When soil fails in shear, what are the factors that affect soil shear strength?

Soil shear strength is influenced by several factors:

1. Soil Type: Different types of soil have different shear strengths. For example, sandy soils have a higher shear strength than clay soils due to their granular structure.

2. Moisture Content: The amount of water present in the soil can significantly affect its shear strength. As the moisture content increases, the soil becomes more susceptible to shearing.

3. Density: The denser the soil, the higher its shear strength. This is because denser soils have more particles per unit volume, which increases the frictional resistance.

4. Stress History: The previous stress history of the soil can also affect its shear strength. Soils that have been previously compressed tend to have higher shear strength.

5. Temperature: Temperature changes can affect the soil's shear strength. For instance, freezing can increase the shear strength of the soil.

6. Rate of Loading: The rate at which the load is applied to the soil can influence its shear strength. Rapid loading tends to decrease the shear strength.

7. Soil Structure: The arrangement of soil particles and the presence of voids or spaces between them can also influence the soil's shear strength.

8. Organic Matter: The presence of organic matter in the soil can decrease its shear strength. This is because organic matter tends to hold water, which can weaken the soil structure.