The total lateral pressure ($P_{\text{total}}$) exerted on the basement wall at a specific depth is the sum of the lateral pressure contributed by the soil skeleton (effective stress) and the hydrostatic pressure contributed by the water (pore water pressure).

1. Identify Given Parameters and Required Depth

• Required Depth ($Z$): $2.0 \text{ m}$ below Ground Level (GL).
• Soil Water Level (WL): $1.0 \text{ m}$ below GL.
• Lateral Soil Pressure Gradient (due to effective stress, $G_{\text{soil}}$): $4.5 \text{ kN/m}^2$ per metre of depth ($4.5 \text{ kPa/m}$).
• Hydrostatic Water Pressure Gradient ($G_w$): $9.8 \text{ kN/m}^2$ per metre of depth ($9.8 \text{ kPa/m}$).

2. Analyze Soil and Water Pressure Contributions

The total lateral pressure $P_{\text{total}}(Z)$ is:

$$P_{\text{total}}(Z) = P_{\text{soil}}(Z) + P_{\text{water}}(Z)$$

A. Lateral Soil Pressure ($P_{\text{soil}}$)

The lateral soil pressure due to effective stress increases linearly with depth $Z$. Note that the given $G_{\text{soil}}$ already incorporates the lateral earth pressure coefficient ($K_a$ or $K_0$).

$$P_{\text{soil}}(Z) = G_{\text{soil}} \cdot Z$$

At $Z = 2.0 \text{ m}$:

$$P_{\text{soil}}(2.0) = 4.5 \frac{\text{kN/m}^2}{\text{m}} \cdot 2.0 \text{ m} = 9.0 \text{ kN/m}^2$$

B. Hydrostatic Water Pressure ($P_{\text{water}}$)

Water pressure acts only below the sub-soil water level ($Z_{\text{WL}} = 1.0 \text{ m}$).

Depth below WL at $Z = 2.0 \text{ m}$ is: $h_w = Z - Z_{\text{WL}}$.

$$h_w = 2.0 \text{ m} - 1.0 \text{ m} = 1.0 \text{ m}$$

The hydrostatic pressure of water is:

$$P_{\text{water}}(2.0) = G_w \cdot h_w$$ $$P_{\text{water}}(2.0) = 9.8 \frac{\text{kN/m}^2}{\text{m}} \cdot 1.0 \text{ m} = 9.8 \text{ kN/m}^2$$

3. Calculate Total Lateral Pressure

The total lateral pressure at $2.0 \text{ m}$ depth is the sum of the soil and water contributions:

$$P_{\text{total}}(2.0) = P_{\text{soil}}(2.0) + P_{\text{water}}(2.0)$$ $$P_{\text{total}}(2.0) = 9.0 \text{ kN/m}^2 + 9.8 \text{ kN/m}^2$$ $$P_{\text{total}}(2.0) = 18.8 \text{ kN/m}^2$$

4. Final Formatting

Rounding off to one decimal place:

$$P_{\text{total}} = 18.8 \text{ kN/m}^2$$

This result is at the upper limit of the constraint range [14.3, 18.8].