This article is focused on the analysis of the use of distributed fibre-optic technology for security monitoring of road tunnel and motorway tunnel structural load. The authors focused on the measurements of deformation utilizing Brillouin Time Domain Reflectometry (BOTDR). The principle is based on the measurement of stimulated Brillouin scattering. The article describes and analyses real measurements within a period of 5 months, which were carried out during the tunnelling and the whole process of building a new tunnel in Žilina, Slovakia. The performed experimental measurements were carried out using a standard optic telecommunication cable with water-absorbing aramid yarns and a jacket with a diameter of 4.2 mm. The contribution of this article lies in the introductory analysis of the implementation and use of the fibre-optic technology for security monitoring of road tunnel and motorway tunnel structural load.

The paper deals with soil improvement using polyester fibres of length 70mm mixed in soil SC as random reinforcement in amount of 0.5%, 1.0% and 1.5%. Improvement of soil was measured by direct shear tests, using shear box of size 0.3m x 0.3m x 0.15m. It will be shown that for tested soil, optimal amount of fibres is 1.0%, when increase of angle of internal friction was up to 6.0o (from 45.3o to 51.3o) and increase of cohesion was up to 17.5kPa (from 0kPa to 17.5kPa) in comparison with soil without fibres

This paper is focused on sensitivity analysis of the behavior of subsoil foundation systems by considering the variant properties of a fiber concrete slab that result in different relative stiffness of the whole cooperating system. The character of the slab and its properties are very important for the character of external load transfer. However, the character of the subsoil also cannot be neglected because it determines the stress–strain behavior of the entire system and, consequently, the bearing capacity of the structure. The sensitivity analysis was carried out based on experimental results, which included both the stress values in the soil below the foundation structure and settlements of the structure that are characterized by different quantities of fibers in it. Flat GEOKON dynamometers were used for the stress measurements below the observed slab, the strains inside the slab were registered by tensometers, and the settlements were monitored geodetically. This paper is focused on the comparison of soil stresses below the slab for different quantities of fibers in the structure. Results obtained from the experimental stand can contribute to more objective knowledge of the soil-slab interaction, the evaluation of real carrying capacity of the slab, the calibration of corresponding numerical models, the optimization of quantity of fibers in the slab and finally, contribute to higher safety and more economical designs of slabs.

In this paper the experimental work in the field of evaluation the liquid limit is described. Two different types of soil were analyzed – loam (intermediate plasticity) and sodium bentonite (high plasticity). Two basic methods were used for the evaluation of the liquid limit – Casagrande percussion (cup) method and cone penetrometer method. Two approaches were applied to the evaluation of liquid limit based on cone penetrometer test (30°/80g cone) – standard method assuming 20mm penetration at liquid limit and new calibration line for cone penetrometer liquid limit - NCCLL (Mohajerani). Experimentally obtained calibration line assumes the influence of depth of cone penetration at liquid limit on undrained shear strength, which is not unique for all types of soils. The paper presents the comparison of results of liquid limit based on the previously mentioned methods. Presented results of laboratory tests show, that bentonite liquid limit based on the standard cone penetration test (using 20mm penetration) is significantly lower in comparison with Casagrande liquid limit. On the other hand was verified very significant consistency of Casagrande liquid limit and liquid limit based on NCCLL (evaluated depth of penetration 29mm). Obtained results indicate the need for further research in this area

Shape and material optimization of building structures, including reducing the amount of concrete used, are very important aspects in sustainable construction. Numerical modelling is currently used very effectively to design optimized and sustainable structures, including their interaction with the surrounding rock environment. This paper is focused on the three selected factors of numerical modelling of fibre concrete slab and subsoil interaction: (1) the constitutive model of fibre concrete slab, (2) deformational and strength characteristics of subsoil, (3) effect of interface elements. The specialized geotechnical software Midas GTS NX, based on the finite element method, was used for the modelling of this task. Numerical results were compared with the experimental measurement of vertical displacements on the upper surface of slab. In the presented study, three constitutive models of slab recommended in MIDAS GTS NX code for modelling concrete behaviour (elastic, Mohr-Coulomb and Drucker-Prager) were applied. In addition, the sensitivity analysis with respect to the deformational and strength characteristics of subsoil was performed. The numerical study also presents the effect of the interface elements application on the slab behaviour. The numerical results of maximum vertical displacements based on the Drucker-Prager and elastic model underestimated both the experimental results and numerical results based on the Mohr-Coulomb model. From the qualitative point of view (shape of deflection curve), the numerical simulation showed the better agreement of the Mohr-Coulomb constitutive model with the experimental measurements in comparison with the other two investigated constitutive models. The performed parametric study documented that reduction of the strength and deformational characteristics of subsoil leads to the increase of maximum vertical displacements in the centre of slab, but the experimentally measured deflection curve, including uplift of slab and gapping occurrence between the slab and subsoil, was not achieved without the interface application.

This paper presents an approach that enables the specific characteristics of a primary tunnel lining implemented using numerical modelling to be taken into account during its design. According to the fundamental principles of the New Austrian Tunnelling Method, the primary lining undergoes time-dependent deformation, which is determined by its design. The main design element is shotcrete, which, shortly after its application, interacts with the surrounding rock mass and steel arch frame. The primary lining ensures the equilibrium stress–strain state of “rock mass–tunnel lining” during excavation. The structural interaction varies depending on the hardening of the shotcrete, the rheological properties of the rock mass, and other factors. The proposed approach uses the Homogenisation software application, which was developed by the Faculty of Civil Engineering at the Department of Geotechnics and Underground Engineering of the VSB—Technical University of Ostrava. This software allows the heterogeneous structure of the lining to be considered by replacing it with a homogenous structure. The parameters of the homogeneous primary lining, which take into account the steel reinforcement elements and the time-dependent property of the shotcrete, are included in numerical models.