The Significance Of The Tectonic Deformation Features And Its Impact On Stability Of Feifengshan Area, The Northern Section Of Mountain Longmen

In recent years, the earthquakes occur frequently in Mountain Longmen area, especially in Wenchuan in 2008, due to its strength, superficial source and high intensity, the influence spread to more than half of China, resulting in a significant persons and property loss in more than 100,000km2, which is the most damaging earthquake since the founding of New China. In result, it also made an important impact to the regional geology and geological stability of faulting zone in Mountain Longmen area.And Moungtain Feifeng region is in the morthern section of Mountain Longmen faulting zone, is the junction of Yangtze plate, Songpan block and Sabina-Qinling orogenic belt system. It can be divide into 3 third-class structural units from northwest to southeast, those are centeral nappe zone and foreland nappe zone in Mountain Longmen Mountain and Sichuan basin. Influenced by a variety of geological units tectonic activity, the study area at the edge of the active area, and its structure became more complex because of it affected by the force in different directions in multi-stage.Aiming at the problem of the stability of disposal site, this research will provide technical support of disposal stable evaluation and reinforcement, it is important to ensure site security, while the breakthrough of some theoretical reseaches have important reference and guidance for the similar project.Based on the use of technical methods in structural geology and macro-grasp on reseach progress and achievements in Mountain Feifeng and its adjacent areas, the writer have a preliminary understanding of constructed dynamic mechanism through conducted a detailed study about the construction of geometric features, kinematic characteristics, structural combination of features in the area, and then construct the evolutionary history of the study area.The weriter defined the characteristics of tectonic units and stress evolutionary sequences in Mountain Feifeng areas by field geological survey work and analysis of structure data. After the structure outline formed, the Mountain Feifeng also experienced more multi-stage stress, and gradually formed a structure forms now.Based on the systematically summarize the results of previous studies and the field investigation and data analysis, the conclusion of the structural characteristics and evolution in Mountain Feifeng are as follows:The first phase is the X type joints and folds formed, the stress from NW-SE; the second phase is the fault slip properties formed, the main stress from N-S; the third phase is the folds and reversed fault formed, the stress from NE-SW; the fourth phase is jointed dense band formed, the early nature is thrusting, the main stress from E-W; the fifth phase is tensile stress formed, mainly the X joints directed N-S showed the nature of normal faults; the sixth phase is little fault slip properties formed, the main stress from NW-SE.From engineering geological analysis of the actual needs, that the greater impact of the site which are mainly the following groups:1、The steep dip faults in the W-E direction are mostly pressure breccia belts, and the breccia consolidation is hard, welding two sets. There are no activities since epipleistocene from the above dating data of a few mud faults.The calcite veins of 2 stages are filled in joint density belts and there is no sign of quaternary activity.2、The joint density belts in the N-S direction are products of brittle- ductile deformation in the macroscopic observation sites: there is a complex corrugation structure between 2 joints in the belt, and there are some abrasions and calcite stretching lineations in the joint plane. The small faults in the Huitanzi, out of the site, had released tectonic stress of the same direction of the structure in the activity of epipleistocene. The activity of epipleistocene was creep rather than designing due to it was in the mudstone and had a little influence on stability of site.3、Concordant faulted belt or mudding dissection beltThere are some activities in concordant faulted belt or mudding dissection belt, the active points are scattered. It indicated that there were some bedding slidings occurred and had no penetrably large-scale activities since epipleistocene.