Grillage base is a commonly used foundation system in civil engineering. It is typically used to support columns or walls and consists of a network of beams or slabs that distribute the load from the structure to the soil. When designing a grillage base, several factors need to be considered, including bending, shear, compression, and web crippling. Let's discuss each of these factors in detail.

1. Bending:
Bending refers to the flexural behavior of the grillage base under the applied load. The beams or slabs in the grillage base experience bending moments due to the load from the structure. To ensure the stability and structural integrity of the grillage base, it is essential to check whether the beams or slabs can resist the bending moments without exceeding their allowable stress limits. Therefore, statement 1 is correct.

2. Shear:
Shear refers to the force that acts parallel to the surface of the grillage base. It is important to consider shear forces because they can cause the grillage beams or slabs to fail in shear. Shear failure occurs when the applied shear force exceeds the shear capacity of the grillage base. Therefore, statement 2 is correct.

3. Compression:
Compression refers to the force that acts perpendicular to the surface of the grillage base. It is crucial to check the compressive strength of the grillage base to ensure that it can withstand the applied load without excessive deformation or failure. Compression failure can occur if the applied compressive force exceeds the compressive strength of the grillage base. Therefore, statement 3 is correct.

4. Web Crippling:
Web crippling is a phenomenon that occurs when the web of a beam or slab in the grillage base fails due to excessive deformation or local buckling. It typically happens near the supports or load points where the load is concentrated. To prevent web crippling, the design of the grillage base should consider the web crippling strength of the beams or slabs. Therefore, statement 4 is correct.

In conclusion, all the given statements (1, 2, and 4) are correct. The grillage base should be checked for bending, shear, compression, and web crippling to ensure its stability and structural integrity under the applied loads.