Show I I PLAN TO PREVENT TO DAMS WASHINGTON March 29 History History I may not repeat itself with wih visitations of such devastating floods as occurred In Dayton Ohio and foods Johnstown a Pa If I enI engineering en en- skill ski can cn fully comprehend hend the I i problem of earth dam da construction Is the object of an designed by A. A T. T of the tle United States bureau of public roads The device has baa for Us its purpose the accurate measurement measurement measure measure- ment merit is of pressures produced by granular I materials while the earth eart dam is being built S bui Heretofore Heretofore the principal obstacle of I obtaining correct measurements S of the earth fills lt has ze been the weighing t Instrument instrument ment itself the itself the Itsel-the the device being bell a disturbing I element In the earth or o ther ter granular substance during the he pressure taking ng d process ce Seemingly e l t the instrument en of f the bureau rea of l IO roads a has surmounted stir sur mounted this difficulty and the observer can can take readings even though the te pressure pressure pre pre- pres pres- sure sue cell Is planted plated feet teet deep in inthe inthe the ground goud MEASURING INSTRUMENT The soil soi pressure measuring Instrument instrument ment consists of an airtight cell cel made mae of cast iron described as having a diameter diameter dam dam- eter in size equal to that of ot a a saucer The top part of the cell cel is 1 linked to the bottom compartment by y an extremely thin brass bras diaphragm Which diaphragm which Is about abut abutas as thick and flexible flexible- as a a a. strip of pa pa- pa- pa per Waterproof covering protects the cell cel from moisture Leading into the cell cel Isa is isa isa a laid small smal an electric air pipe wire through trough which is I also ao For Instance If I. I the pressure prese measurements measurements measure measure- de desired desired de- de ments of a high retaining wall wal are arc sired First attach the Instrument Instent to the tha wall wan before the earth eart fill rl Is placed pled In contact with the wall wal and ad the small smal pipes leading from the coils colls cols are are- laid lid up to the top of the te wall wl After Ater the earth earh fill fillIs fillis fl Is made readings of the pressure pressure- are taken by the use of an box bOL taen The air is allowed to flow very grad gradually eu through the g air pipe o into nto ro i the cell USE IN IN OHIO p Should the air pressure presure within the te cell cel overbalance the soil pressure acting against the outside of the cell cel electric contact is broken within the te cell cel through the movement of ot the diaphragm due to the air pressure This movement In all al cases Is less than one thousandth ten of an Inch and frequently only one hun hun- thousandth of an inch When Ven the electric contact n Is broken the air pres pressure sure In the t pipe Is Instantly 1 observed se lr the results being equal to the soil pressure The Miami conservancy district a a. cooperative cooperative co co- co operative agency empowered to spend vast sums of money in ill in the valhey valley val val- ley hey Ohio to safeguard the area from froma a a. recurrence of floods similar to the foods Dayton Inundation In 1913 11 has Installed these Instruments in five enormous earth dams In the process of construction Monthly readings of the soil pressure measurement devices are being taken with results thus far Indicating Indicting only a a. materials rials In inthe hardening of ot the granular mat I the thio dams clams |