of loss slake index was introduced and determined using 30 samples. Based on the results obtained, according to the degradation type observed after the slaking, the samples were grouped into three groups. Based on the presented results, a classification with the defined criteria for high, medium, and low durability has been suggested for the purpose of a durability analysis of the cuts in marls.
•New insight into durability of marls from Dalmatian region, Croatia.•Full dataset for 70 samples of marl including durability and physical properties.•Performance of standard slake durability test evaluated and improvements suggested.
Durability is one of the most important engineering properties of weak and clay-bearing rocks. Weathering can induce a rapid change in rock material from initial properties to soil-like properties. ...The sensitivity of a rock type against weatherability is usually described by a durability parameter, such as the slake durability index. However, marl resistance is not detected satisfactorily by the durability indices by using slake durability test as suggested by ISRM for two wetting–drying cycles. The results of this study are obtained from samples of compact or laminated eocene marls from region of Dalmatia, Croatia. The samples were subjected to 4 cycles of slake durability, point load tests, determination of dry density, determination of carbonate content and absorption of water. The scatter of data suggests that strength probably has no influence on the durability of marls. On the other hand a separate group of marl samples have a second-cycle slake durability index higher than approximately 85%, and the durability of these samples is classified as “medium-high” to “high”, although the visual inspection of samples after testing, suggests that they should have “medium” to “low” durability classification. According to obtained results these samples of marl fulfil the criterions for the durability classification: a carbonate content lower than approximately 65%, a dry density lower than 2.4 Mg/m
3
, and values of water absorption higher than 5%.
Determination of the change in strength based on simulation of weathering process in laboratory conditions is described in the paper, using marl samples taken from flysch formations in the region of ...Dalmatia. The testing has revealed that the proposed weathering simulation in laboratory can be conducted within acceptable time frames. Because of the observed change of shear strength parameters as related to values corresponding to the strength of material described as soil, it is sometimes necessary to use soil testing devices so as to take into account the load range applied in individual types of testing devices.
Terrestrial laser scanning (TLS) in combination with Unmanned Aircraft System (UAS) and modern computer based photogrammetry is currently the best approach for the acquisition of high-resolution 3D ...spatial information. Highly realistic 3D spatial data sets are becoming the basis for detailed geological studies, providing a multidisciplinary approach in the study and research of both underground and above ground sites. To emphasize the variety of possible implementations of these state-of-the-art methodologies, four characteristic and yet quite different case studies are presented where such geodetic techniques are successfully employed. The presented case studies demonstrate that TLS and UAS photogrammetry, as non-contact surveying methods, are able to reduce survey time and total project costs. As added value, they provide high-resolution data that can be analyzed in a virtual environment from a sedimentological or structural aspect. Stored digital documentation also allows future multi-temporal spatial data comparison at any timeframe and scale, thus enhancing any target geological data gathering and analyses at the studied sites.
Recent development of lightweight and small size multi-frequency GNSS receivers allows determination of the precise position of the moving platform and spatial data acquisition without the need for ...setting up and measuring of ground control points. The main advantage of this approach is a higher operational capacity with reduced time and cost of field measurement. This relates to fieldwork in inaccessible areas with demanding terrain configuration. In this paper development and use of a UAS with direct georeferencing of camera sensor for spatial data acquisition is described, and the possibility of 3D scene reconstruction based on the precise position of the camera with predetermined interior parameters is examined. Modern computer vision-based SfM photogrammetry algorithms are used for determining attitude parameters and reconstruction of the scene. For that purpose, several tests on two different test fields were performed using various system parameters for collecting and analysis of several spatial data sets. The presented results demonstrate a satisfactory accuracy (3.1 cm planar and 6.4 cm spatial) of the system for various applications in geodesy.
Weathering of soft rocks is usually considered as an important factor in various fields such as geology, engineering geology, mineralogy, soil and rock mechanics, and geomorphology. The problem of ...stability over time should be considered for slopes excavated in soft rocks, in case they are not protected against weathering processes. In addition to disintegration of material on slope surface, the weathering also results in shear strength reduction in the interior of the slope. Principal processes in association with weathering are discussed with the examples of marl hosted on flysch formations near Split, Croatia.
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