Road Cut Stability Climate Sandbox

How fast can a stable road cut become unstable under wetter climate

Time is discrete days. Total simulated days is N. Day index is t and takes values 1, 2, 3, …, N. The vertical marker in the charts is the selected day t.

Rain and climate forcing

N number of days

R̄ baseline mean daily precipitation (mm per day)

Fstorm storm day frequency (0 to 1)

Cstorm storm persistence (0 to 1)

Mext storm intensity multiplier in future

Show baseline vs future in snapshots

Baseline uses Rbase(t). Future uses Rfuture(t) with stronger storms via Mext. All rain is in mm per day. Time axis is days.

Drainage and pore pressure response

d drainage rate (per day)

θ0 initial water content (percent)

θcrit water threshold for positive u (percent)

ku pore pressure gain (kPa per water fraction)

Impaired drainage when very wet Wet weakening of c and φ and loss of suction

d is a simple drainage parameter: each day removes a fraction d of the water content above a minimum. u(t) is a proxy pore pressure that activates once θ(t) exceeds θcrit.

Road cut geometry and shear strength

βcut road cut angle (deg)

αlayer weak layer dip (deg)

H road cut height (m)

zslip depth to slip surface below road surface (m)

γ unit weight (kN per m3)

c̄ cohesion mean (kPa)

sc cohesion sd (kPa)

φ̄ friction mean (deg)

sφ friction sd (deg)

Nmc Monte Carlo runs

Pfcrit failure alert threshold

t day shown

Peak Pf day selects the maximum Pf day of the curve that is shown. First exceed selects the earliest day where Pf(t) is above Pfcrit.

Snapshot legend
Road is the double line at the bottom left. The steep grey face on the right is the road cut. Thin parallel lines are bedding. Thick colored line is the weak layer used for stability. Blue tint increases with u(t). Red tint increases with Pf(t). Line thickness increases as FS approaches 1.

Pressure legend
Black line: lithostatic σv(z) = γrock z
Blue line: hydrostatic uh(z) = γw z
Black dot: u(t) at depth zslip

Risk summary

Equations used
σn = γ zslip cos²(αlayer), τ = γ zslip sin(αlayer) cos(αlayer).
σn prime = max(0, σn − u(t)).
S = c + σn prime tan(φ).
FS(t) = S / τ.
Pf(t) is the fraction of Monte Carlo samples where FS(t) is below 1 using c and φ sampled from means and standard deviations.