Rockfall hazard analysis for Na´an-Jerusalem railway

Structure Type: Analysis of slopes
Client: Israel Railways
Following reports of rock fall on railroad track to Jerusalem and the nearby strip during the restoration work on the Na’an – Jerusalem railway, Gash Company was hired to create database of all the slopes along the railway, to evaluate the risk and to suggest proper solutions. So far the first stage of creating slope inventory and preliminary rating was done for all the slopes and also a second stage investigation was done as will discussed in the following paragraph.
The method of rating and the classification system were developed by the Federal Highway Administration (FHWA) and it is published in a manual “Rockfall Hazard Rating System – Participant’s Manual” (RHRS).

In addition detailed rating and cost estimation was done for a specific slope that was evaluated on the first hand as the most dangerous.
Gash Company is the only office in Israel that learned the subject, purchased designated software such as “Rockfall”, and acquired experience investigating and rating slopes up to the day of writing these words.

Slope Inventory and Preliminary Rating
Engineers of Gash Company gathered information by inspecting the slopes along the railway accompanied with experienced geologist that knows the area well. The slope inventory is categorized to a preliminary rating in order to estimate the potential for rock fall on railway Na’an – Jerusalem. The inventory includes a preliminary rating to three broad manageably sized categories: “A”, “B” and “C” as seen in the next table.

Usually the amount of slopes is large and the time and money that need to be invested in order to take care of it all is too big. The purpose of the preliminary rating is to group the slope sections inspected during the slope inventory and to define a list of priorities for evaluation and eventually also for taking care of.
As part of the preliminary rating that was done for Israel Railways, all of the slope sections that were suspected to be of criteria “B” were also further investigated by using “Rockfall” software in order to confirm the criteria definition and to “feel” the slope behavior.
No sections got the highest rating “A”.

Detailed Rating and Cost Estimation
Detailed rating and cost estimation was done for a specific slope section that was defined in the first place as one of the most dangerous to rock fall activity. As part of this analysis Gash engineers examined different paths of fall for rocks along the slope, and carried out computerized analysis with two different designated programs. In addition different possible solutions were examined including warning systems, active and passive reducing risk systems and other different solutions for preventing the risk of rock fall such as constructing a tunnel or change of railway path.

All of the solutions were examined with cost estimation in order to have an intelligent decision of the best solution.