# A Classification Tree for Modeling Ground Fractures from Subsidence
## 3 Modeling of Ground Cracking
### Tree Structure
\begin{table}
\begin{tabular}{c c c} \hline
**Parameter** & **Definition** & **Units** \\ \hline \multicolumn{3}{c}{Geotechnical inputs} \\ \hline Water content W\% & W\%, also known as natural water content or natural & \\ Water content W\% & moisture content, is the ratio of the weight of water to the & \% \\  & weight of the solids in a mass of soil. & \\ \hline Liquid limit LL & LL is the water content where the soil starts to behave as a & \% \\  & liquid. & \\ \hline Plastic limit PL & PL is the moisture content at which a fine-grained soil & \% \\  & cannot be remolded without cracking. & \% \\ \hline Plasticity index IP & PI is a quantity which is the range of the water content over & \% \\  & which the soil remains in plastic state. & \\ \hline N\({}_{\text{SPT}}\) & It is the number of blows required to penetrate 30 cm depth, \\  & known as the “standard penetration resistance SPT”, used \\  & to estimate some important geotechnical engineering & Number of blows \\  & properties of the soil. & \\ \hline Inclusion & Sufficiently thin semirigid layer & I–V, danger levels—function of \\  & & stiffness, thickness, and depth \\ \hline Superficial filling & Surface layer composed of low-quality fill (garbage, \\  & construction waste) & Meters \\ \hline USCS & The world-accepted geotechnical soil classification. & \\ \hline Cohesion/friction values & Cohesion refers to shear strength under zero normal stress, \\  & or the intercept of a material’s failure envelope with shear \\  & stress axis in the shear stress–normal stress space. \\  & Friction angle is derived from the Mohr–Coulomb failure \\  & criterion, used to describe the friction shear resistance of \\  & soils (together with the normal effective stress). & \\ \hline Soft deposits thickness & Thickness of the soft clay layers; the materials susceptible to \\  & consolidation due to pumping in deep layers are here. & Meters \\ \hline Amplification & It is the amplification factor used to account for site effects, \\  & i.e., how a site condition modifies the rock acceleration & Dimensionless \\  & response spectra. & \\ \hline Soil period & The period is the time interval required for one full cycle of \\  & a wave. It depends on the characteristics of the soil deposits. & Seconds \\ \hline Depth of the basement & Measured from the surface, it refers to the depth at which \\  & the layer considered firm is found. & Meter \\ \hline Slope of the basement & It refers to the slope of the layer considered firm. & Grades \\ \hline  & Anthropic parameters & \\ \hline Housing level & It refers to the classification of houses, including their & Number of floors, from one to five \\  & weight (related to build height) and structure solution & and, the structuration as \\  & (included foundation and superstructure). & precarious, barely, and complete. \\ \hline Size of the streets & It refers to the traffic load that goes from a minimum local & Number of lanes. \\  & flow to very heavy load motor transport circulation. & \\ \hline Pumping wells & It is expressed as the distance between the closest & X and Y, meters \\  & pumping-well(s) and the studied site. & \\ \hline Groundwater level & Referred to as the water table, this represents the top of the & \\  & saturated zone; above the water table lies the unsaturated & Meters \\  & zone. & \\ \hline \end{tabular}
\end{table} 
Table 1: Input parameters description. Beyond its predictive power, this tree uncovers parametric relationships of paramount importance. The first partitioning of the data, the purest subset, is based on the characteristics (stiffness, thickness, and depth) of a stratum called inclusion. This clayey-sand layer is minor (its thickness varies between 50 and 400 cm) and ranges from a compact and fragile material to a soft, ductile soil mass. The depth of this stratum increases as it moves away from the steep gradient of the bedrock (underlying the clay layers), practically vanishing when the slope approaches zero (Figure 10).