NR NR/CIV/SD/TUM/301 ISSUE P3 PDF

Introduction

This Technical User Manual is aimed at providing advice on the application of netting systems to cuttings using the standard details shown on the Network Rail suite of standard details for earthworks. The netting systems are split into two distinct systems, the high tensile, active netting systems and the passive non-stressed netting systems. The differences between these systems will be made clear within this document.

The standard details and issues addressed in this Technical User Manual relate to “rock” slopes. The term “rock” is used to differentiate between rock and soil slopes to the extent that no advice is given on methods of dealing with soil slope stability although the systems described can be used to deal with slopes containing soil usually in combination with weathered rock. For example, any containment system can be designed to contain soil in the same way as rock and there are many examples where the debris from a rockfall becomes a soil or slurry material when combined with water

Active systems are those which are designed to stabilise slopes so that the rock or soil does not have to move in order for the stabilisation system to generate restraint. Therefore it is expected that, in the case of netting systems, the netting exerts some form of stabilising force onto the slope material. Active systems require detailed investigation and design to ensure that they operate effectively and provide the desired level of reliability. Therefore only limited advice on system selection and details is given in the manual. In addition the active systems are generally constructed using proprietary systems and the advice from the specialist manufacturers or their technical literature should be sought during the design and specification stage

Passive systems are those that allow movement of the rock or soil before the reactive forces are generated by the system. This may involve a system that retains the material (a retention system) or one that allows the soil or rock to fall or slide in a manner that does not endanger the railway or associated infrastructure or personnel. This is referred to as a containment system. Examples of retention systems would be unstressed anchorages or netting placed locally around an isolated block of rock. Examples of containment systems are draped netting over a slope or rock catch fencing or debris barrier at the toe of a slope.

This Technical User Manual and associated Standard Details deal with netting used in two particular applications which are:

•  Active high tensile netting retention systems

•  Passive non-stressed netting containment systems

The active high tensile system described and detailed makes reference to a single proprietary system. This is necessary as it is not possible create generic configurations without reference to some particular system. Alternative systems may be available and, within the limitations described in the following sections, these alternative systems may be adopted with appropriate modifications to the specifications

The passive non-stressed netting systems are more generic and three alternative arrangements are described in this manual. However it has been necessary to refer to a particular netting system in order to develop the details.

Consequently reference to particular manufacturer’s products or specifications should not be construed as advice to preclude the use of alternative systems, which can be relatively easily substituted providing the Scheme Designer accommodates the particular characteristics of the materials into the design and adjusts the specification accordingly