Abstract
Spatial response is a feature of rock deformation in regions surrounding large-scale underground caverns and includes significant vertical components due to the construction method of layered excavation. This vertical response is different to the longitudinal response of excavation deformation surrounding shallow tunnels. The study of longitudinal deformation profiles (LDPs), which describe the spatial response of longitudinal tunnel excavation and surrounding rock deformation, is a mature field. However, there has been no independent discussion of the relationship between vertical excavation and the spatial response of deformation in large-scale underground caverns nor the incremental characteristics of layered excavation. In this paper, we define the attenuation function λ x of unloading strength based on theoretical analyses and numerical simulations. We also propose the concept and form of the vertical deformation profile (VDP) curve for the first time and apply it to the Baihetan and Lianghekou Hydropower Stations. After fitting the complete VDP curve with a Levenberg-Marquardt algorithm, we verify its validity by comparing predicted data with in situ monitoring data. The curve can be used to quantitatively analyze the relationship between layered excavation and incremental deformation of surrounding rock, providing a basis for the rapid evaluation of staged deformation during the excavation of large underground caverns. This study has practical significance for the control of deformation in rock surrounding excavations and decision-making during the construction progress.
Highlights
80% of China’s hydropower resources are concentrated in the southwest [1]
Following the principles underlying the longitudinal deformation profiles (LDPs) curve, we firstly proposed the concept of the vertical deformation profile curve; the vertical spatial response mechanism of rock deformation control and face vertical excavation in large underground caverns is studied; we define the attenuation function λðxÞ of unloading strength and deduce the form of the VDP curve by FLAC3D numerical simulation
We firstly proposed the concept and constructed a VDP curve suitable for rock mass with high integrity and few fissures or faults on the basis of theoretical analysis and in situ monitoring data
Summary
80% of China’s hydropower resources are concentrated in the southwest [1]. Landforms in this region have heavy rainfall, numerous mountains, and large drops, providing abundant hydropower resources along the Jinsha, Yalong, Dadu, and Lancang Rivers. Following the principles underlying the LDP curve, we firstly proposed the concept of the vertical deformation profile curve; the vertical spatial response mechanism of rock deformation control and face vertical excavation in large underground caverns is studied; we define the attenuation function λðxÞ of unloading strength and deduce the form of the VDP curve by FLAC3D numerical simulation. The validity of this VDP curve is tested by using in situ monitoring data of two engineering projects and the physical meaning of key parameters in the VDP curve explained. Because these physical explanations are clear, the VDP curve is suitable for the evaluation of phased deformation of large-scale underground caverns
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