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Crib Sheet for use with UniPile and UniSettle
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4. Fit to Loading Test Load-movement Results - kN6. CPTu Soil Charts
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Bengt H. Fellenius, Dr.Tech., P.Eng.
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Ideally, the pile-head load-movement curve measured in a static loading test should turn to a continuing When preparing the input for the soil layering, of course, a soil boring log is indispensable. When the
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Report to UniSoft Ltd., August 5, 2013 (updated August 2016)movement for no increase of load, i.e., a plastic response defining the pile capacity of the test. Or even boring log is combined with the records of a CPTu sounding, the value of the information is greatly enhanced,
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more obvious, the curve should reach a peak value from which the load reduces with further movement. because the CPTu records provide the numerical values that can be used either directly or assist in choosing
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In most actual cases, however, the load movement curve keeps increasing for increasing load. As the the effective stress parameters. Moreover, the CPTu profile helps in detailing the soil layer delineation.
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This workbook contains the following seven template worksheets.foundation design based on the results of the static loading test requires deriving a capacity value from the The 7th sheet is intended to assist with the latter process. It is prepared for input of CPTu data
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test results, several definitions on capacity determined from the load-movement curve have developed.consisting of depth, cone stress, sleeve friction, and U2 pore pressure and it is assumed that the data are
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1. Strength and Density Classificationavailable in a text file and can be clipped and pasted into the template. The SI-units for this input are
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2. UniPhase SI-units and UniPhase English unitsSome persons define the capacity at the applied load when the pile head movement equals 10% of the MPa for the cone stress and kPa for the other three. Thus, if the data are in these units, no conversion is
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3 m and E conversionspile diameter. This definition is not useful other than for very small pile diameters. It originates in anecessary for the processing prepared in the sheet. If the data are in other units, the appropriate
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4. Fit to Loading Test - kNmisquote of Terzaghi's 1942 recommendation that capacity should not be evaluated before the pile toe hasconversions must be added to cells D9 through G9.
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5. Fit to Loading Test - %moved 10% of the pile toe diameter. Because the maximum pile toe movement in most static loading tests
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6. t-z and q-z functionsis usually no more than about 0.25 to 0.5 inch, that is, rarely more than about 15 mm, most of the times,The cone data are plotted in three types of classification charts: the Eslami-Fellenius (1997), the Robertson
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7. CPTu Soil Chartsthe mis-applied quote is not suitable.and Campanella (1986), and the Robertson (1990) charts. The records shown in the sheet template are from an
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 actual cone sounding. However, data from three intermediate depths, where the soil type gradually changed from
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The spreadsheets are protected, but for a few cells, These are not locked because they are intended for user'sThe sheet called Fit to Loading Test - kN, enables a user to input the load movement data from a static one type to the next, have been removed to more clearly show the differences between the soil layers.
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input. The not-protected cells have blue bold text and are shaded in yellow. No passward is used so the User is free toloading test and to fit these data to seven analysis methods: the Chin-Kondner and the Decourt hyperbolic plots,
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unprotect the sheets. The following presents the background to the spreadsheets and explains how to use each sheet.and the Hansen 80-% method, as well as the Ratio, Vander Veen (Exponential), Zhang, and Vijayvergiya methods.It is an enjoyable exercise to compare the soil types determined from a set of cone data plotted in the three
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The first three provides the means for determining a capacity from the fitted curve. The sheet also provides a meansgraphs to each other and to the soil boring descriptions.
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 to determine the Davison Offset Limit, usually a conservative value.
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1. Strength and Density ClassificationThe user can overwrite the input columns (the four left-most columns) with own data and also add rows
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For each fitting method, two or three values are input as indicated by the blue bold, yellow-shaded text. as needed to see the data plotted in the charts and profile diagrams.
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As evidenced in many geotechnical reports and publications, the use of common classifications of The input values determine best fit of the theoretical curve to the test actual curve. The user selects the
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strength and density of soil and rock are often vague and, sometimes, even incorrect. The first input guided by the graphs for each method.The sheet is protected, but all graphs can be adjusted as to scale and format. Moreover, the protection
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spreadsheet is intended for a "look-up" reference to a few primary classifications. Clay and rock are has no password, so the user is free to unprotect and change any and everything. Before doing so
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considered cohesive material and have strength expressed in unit force—stress. Coarse-grained soil The example test data are from an actual test that reached plunging mode failure. For such a test response,however, make a back up of the sheet, so the original template can be restored if need be.
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(sand, gravel, etc.) are not classified by strength, but by density, and, sometimes, by compressibility, the there is little need for evaluating the capacity by any of the methods. However, where no "failure" value
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denser the soil, the less compressible it is (see Section 2).is obvious by eye-balling the load-movement curve, one or other of the methods will be useful.
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2. Compressibility Conversions — m and EThe sheet is protected, but all graphs can be adjusted as to scale and format. Moreover, the protection
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has no password, so the user is free to unprotect and change any and everything. Before doing so
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Characterizing soil compressibility by the Janbu modulus number, although mathematically equal to the however, make a back up of the sheet, so the original template copy can be restored if need be.
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Cc-e0 and E-modulus approaches, is very advantageous because the modulus number characterizes the soil
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compressibility in a single, whole number ranging from the softest, most compressible soil, to the densest, least 5. Fit to Loading Test - %
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compressible soil. In contrast, characterizing compressibility conventionally by the two independent
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parameters Cc and e0 turns the characterization into a difficult juggling act.Sometimes results from a static loading test have been normalized to a perceived "capacity" assigned a
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value of 100 %. The sheet named "Fit to Loading Test - %" is prepared to let the user fit the set of theoretical curves
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The sheet includes a table copied from the Red Book (Fellenius 2012) containing typical and normally conservativeto the actual test data normalized to 100 % of the "perceived "capacity".
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modulus numbers. The numbers are intended for reference only. Below that table is a comparison tables that offers
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direct the conversion to "m" from the "Cc- e0" and vice versa. The additional information consists of excerpts from
Also this sheet is protected, but, again, no password is required to unprotect.
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the Red Book. My web site has a template for calculation of lab test results: "229 Compressibility&ModulusNumber.xls".
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In the back-analysis of data from a test on an instrumented pile, the input for the shaft response, i.e., the shaft
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3. Phase Relations SI-units and English unitsshear along an element of the pile and the pile toe movement are expressed as a t-z and a q-z function,
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respectively. This 6th sheet enables the user to fit six t-z/q-z functions to actual test data and to establish
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Frequently, when pursuing geotechnical calculations, one needs a quick means to determine a soil density which function that is most relevant to measured load movement values. The sheet requires that the user normalizes
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value from knowing the water content, or from knowing the water content and density to determine the the actual data so that the loads are expressed in percent of the value perceived as the relevant ultimate resistance.
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degree of saturation, or from knowing the density to determine the void ratio. The spreadsheet lists the
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phase system relations applicable to the calculations and displays three slightly different ways (I through IV)Note, in using the Chin-Kondner (hyperbolic curve) t-z/q-z functions in UniPile, the assumed "target" resistance
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for doing the phase calculations. The user can choose between either a sheet in SI-units or in English units. is the 100-% value as input for the soil layers. The inverse of the C1-value is the load at ultimate (infinite) movement.
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Each version also shows the values converted to the other system of units. The sheets are a development
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of UniSoft's former UniPhase program.When using the Hansen function in fitting to results of a static loading test, it is often useful to change the input
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ultimate shaft resistance to a value of 125 % of the considered shaft shear and assign it (it becomes the "new"
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The UniSettle and UniPile software require the input of density and void ratio and the sheet simplifies the 100-% value) to occur at a movement four times larger than the movement actually expected for the shaft shear. The
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calculation when one or the other is not directly known, saving the time to look it up.original ultimate shaft shear is 80 % of the boosted shaft shear and it occurs at a quarter of the input movement.
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The "TRUE" or "FALSE" cells show whether the calculated Degree of Saturation, S, is less or more than 100%.
Note, the t-z functions used for simulating theshaft shear response of the individual pile elements are not the same
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Unrealistic input can result a calculated "S" larger than 100 %, which is an unrealistic state.as the t-s function that would fit the results of a simulation of the total shaft load-movement.
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For additional comments on the use of t-z and q-z functions in evaluating the results of a static loading test,
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see the "Red Book" Chapter 8, Section 11.
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Fellenius, B.H., 2013. Crib Sheet for use with UniPile and UniSettle. Report to UniSoft Ltd. (www.Fellenius.net).
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