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.
Soil nails are components retaining a ground to give it support particular in cases when the ground doesn’t satisfy fully the requirements and it is expected an excessive deformation or the worst a collapse. Today in all geotechnical applications the soil nails are arranged in the simplest way i.e. they are all parallel and almost perpendicular the boundary face of the ground body to be bound. Submitted article is a feasibility study on application the soil nails in another a nonparallel scheme of nails arrangement. The nails are located in two closely adjacent parallel plains. The nails are inclined in each plain with regard to a boundary face of the ground body and the nail inclination heads in opposite direction in each plain. This way the nails build up a quasi-web scheme in the ground. Article analyzes the effect of the quasi-web scheme nails arrangement on the ground and looks for an exact solution to evaluate effect on ground strength and strain behavior. The force balance approach is employed for the exact analysis.
A steel concrete lining is today the common ground massive retaining structure implemented shortly after the excavation of an opening. The constituent elements of the steel concrete lining are layers of shotcrete and steel arch frames. This simple structure has many unique features which set it apart from the conventional reinforced concrete constructions. Without simplification these features doesn’t allow to carry out design and evaluation of steel concrete lining by relevant design and evaluation methods convenient to the conventional reinforced concrete constructions. The main differences are construction process, yielding curve of structure and determination of external load. In the case of a steel concrete lining its external load is product of mutual work of both the ground massive and the lining. The value of load depends on the yielding curves of the lining and the ground massive. The yielding curve of a ground massive is objective and conditioned on strength strain properties of ground massive and primary stress state. The yielding curve of a steel concrete lining relates lining design specification. The process of construction affects the value of load too. The article analyzes the steel concrete lining focusing the influence of lining design parameters on its yielding curve. It looks for a way to control the ground massive behavior and as well as to engage it more in an effort with lining to stabilize subterranean work. The themes of the analysis are: static and deformation parameters of the cross-section of the steel concrete lining with regard to the construction stage and dependency of hardening shotcrete; interaction between of steel concrete lining and ground massive based on yielding curves; assessment of a stress state across the steel concrete lining section in the steel concrete lining constituent elements. The analysis is carried out on mathematical models that combine analytical and numerical methods.
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