Predictive And Early Warning Study On Critical Displacement Of Danbo Upper Deformation Body Of Yalong River

The Danbo deposit is located on the right bank of the Yangfanggou Hydropower Station dam,which is a complex with material composition,structure and complexity.The previous survey showed that the accumulation body will be unstable and destroyed after the water storage,and the design unit will adopt the middle and upper load shedding and the lower anti-slide pile prevention and control engineering measures.During the construction process,due to continuous rainfall,the upper part of the piled body produced obvious macroscopic deformation on July 14,2017.By November 3,2017,the cumulative maximum deformation of the trailing edge of the deformed body reached 2.3m,but the whole body of the deformed body There is no instability.Therefore,based on the research of deformation mechanism,the research on the critical displacement of deformation body has practical significance for construction safety,and has certain theoretical significance for the prediction and warning of similar accumulation deformation in the Yalong River Basin.Based on the geological structure,macroscopic deformation characteristics and monitoring data of the deformed body,the deformation factors and deformation mechanism of the deformed body are analyzed.The deformation mechanism of the deformed body is confirmed by FLAC3 D numerical simulation software,and the geological-mechanical-deformation model is established and predicted.The critical displacement of the upper deformation body of the Dan wave is analyzed.Finally,the deformation body is subjected to early warning grading research and the monitoring scheme is optimized.The main research results are as follows.(1)The denier deposit is a stack of material composition,structure and complexity.The lower part of the deposit is the collapse accumulation area(I area),and the upper part is the ancient landslide accumulation area(II area).The upper deformation body is a partial resurrection of the ancient landslide deposit.The distribution elevation is 2340-2430 m,which is roughly bell-shaped,106 m wide from north to south,145 m from east to west,and about 150,000m3.The underlying bedrock is the Triassic Upper Cretaceous(T3z)gray metamorphic calcareous quartz sandstone with black cloud quartz schist and slate.(2)The deformation characteristics of the deformed body are characterized by the deformation characteristics of the sliding landslide,the trailing edge is a curved pull crack,and the geese-shaped dilatancy cracks are distributed on both sides.According to the geological structure and deformation characteristics of the deformed body,combined with the monitoring data of surface displacement,the deformation mechanism of the deformed body is as follows: the deformed body is inside the ancient landslide accumulation body,and the excavation of the fourth and fifth-level construction access roads at the leading edge must be To the extent,the condition of the leading edge is changed.Under the condition of continuous heavy rainfall,the trailing edge clears the rainwater into the slip zone,which makes the shear strength of the ancient sliding body slip greatly reduced.The anti-sliding force of the edge is less than the sliding force,resulting in the deformation of the upper deformation body.(3)The FLAC3 D software was used to simulate the deformation of the upper deformation body of the denier under natural conditions,excavation conditions and excavation + rainfall conditions.It is found that the deformed body is in a substantially stable state in the natural state.Under the conditions of excavation and upper excavation of the leading edge construction,there is no significant change in the total displacement as a whole.Under excavation + rainfall conditions,the maximum deformation of the deformed body reached 2.3m,and the deformation profile of the "post-large and small" was generally consistent with the actual situation.(4)A geological-mechanical-deformation model suitable for the upper deformation body of the d-wave is established,and the trailing edge monitoring point B2 with the largest deformation is selected as the characteristic point of the deformed body to judge the stability of the whole deformed body.Using the strength reduction method,the B2 monitoring displacement under different reduction factors is obtained,and a function formula satisfying the exponential equation is obtained by summarizing and fitting.Finally,the upper deformation of the super-deformation body is lost when the total displacement of the monitoring point B2 reaches 6.69 m.Steady destruction.(5)With reference to the four-level early warning grading of the "Emergency Response Law of the People’s Republic of China",an early warning grading system suitable for the upper deformation body of the Dan wave was established.According to the existing monitoring measures of the deformed body,monitoring and optimization measures are proposed from four aspects: surface displacement monitoring,deep displacement monitoring and surface crack monitoring,and themonitoring and early warning system of the upper deformation body of the Dan wave is further improved.