Question

Soil collected from the site is found to have ${\gamma }_t=18.5kN/m^3,w\%=8.6\%$, and $G_s=2.67$. After a heavy rainfall overnight, $10\%$ increase in the degree of saturation $S_r$ was observed. Determine:

a. the degree of saturation $S_r$ of the soil before the rainfall

b. the void ratio e of the soil before the rainfall

c. The water content w\% after $10\%$ increase in $S_r$

${}_{\mathrm{d.\; The\; unit\; weight \gamma h">\gamma h\gamma h after 10\%">10\%10\% increase\; in Sr">Sr}}$

Answer 1

Solution

a. the degree of saturation $S_r$ of the soil before the rainfall

b. the void ratio e of the soil before the rainfall

c. The water content w\% after $10\%$ increase in $S_r$

${}_{\mathrm{After\; the\; rainfall, Sr\prime =1.1Sr=1.1\times 0.4272=0.46992\cong 0.47">S\prime r=1.1Sr=1.1\times 0.4272=0.46992\cong 0.47Sr\prime =1.1Sr=1.1\times 0.4272=0.46992\cong 0.47 We\; suppose}}$

${}_{\mathrm{that\; the\; rain\; water\; filled\; only\; the\; air\; space\; in\; soil\; void\; and\; there\; is\; no\; swelling}}$

${}_{\mathrm{or\; volume\; increase\; of\; soil\; so\; the\; void\; ratio\; e\; remains\; constant.}}$

${}_{\mathrm{Then\; we\; apply}}$${}_{\mathrm{the\; relation}}$

${}_{\mathrm{d.\; The\; unit\; weight \gamma h">\gamma h\gamma h after 10\%">10\%10\% increase\; in Sr">Sr}}$

${}_{\mathrm{Sr">}}$