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<br />e <br /> <br />; <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />e <br /> <br />EM 1110-2-1913 <br />31 Mar 78 <br /> <br />undrained shear strength. The apparatus and procedure for performing <br />this test are described in Appendix D of EM 1110-2-1907 (ref. A-3a(8)). <br />The results from this test may be greatly in error where shells or <br />fibrous organic material are present. Also, test results in fat clays <br />must be corrected using empirical correction factors as given by Bjerrum <br />(ref. A-5a) but these are not always conservative. <br /> <br />2-13. Groundwater and Pore Pressure Observations. Piezometers to <br />observe groundwater fluctuations are rarely installed solely for design <br />purposes but should always be installed in areas of potential under- <br />seepage problems. The use and installation of piezometers are described <br />in EM 1110-2-1908 (ref. A-3a(9)). Permeability tests should always be <br />made after installation of the piezometers; these tests provide informa- <br />tion on foundation permeability and show if piezometers are functioning. <br />Testing and interpretation procedures are described in EM 1110-2-1908 <br />(ref. A-3a(9)). <br /> <br />2-14. Field Pumping Tests. The permeability of pervious foundation <br />materials can often be estimated with sufficient accuracy by using <br />existing correlations with grain-size determination; see TM 5-818-5 <br />(ref. A-2)). However, field pumping tests are the most accurate means <br />of determining permeabilities of stratified in situ deposits. Field <br />pumping tests are expensive and usually justified only at sites of <br />important structures and where extensive pressure relief well installa- <br />tions are planned. The general procedure is to install a well and <br />piezometers at various distances from the well to monitor the resulting <br />drawdown during pumping of the well. Appendix III of TM 5-818-5 <br />(ref. A-2)) gives procedures for performing field pumping tests. <br /> <br />2-11 <br /> <br />J <br />