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In the context of underground construction projects such as large-scale linear projects, knowledge of subsoil geotechnical properties is of major importance. An effective way to analyze and represent the variability of these properties is to use geostatistical methods. Despite the good performance of such methods, their use is not yet widespread in the field of underground projects. This paper aims to show the usefulness of geostatistics in the field of tunneling by proposing an original 3D sectoral modeling approach that allows dividing the geological formations in homogeneous geotechnical areas to better take into account the vertical and lateral variations of geotechnical properties. The approach is tested by developing a 3D geostatistical model of the pressuremeter tests on a section of a massive tunneling project in Paris (France): the Grand Paris Express. A strong focus is also made on the model input data: a methodology is proposed to overcome the limitations of the pressuremeter test in order to better study the spatial variability of the net limit pressure. A twofold analysis is conducted by comparing the modeling results obtained with and without pressuremeter data processing and those obtained with and without sectoral modeling. The results of the comparison show that: a) data processing is useful to better discern areas of extremes values of net limit pressure; b) dividing the geological units into homogeneous geotechnical sectors provides an advantage for geological units with geotechnical heterogeneities, as it leads to improved reliability of results. • An original 3D geostatistical modeling method for tunneling project is proposed. • Net limit pressure re-evaluation overcomes the pressuremeter test limitations. • Statistical methods identify homogeneous geotechnical areas within heterogeneous geological formations. • Sectorisation modeling outperforms global modeling for lateral geotechnical heterogeneities. [ABSTRACT FROM AUTHOR]

Methodologies have been developed to establish realistic water-table maps using geostatistical methods: ordinary kriging (OK), cokriging (CoK), collocated cokriging (CoCoK), and kriging with external drift (KED). In fact, in a hilly terrain, when piezometric data are sparsely distributed over large areas, the water-table maps obtained by these methods provide exact water levels at monitoring wells but fail to represent the groundwater flow system, manifested through an interpolated water table above the topography. A methodology is developed in order to rebuild water-table maps for urban areas at the city scale. The interpolation methodology is presented and applied in a case study where water levels are monitored at a set of 47 points for a part urban domain covering 25.6 km close to Bordeaux city, France. To select the best method, a geographic information system was used to visualize surfaces reconstructed with each method. A cross-validation was carried out to evaluate the predictive performances of each kriging method. KED proves to be the most accurate and yields a better description of the local fluctuations induced by the topography (natural occurrence of ridges and valleys). [ABSTRACT FROM AUTHOR]

The paper presents the results of a new geostatistical approach to generate bathymetric surface models from point measurement converted into continuous contour surfaces of reservoir bottoms in Uzbekistan. Sedimentation of reservoirs raises engineering, environmental and economical issues for the communities around the world in areas affected by a strong water deficit. Because of Uzbekistan's arid climatic conditions, and uneven spatial and temporal water resources distribution, responsive and innovative water availability assessment surveys of all major water reservoirs are required. Bathymetric surveying is a traditional method that is carried out for the estimation of reservoir volumes and surface areas of the corresponding reservoir stages in order to assess the water availability. Volume and surface area differences derived from multiple surveys of a reservoir provide storage loss estimates over time due to sedimentation. However, two main factors, such as intensive field data measurement and post data-processing, often limit the frequency of these surveys. Alternatively, innovative depth measurement technologies coupled with contouring and surface mapping programs provide automated reservoir volume and surface area calculations. This significantly reduces time, workload and financial burdens for reservoir sedimentation projects. This research proposes the use of geostatistical approach to assess the reservoir sedimentation in the Akdarya reservoir of Uzbekistan. The geostatistical approach includes (semi-) variogram analysis and interpolation (kriging and simulations-turning bands) techniques predicting values at unsampled locations for generating digital bathymetric surface models of reservoir bottom conditions in order to calculate the volume and surface area at a given water elevation. The simulation enables to have range of reservoir volumes and surface areas with the same probability, in comparison to the kriging and traditional methods. This gives a real estimation of the resource availability for water operators to manage natural resources and hydraulic infrastructure in a sustainable manner. [ABSTRACT FROM AUTHOR]