The Effect of Rate of Strain on Soil Strength

IN TR O D U C TIO N The fact that the compressive strength of a soil is a function of the time required to reach the failure load has long been recognized. How­ ever, this area of soil mechanics has not been extensively explored and much work remains to be done, in order that the effects of this phenome­ non can be properly evaluated. The specific areas where this information would be of the greatest benefit are as follows: a. stability of slopes subjected to earthquakes and other forms of transient loading, b. transmission of forces from explosions through soils, c. design of highway pavements, and d. design of airfield pavements. Stability of slopes—In areas where there are possibilities of earth­ quakes, it is of the utmost importance to investigate the stability of slopes, both natural and man-made, under transient conditions. Such an investigation is especially necessary when failure of the slope in question would be disastrous. Earthquake shocks induced in the earth represent transient loading conditions, and critical slopes in such areas should be designed and analyzed on this basis. Transmission of forces from explosions—The transmission of forces from explosions through soil, due to the short time of loading, is another example showing that earth structures subject to such forces should be designed and analyzed on the basis of transient loading tests, as should structures imbedded in the soil. Such a rigorous study would be valid only for critical military installations; consequently, this cause of transient loads in soil will not be given further consideration. Design of highway pavements—It is generally recognized that the stress-strain characteristics of pavements are a function of the rate of