Development and Operation of an IT-based Efficient Cut Slope Management System to Reduce Damages on Road Cut Slope

Development and Operation of an IT-based Efficient Cut Slope Management System to Reduce Damages on Road Cut Slope

Koo, Ho-Bon?1), Rhee, Jong-Hyun?2), Yoo, Ki-Jeong?2), Kim, Jin-Hwan?2)

*1) Researcher Fellow, Geotechnical Engineering Research Department, Korea Institute of Construction Technology,
[email protected]
*2) Researcher, Geotechnical Engineering Research Department, Korea Institute of Construction Technology

Abstract

Even though the country of the Republic of Korea needed to expand of national road system, they had to be concerned about the road facility itself because of the hasty opening, underdeveloped economic situation and poor technology, so the stability of cut slopes that break the natural parallel condition of the mountain district couldn't have interest. In the past, risky cut slopes have been dealt after they've been collapsed through post-management measures, KICT (Korea Institute of Construction Technology) and the government MOCT (Ministry of Construction and Transportation) have developed and operated CSMS (Cut slope management system) project in order to maintain the stability of cut slopes nationwide since Dec. of 1997.
The cut slopes scattered nationwide have been inventoried through CSMS project, from which they classified the risk grade into 5 grades, arranged investigation priority orders and have investigated them from high to low grade slopes year by year. With these data, they determine the optimized counter-measurement by analyzing stabilization of such characteristics. The data obtained from a series of processes have been data-based using GIS (Geographic Information System) with which investment priority order of each year is suggested by CSMS and types of information required for road construction design are provided accordingly.
Recently, RTMS (Real Time Monitoring System) combining civil engineering and IT (information technology) was constructed, monitoring risky cut slopes and a method to remotely monitor them at office or by mobile communication was also developed. Furthermore, a disaster-preventive PWS (Previous Warning System) combining CSMS and RTMS is being worked to prevent any safety accident beforehand by giving a notice to the public using road as soon as any risk indication of cut slopes is detected. As part of this PWS construction project, rockfall hazard lights have been installed and operated around several cut slopes in 2004 to review the applicability and effectiveness.

Key words: Cut slope management system, investigation priority order, investment priority order, Real Time Monitoring System


1. Introduction

The country(Korea, Republic) needed to expand road system nationwide in order to reconstruct and develop the national economy in 60's and 70's, during which a number of cut slopes had been created due to the topographical conditions that 70% and more territory is covered with mountainous districts. Since 1960's, when the nation's industrialization started, they had to be concerned about the road facility itself because of the hasty opening, underdeveloped economic situation and poor technology, so the stability of cut slopes didn't matter at all. Risky cut slopes that have been created then are still lay here and there and threatening us every year. Years ago, cut slopes have been dealt after they've been collapsed through post-management measures but recently, the government changed the direction and worked for the prevention of any potential collapses in order to protect people's lives and properties, cutting off any possibility beforehand. As part of it, KICT has developed and operated CSMS project in order to maintain the stability of cut slopes nationwide since Dec. of 1997.
CSMS is to take preventive actions against disasters by grasping any risky cut slopes in advance, not like the existing countermeasures, which have been normally taken after the collapses. Meanwhile, the cut slope monitoring system has been recently developed to take any measures against unexpected collapse by detecting ground movements using unmanned real time monitoring in advance.

2. Development and Operation Status of CSMS

Since 1998, the nation's road administration, KICT and MOCT have established a series of maintenance system from executing the on-the-spot survey, stability interpretation and determination of preventive construction methods for cut slopes, which were distributed around the national road of 12,477km in order to prevent them from being collapsed and maintain them efficiently and then, the established measures for any risky cut slopes constructed before have been followed chronologically.
The cut slopes scattered nationwide have been inventoried through CSMS project, from which they classified the risk grade into 5 grades, arranged investigation priority orders and have investigated them from high to low grade slopes year by year. With these data, they determine the optimized counter-measurement by analyzing stabilization of such characteristics. The data obtained from a series of processes have been data-based using GIS so that site information and properties information of individual cut slopes can be seen at a glance, with which investment priority order of each year is suggested by CSMS and types of information required for road construction design are provided accordingly.
From December, 1997 to March, 2004, a study for the in-site survey, stability interpretation and determination of preventive construction methods for cut slopes has been worked to implement CSMS. In addition, with the continuous on-the-spot surveys, we've databased the survey results about these cut slopes around the national road and developed investigation priority order technique and investment priority order technique(see Figure 1).

Figure 1. Flowchart of CSMS

2.1 On-the-spot Survey, Stability Interpretation and Preventive Measures for Cut Slopes

In-site survey for cut slopes to be investigated by a team consisting of cut-slope experts provides the data necessary for establishing stability interpretation and preventive construction methods, aiming at preventing any disasters resulting from the collapse in advance. For the survey, they investigated direct or indirect factors having an influence on the stability.
The stability interpretation is executed by entering the soil parameters obtained from the indoor test and in-site examination into a commercial program for interpreting slope stability. Depending on elements and dynamic movement characteristics, cut slopes can be divided into rock cut slope, earth cut slope and compound cut slope mixed with both. Figure 2 shows the explanatory diagram of the stability interpretation classified by the elements of cut slopes.
The preventive construction methods are primarily selected, based on the applicability to the situations of possible collapse and expected impact from a collapse, which are resulted from the previous in-site survey and stability interpretation while a construction method, which is most suitable for individual cut slopes considering expected damages from collapse, construction availability and economic efficiency is selected accordingly. The construction methods for cut slopes can be roughly divided into protective construction method and reinforcement construction method. The former one is to prevent the safety rate of cut slope from being reduced due to rainwater and weathering although a cut slope is secured by the reference safety rate while the latter is collectively called construction methods to secure and maintain the reference safety rate by increasing resistance against any movements of a cut slope or diminishing activity of it.

Figure 2. Explanatory diagram of the stability interpretation classified by the elements of cut slope

2.2 Techniques of Investigation Priority Order and Investment Priority Order

In the determination of investigation priority order, after executing the field investigation for cut slopes all around the nation, the data is databased. Selecting collapse factors from case analysis of the past cut slope collapse and determining similar survey checklist by overseas countries, the checklist that may be filled even by non-experts is prepared and the weights of each factors listed are given to determine the investigation priority order.
In the investment priority order technique for cut slopes, which is important to execute CSMS efficiently, the priority order to invest the national budget is determined by considering the degree of relative risk and the spreading degree from unexpected collapse. In short, the investment priority order is determined by using risks to be accompanied with expense and the possibility of collapse.
Figure 3 shows the flow of the above-stated procedures.

Figure 3. Schematic view of CSMS
2.3 Classification of Maintenance Degrees

In case of cut slopes between 1996~1999, about 50 collapses occurred annually but since 2000 when 'CSMS' study-related construction methods for prevention that started from December 1997, were applied, it reduced to 25 sites, showing 50% down than before(see Table 1). However, the typhoon, Rusa(76 mm/hr, 897.6 mm /daymax.) with a record-breaking rainfall caused plenty of cut slope collapses and the typhoon, Maemi in 2003 locally damaged the territory, consequently increasing the cut slope collapse, so the necessity to have the classification of cut slopes depending on degrees gains the force in order to deal with unusual rainfall from the recent unusual change in the weather. Therefore, considering extraordinary rainfall due to unusual change in the weather such as sudden torrential rainfalls, the determination of priority investigation was introduced to turn out the characteristics of collapse of the domestic cut slopes and take countermeasures, executing the classification. The causes of collapse was obtained by analyzing the characteristics of collapse for the collapsed cut slopes for the past 5 years(1998~2002) and the maintenance degrees by classification were determined, maximizing the efficiency of cut slope management.
The establishment of the criteria for risk and the standard of risk degrees(5 classes; A, B, C, D and E) have been classified into 5, considering any duplication of collapse causes by sites with cut slopes.

Table 1. Rockfalls and landslides occurred around the Nat'l road for the last 8 yrs

Year
Damage 1996 1997 1998 1999 2000 2001 2002 2003 Total
No. of Sites 43 59 87 50 29 22 81 52 423
Damaged Properties 5 vehicles None 3 vehicles 115 vehicles 4 vehicles 2 vehicles 21 vehicles 3 vehicles 49 vehicles
Casualties 1 slightly injured person
1 victim None None 2 slightly injured
1 victim 1 slightly injured n 1 seriously injured
1 victim 5 slightly injured
3 victims 3 slightly injured 12 slightly injured
1 seriously injured
6 victims
Note - - - - - - Typhoon Rusa Typhoon Maemi -

3. Cut Slope Database System

The database system systematically constructed through the CSMS study allows them to see geographical information and properties of risky cut slopes nationwide using GIS Information System)(see Figure 4). The cut slope database system consists of the database with kinds of spatial information and properties and the unique interface program to link them to users. The database is also subdivided into the map database group related to GIS numerical map, which is used basically in the database, and the database group of cut slopes related with various characteristics of cut slopes gained from the steps of the current status investigation and the in-site survey. In addition, to prevent the construction of such a system being stopped as a trial, it was structured to be easy for input/output and compatible with data formats besides its analytic function and also intended to analyze accumulative data and to prepare countermeasures as well as investigate the slopes by the risk degree analysis and determine the investment priority order.

Figure 4. CSMS Database

4. Development and Operation of RTMS

Recently, RTMS combining civil engineering and IT was installed on risky cut slopes to monitor them at office or by mobile communication. As such, the state-of-the-art technology is also developed to prevent any disasters around the sites monitored(see Figure 5). RTMS is installed and operated on 34 sites with cut slope(4 in 2002, 15 in 2003 and 15 in 2004) and it is planned that more 100 sites where cut slopes that may be difficult to secure permanent stability have been found will have the system until 2009. In the meantime, with the operation of RTMS, the positive effects such as saving the national budges, immediate measures for any damages on persons or properties and collection of huge data about the movement characteristics of found cut slopes in the territory are shown to the public. It is expected that utilizing RTMS will devote to the credibility of the disaster prevention for taking advanced measures against disasters as the system is grafted to the road industry with the image as the developed IT country. A site to install RTMS is selected by the following conditions and operated.

- Large cut slope(higher than 30 m)and upper natural slope of which degree is 30 and more, in case any preventive construction method requires plenty of expenses, preventive area of cultural assets and environment-protective area, natural cut slope to be hardly investigated, and in case any preventive construction method is limited due to conditions of a cut slope.

Connected with RTMS, it is also studied on rockfall hazard light, one of transportation interruption system by early warning through automatic or remote control in case of any movement or collapse. The light system is functionally used to give a warning sign to users of a risky road in case any risk sign is detected from a cut slope and to automatically cut off use of a road for transportation until any authorized officer checks the situation at the site, primarily preventing any accident. In addition, it will help KICT and NRCO (National Road Control Office) establish their roles and is expected to contribute to the extension and development of RTMS. Figure 6 shows the schematic diagram of cut slope rockfall hazard lights installation.
Out of sites where RTMS are installed, 2 sites with cut slope, in which movements are frequently monitored and daily traffic is heavy enough and which are selected by the standards, is with rockfall light system and Figure 7 shows the view.

Figure 5. Schematic Diagram of Real-time Cut Slope Monitoring System and Monitor Installation

Figure 6. Schematic Diagram of Cut Slope Rockfall Hazard Lights Installation

Figure 7. View of Rockfall Hazard Lights installed and operated

5. Conclusion and Plans for the Future

The study was intended to construct the aggressive disaster prevention system by grasping any risky cut slopes in advance, unlike the existing negative disaster prevention method, in which countermeasures are taken after a collapse of cut slope. It was planned to prevent any disasters from cut slopes by establishing the maintenance class, especially for unexpected torrential rainfall in 2003 and executing the sites with cut slopes, which have been classified as risky cut slope annually.
CSMS is being reviewed in various ways for its technology, efficiency and applicability and the direction to develop the management system in the future can be summarized as follows. Further studies on suggestion of standards of indoor tests for RTMS installation and its warning system installation will be executed. Especially, the previous warning system aims at preventing any safety accidents in advance in case any risky indication is detected at cut slopes by giving a signal to users of a road for transportation and in 2004, its applicability and efficiency will be reviewed by installing rockfall hazard lights as a previous waning system. Meanwhile, it is to be constructed the integrated management system for any risky cut slopes by video-monitoring, which consists of rockfall hazard lights, RTMS and web camera.

References

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