The Alxa area is a candidate site for China's high-level radioactive waste (HLW) repository. In-situ stress measurements using hydraulic fracturing were performed to directly estimate the present-day stress field of the Alxa area. Variation of the in-situ stress components with depth in two sub-sites (i.e., Nuorigong, and Tamusu) was analyzed based on valid hydraulic fracturing data obtained from two sub-vertical boreholes. The results reveal that the horizontal stresses in the Alxa area present an intermediate or low level. The in-situ stress magnitudes are consistent within the crustal frictional strength range that predicated using the Coulomb frictional-failure theory incorporating frictional coefficients of approximately 0.6–1.0. The maximum horizontal stress in the Alxa area is dominantly oriented in the NNE–SSW direction which is consistent with the direction of the tectonic stress field of northwest China. The estimation of the in-situ stress measurement results provides critical knowledge of the engineering geological characteristics of this candidate area, and support on potential underground excavation.
