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Nilanjan Bhowmick AIR 3, CSIR NET (Earth Science)
- IIT JAM
- Geology (GG)
How pore pressure decreases the shear strenght? what is upstream diiping bed and downstream dipping ? which is useful.
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Veer vikram singh
if you shift circle towards left then point of contact will have lower shear as well as normal strength wrt previous condition
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Veer vikram singh
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Failure occurs at a point where the mohr envelop (red line passing through origin) touches the Mohr circle. if you shift the circle towards left then point of contact will have low shear strength.
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Veer vikram singh
downstream dipping: Geological horizons or beds whose dip direction aligns with the direction of flow of river. upstream dipping: Geological horizons or beds whose dip direction is opposite to the direction of flow of river. for example suppose a river is flowing from north to south and a rock bed is dipping towards south then the bed will be said to downstream dipping. shear strength = cohesion + normal stress X tan(phi) increasing pore pressure decrease normal strength hence will decrease overall strength of rock
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but sir this figure the Mohr circle radius is constant so shear strength is fix but normal stress is changing
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Sajan sarthak
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Shear strength of spoil material decreases with decrease of cohesive strength while normal stress and angle of internal friction remain same (Chaulya, 1993). This decrease in shear strength reduces stability of dump. Shear strength of spoil material also decreases as the angle of internal friction decreases, which in turn reduces stability of the dump.
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thank you sir
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yes sir 👍
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Rahul kumar Best Answer
Pore pressure decreases the shear strength of rock and leading to the failure of slope. According to Mohr-Coulomb failure criteria: [ Shear strength = cohesion + (normal stress) × tan(angle of friction) ] Pore water pressure reduces the cohesion, which means that frictional forces will decrease. Decrease in the cohesion value will lead to decrease in the shear strength of the material (according to Mohr-Coulomb criterion given above). Upstream dipping bed- Bed dipping opposite to the dominant flow direction (eg. dip direction of foreset beds in antidunes). Downstream dipping bed- Bed dipping towards the dominant flow direction (eg. dip direction of foreset beds in case of dunes). Downstream dipping beds are considered as more useful because it gives the idea about palaeoflow direction of the region.