In which type of shear failure does the failure surface NOT extend up to the ground surface when a strip footing rests on loose sand or soft clay?

 General shear failure:

The following are the typical characteristics of general shear failure.

(i) It has well defined failure surfaces, reaching up to ground surface
(ii) There is considerable bulging of sheared mass of soil adjacent to the footing
(iii) Failure is accompanied by tilting of the footing
(iv) Failure is sudden, with pronounced peak resistance
(v) The ultimate bearing capacity is well defined

Local shear failure:

• Following are typical characteristics of local shear failure.
• Failure pattern is clearly defined only immediately below the footing
• The failure surfaces do not reach ground surface.
• There is only slight bulging of soil around the footing.
• Failure is not sudden and there is no tilting of footing.
• Failure is defined by large settlements.
• Ultimate bearing capacity is not well defined.

Punching shear failure:

Following the characteristics of punching shear failure:

(i) No failure pattern is observed and the failure surface, which is vertical or slightly inclined, follows the perimeter of the base.
(iii) There is no bulging of soil around the footing.
(iv) There is no tilting of footing.
(v) Failure is characterised in terms of very large settlements.
(vi) The ultimate bearing capacity is not well defined.

Confusion PointsWhy punching shear failure is not correct ? 

In punching shear failure, there is no failure pattern, while in local shear failure, there is failure pattern but it does not reaches the ground surface, also in given question type of foundation is strip footing and in punching shear failure we generally use deep foundation