Cyi

Average pressure head at base of soil column: ha = — = 0.95 m "

Average hydraulic gradient through soil column: ik = — = 0.158

Static pore pressure at wall toe: u0 = yw x d = 58.9 kPa Excess pore pressure at wall toe: au = yw x ha = 9.3 kPa Total pore pressure at wall toe: u = u0 + au = 68.2 kPa Total vertical stress at wall toe: ov = ykx d = 102 kPa Effective vertical stress at wall toe: c'v = av - u0 = 43.1 kPa d kN

Self-weight of soil column is: Wk = ykx d x — = 306-

I \ d kN Submerged weight of soil column: W'k = (yk - yw) x d x — = 129.4-

Characteristic seepage force: Sk = Yw x ikx d x — = 28-

Effects of actions

Partial factors on destabilizing permanent and variable actions are yG dst = 1.35 and yq dst = 1.5 and on stabilizing permanent actions yG,stb = 09

Verification of stability against piping using seepage force and submerged weight

Design destabilizing seepage force: Ed dst = Yg dstx ^k =

m kN

Design stabilizing weight: Edstb = YGstbx W'k = 116.5-v m

The degree of utilization is:

The design is unacceptable if the degree of utilization is > 100%

Verification of stability against piping using pore pressure and total stress

The degree of utilization is:

Verification of stability against piping using pore pressure and total stress

Alternatively...

Traditional lumped factor of safety

Terzaghi & Peck defined the factor of safety against piping as:

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