Remedies For NH-44 During Landslides— Part 2

Part 1 of the series about understanding landslides in Kashmir elucidated the science behind it. Part 2 will try to suggest remedies to make NH-44 friendly, secure and less inaccessible during landslide hazards

THE occurrence of landslides, particularly at and around the urbanisation sites (e.g. construction areas), and specifically along the track of Jammu and Kashmir National Highway NH-44 is a common concern that has caused severe problems in the past, and it continues. The length of road is just 287-km, therefore, travel should ideally complete only in a few hours. However, since it is curly for most of its length, it often takes more than 6 hours by small cars, and even a longer duration for bigger vehicles to complete the journey.

A typical Kashmiri shudders with pain, agony, and unrest on discovering that one of their dear ones will be using NH-44 to travel to Jammu. It reminds them of past incidents of road blockage, landslide, and unfortunate deaths. Therefore, the highway that reveals some of the most beautiful sceneries in the world has become synonymous with death and destruction.

The travellers and drives are usually filled with stories of sorrow, distress and helplessness, which are partly because the road is narrow, and dangerous. It is cut through mountains, which at various places is prone to various kinds of downslope movements that often cause road blockage and severe problems to travellers. Unfortunately, this makes it one of the most dangerous roads for road related accidents.

During winters the road is usually closed because the snow related incidents force the authorities to either allow one sided transport or restrict/stop the movement. It is then that the entire Kashmir is cut-off from the rest of the globe as it is the only road link that connects Kashmir with the outside world.

Therefore, it is important to map, understand, and work on a remedial planning to make the NH-44 traveller friendly and safe, which could be possible if the road is widened, properly maintained and closely monitored. Below, I am providing a framework that could help in minimizing the downslope movements to a large extent.

Construction of roads

Construction of roads is always a challenge in mountainous regions, and such challenges multiply with time because maintenance is also quite difficult and costly. When roads are constructed in mountainous rough terrains then dynamite is used to break the mountains, which also makes rocks weak by the formation of induced fractures during blasting. These cracks and fractures can become future sites of rock slides downslope, and can potentially damage the road.

This problem becomes severe in regions, which are geologically weak and have structural discontinuities that are exacerbated by blasting. Therefore, special care has to be taken while constructing roads or any other structure that could become unstable because of the imposed stress and new environmental conditions that makes weathering, erosion, and instability of slopes much easier.

Proper slope stability procedures should be adapted. It is achievable if, at least, geologists and engineers work together because it needs expertise of both professions.

Landslide hazard mapping

Landslide hazard mapping is not only important but also a vital step to secure life of roads, buildings, and people. Therefore, proper landslide hazard mapping should be immediately started throughout Jammu and Kashmir, and particularly in regions that are prone to downslope movements, which include the vital NH-44.

People ought to know when to travel and when not, and that should be properly monitored through a dedicated website where all of the information on NH-44 should be made available. It should have all hazards maps where people can easily know more about the science and procedure of landslide movements along the highway. Big road sign boards with information on landslide hazard zones have to be placed along the entire strength of NH-44, which will greatly help people.

Mapping of slope material

It is logical to think that any material which can destabilize the slope can cause down slides. Therefore, the physical and chemical properties of slope material are very important to understand the landslides. For example, solid rocks (like granite) can form stable slopes even at greater slope angles because of their stronger internal strength. However, some stronger rocks can become inherently weak if these are underlain by weaker rocks. For example, if a slope is made up of different layers of rocks, which have different physical and chemical properties, the chances of a landslide will increase. If a weak rock (e.g. mudstone) is sandwiched between hard rock layers (say sandstone), it will make the slope susceptible to failure, because this layer has low shear strength. Similarly, loose unconsolidated sand has no cohesive strength, which can become prone to sliding. Clay minerals are particularly interesting, because their properties directly affect landslides. Some of these minerals can expand when water enters their structure.

For example, such types of clay minerals are smectites or montmorillinites. Once water enters them, it increases their volume because of water absorption. However, when these minerals dry out, which means the water is taken out; it causes contraction. The expansion and contraction can make a rock layer weak and therefore prone to sliding. This kind of behaviour is also quite remarkable in Peat, which is an organic-rich material and is accumulated in the bottoms of swamps as decaying vegetable matter. The soils which contain such materials are called Expansive and Hydrocompacting Soils.

Some soils (called Sensitive Soils) have clay minerals arranged in a random fashion and therefore, there are a number of pore spaces (voids) between the particles, which are usually filled with fluids (this arrangement is referred to as the “House of Cards”). Often the grains are glued together by salts (such as gypsum, calcite or halite). However, when water infiltrates into the soil, it is absorbed on the clay surface and also enters the pore spaces to dissolve the salts, which leads to the complete collapse of the house of cards. If such soil is put through contraction or some sort of disturbance then the structure is rearranged and the spaces are reduced. This can cause the landslide movement, because the shear strength of the material is reduced. Therefore, it is important to map the type of rock and soil in regions that are prone to downslope movements, so that a scientifically robust landslide mapping is achieved, which is definitely missing at the moment. It also requires a proper drainage system so that water is not allowed to weaken the rock or soil, which will facilitate the slope failure.

Furthermore, bedding planes are again another critical aspect, which could cause landslides; because in the geological sense these are the planar layers that are formed during the sediment deposition and compaction processes. It means bedding planes are weak boundaries, and water or fluid can enter along these planes and can enhance downslope movement. Therefore, these are also called the planes of weakness and in rocks these usually record a change in depositional circumstances, which are generally represented by changes in grain size, composition, colour etc.  Similarly, faults, fractures, joins  can cause structural weakness, because along these planes the fluids can penetrate the material and can cause the contraction or expansion, which enhances the weathering and erosion of the material and ultimately it may cause landslides. Also, if these weaker planes are parallel to the sloping surface, the material can easily be taken down the slope under the influence of gravity. Metamorphic rocks are those rocks which are formed due to changes in pressure, temperature, deformation and fluids over a long period of geological time. Generally, due to the intense deformation these rocks form closely spaced layers (called foliation, similar to bedding), along which the material becomes susceptible to failure. These planes are the planes of structural weakness, because fluids can enter through these surfaces and alter the material through physical and chemical processes. Also, if these weaker planes are parallel to the sloping surface, the fluids reduce the shear strength of the material, which can easily be taken down the slope under the influence of gravity.

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Dr Afroz Ahmad Shah

Author is Assistant Professor in Structural Geology, Physical & Geological Sciences at the Universiti Brunei Darussalam. He can be reached at: [email protected]

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