Please answer the following as soon as possible please make

Please answer the following as soon as possible. please make clear handwriting so i can read. typing is better. many thanks

1- Consider a site where the groundwater table is at the ground surface. Explain in words (no equations) why the vertical effective stress does not change if the groundwater rises above the ground surface.

2- Convince me why the long-term (i.e. drained) strength is often more critical than the short-term (i.e. undrained) strength for over-consolidated clays?

3- Consider a sample of sand with an initial void ratio equal to critical (ecrit) subjected to a confining pressure less than critical. How would you expect the volume of the sample to change when sheared under drained conditions? How would you expect the pore water pressure of the sample to change when sheared under undrained conditions?

4- Whydoover-consolidatedclaysexhibithigherpeakdrainedstrengthatlowerconfining stress compared to normally consolidated clays? What happens at larger confining stresses?

Solution

As we know that,

Effective vertical stress = Total stress - pore water pressure

As ground water table is at ground level,when water table is rises above ground level as there is no soil, only water is availabe above the ground level that means dansity = 9.81KN/M3 will be used for both total stress calculation and pore water pressure calculation, so we can say the increase in total stress is same as increase in pore water pressure so there will ne no change in Effective vertical stress.

Change in total stress = change in pore water pressure

therefore,Effective vertical stress remains same in this type of condition.