8N-20 represents the formula for lightweight dynamic probing, with the standard substitute formula being R = (0.8 × N - 2) × 9.8 (where R is the allowable bearing capacity of the foundation in kPa, and N is the number of blows with the lightweight probe). Dynamic probing is classified into three types: lightweight, heavy-duty, and super-heavy duty. Currently, contractors generally use lightweight and heavy-duty probes. Lightweight probing equipment is suitable for sandy soil, silt, and clayey soil foundation testing ( ordinarily requiring soil to contain no crushed or cobble stones). It is portable, simple to operate, and requires less manpower, as it involves recording the number of blows for every 30 cm of penetration. Heavy-duty probing equipment is suitable for all types of soil and is the most widely used method by contractors for testing soil bearing capacity. This method employs a 63.5 kg center-hammer with a 76 cm drop height to drive the probe into the soil, with the number of blows recorded for every 10 cm of penetration. The substitute formula for heavy-duty probing is y = 35.96x + 23.8 (where y is the allowable bearing capacity of the foundation in kPa, and x is the number of blows with the heavy-duty probe).