Notice of RetractionEvaluation on the Stability of Rock Mass Deformation Based on Chaotic Muation -RPNN Model
To analysis the stability of rock mass long-term developing deformation,the chaotic muation -RPNN model is built. Combining the chaos theory,the muation theory is introduced, and the stability of rock mass deformation is evaluated by chaotic muation -RPNN model. The lost measured displacement data are interpolated by using the higher order polynomial methos, and the long-term displacement is forecasted,and the stability of rock mass long-term developing deformation is analyzed. Research shows that the strend of predicted displacement is approximately the same as that of measuring displacement,and there is no suddenly dropped or sudden increased phenomena,and the displacement increasing strend of some measuring point remains stable with Lower growth trend, and the deformation of rock mass is strending to be stable.
Analysis on characteristic parameters of deformation of rock around underground powerhouse based on chaos theory
In order to explore the rules of deformation of rock around underground powerhouse, the chaos theory is introduced and the chaos characteristic parameters are studied systematically and fully.Correlation dimension D is determined by improved G-P method,and maximum lyapunov exponent λ_1 is calculated by using the values of embedding dimension m and delay time τ computer from synthetic analyzing G-P method,C-C method and multiple autocorrelation method.Combining multi-points measuring displacement data of rock around Xiaowan underground powerhouse,the results show that multi-points measuring displacement data at crown apex and those at the measuring-point in 30m depth of arch aboutment do not have the chaos dynamic feature,but the others of arch abutment and those in wall have chaos feature,thus D0,m and τ are optimized,λ_10.So the study provides a new thought for the deformation rules of rock around underground powerhouse.
O2 constraints from Paleoproterozoic detrital pyrite and uraninite
Redox-sensitive detrital grains such as pyrite and uraninite in sedimentary successions provide one of the most conspicuous geological clues to a different composition of the Archean and early Paleoproterozoic atmosphere. Today, these minerals are rapidly chemically weathered within short transport distances. Prior to the rise of oxygen, low O2 concentrations allowed their survival in siliciclastic deposits with grain erosion tied only to physical transport processes. After the rise of oxygen, redox-sensitive detrital grains effectively vanish from the sedimentary record. To get a better understanding of the timing of this transition, we examined sandstones recorded in a scientifi c drill core from the South African 2.415 Ga Koegas Subgroup, a mixed siliciclastic and iron formation–bearing unit deposited on the western deltaic margin of the Kaapvaal craton in early Paleoproterozoic time. We observed detrital pyrite and uraninite grains throughout all investigated sandstone beds in the section, indicating the rise of oxygen is younger than 2.415 Ga. To better understand how observations of detrital pyrite and uraninite in sedimentary rocks can quantitatively constrain Earth surface redox conditions, we constructed a model of grain erosion from chemical weathering and physical abrasion to place an upper limit on ancient environmental O2 concentrations. Even conservative model calculations for deltaic depositional systems with suffi cient transport distances (approximately hundreds of kilometers) show that redox-sensitive detrital grains are remarkably sensitive to environmental O2 concentrations, and they constrain the Archean and early Paleoproterozoic atmosphere to have <3.2 × 10 –5 atm of molecular O2. These levels are lower than previously hypothesized for redox-sensitive detrital grains, but they are consistent with estimates made from other redox proxy data, including the anomalous fractionation of sulfur isotopes. The binary loss of detrital pyrite and uraninite from the sedimentary record coincident with the rise of oxygen indicates that atmospheric O2 concentrations rose substantially at this time and were never again suffi ciently low (<0.01 atm) to enable survival and preservation of these grains in short transport systems.