Show ROA MUST BE PROPERLY PREPARED soils which absorb and retain it large of moisture give the most trouble jn n the construction 0 of roods roads these are tile various forms forma of 0 clay and a few of the heavier loams coams they are because they cannot be drained by side ditches 0 or r tile when frozen tile the wet vet soil ex cx panda and lifts the pavement when it dries 9 out it often so materially that wide cracks form setting up tip tensile stresses in the stab slab above which muy may prove disastrous cheo the dried soil again absorbs moisture in 0 it expands lifting tile slab unless laboratory tests testa have located the rood good and bad soils in n the project the inspector must depend upon personal observation alone ask those who live along the rond where the worst spots appear each cpr spring in accompany tile the roller and note filly any spongy places keep your eyes open for seepage water hog bog holes or short deep spongy spots pots are usually caused by a pocket in fit an impervious underlying s stratum t ra t u in water from sonic some higher point la Is caught in tills this pocket and then absorbed sort by the lie earth above there are several methodi of rein edding bog holes if not too deep they may be drained Irn ined by cutting through the impervious stratum and laying tile to tile the bottom of the po elret when the bog hole Is formed by it a rock pocket it will probably be necessary ian to intercept tile the seepage water before it roaches reaches tile the rond road or to remove the spongy material and replace it with cinders sand gravel or crushed stone if tile lie spongy soil soft extends for sonic some distance along the roadway its removal would be too expensive if the other suggested courses seem Imp impracticable and it Is impossible or inadvisable Inn dvis to relocate the lie road the plastic material can be greatly improved by harrowing sand into it until n 6 inch crust Is formed tills this crust should be 8 B 10 to 0 9 10 sand sometimes a I 1 inch sand cushion la Is placed under tinder tile the slab with such treatment there Is little danger that tile the pavement will bo be duni damaged aged hydraulic time lime or light road oil it harrowed into the soil has proved beneficial in stabilizing adobe and heavy clay the light soil encountered in past bogs will support it ft pavement pil much as water supports a boat and need not be feared jt it will however settle under the lie superimposed load and fit at ill approaches pro aches of should bre be removed moved and replaced with stable soil near the bridge the solidity of if the nil fill should be gradually reduced ns as the distance from the bridge increases so that the change from firm to yielding foundation will not be too abrupt |