What is the engineering significance of major discontinuity system in Nepal Himalaya and mention the different types of engineering problems in siwaliks. [2073 Magh] [3]

Engineering Significances of Discontinuities:

• The thrust zones are weak, porous, unstable and incompetent and hence most undesirable geological features that endanger the stability of engineering structures and also creates leakage problems.
• an active thrust occurring close to an engineering sites is vulnerable to earthquake and as such sites should be avoided from construction of any heavy strucyures.
•  Thrust influences the movement of surface water , also causes  the sudden change in the courses of rivers may be due to thrusting.
• These thrust zones are prone to landslides, rockfalls, debris flows, earth flows, mudflows etc.

Talking about the geological hazards of siwaliks, since this zone has noticeable releif change and steep, there is possibility of landslides and slope failures. Lower siwaliks is dominantly composed of weak mudstone, which are highly susceptible for weathering and therefore erosi....

Engineering Significances of Discontinuities:

• The thrust zones are weak, porous, unstable and incompetent and hence most undesirable geological features that endanger the stability of engineering structures and also creates leakage problems.
• an active thrust occurring close to an engineering sites is vulnerable to earthquake and as such sites should be avoided from construction of any heavy strucyures.
•  Thrust influences the movement of surface water , also causes  the sudden change in the courses of rivers may be due to thrusting.
• These thrust zones are prone to landslides, rockfalls, debris flows, earth flows, mudflows etc.

Talking about the geological hazards of siwaliks, since this zone has noticeable releif change and steep, there is possibility of landslides and slope failures. Lower siwaliks is dominantly composed of weak mudstone, which are highly susceptible for weathering and therefore erosion is prominent in this zone. Simalarly, plain failure, wedge failure, and toppling failure are possible in middle siwaliks. Upper siwaliks consists of conglomerates, which after loss of cementing materials by weathering become vulnerable for slope failures and landslides. The streams and rivers can easily corrode these materials very easily ,as a result of which they carry large amount of sediments. Some geological problems of this region are:

• Landslides,
• Slope failure,
• Debris flow,
• Gully erosion,
• River cutting,
• Swamp and badland development in dun valleys,
• Stone extraction has led to creep of whole region.