ABSTRACT

2D FEM simulation of formation of Lucina Riverbed at Zermanice Dam site is described in the paper. The work made use of geological-historical study of Academic Zaruba (1956), which showed that erosion of the valley in geological time induced viscoplastic flow and bulging of the marly shale forming the valley. This resulted in a landslide breaking the overlying teschenite sill into separate blocks. This process was simulated using Perzyna's theory of viscoplasticity. The model is a part of an extensive modeling program aiming at stability analysis of the Zermanice Concrete Dam revealing unusual performance according to the long-term monitoring results. To get proper input data for the 3D model fitting the measurement results, a series of local and regional models allowing for step-by-step calibration of mechanical, hydraulic, thermal and rheological parameters of bedrock according to the monitoring results was applied. The presented model aimed at estimation of the in situ stress state of the valley and the rheological parameters of the marly shale.

INTRODUCTION

The 36 m high Zermanice Concrete Dam, built in very difficult geological conditions in the middle of the last century, reveals long-term uneven heave, tilting and horizontal displacements with constant or increasing velocity, which questioned its safety.

In order to assess the safety of the dam and predict its further behavior, a stability study consisting of extensive archival survey (Svancara 2002, 2003) and modeling work was carried out (Dolezalova et al. 2003, 2004, Hladik & Dolezalova 2004). A large 3D FEM model simulating the observed performance of the dam and its foundation according to the long-term monitoring results was elaborated. To solve the data limited problem, a step-by-step modeling procedure a series of 2D local and regional FEM models - allowing for calibration of mechanical, hydraulic, thermal and rheological parameters of rock according to the measurements was applied.

The paper focuses on the 2D regional FEM model simulating the formation of the valley in geological time. Via modeling these events the rheological constitutive law and parameters of bedrock and the in situ stress state of the valley could be estimated.

The work made use of geological-historical study of Academic Zaruba elaborated for the site (Zaruba 1956). The dam site is formed by weak Cretaceous marly shale, which was originally covered by competent teschenite sill. Erosion of the valley in geological time induced viscoplastic flow and bulging of weak underlying shale, which resulted in a landslide disturbing their structure and breaking the overlying teschenite into separate blocks.

The 2D FEM model simulates the above process using Perzyna's theory of viscoplasticity. The input for modeling was worked out by Svancara & Bilek (2003) and Novosad (2003). Based on Zaruba's study it estimates the most probable geology, geometry and chronology of the formation of the valley.

In the paper, the dam and the dam site, the monitoring results and the modeling concept are dealt with in brief, while the theory of multiface viscoplasticity, the FEM model, the solution procedure and the results obtained are described in more detail.

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