In situ monitoring and 3D geomechanical numerical modelling to evaluate seismic and aseismic rock deformation in response to deep mining

AbstractThe stability of submarine slopes is often characterized using campaign-based geophysical and geotechnical measurements in combination with numerical modelling. However, such one-off measurements do not reflect transient changes in slope stability. In situ monitoring of physical parameters critical for slope stability over periods of months to years can provide crucial information on slope stability and can also be used in an early-warning system for submarine landslides and the possibly resulting tsunamis. We review existing techniques that are capable of monitoring seafloor deformation over long periods of time. Based on numerical models we can identify the magnitude of parameters related to landslide-induced seafloor deformation. Simulations of three different failure scenarios up to the point of failure show that the development of the stress state of a slope and hence stability over time can be captured by measurements of tilt, pressure and strain at the seafloor. We also find that different failure mechanisms induce different deformation signals at the seafloor, in particular tilt. Hence, with a site- and target-specific survey design (or a large pool of instruments), seafloor deformation measurements in combination with numerical modelling can be used to determine the temporal evolution of slope stability as well as to identify underlying failure mechanisms.

Download Full-text

In Situ Monitoring and Numerical Experiments on Vertical Deformation Profiles of Large-Scale Underground Caverns in Giant Hydropower Stations

Geofluids ◽

10.1155/2021/6673825 ◽

2021 ◽

Vol 2021 ◽

pp. 1-12

Author(s):

Hao Wu ◽

Jian Liu ◽

Xiaogang Wang ◽

Lipeng Liu ◽

Zhenhua Tian

Keyword(s):

Large Scale ◽

Surrounding Rock ◽

In Situ Monitoring ◽

Rock Deformation ◽

Vertical Deformation ◽

Spatial Response ◽

Underground Caverns ◽

Hydropower Stations ◽

The Relationship

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.

Download Full-text

Application of Long Anchor in Support Optimization of Soft Rock Tunnel

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.368-370.1614 ◽

2013 ◽

Vol 368-370 ◽

pp. 1614-1624

Author(s):

Yang Sun ◽

Jian Ping Chen ◽

Wei Zheng ◽

Li Yu

Keyword(s):

Soft Rock ◽

Surrounding Rock ◽

Parameters Optimization ◽

In Situ Monitoring ◽

Rock Deformation ◽

New Thought ◽

Supporting Structure ◽

Rock Tunnel ◽

Surrounding Rock Deformation

supporting structure parameters optimization is always a research focus in soft rock tunnel. Combined with Youfangping tunnel in Guzhu highway, the scheme of long anchor supporting has been provided. Usually the length of systematic anchor was determined according to experience, it often not reasonable. In order to determine the length of anchor, in-situ wave velocity test and theoretical calculation was used, and with the consideration of safety and economy, the length of anchor was determined as 4.5m finally; At the same time combined with in-situ monitoring measurement, two test sections was selected, and with the comparison of the designed supporting scheme and the original strong supporting scheme, it can be found that: no matter from the sight of surrounding rock deformation, stress applied on surrounding rock or force pattern of supporting structure, the supporting form by lengthening anchor can control surrounding rock deformation more effectively, can improve the bearing capacity of surrounding rock fully and improve the effect of supporting structure. And the supporting scheme of long anchor was more reasonable than the strong supporting scheme. This long anchor supporting scheme can provided new thought to supporting design of soft rock tunnel in Guzhu highway.

Download Full-text