Genetic Research On Deep Water Conducting Fracture Zone In The Dam Of Songta Hydropower In Tibet

The proposed study area is located Songta Nujiang hydropower dam,dam area experienced complex magmatic activities,volcanic activity and multi period tectonic action,the slope rock mass developed the normal structural plane,at the same time,the deep slope developed water conducting fracture zone,the rupture zone makes the slope rock mass structure more complicated.There is an important theoretical and practical significance to in-depth study and clarify the formation mechanism of the deep water conducting fracture.This paper started from the geological background of dam area,detailed analyzed the features of the lithology,geological structure,ground stress conditions and valley development history.Based,combined with field investigation of flat tunnel data and sketch,expounds the mechanics conditions of slope rock,stress characteristics of rock slope;and on the deep slope water conducting fracture phenomena were described in detail,analysis of microscopic characteristics of the rupture and deformation,obtained rock slope deep water conducting fracture of the formation mechanism of the qualitative analysis,combined with the measured stress data,three-dimensional numerical simulation of the cutting process is carried out under the valley,study guide slope deep water formation and evolution rupture.The specific research contents and results are as follows:(1)Through the dam adits on-site survey,deformation rupture phenomenon of field sketching,and comprehensive mapping deformation and fracture analysis of the phenomenon,we get rock mass unloading characteristics and slow crack development characteristics typical of the slope and shape of fission in slow breakdown phenomenon,through the analysis of the deformation and fracture,we known these stars slope supergene alteration range.Combined the relations of the dam dykes and fault dislocation,and field measurement direction of stress,we can conclude that the role of the dam area to get through three tectonic stress field: NE stress field → NWW stress field → NNW-SN stress field.(2)Characteristics of water conducting fractured slope supergene alteration within the scope of geological classification obtained: Fault relaxation hydraulic conductivity type,dikes relaxation hydraulic conductivity type,steeply dipping fracture hydraulic conductivity type relaxation and slow crack in hydraulic conductivity type.These guide water main ruptured water is characterized by soaking,dripping water and strand state,and the water flowing fractured right bank of the left bank more than the development.Its main causes are rock by regional and vertical and lateral unloading slope stress field adjustment formed by the action,and since the Nujiang valley intermittent fast cut,slope stress migration adjustment,with the original dam interaction veins,faults and other weak structure plane formation.(3)For slope supergene alteration range in the water flowing fractured,which is characterized by having a horizontal depth of large and small vertical depth from the riverbed,and no major structural weakness in the face near the range,you can not use the normal unloading theoretical explanation.We know that in the valley cut concave bank formation process,under constant NNW-SN compressive stress field,the concave bank will stress differentiation and concentration,increased parallel slope σ1,σ3 vertical slope decreases,generating slope parallel to the tensile fracture,which is the main cause of the right bank of SN conducting water rupture.Left Bank NEE conducting water ruptured strike(N65 ° E ～ N75 ° E)and present tectonic stress dam principal stress direction(NNW ～ SN direction)almost vertical,apparently the main compressive stress to the NNW-SN tensile fracture is difficult to form cracks NEE direction,and therefore it should be considered early in the tectonic stress field related.(4)Numerical simulations show that the left bank NEE condcuting water and right bank SN conducting water are broken beyond superficial portion of the plastic zone model,which proves that the two are not due to the slope supergene role in the formation.Meanwhile,on the right bank SN conducting water break in each of the tectonic stress field views,while having plastic changes,but significant changes in the SN to the plastic under the tectonic stress field of times greater than the rest,the same way the left bank of NEE conducting water break though in the period there are also changes in stress field at times,but its plastic zone SN tectonic stress <NE <NWW tectonic stress the role of the tectonic stress.Finally,each monitoring point displacement monitoring,found that positive displacement hydraulic conductivity formed on both sides of the rupture zone difference,indicating that there had extensional deformation,numerical simulation better verify the previously inferred.