DirtSmuggler
Geotechnical
- Sep 29, 2021
- 29
Hello
Thanks in advance for all who provide feedback.
I've just started using this software, Ensoft SHAFT, in order to do a drilled shaft design for a project. It's for overhead sign structures.
The problem I have is that tip resistance goes to zero half way into the weathered rock layer, and stays at zero during rock layer. I would think tip resistance (Qb) would do the opposite and jump up higher in weathered rock and rock layer, similar to how the skin friction behaves. What am I doing wrong? What am I missing?
See the output below. Qb goes to zero once entering the weathered rock layer and rock layer.
---------------
New Pile
PROPOSED DEPTH = 10.0 FT
----------------
NUMBER OF LAYERS = 3
------------------
WATER TABLE DEPTH = 0.0 FT.
-------------------
FACTOR OF SAFETY APPLIED TO THE ULTIMATE SIDE FRICTION CAPACITY = 2.50
-------------------------------------------------------
FACTOR OF SAFETY APPLIED TO THE ULTIMATE BASE CAPACITY = 3.00
------------------------------------------------------
SOIL INFORMATION
---------------
LAYER NO 1----SAND
AT THE TOP
SIDE FRICTION PROCEDURE: Ko METHOD
LATERAL EARTH-PRESSURE COEFFICIENT - Ko = 5.000E-01
INTERNAL FRICTION ANGLE, DEG. = 4.500E+01
BLOWS PER FOOT FROM STANDARD PENETRATION TEST = 8.800E+01
SOIL UNIT WEIGHT, LB/CU FT = 1.250E+02
MAXIMUM LOAD TRANSFER FOR SOIL, LB/SQ FT = 1.000E+10
DEPTH, FT = 0.000E+00
AT THE BOTTOM
SIDE FRICTION PROCEDURE: Ko METHOD
LATERAL EARTH-PRESSURE COEFFICIENT - Ko = 5.000E-01
INTERNAL FRICTION ANGLE, DEG. = 3.500E+01
BLOWS PER FOOT FROM STANDARD PENETRATION TEST = 1.900E+01
SOIL UNIT WEIGHT, LB/CU FT = 1.250E+02
MAXIMUM LOAD TRANSFER FOR SOIL, LB/SQ FT = 1.000E+10
DEPTH, FT = 6.500E+00
LAYER NO 2----DECOMPOSED ROCK
AT THE TOP
ELASTIC MODULUS OF GRAVEL, LB/SQ IN = 2.089E+06
POISSION RATIO OF GRAVEL = 2.500E-01
BLOWS PER FOOT FROM STANDARD PENETRATION TEST = 5.000E+01
SOIL UNIT WEIGHT, LB/CU FT = 1.450E+02
MAXIMUM LOAD TRANSFER FOR SOIL, LB/SQ FT = 1.000E+10
DEPTH, FT = 6.500E+00
AT THE BOTTOM
ELASTIC MODULUS OF GRAVEL, LB/SQ IN = 2.089E+06
POISSION RATIO OF GRAVEL = 2.500E-01
BLOWS PER FOOT FROM STANDARD PENETRATION TEST = 5.000E+01
SOIL UNIT WEIGHT, LB/CU FT = 1.450E+02
MAXIMUM LOAD TRANSFER FOR SOIL, LB/SQ FT = 1.000E+10
DEPTH, FT = 8.500E+00
LAYER NO 3----STRONG ROCK
AT THE TOP
DIAMETER OF SOCKET, FT = 2.000E+00
SPACING OF DISCONTINUITIES,FT = 1.000E+00
THICKNESS OF INDIVIDUAL DISCONTINUITIES,FT = 1.000E-03
UNIAXIAL COMPRESSION STRENGTH OF ROCK,LB/SQ FT = 1.440E+05
UNIAXIAL COMPRESSION STRENGTH OF CONCRETE,LB/SQ FT= 7.200E+05
ELASTIC MODULUS FOR THE INTACT ROCK, LB/SQ IN. = 1.204E+07
ROCK QUALITY DESIGNATION (RQD) % = 8.800E+01
SOIL UNIT WEIGHT, LB/CU FT = 1.600E+02
DEPTH, FT = 8.500E+00
AT THE BOTTOM
DIAMETER OF SOCKET, FT = 2.000E+00
SPACING OF DISCONTINUITIES,FT = 1.000E+00
THICKNESS OF INDIVIDUAL DISCONTINUITIES,FT = 1.000E-03
UNIAXIAL COMPRESSION STRENGTH OF ROCK,LB/SQ FT = 1.440E+05
UNIAXIAL COMPRESSION STRENGTH OF CONCRETE,LB/SQ FT= 7.200E+05
ELASTIC MODULUS FOR THE INTACT ROCK, LB/SQ IN. = 1.204E+07
ROCK QUALITY DESIGNATION (RQD) % = 8.800E+01
SOIL UNIT WEIGHT, LB/CU FT = 1.600E+02
DEPTH, FT = 2.000E+01
INPUT DRILLED SHAFT INFORMATION
------------------------------
MINIMUM SHAFT DIAMETER = 2.500 FT.
MAXIMUM SHAFT DIAMETER = 2.500 FT.
RATIO BASE/SHAFT DIAMETER = 0.000 FT.
ANGLE OF BELL = 0.000 DEG.
IGNORED TOP PORTION = 5.000 FT.
IGNORED BOTTOM PORTION = 0.000 FT.
ELASTIC MODULUS, Ec = 3.500E+06 LB/SQ IN
COMPUTATION RESULTS
-------------------
- CASE ANALYZED : 1
VARIATION LENGTH : 1
VARIATION DIAMETER : 1
DRILLED SHAFT INFORMATION
-------------------------
DIAMETER OF STEM = 2.500 FT.
DIAMETER OF BASE = 2.500 FT.
END OF STEM TO BASE = 0.000 FT.
ANGLE OF BELL = 0.000 DEG.
IGNORED TOP PORTION = 5.000 FT.
IGNORED BOTTOM PORTION = 0.000 FT.
AREA OF ONE PERCENT STEEL = 7.069 SQ.IN.
ELASTIC MODULUS, Ec = 3.500E+06 LB/SQ IN
VOLUME OF UNDERREAM = 0.000 CU.YDS.
SHAFT LENGTH = 10.000 FT.
PREDICTED RESULTS
-----------------
QS = ULTIMATE SIDE RESISTANCE;
QB = ULTIMATE BASE RESISTANCE;
WT = WEIGHT OF DRILLED SHAFT (FOR UPLIFT CAPACITY ONLY);
QU = TOTAL ULTIMATE RESISTANCE;
QBD = TOTAL ALLOWABLE LOAD USING A FACTOR OF SAFETY
APPLIED TO THE ULTIMATE BASE RESISTANCE;
QDN = TOTAL ALLOWABLE LOAD USING FACTORS OF SAFETY
APPLIED TO THE ULTIMATE SIDE RESISTANCE AND
THE ULTIMATE BASE RESISTANCE.
LENGTH VOLUME QS QB QU QBD QDN QU/VOLUME
(FT) (CU.YDS) (TONS) (TONS) (TONS) (TONS) (TONS) (TONS/CU.YDS)
6.0 1.09 0.54 54.66 55.20 18.76 18.44 50.60
7.0 1.27 1.16 55.02 56.18 19.50 18.80 44.14
8.0 1.45 7.93 55.02 62.95 26.27 21.51 43.28
9.0 1.64 14.88 0.00 14.88 14.88 5.95 9.09
10.0 1.82 50.65 0.00 50.65 50.65 20.26 27.86
AXIAL LOAD VS SETTLEMENT CURVES
-------------------------------
LOAD SETTLEMENT RELATIONSHIP
------------------------------------------
TOP LOAD TOP MOVEMENT
TONS IN.
5.0138E+01 1.0637E-02
5.0138E+01 1.0637E-02
5.0138E+01 1.0637E-02
5.0138E+01 1.0637E-02
5.0138E+01 1.0637E-02
5.0138E+01 1.0637E-02
5.0138E+01 1.0637E-02
5.0138E+01 1.0637E-02
5.0138E+01 1.0637E-02
5.0138E+01 1.0637E-02
5.0138E+01 1.0637E-02
5.0138E+01 1.0637E-02
5.0138E+01 1.0637E-02
5.0138E+01 1.0637E-02
5.0138E+01 1.0637E-02
Thanks in advance for all who provide feedback.
I've just started using this software, Ensoft SHAFT, in order to do a drilled shaft design for a project. It's for overhead sign structures.
The problem I have is that tip resistance goes to zero half way into the weathered rock layer, and stays at zero during rock layer. I would think tip resistance (Qb) would do the opposite and jump up higher in weathered rock and rock layer, similar to how the skin friction behaves. What am I doing wrong? What am I missing?
See the output below. Qb goes to zero once entering the weathered rock layer and rock layer.
---------------
New Pile
PROPOSED DEPTH = 10.0 FT
----------------
NUMBER OF LAYERS = 3
------------------
WATER TABLE DEPTH = 0.0 FT.
-------------------
FACTOR OF SAFETY APPLIED TO THE ULTIMATE SIDE FRICTION CAPACITY = 2.50
-------------------------------------------------------
FACTOR OF SAFETY APPLIED TO THE ULTIMATE BASE CAPACITY = 3.00
------------------------------------------------------
SOIL INFORMATION
---------------
LAYER NO 1----SAND
AT THE TOP
SIDE FRICTION PROCEDURE: Ko METHOD
LATERAL EARTH-PRESSURE COEFFICIENT - Ko = 5.000E-01
INTERNAL FRICTION ANGLE, DEG. = 4.500E+01
BLOWS PER FOOT FROM STANDARD PENETRATION TEST = 8.800E+01
SOIL UNIT WEIGHT, LB/CU FT = 1.250E+02
MAXIMUM LOAD TRANSFER FOR SOIL, LB/SQ FT = 1.000E+10
DEPTH, FT = 0.000E+00
AT THE BOTTOM
SIDE FRICTION PROCEDURE: Ko METHOD
LATERAL EARTH-PRESSURE COEFFICIENT - Ko = 5.000E-01
INTERNAL FRICTION ANGLE, DEG. = 3.500E+01
BLOWS PER FOOT FROM STANDARD PENETRATION TEST = 1.900E+01
SOIL UNIT WEIGHT, LB/CU FT = 1.250E+02
MAXIMUM LOAD TRANSFER FOR SOIL, LB/SQ FT = 1.000E+10
DEPTH, FT = 6.500E+00
LAYER NO 2----DECOMPOSED ROCK
AT THE TOP
ELASTIC MODULUS OF GRAVEL, LB/SQ IN = 2.089E+06
POISSION RATIO OF GRAVEL = 2.500E-01
BLOWS PER FOOT FROM STANDARD PENETRATION TEST = 5.000E+01
SOIL UNIT WEIGHT, LB/CU FT = 1.450E+02
MAXIMUM LOAD TRANSFER FOR SOIL, LB/SQ FT = 1.000E+10
DEPTH, FT = 6.500E+00
AT THE BOTTOM
ELASTIC MODULUS OF GRAVEL, LB/SQ IN = 2.089E+06
POISSION RATIO OF GRAVEL = 2.500E-01
BLOWS PER FOOT FROM STANDARD PENETRATION TEST = 5.000E+01
SOIL UNIT WEIGHT, LB/CU FT = 1.450E+02
MAXIMUM LOAD TRANSFER FOR SOIL, LB/SQ FT = 1.000E+10
DEPTH, FT = 8.500E+00
LAYER NO 3----STRONG ROCK
AT THE TOP
DIAMETER OF SOCKET, FT = 2.000E+00
SPACING OF DISCONTINUITIES,FT = 1.000E+00
THICKNESS OF INDIVIDUAL DISCONTINUITIES,FT = 1.000E-03
UNIAXIAL COMPRESSION STRENGTH OF ROCK,LB/SQ FT = 1.440E+05
UNIAXIAL COMPRESSION STRENGTH OF CONCRETE,LB/SQ FT= 7.200E+05
ELASTIC MODULUS FOR THE INTACT ROCK, LB/SQ IN. = 1.204E+07
ROCK QUALITY DESIGNATION (RQD) % = 8.800E+01
SOIL UNIT WEIGHT, LB/CU FT = 1.600E+02
DEPTH, FT = 8.500E+00
AT THE BOTTOM
DIAMETER OF SOCKET, FT = 2.000E+00
SPACING OF DISCONTINUITIES,FT = 1.000E+00
THICKNESS OF INDIVIDUAL DISCONTINUITIES,FT = 1.000E-03
UNIAXIAL COMPRESSION STRENGTH OF ROCK,LB/SQ FT = 1.440E+05
UNIAXIAL COMPRESSION STRENGTH OF CONCRETE,LB/SQ FT= 7.200E+05
ELASTIC MODULUS FOR THE INTACT ROCK, LB/SQ IN. = 1.204E+07
ROCK QUALITY DESIGNATION (RQD) % = 8.800E+01
SOIL UNIT WEIGHT, LB/CU FT = 1.600E+02
DEPTH, FT = 2.000E+01
INPUT DRILLED SHAFT INFORMATION
------------------------------
MINIMUM SHAFT DIAMETER = 2.500 FT.
MAXIMUM SHAFT DIAMETER = 2.500 FT.
RATIO BASE/SHAFT DIAMETER = 0.000 FT.
ANGLE OF BELL = 0.000 DEG.
IGNORED TOP PORTION = 5.000 FT.
IGNORED BOTTOM PORTION = 0.000 FT.
ELASTIC MODULUS, Ec = 3.500E+06 LB/SQ IN
COMPUTATION RESULTS
-------------------
- CASE ANALYZED : 1
VARIATION LENGTH : 1
VARIATION DIAMETER : 1
DRILLED SHAFT INFORMATION
-------------------------
DIAMETER OF STEM = 2.500 FT.
DIAMETER OF BASE = 2.500 FT.
END OF STEM TO BASE = 0.000 FT.
ANGLE OF BELL = 0.000 DEG.
IGNORED TOP PORTION = 5.000 FT.
IGNORED BOTTOM PORTION = 0.000 FT.
AREA OF ONE PERCENT STEEL = 7.069 SQ.IN.
ELASTIC MODULUS, Ec = 3.500E+06 LB/SQ IN
VOLUME OF UNDERREAM = 0.000 CU.YDS.
SHAFT LENGTH = 10.000 FT.
PREDICTED RESULTS
-----------------
QS = ULTIMATE SIDE RESISTANCE;
QB = ULTIMATE BASE RESISTANCE;
WT = WEIGHT OF DRILLED SHAFT (FOR UPLIFT CAPACITY ONLY);
QU = TOTAL ULTIMATE RESISTANCE;
QBD = TOTAL ALLOWABLE LOAD USING A FACTOR OF SAFETY
APPLIED TO THE ULTIMATE BASE RESISTANCE;
QDN = TOTAL ALLOWABLE LOAD USING FACTORS OF SAFETY
APPLIED TO THE ULTIMATE SIDE RESISTANCE AND
THE ULTIMATE BASE RESISTANCE.
LENGTH VOLUME QS QB QU QBD QDN QU/VOLUME
(FT) (CU.YDS) (TONS) (TONS) (TONS) (TONS) (TONS) (TONS/CU.YDS)
6.0 1.09 0.54 54.66 55.20 18.76 18.44 50.60
7.0 1.27 1.16 55.02 56.18 19.50 18.80 44.14
8.0 1.45 7.93 55.02 62.95 26.27 21.51 43.28
9.0 1.64 14.88 0.00 14.88 14.88 5.95 9.09
10.0 1.82 50.65 0.00 50.65 50.65 20.26 27.86
AXIAL LOAD VS SETTLEMENT CURVES
-------------------------------
LOAD SETTLEMENT RELATIONSHIP
------------------------------------------
TOP LOAD TOP MOVEMENT
TONS IN.
5.0138E+01 1.0637E-02
5.0138E+01 1.0637E-02
5.0138E+01 1.0637E-02
5.0138E+01 1.0637E-02
5.0138E+01 1.0637E-02
5.0138E+01 1.0637E-02
5.0138E+01 1.0637E-02
5.0138E+01 1.0637E-02
5.0138E+01 1.0637E-02
5.0138E+01 1.0637E-02
5.0138E+01 1.0637E-02
5.0138E+01 1.0637E-02
5.0138E+01 1.0637E-02
5.0138E+01 1.0637E-02
5.0138E+01 1.0637E-02