To meet the increasing demand on electric power in Shandong peninsula, China, local government plans to build a pumped-storage hydropower station. To help the engineering design, hydraulic fracturing in-situ stress measurements were conducted in five boreholes during the geotechnical investigation. In the underground facility cavern zone, the measured maximum horizontal stress sH ranges from 9.35 to 17.75 MPa, the minimum horizontal stress s h is between 5.97 and 9.75 MPa, and the vertical stress sV varies from 9.34 to 11.48 MPa. In the high-pressure, bifurcated pipeline area, sH is between 11.44 and 19.51 MPa, s h between 7.10 and 13.01 MPa, and sV between 10.66 and 12.39 MPa. The orientation of sH is N66.6~87.6°W. All the measurements indicate a strike-slip stress regime. One numerical model of the engineering area was established to represent the major geological engineering features. By applying laboratory and field testing results to the model, continuous stress distribution in the whole engineering area was calculated. The results are consistent with that indicated in the World Stress Map.
Knowing the in-situ stresses around a future subsurface infrastructure is very important to the design engineer. Conventional in-situ stress measurement techniques include hydraulic fracturing method and over-coring method [2, 10]. Recent development is the integrated stress determination method (ISDM), in which several techniques are utilized [1]. Due to the limitation of time, cost, and sometimes, site conditions, only a restricted number of well-planned in-situ stress measurements can be conducted in each project in the engineering area. These results are usually scattered, and represent the insitu stresses around the measured spots [5]. To obtain a three dimensional distribution of in-situ stresses in the whole engineering area, numerical modeling cab ne a useful tool. Numerical modeling techniques include finite element, finite difference, discrete element, and boundary element methods; among which finite element method has been most widely used [3]. Weather the insitu measurement-based, numerical modeling-expanded distribution of the stresses in the engineering area is reasonable can be qualitatively verified using tectonic and structural geology analysis. This analysis can be used to check if the above determined in-situ stresses in the engineering area would have consistent orientation with regional stresses [4]. In this paper we demonstrated an integrated method for in-situ stress determination by combining hydraulic fracturing stress measurements with numerical modeling and regional geological analysis through its application to a pumped-storage hydro-power station in Shandong peninsula, China.
To meet the increasing demand on electric power in Shandong peninsula, China, the local government plans to build a pumped-storage hydropower station based on consideration of the regional waterpower resources and geological engineering conditions. This hydro-power station, with a designed capacity of 1,800 MW, consists of an upper reservoir, a lower reservoir, a water tunnel system, the underground power-generation caverns and other facilities (Fig.1). Geologically, the engineering area is inside the Sino- Korea meta-platform, to the east of the Tanlu faulting belt. Regionally it belongs to the Jiaonan-Wendeng platform uplift.
