In stone classification, what is the requirement for the mixture of pieces by weight in relation to the midsize indicated as d50?

The requirement for the mixture of pieces by weight in relation to the midsize indicated as d50 specifies that 50% of the stone must be below this midsize. The d50 measurement is a critical component in material classification, as it denotes the size at which half of the particles in a sample are smaller and half are larger. This means that the distribution of stone sizes can impact erosion control effectiveness and overall project performance.

Having 50% of the stones below the d50 ensures that there is a well-balanced mixture, which can enhance the stability and effectiveness of the stone in controlling erosion and sediment. This classification helps in meeting engineering and environmental specifications, making it essential for proper erosion and sediment management practices. The other choices either suggest incorrect percentages or irrelevant material specifications which do not pertain to the key concept of size distribution outlined by d50.