User Manual
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1. pr a ee r R ee Hak S s ee n r han s a m R M E m hc m E lL UL a l a es n at a m Se m m m e m a mm mm m e mm m m m m m ma m m m s m ES SE m m m m m m g m m m m mr P e e e e m e m P e m m m m e e m e E e m m m 1155 Figure 5 Example 3 1 The fill has a unit weight of 20 kN m and is 4 m thick As the WT is at the ground surface in this example the sand layer can be modelled as a single layer with 19 kN m The layering is entered as shown in Figure 6 the WT depth is set at 3 m and the plotting range from Zmin O tO Zmax 9 m These parameters modelling the applied surcharge pressure always give the stress conditions after dissipation has finished Immediately after the fill has been placed there has been no time for dissipation to have taken place so the effective stress conditions in the clay will be unchanged from their original values The original effective stress may be obtained by setting the thickness of the fill or unit weight or both equal to zero so there is no surcharge Note however that the total stress and pore pressure from such an analysis will not match those under immediate surcharge loading both values will be increased by the surcharge pressure 80 kPa Many years after fill placement the pore pressures have dissipated and the analysis parameters shown in Figure 6 will give the correct values of all three stress pressure components These values are compared in Table 3 Table 3 Co2. Table 1 Comparison of Stress_CSM8 and hand calculations Example 3 1 Depth Method Total stress Pore pressure u Effective stress o y m kPa kPa kPa Hand calculation 51 0 U 51 0 Stress_CSM8 51 00 0 00 51 00 Handcalculation 96O O n4 l Stress_CSM8 91 00 19 62 71 38 Hand calculation 167 0 58 9 108 100 l Stress_CSM8 amp 167 00 58 86 108 14 Stress CSMS8 User s Manual Stress pressure kPa U 50 100 150 200 Depth BGL m 0 50 100 150 kN m 0 1 b 3 m 5 b 7 Cla Y 8 g l 0 10 Figure 4 Comparison stress profiles from a Stress_CSM8 and b main text Figure 3 2 For the case of a 1 m thick zone of capillary suction in the sand above the WT as noted in the main text the only effect is to increase the unit weight of the sand from dry to saturated between 2 3 m This may be accomplished in Stress_CSM8 by altering the thickness of the upper two layers so that the dry layer is 2 m thick and the saturated layer is 3 m thick leaving the WT at the same depth The resulting values of stress pressure using the query tool are compared to the no capillary zone case considered previously in Table 2 It can be seen that as described in the main text the effect of the capillary zone is to increase both total and effective stresses by 3 kPa below 3 m depth Table 2 Comparison of values capillary zone versus no capillary zone Example 3 1 Depth Method Total stress Pore pressure u Ef
3. Stress CSMS8 A spreadsheet tool for determining the one dimensional stress field within the ground for hydrostatic fluid conditions using the Finite Difference Method FDM USER S MANUAL J A Knappett 2012 This user s manual and its associated spreadsheet Stress_CSM8 xls accompanies Craig s Soil Mechnics 8 Edition J A Knappett amp R F Craig Stress CSMS8 User s Manual 1 INTRODUCTION This manual will explain how to use the spreadsheet analysis tool Stress _CSM8 xls to determine the total stress pore pressure and effective stress distributions with depth within layered soil profiles using a simple finite difference method The spreadsheet has the following features Ability to model up to 10 distinct soil layers of different unit weight Model soil up to 150 m thick Model a water table WT both below and above the surface of the ground Include hydraulically confined layers where artesian conditions exist Model surcharge loading at the surface of the ground e g embankments fill Automatically produce an A4 output sheet with the stress profiles shown graphically This manual is structured as follows Section 2 The basic structure of both the workbook Stress_CSM8 xls and the worksheet used to perform the analyses will be described and the principle of operation will be highlighted Section 3 This section will describe how to use this simple tool to analyse a range of different ground co
4. WT depth these values should be positive to indicate depths BGL In the Output data section the profiles of total stress pore pressure and effective stress are plotted over the depth range specified by Zmin and Zmax An equivalent borehole log is plotted to the right of this data over the same depth scale showing graphically the layering in the soil All calculations are done automatically and immediately i e there is no need to press F9 following data input The Data query section allows for direct numerical output of the total stress pore pressure and effective stress at any depth specified by the user for use in subsequent analyses The sheets are protected so that only data input cells can be edited by the user The entire Calculations worksheet is similarly protected This is to prevent accidental over typing of formulae which may affect the functionality of the spreadsheet However the protection is not password protected so the protection may be removed Tools gt Protection gt Unprotect Sheet in Microsoft Excel if users wish to investigate the calculation procedures used SOIL amp GROUNDWATER DATA OUTPUT DATA graphical Data input Figure 1 Workbook structure Stress CSMS8 User s Manual 3 MODELLING To illustrate how the spreadsheet may be used to model different ground and groundwater conditions this section will consider the worked examples 3 1 and 3 2 presented in the main text Output sheets fr
5. ach with a distinct unit weight can be included Unit weight should be saturated if the material is below the WT and dry if the material is above the WT These should be input with Layer being the uppermost layer By inputting the thickness of each layer the spreadsheet will automatically determine the depths BGL of the top and bottom of each layer The depth of the WT BGL is also given N B for WT below the ground surface the value should be positive If a 2 Stress _CSMS User s Manual surcharge e g due to fill material is acting on the surface to increase the total stress the thickness and unit weight may be entered If only the surcharge pressure is known an equivalent unit weight and thickness should be input the product of which will give the appropriate pressure If a layer is under artesian pressure the level of the piezometric surface above ground level AGL can be input this is the height AGL of the water level as measured in a standpipe sunk into the artesian layer and is therefore suited to the input of measurements taken directly from the field If the WT is below ground level the spreadsheet will automatically calculate the additional head in the artesian layer and add this to the hydrostatic pressure to get the correct overall pore water pressure in the layer Finally the user can enter a depth range over which the resulting stress pressure profiles will be plotted by varying the values Of Zmin and Zmax N B as for
6. fective stress o y m kPa kPa kPa No suction 51 00 0 00 51 00 Capillary zone 54 00 0 00 54 00 Nosuction o 91 00 1969 71 38 i Capillary zone 94 00 19 62 74 38 o Nosucion 16700 e 5886 1084 Capillary zone 170 00 58 86 111 14 Stress CSMS8 User s Manual Example 3 2 WT at surface surcharge The problem geometry is shown in Figure 5 This problem additionally demonstrates e how to model WT at the ground surface e how to model the effect of a surcharge acting at the ground surface Fill m a eee eee ee e e m e se m m m m m e e e m e e ee e e M e e e e e e e e e m e m m m m m e e e e l m e e e e e m e m e m e m m m m e e ee E e e m e m m m m m m m m m e m m m m e m e e m e m m m m m m m r m em m m m m e m e m l m e m e m e m m m m m m m m m m m m e m e m e mm d ma ma e b m R A SR r e a e B e e E e be e e HM mi ba so R e Re mE e R lt MEF eS ee BB ee e di Se ee SS sO ies S m m m e m m m e m U E e m m a E A m m m m m a m e me eee a e E m e am ED Fe mi ar a to dg aB e tt e m e a g ct e d m am H R ht Le l he hr _ m e m m e e R e 6 R S A e E e R m e a e m m e m t te eE ge ts l E R e m m m 5 e a m m R m a S m 6 E e E e G r S F maa Ss oe ee i B e E t m oo E m E e r P e e M a R E e e e E l m 2 5 2 SS SS SS SS SS e e m eS r eS SS ES SS iS SS m ES SE TS ES SS ES ES ES m e e m Se Se eS a 66 5
7. mparison of values for surcharge loading Example 3 2 Case Model for o Oy u O y d y from main text kPa kPa kPa kPa Immediate No surcharge 155 00 80 78 48 80 76 52 76 5 After dissipation Surcharge 235 00 78 48 156 52 156 5 Stress _CSMS8 User s Manual Soil layering Groundwater conditions Layer thickness Artesian head AGL WT depth BGL oo m kN m sl asili Surcharge L Sili thickness 4im surcharge o0 kPa Plot depth range ma a Figure 6 Data input Example 3 2 Modelling the case of WT above ground surface One further special but relatively common case must be considered It is often necessary to analyse ground conditions when the WT is significantly above the ground surface Examples may be the soil forming a river bed or for larger depths seabed or ground which has been flooded Under these conditions the WT has two effects 1 to increase the hydrostatic pore pressure at the ground surface 2 the weight of the water applies additional total stress i e surcharge at the ground surface In Stress_CSM8 this is modelled by combining the WT depth and surcharge parameters For a WT of height H above the ground surface the following parameters are set Groundwater conditions e WT depth BGL H Surcharge e y 9 81 e thickness H
8. nditions by considering worked examples from the main text 2 PROGRAMME DESCRIPTION The spreadsheet analysis tool consists of two worksheets The first Data input is the worksheet which is used to interact with the spreadsheet There are various cells for inputting data and the graphical output 1 e a graph showing the profiles of total stress pore pressure and effective stress with depth is also shown on this worksheet The second worksheet Calculations is non editable and performs the various calculations on the input data to determine the stresses pressures over a fine depth scale every 0 1 m up to 150 m BGL and the extraction of data for automatic plotting over a depth range defined by the user The structure of the workbook is shown in Figure 1 Data input In the Project ID section basic information relating to the project or example being analysed is inputted along with details of user who prepared the calculations for auditing purposes This information is not required for analysis but appears in the header boxes when the output sheet is printed and should be included as a matter of course If the workbook is use to analyse data from a borehole log or CPT sounding see Chapter 6 in main text then the identifier ID of the hole sounding or grid coordinates may be input for reference The Soil amp groundwater data section is where all of the information required for calculation is input by the user Up to 10 soil layers e
9. om Stress _CSM8 for all of these examples are provided in the Appendix Example 3 1 WT below ground surface layered soil The problem geometry is shown in Figure 2 This problem demonstrates e how to model ground with multiple soil layers e how to model a layer of soil through which the WT passes i e WT below ground surface e how to model a zone of capillary suction Figure 2 Example 3 1 Initially the case of no capillary suction is considered Because the WT passes through the sand layer the soil above 0 3 m and below 3 5 m will have different unit weights dry 17 kN m and saturated 20 kN m respectively These therefore need to be modelled as separate layers within Stress_CSM8 The layering is entered as shown in Figure 3 the WT depth is set at 3 m and the plotting range from Zmin 0 to Zmax 9 m Using the Data query the values of total stress pore pressure and effective stress at 3 5 and 9 m can be obtained for comparison with the values calculated by hand in Example 3 1 of the main text A comparison of these values is shown in Table 1 The profiles of stress plotted against depth are compared in Figure 4 Stress CSMS8 User s Manual Soil layering Groundwater conditions Layer thickness Artesian head AGL WT depth BGL m sand U sand 3 Clay 4 Surcharge 5 B a EEE a H thickness Pg m S 4 surcharge U kPa 10 Plot depth range zmax S Ofm Figure 3 Data input Example 3 1
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