| With the vigorous development of port and shipping industry and the implementation of the strategy of Yangtze River Economic Belt,the underwater reef blasting project presents the tendency of great bulk,large charge and huge water depth as a whole.The complicated environment in the working area also requires strict control standards to the harmful effect in the underwater drilling blasting.As a vital protection object in the waterway,the bank slope adjacent to the blasting area certainly bears seismic wave effects of underwater drilling blasting due to the navigation demand and dredging design,and the failure of the slope will be easily occurred under the incorrect operation.Additionally,the bank slope displays a more unstable state when encountered extreme rainfall during the reef blasting process.At present,the researches on the instability of bank slope in the reservoir area mainly concentrate on the issue of water-induced degradation caused by the rainfall infiltration and regular reservoir water level fluctuation,and the blasting vibration degradation effects mostly exist in the researches of mines,tunnels and roadbed slopes.However,the study on the dynamic response characteristics of the bank slope subjected to seismic waves of underwater drilling blasting is obviously inadequate.According to the trait of underwater reef blasting,the bank slope near the explosion area is prone to damage and crack due to the disturbance of underwater blasting excavation.Coupled with the frequent blasting action and long construction period,the dynamic stability of the bank slope is poor after construction process and it is easy to collapse under the influence of reservoir water erosion and rainstorm weather.The study of blasting vibration and multi-factor coupling is of great significance for dynamic stability analysis and revealing the failure mode of bank slope in reef blasting area.Therefore,it is urgent to conduct a detailed study on the vibration response characteristics and stability analysis of the bank slope under the influence of underwater drilling blasting so as to improve the safety control theory and guide the construction of underwater drilling blasting.Focused on the study of seismic wave vibration effect,this paper chose bank slope adjacent to the underwater drilling blasting as the engineering background,and the waterway regulation project of liantuo section between two dams was selected as the engineering object,by means of investigation,theoretical analysis,vibration test and numerical simulation,the dynamic response characteristics and stability evaluation of reservoir bank slope under underwater drilling blasting were studied.Detailed conclusions were listed as follows:(1)Study on the blasting vibration propagation law of reservoir bank slope: on the basis of detailed field investigation and analysis of underwater drilling blasting scheme,the blasting vibration field tests of the bank slope of the library were carried out,and the vibration propagation law of the bank slope under underwater drilling and blasting was obtained.Besides,based on dimensional analysis,the blasting vibration velocity calculation model considering the effect of water depth and elevation was also established.(2)Study on time-frequency energy characteristics of bank slope vibration under underwater drilling blasting: by the methods of wavelet decomposition and reconstruction,adaptive time-frequency analysis,the characteristics and distribution laws of timefrequency energy were studied from characteristic parameters,signal parameter extraction technology,time-frequency energy distribution law and micro-delay identification.The time-frequency energy of blasting vibration is taken as the main characteristic index,and the characteristic parameters of blasting seismic wave are extracted by combining with different time-frequency analysis technology.WT-AOK time-frequency analysis method was used to reveal the time-frequency energy distribution of seismic wave of underwater borehole blasting under different conditions.Finally,CEEDMAN-HHT time-frequency method was used to identify and confirm the delay time of underwater controlled blasting,which provides technical support for the control of harmful effects of blasting vibration on the bank slope of the reservoir.(3)Study of dynamic response mechanism of reservoir bank slope under underwater drilling blasting: According to the construction characteristics of underwater drilling blasting,the blasting process and propagation characteristics are analyzed by ANSYS numerical software.Besides,the critical pitch,slope angle and water depth on the dynamic response of the slope were analyzed by various underwater drilling blasting models under different conditions,the stress,vibration velocity and displacement of pier dynamic response evolution were studied to reveal the dynamic response characteristics of reservoir bank slope,which provides theoretical basis for underwater drilling blasting control technology.(4)Study on stability evaluation of reservoir bank slope under underwater drilling blasting: on the basis of engineering geological survey,the possibility of slope deformation and failure were preliminarily judged.According to the limit equilibrium theory,a quasi-static calculation method was proposed in consideration of the blasting load on the slope stability.Geo Studio numerical simulation software was used to analyze the stability of the bank slope under blasting vibration with stability coefficient and permanent displacement as evaluation indexes.The simulation results displayed that the minimum value of stability coefficient reached 1.095 and the permanent displacement was 2.13 cm when combined Newmark method,so it was concluded that the danger degree of blasting vibration induced landslide was medium.However,when considering the blasting vibration load coupled with rainfall infiltration,the stability coefficient was0.989 and the permanent displacement was 6.7 cm,therefore,the landslide was evaluated as high risk,and the slope was in an extremely unstable state after construction.In the natural state,the failure mode of the bank slope presents slow collapse type,and under the synergistic effects of rainstorm and blasting vibration,the slope destruction process is evidently accelerated.Combined with Zolotalev diagram method,The bank slope collapse will not directly cause the failure of S334 highway,but the deformation of the outer shoulder of the highway will certainly affect the safety and stability of the highway and the engineering effect of dredging area.(5)Study on stability criterion of reservoir bank slope under underwater borehole blasting: the influences of factors on the stability criteria were summarized from the geological conditions,characteristics of the bank slope,explosion source feature and construction and blasting environment,and the particle peak vibration velocity and stability coefficient were selected as the main criteria for the stability of the bank slope.Then,a dynamic stability evaluation method based on stability coefficient and permanent displacement method was proposed for the bank slope.Based on the numerical simulation results of dynamic response,the statistical relationship between the peak tensile stress and the composite peak vibration velocity was established.Finally,according to the bank slope vibration test and time-frequency energy distribution characteristics,the concept of importance correction coefficient was introduced,and the safety criterion of vibration velocity of bank slope under underwater drilling blasting was put forward comprehensively combined with the existing blasting safety regulations. |
PDF Full Text Request