Geostatistical modeling of uniaxial compressive strength along the axis of the Behesht-Abad tunnel in Central Iran

Abstract

Uniaxial compressive strength (UCS) is one of the most significant factors in the stability of rock engineering projects and is vastly used during the design and construction stages of underground excavations. Distances between exploratory boreholes is typically large during the preliminary studies of a majority of geotechnical projects. As a result, estimation of UCS values based on the scant data obtained from these distant boreholes is crucially important. Thus, the use of geostatistical estimation and simulation methods can lead to a significant reduction of errors and exploratory costs. In this regard, the present paper ties simulation and estimation of UCS values of the rock material between boreholes of the Behesht-Abad tunnel in central Iran using the Stanford Geostatistical Modeling Software (SGEMS). Variography showed the acceptable spatial distribution (9,477 m) of UCS parameters in the area under investigation. Also, cross-validation proved the high accuracy (98 %) and reliability of the results of the developed model. Then, considering the condition of the datasets and engineering judgmentvalues, the model outcomes were analyzed. It was concluded there is high similarity between the geostatistical estimation/simulation and engineering judgments. Application of geostatistical simulation methods in conjunction with estimation in rock research indicates these methods are performed in a rather different aspect from those of common validation processes. Furthermore, the combination of geostatistical estimation/simulation and engineering judgment led to better identification of the pros and cons of geotechnical explorations in each tunnel route.