The Modified Matlock Method

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Sharlene Dean
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1 The Modified Matlock Method March 29, Introduction The modified Matlock approach is used for cyclic loading of very stiff clays (s u > 100 kpa) [1]. Gensod already generates p-y curves for soft clays using the Matlock approach. This is achieved by setting PYCODE=284 in the SOIL LAYER DIVISIONS AND CODES FOR PY/TZ/QZ SECTION in the Gensod.inp file [2]. This will tell Gensod to use the API 1984 edition rules. We have now modified Gensod to also generate p-y curves using the modified Matlock. shown in figure 1. A comparison of the modified Matlock and regular Matlock is The ultimate lateral resistance is calculated in a similar way as Splice does for soft clays using the regular Matlock approach (API284). ( ) Z p u = min 3S u + γ avr Z + APIJS u D, 9S u The depth of the reduced resistance zone is in SPLICE calculated as follows: ( ) 6D Z r = max γ avr D/S u + APIJ, 2.5D (2) (1) y c is given as: y c = 2.5ɛ c D (3) See Table 1 and Table 2 for definitions of the symbols. To use the modified Matlock method set PYCODE=570 in the Gensod.inp file. 1

2 p p u Matlock ɛ c =0.005 Mod Matlock ɛ c =0.005 Z >Z r Mod Matlock ɛ c =0.005 Z =0.5Z r y D Figure 1: Matlock and modified Matlock. 2

3 Symbol Description Value Unit D diameter 1.0 m γ s average soil density 10 kn/m 3 Z layer midpoint 5 m S u undrained shear strength 150 kpa APIJ J factor to find the depth of the reduced resistance zone ɛ c strain at half maximum stress in undrained compression test Table 1: Nomenclature and example values input values. Symbol Description Equation Value Unit p u ultimate lateral stress kpa depth below surface Z r to bottom of reduced 2 10 m resistance zone y c defined by equation Table 2: Nomenclature and example values, calculated values. 2 Example A simple pile with one soil layer has been generated. The Gensod.inp is listed in the end of this section. Table 1 shows the input values used, while Table 2 shows the values calculated by Gensod using the formulas in the previous chapter. The resulting p-y curve generated by Gensod using PYCODE=570 is shown in Figure 2. The calculated p and y values are given in Table 3. P [kpa] Y [m] Table 3: Gensod calculated values for modified Matlock. 3

4 p [kpa] y [m] Figure 2: The p-y curve calculated by Gensod. 4

5 GENSOD TEST EXAMPLE 05 SINGLE PILE SINGLE LAYER MODIFIED MATLOCK ****************** CONTROL SECTION 1.0 CONFRC OLD-FORCE-UNIT = CONFRC * NEW-FORCE-UNIT 1MN = 1000*1KN 1.0 CONLTH OLD-LENGTH-UNIT = CONLTH * NEW-LENGTH-UNIT 1M = 3.28*1FT 1 NUMTYP NUMBER OF DIFFERENT SOIL TYPES 1 NUMTQZ NUMBER OF LINES IN THE T-Z / Q-Z DATA TABLE BELOW 1 NUMLAY NUMBER OF SOIL LAYERS 0 NUMDSP NUMBER OF Z-LEVELS WITH GIVEN SOIL DISPLACEMENTS 1 MIDBOT P-Y ETC COMPUTED AT : 1=LAYER-MIDPOINT 2=LAYER-BOTTOM 10.0 GAMMAW UNIT WEIGHT OF WATER (10.0 KN/M3 IN SI-UNITS) ATMPRS ATMOSPHERIC PRESSURE (101.3 KN/M2 IN SI-UNITS) 20.0 ZCYCL Z-LEVEL DOWN TO WHICH CYCLIC P-Y DATA SHALL BE GENERATED SUSTIF USE STIFF CLAY P-Y PROCEDURES IF SU.GT.SUSTF (API ONLY) 2 JPRINT PRINTED OUTPUT DATA (0=NONE 1=SOME 2=FULL) 1 JECHO ECHO PRINT OF INPUT FILE NF14 TO FILE NF16 (0=NO 1=YES) ****************** MATERIAL COEFFICIENTS SECTION 1.00 SFTPHI MATERIAL COEFFICIENT ON TAN(PHI) 1.00 SFSU MATERIAL COEFFICIENT ON UNDRAINED SHEAR STRENGTH 1.00 SFSKF MATERIAL COEFFICIENT ON PILE SKIN FRICTION 1.00 SFSIGT MATERIAL COEFFICIENT ON PILE TIP RESISTANCE ****************** PILE DIAMETERS AND GROUP EFFECTS SECTION 1 NUMDIA NUMBER OF PILE DIAM FOR WHICH P-Y/T-Z/Q-Z DATA IS WANTED 1.00 NUMDIA PILE DIAMETERS IN INCREASING ORDER ESOL0 E-SOIL FOR GROUP EFFECT CALCULATION : 1000 ESOL1 ESOIL(Z) = ESOL0 + ESOL1*Z 0.5 POSAVR SOIL AVERAGE POISSON S RATIO FOR GROUP EFFECTS ****************** SOIL SURFACE AND GROUND WATER SECTION 0.0 ZSURF Z-LEVEL OF NON-SCOURED SOIL SURFACE 0.0 SCRGEN DEPTH OF GENERAL SCOUR BELOW ZSURF 0.0 SCRLOC DEPTH OF LOCAL SCOUR BELOW ZSURF 5

6 20. SLOPE SIDE SLOPE (DEGREES) OF LOCAL SCOUR HOLES 0.0 ZGRWT Z-LEVEL OF GROUND WATER TABLE 10 GAMPWP UNIT WEIGHT OF GROUND WATER (USED TO FIND PORE WATER PRSS) ****************** LOADS AT SOIL SURFACE SECTION 0.0 SIGSRF VERTICAL STRESS AT SURFACE 0 DPEMB VERTICAL STRESS UNDER EMBANKMENT LOADING 2.3 AEMB WIDTH A OF EMBANKMENT SLOPING PART 3.0 BEMB PILE POSITION W.R.T. EMBANKMENT TOE (POSITIVE OUTSIDE) 0.0 DPCIRC VERTICAL STRESS UNDER CIRCULAR LOADED AREA 0.0 RADIUS RADIUS OF CIRCULAR LOADED AREA (PILE IS IN CENTER) 1 NUMFRC NUMBER OF VERTICAL POINT FORCES AT SOIL SURFACE 0 POINT FORCE VALUES 2.5 HORIZONTAL DISTANCE TO PILE AXIS ****************** SOIL TYPE AND PROPERTY SECTION TYP GAMTOT PHI SU.Z=0 SU.Z=100 EPSC OCR API-J OPEN TRES/TMAX TZZRES ****************** SKIN FRICTION AND TIP RESISTANCE (T-Z/Q-Z) SECTION 10.0 ZONINF (ZONE OF INFLUENCE) / (PILE RADIUS) FOR TZCODE = RFTZ CURVE FITTING FACTOR RF FOR TZCODE = 200 ZLEV SKIN-CMP SKIN-TNS G0-SOIL DSPTZ/DIAM SIG-TIP POIS DSPQZ/DIAM ****************** SOIL LAYER DIVISIONS AND CODES FOR PY/TZ/QZ SECTION P-Y CODES : 000=MANUAL 100+N=AUTO 2YY=API 3YY=DNV (YY=YEAR E.G. 287) T-Z CODES : 000=MANUAL 100+N=AUTO 200+N=MISCELL PROCUDURES Q-Z CODES : 000=MANUAL 100+N=AUTO 200+N=MISCELL PROCEDURES LAYERS TYP ZBOTM PYCODE TZCODE QZCODE ****************** MANUAL P-Y (LATERAL RESISTANCE) DATA SECTION LAY DIAM NUMPNT LINE1 : P-VALUES (F/L**2) LINE2 : Y-VALUES (L) 6

7 ****************** P-Y (LATERAL RESISTANCE) DATA MODIFICATION SECTION LAYERS DIAM P-FACT Y-FACT Y-GAP P-PEAK-FACT P-RESID-FACT Y-RESID-FACT ****************** MANUAL T-Z (SKIN FRICTION) DATA SECTION LAY DIAM NUMPNT LINE1 : T-VALUES (F/L**2) LINE2 : Z-VALUES (L) ****************** T-Z (SKIN FRICTION) DATA MODIFICATION SECTION LAYERS DIAM CMP-FCT TNS-FCT TZZ-FCT T-RESID-FCT Z-RESID-FCT ****************** MANUAL Q-Z (PILE TIP RESISTANCE) DATA SECTION LAY DIAM NUMPNT LINE1 : Q-VALUES (F/L**2) LINE2 : Z-VALUES (L) ****************** Q-Z (PILE TIP RESISTANCE) DATA MODIFICATION SECTION LAYERS DIAM CMP-FCT TNS-FCT QZZ-FCT Q-RESID-FCT Z-RESID-FCT ****************** GIVEN SOIL DISPLACEMENTS AND OPEN HOLE SECTION ZLEV DSP-X DSP-Y DSP-Z HOLE-DIAM END OF GENSOD INPUT FILE References [1] N. D. P. Barltrop and A. J. Adams. Dynamics of Fixed Marine Structures. Butterworth-Heinemann Ltd., 3 edition, [2] Carl J. Frimann Clausen. Gen-um. Technical report, June

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