The Surrounding Rock Rapid Classification And Geological Advanced Prediction In Construction In Liuhuangqian Expressway Tunnel

In the highway tunnel engineering, the geological data of the design stage is based on the geological surveying, at this stage, Geological survey was mainly geological mapping, attach to the necessary drilling and surface geophysical exploration(for example ,seismic refraction wave to probe)etc. Due to less bore, the range controlled by the bore is little, therefore the express of the larger scope and deep rock lithology and its geological features is not enough. In the geological survey report the engineering geological evaluation, and the judge surrounding rock classification are likely inconsistent with the actual situation. And the geological conditions in underground engineering are vastly different. Because of these the design and construction of the tunnel become greater "blindness" .Therefore it is necessary to make rapid surrounding rock classify timely and to predict the rock classification and the unhealthy geological phenomenon within a certain range before excavating work face, for example, faults, high ground stress and so on.In tunnel construction, rapid surrounding rock classification and advanced geological prediction are not only the basis of the tunnel's support design and construction, but also an essential problem for the evaluation of surrounding rock stability, the shape of section design, the construction methods, support, lining and planning dissipative material. Just because of its so important role, the issue presented and studied on the tunnel and underground engineering construction is of great significance.So far, the domestic and overseas methods of surrounding rockclassification approach to as many as 100 species. And the BQ classification from "Code for design of Road Tunnel" (JTG D70-2004) includes both qualitative and quantitative ways. Because the more factors are involved in BQ classification, it can evaluate surrounding rock stability more completely. Therefore, in Anhui Liuhuangqian Expressway tunnel construction it is more accurate and reliable to use the [BQ] value of the two-step-way to classify in the construction site.This paper's subject is the Banhe tunnel of Liuhuangqian Expressway for the study. Based on the "Code for design of Road Tunnel", the surrounding rock of ZK65+912, ZK65+900, YK65+973, YK65+955 section in Banhe tunnel construction site is classified rapidly. In ZK65+900 section it remains rock-level IV; in the remaining three section rock-level changes from Class IV in former design to the lower level V. Thus, the inaccurate rock classification in the original design is corrected, and accordingly the form of support makes the corresponding optimization and change, from Class IV general to V intensification. Meanwhile, in order to improve the BQ classification test measures the relationship of Rc from two different ways (point load test and springback test) is determined using nonlinear regression analysis, and the relationship curve is fitted out, the curve equation R = 116.17(1 ?e?0.0146R)htdhz .The aim is that the relatively simple and rapid springback test replaces the relatively cumbersome point load test.For comparison and certification with the BQ classification, this paper also uses the gray clustering method to make the surrounding rock classification including ZK65+900,ZK65+912,YK65+973 section in Banhetunnel and YK60+375 section in Wangchaling tunnel. Preliminary results are Class II, III, IV and IV, its corrected results are Class III, IV, V and V. As a result, the two classification results coming from the gray clustering and the BQ classification from "Code for design of Road Tunnel" are the same. Thus, the Fixed weight clustering is applicable and accurate in highway tunnel in rock-level rapid.Besides making the rock classification, we predict the unhealthy geological phenomenon within a certain range before excavating work face ZK64+300 section in Taiyanghe Tunnel and ZK55+485 section in Mozitan I tunnel by using geometric analysis and seismic elastic wave method in order to prevent the geological disasters in tunnel construction process, for example, faults belt, rock property, high ground stress, underground water and so on. The results are as following: 1) There is one near erect fault(inclination 88°) the included angle between the trend of which and the tunnel's axial direction approaches to 20°in the middle of ZK64+300 section of the Taiyanghe tunnel. Through the fault occurrence's analysis this fault will disappear in the place 20m around in the front of excavation work face. And the prediction is that within 20m range(ZK64+300~ZK64+280) the surrounding rock classification is Class V. 2) By the seismic elastic wave method analysis we predict that there is the reflection interface of an anomalous zone in front of ZK55+485 section 15m ( ZK55+500)around in Mozitan Tunnel. 3) In Banhe tunnel the rock-level changes from Class IV to Class V within ZK65+912 ~ZK65+980 range, In Mozitan I tunnel within ZK55+485~ZK55+500 range the rock-level is Class IV. 4) In all the tunnel there is no phenomenon of the high ground stress; 5) Because in Mozitan Itunnel ZK55+485~ ZK55+500 range lies in the tectonic fracture zone in the process of excavation, and the groundwater case is moisture and slightly dripping in working face. Therefore, it is possible to appear water burst and water inrush in this range. Suggested to beat advanced exploring water hole before excavation and do intuitionistic forecast to prevent disaster occurrence.