GISdevelopment.net ---> AARS ---> ACRS 1990 ---> Poster Session Q Application of Remote Sensing in the investigation and analysis of activity of Geologic Disasters along Railways Zhuo Baoxi, Cheng Yuzhang, Pan Zhongren, Cao Linying, Li Hongmiao, Li Haimin Shanxi Remote Sensing Centre, Taiyuan, China Professional Design Institute, Ministry of Railway of China Beijing, China Xu Hong, Ma Rongbing Southwestern Jiaotong University, China Abstract Geologists of Chiinese railway departments have done a lot of work using remote sensing technology to prevent and cure railway engineering geologic calamities and achieved a good result and obtained valuable information about railway engineering geologic disaster. This paper describes the necessity of using remote sensing to investigate geologic conditions, along existing railways taking some sections of Long-Hai, BaoCheng and Cheng-Kun railway as examples and explains some methods using remote sensing to investigate and analyse the conditions of geologic disasters such as landslide, clooapse and mud-rock flow with the result we have made. The advantages of using remote sensing in the investigation and analysis are showed convincingly in the paper by means of reliable data and real example of remote sensing image interpretation. Introduction It is well known that the railway traffic is economic main lifeline in our country. But it often happens that railway traffic is held up due to geologic calamities every year, which cause enormous econo2mic losses. During the treatment of railway engineering geologic disaster the first thing is only to clearly investigate the condition of the disasters which may effect railway safety before they can be treated perpectly. Because the railway lines in China are tens of thousand kms long, the traditional method alone obviously can not carry out such investigation. Fourtunately remote sensing technology can provide us a useful means for the purpose indeed. The application of Remote Sensing in the investigation of Landslide and collapse A comparatively good effect can be reached using remote sensing to investigate the conditions of landslides and collapses. Now let’s take the landslides and collapses along the two sections of railway as examples, one is Baoji to Tianshui of Long –Hai railway and the other is Baoji to Lueyang of Bao-Cheng railway to discuss the effect as below. 1. The Practical Method and Effect During the investigation we mainly used 1:10,000-1:25,000 black and white aerial photos taken at various times and in some local regions we also used color infra-red photos. They were the basic image information for the investigation of geologic calamities and the analysis of it’s condition changing, and they were largely used for the analysis of individual disaster sites. In order to study the topographic and geologic macrostructure analysis of disaster area, Landsat MSS images were used and various kinds of images were enhanced using different image processing methods. The Operating procedure of the investigation using remote sensing was the same as the one of conventional investigation. The range of the investigation in which image interpretation was made was 1 km wide 0n each side of the railways and the ground area of the investigation was 2,600 squre kms in total. After remote sensing image interpretation, various kinds of thematic maps and cards of geologic calamity sites were compiled, and therefore the condition of the geologic disaster sites along the two sections of the railway were grasped generally. According to the statistics of image interpretation, 61 landslides and 94 collapses along the railway section from Baoji to Tianshui were found , but only 15 landslides and 54 collapses had been registered by railway engineering departments before that time. 2. The Analysis of Causes and distribution Law of the Geologic Disasters It was fond that landslides and collapses were closely related with lithology. Most of landslides along Baoji to Tianshui railway section occurred in loess area, there were 271 landslides in loess area and they accounted for about 71% of the total landside number in the investigation area. There were 51 landslides in broken metamonphic rock area and they accounted for about 13.5% of the total landside number. There were 54 landsides in weathered granite area and they accounted for 14.3% of the total . It was also found that landside occurred rarely in grevel rock and that only about 0.5% of the total landslides occurred in grevel rock. Most of collapses took place in weathered granite area. There were 102 collapses in weathered granite area and they accounted for about 49.5% of the total, 28 in loess area and about 13.6% of the total. Figure 1 shows the occurence rate of landslide and collapse based on different lithology. Figure 1 Sketch map of the occurrence rate of landslide and collapse related with diffierent lithology 1- Landslides ( or collapse) in loess area 2- Landslide ( or collapse ) in metamorphic rock area 3- Landslides ( or collapse) in gravel rock area 4- Landslides ( or collapse) in granite area We found through the investigation that the development of landslide and collapse and collapse were clearly controlled by the faults structures in the investigation area, and that most of the landslides and collapses in the area between Fenggeling and Boyang happened in recent years. For example, landslide groups in the region of Fenggeling and Putaoyuang were closely related with the main and secondary fault structures of Weihe River, and it could be clearly seen form the remote sensing images. Fig.2 shows the landslides in Putaoyuang region appeared on color infrared aerial photos. They were still unstable althrough they had been treated for a long time. The east landslide marked by arrow ( in white tone on the image) was developing very quickly during the month of September, 1985 and forced the existing railway line to be changed its position. The landslides occurred along the section of Bao-Tian railway were mostly caused by the joint function of surface and ground water, e.g. the landslide in Baijiashan region was closely related to the ground water. the human being activity was another cause of the landslide and collapse, for example the landslide near the place of Tuo Shi and the landslide near the place of Maojiazhuang along the section of Bao-Tian railway were all caused by digging the toes of mountain slope. Figure 2 Putaoyuang Landslides 3. Analysis of Activity of Landslide and Collapse We divided analysis of activity of landslide and collapse into two kinds one for analysis of regional geologic calemity conditions and the other for analysis of individual geologic disaster site conditions. A. The analysis of regional geologic calamity conditions In this case, we interpretated the aerial photos taken at various times, compared with them each other and divided the geologic disasters occurred in the range of 1 km wide on each side of the railway into three groups: stable (I), unstable (II) and new born (III). Then we explained the conditions of the geologic disasters occurred in the region under consideration using the distribution and statatics of the three groups of the geologic disasters. Taking the section of Bao Tian railway as an example, 186 geologic disasters were found using remote sensing image interpretation, of which 76 were stable geologic disasters accounting for 40.9% of the total ones, 101 were unstable accounting for 57.5% and 1.6% of the total ones were new born. In other words. the number of the unstable and new born geologic disasters was larger than stable one in the region. So it could be concluded that h general tendency of the geologic disasters in the region was developing in recent years. B. Analysis of individual geologic disaster site conditions In this case, we analysed the activity conditions of the individual geologic disasters based mainly on the differences of certain of the individual geologic disasters imaged on the aerial photos taken at various times. Table 1 shows the content for comparison of individual geologic disasters using aerial photos of different dated. Table 1 Classification Content stable (I) constantly stable Constantly stable geologic disasters they were all in stable condition showed on photos of different time tend to be stable Geologic disasters which showed active on the previous photos but it showed stable on the photo taken later Unstable (II) Constantly unstable Geologic disasters which showed unstable on the photos of different times tend to be unstable Geologic disasters which shoed stable on the previous photos but showed unstable on the photo taken New borne (III) geologic disasters occured in the period between diffierent time when photos were taken could not be seen on the previous photo but could on later photo After the interpretation about 10 landslides which might threaten the safety of railway traffic in future were found. for example, the appearances of the old landslide near the place of Maojiazhuang, such as sliding wall, intricate sliding steps, fissures in arc-form and slopes in opposite. directions , could be recognized clearly from the aerial photos. SO it was not difficult to conclude that the landslide was in active condition after the comparison of photos taken at different should be stopped immediately, the condition of the landslide should be further determined and that effective measures should be taken to treat the geologic disaster. These proposals were accepted by the departments concerned. And now the landslide is being surveyed and treated. Application of Remote Sensing Technology in the investigation and activity analysis of Mud-Rock Flows along Cheng-Kun Railway Line Since the Shalu section of Cheng-Kun railway was put into operation, mud-rock flows have taken place in the area along the railway frequently. In order to make sure the conditions of the mud-rock flows effectively, remote sensing technology was used. During the work black and white ( 1:15,000—1:50,000) aerial photos of different times and infra-red aerial photos were applied mainly to the interpretation of individual mud-rock flow ditches. Landsat MSS images and TM images were also used mainly for the research of machostructure and developing law of mud-rock flows. Figure 3 Sketch map of the mud-rock flow distribution along the Shalu section of Cheng –Kun railway 1. slight mud-rock flow 2. moderate mud-rock flow 3. serious mud-rock flow Effects of application of remote sensing technology in general investigation and condition research of mud-rock flows: 1. A lot of field work was turned into indoor work, The efficiency and quality of the investigation were raised and the working conditions were improved. The area of investigation along the Shalu section was 3000 square kms. if traditional ground invstigation method had been used, three or four year would have been needed to finish all the work. But as a matter of fact only one year was needed using remote sensing technology and the working efficiency was raised by two to three times. 2. Mud-rock flow ditches were recognized and classified effectively There were about 200 mud-rock flow ditches in total in the area along the Shalu section, of which 78 were recognized using interpretation of remote sensing images and were divided into three classifications: serious, moderate and light (see Table 2). But at the same time and the same area, only 36 of them were recognized using traditional investigation method. Table 2 Classification of mud-rock flows along the Sha-Lu section of Cheng-Kun Railway using remote sensing image interpretation classification harmful degree quantify Serious Moderate slight Unharmful total serious detches 1 9 1 6 17 middle ditches 0 28 7 4 29 light ditches O 3 17 2 22 Total 1 40 25 12 78 3. The interpretation of environmental factors especially the interpretation of cultural features was conducted effectively. All of the environmental factors which may cause mud-rock flows, except the raining in small drainage area, could be interpreted from remote sensing images> Among them the interpretation effect of cultural features was especially satisfactory. The Yanjin ditch was mud-rock flow formed by the waste residue of mining iron in large scale and was clearly recognized from the aerial photos. 4. The effect of activity analysis of mud-rock flow ditches was pretty good According to the interpretation and comparison of 25 mud-rock flow ditches in the area along the She-Lu section appeared on the remote sensing images taken at various times, the inter-pretation effect was thought comparatively good. Taking lizhiyida mud-rock flow ditch as an example, two aerial photos of different dates ( 1965 and 1981) were applied for comparative inter-pretation and good results were obtained ( see Table 3) 5. Remote sensing technology may be an efficient means to build up technical archive of mud-rock flow ditch. Most of the information and data included in the techknical archive of mud-rock flow ditch can be obtained from remote sensing image and they may meet the needs of the technical archive. Especially when the information and data existed in the archive need to be changed or updated it is much easier to collect the new information and data using aerial photos taken at different times than using ground investigation method. Conclusions Remote sensing technology is an advanced, efficient method of geologic survey and can produce clearly economic benefit in the earlier stage to prevent and treat the geologic disasters in the areas along existing railways. References Zhou Baoxi, Ma Rongbing, 1982.” Remote Sensing Principle and Engineering Geological, Interpretation”, Chinese Railway Publish House , pp 151-J172. Pan Zhongren, 1988. “Application of aerial Remote Sensing in Investigation of Mud-rock”, << Remote Sensing in Environment >>, Chinses scientific Publish House, No. 3. Cheng Yuzhang, 1990. “Investigation of Landslide along Bao-Tian Railway and Its Distribution Law,” << Remote Sensing in Environment >>, Chinese Scientific Publish House, No. 3.