Tikrit Journal of Eng. Sciences/Vol.13/No.4/December 2006 ASSESSMENT OF SETTLEMENT OF SHALLOW FOUNDATIONS ERECTED NEAR SLOPES OF SANDY SOIL Dr. Adnan Jayed Zedan Lecturer Civil Engineering Department- University of Tikrit ABSTRACT In this study, the behaviour of shallow foundations near slopes is studied using nonlinear elastic finite element analysis. Forty-four cases of strip footings resting on cohesionless soils that were studied by Sud (1984) [1] through model tests, have been analyzed. Pressure-settlement relations has been compared with experimental results of (Sud, 1984) [1] , and a good agreement between the two has been observed. Ultimate bearing capacity of shallow foundations near slopes was evaluated using the intersection of two tangents of pressure-settlement curve. The values of ultimate bearing capacity agree well also with (Sud, 1984) [1] . A non-dimensional correlation has been developed between the settlement of footing erected near slope (S) and the settlement of footing resting on level ground (S o ). The relationship (S/S o versus De/B) can be expressed by a unique relation for different slope angles (). This relation has been found to be dependent on (35-54) 35
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Tikrit Journal of Eng. Sciences/Vol.13/No.4/December 2006
ASSESSMENT OF SETTLEMENT OF SHALLOW
FOUNDATIONS ERECTED NEAR SLOPES OF
SANDY SOIL
Dr. Adnan Jayed Zedan
Lecturer
Civil Engineering Department- University of Tikrit
ABSTRACT
In this study, the behaviour of shallow foundations near
slopes is studied using nonlinear elastic finite element analysis.
Forty-four cases of strip footings resting on cohesionless soils that
were studied by Sud (1984)[1] through model tests, have been
analyzed. Pressure-settlement relations has been compared with
experimental results of (Sud, 1984) [1], and a good agreement
between the two has been observed. Ultimate bearing capacity of
shallow foundations near slopes was evaluated using the intersection
of two tangents of pressure-settlement curve. The values of ultimate
bearing capacity agree well also with (Sud, 1984) [1].
A non-dimensional correlation has been developed between
the settlement of footing erected near slope (S) and the settlement
of footing resting on level ground (So). The relationship (S/So
versus De/B) can be expressed by a unique relation for different
slope angles (). This relation has been found to be dependent on
(35-54) 35
40
Tikrit Journal of Eng. Sciences/Vol.13/No.4/December 2006
distance of the edge of the footing from slope shoulder; De, and
angle of slope; , while it is independent of the relative density of
sand; DR, and the factor of safety. By knowing the settlement of a
footing resting on a level ground, the settlement of a footing erected
near slope can be evaluated using this correlation.
11. Saran, S., Sud, V. K., and Handa, S. C., (1988), “Footings on
Slopes and Constitutive Laws” Indian Geotechnical Journal,
Vol. 18, No. 3, pp 245-265.
12. Duncan, J. M. and Chang, C. Y. (1970), “Nonlinear Analysis of
Stress and Strain in Soils” Journal of Soil Mechanics and
Foundation Engineering, ASCE, Vol. 96, SM5, pp. 1629-1651.
13. Kondner, R. L. (1963), “Ahyperbolic Stress-Strain Response,
Cohesive Soils” Journal of Soil Mechanics and Foundation
Engineering, ASCE, Vol. 89, SM1, pp. 115-143.
(45-54) 45
50
Tikrit Journal of Eng. Sciences/Vol.13/No.4/December 2006
Table (1) Properties of Ranipur Sand (After Sud, 1984)
S. No. Property M agnitude
1
2
3
4
5
6
7
8
9
10
Type of soil
Effective size (D10)
Uniformity coefficient
Mean specific gravity
Minimum void ratio
Maximum void ratio
Average density in dense state
Relative density in dense state
Average density in medium dense state
Relative density in medium dense state
SP
0.15 mm
1.73
2.646
0.57
0.88
316.3 kN/m
84%
315.95 kN/m
72%
Table(2) Parameters of Constitutive Laws for Ranipur Sand
(After Sud, 1984)
RD 1A 2A 1K 2K
84% 800 220 178.0 2.2
72% 500 200 137.5 1.44
1and a oTable (3) Values of a
(degrees) oa 1a
o30 0.0974 0.5746
o26.6 0.0947 0.6405
o20 0.0853 0.7144
(46-54) 46
51
Tikrit Journal of Eng. Sciences/Vol.13/No.4/December 2006
0
2
4
6
8
9.5
0 100 200 300 400 500 600 700
(10
x k
Pa)
= E
i4
1 aD = 84%R
D = 72%R
kPa3
Fig. 1 Variation of E (1/a) w.r.t. confining pressure for Ranipur sand (After Sud, 1984)
i
= A + K 1
a 1 13
kPa3
Fig. 2 Variation of Konder's (1/b) w.r.t. confining pressure for Ranipur sand (After Sud, 1984)
= A + K 1
b 2 23
(10
x
kP
a)
21 b
D = 84%R
D = 72%R
0
4
8
12
16
20
0 100 200 300 400 500 600 700
Fig. 1 Variation of Ei (1/a) w.r.t confining pressure for Ranipure
sand (After Sud, 1984)
Fig. 2 Variation of Konder's (1/b) w.r.t confining pressure for
Ranipure sand (After Sud, 1984)
(47-54) 47
52
Tikrit Journal of Eng. Sciences/Vol.13/No.4/December 2006
51
259
Sandy S
oil
Footing
4
3000 mm
900 mm
Fig
. 3 F. E
. Mesh
represen
ting
Fo
otin
g-S
oil S
ystem (n
ot to
scale)
120 mm
(48-54) 48
53
Fig
.3
F
.E. M
esh rep
resentin
g fo
otin
g –
soil sy
stem (n
ot to
scale)
Tikrit Journal of Eng. Sciences/Vol.13/No.4/December 2006
DR= 84%, =26.65o, De/B=0.5
0
2
4
6
8
10
12
14
0 20 40 60 80
Pressure (kPa)S
ett
lem
en
t (m
m)
F.E.A.
Sud 1984
DR= 84%, =20o, De/B=1.0
0
2
4
6
8
10
12
14
0 20 40 60 80 100 120
Pressure (kPa)
Sett
lem
en
t (m
m)
DR= 84%, =30o, De/B=2.0
0
2
4
6
8
10
12
14
0 20 40 60 80 100 120 140
Pressure (kPa)
Sett
lem
en
t (m
m)
DR= 72%, =26.65o, De/B=2.0
0
2
4
6
8
10
12
14
16
0 20 40 60 80 100 120
Pressure (kPa)
Sett
lem
en
t (m
m)
DR= 72%, =20o, De/B=2.5
0
2
4
6
8
10
12
14
0 20 40 60 80 100 120 140
Pressure (kPa)
Sett
lem
en
t (m
m)
DR= 72%, =30o, De/B=3.5
0
2
4
6
8
10
12
14
0 20 40 60 80 100 120 140
Pressure (kPa)
Sett
lem
en
t (m
m)
Fig. 4 Pressure - Settlement Characteristics of Strip Footing
(120 mm width)
Fig. 4 Pressure –settlement characteristics of strip footing (120 mm
width)
(49-54) 49
54
Tikrit Journal of Eng. Sciences/Vol.13/No.4/December 2006
=20o
0
2
4
6
8
10
12
14
16
0 50 100 150 200Pressure (kPa)
Sett
lem
en
t (m
m)
horizontal
De/B=0.5
De/B=1.0
De/B=1.5
De/B=2.0
De/B=2.5
De/B=3.0
=26.6o
0
2
4
6
8
10
12
14
16
0 50 100 150 200
Pressure (kPa)
Se
ttle
me
nt
(mm
)
horizontal
De/B=0.5
De/B=1.0
De/B=1.5
De/B=2.0
De/B=2.5
De/B=3.0 b
=30o
0
2
4
6
8
10
12
14
16
0 50 100 150 200Pressure (kPa)
Se
ttle
me
nt
(mm
)
horizontal
De/B=0.5
De/B=1.0
De/B=1.5
De/B=2.0
De/B=2.5
De/B=3.0 c
Fig. 5 Pressure - Settlement curve of the Cases Analysed
(DR = 84%)
a
Fig. 5 Pressure –settlement curve of the cases analyzed (DR=84%)
(50-54) 50
5
Tikrit Journal of Eng. Sciences/Vol.13/No.4/December 2006
=20o
0
2
4
6
8
10
12
14
16
0 50 100 150
Pressure (kPa)S
ett
lem
en
t (m
m)
horizontal
De/B=0.5
De/B=1.0
De/B=1.5
De/B=2.0
De/B=2.5
De/B=3.0
=26.6o
0
2
4
6
8
10
12
14
16
-10 10 30 50 70 90 110 130 150
Pressure (kPa)
Se
ttle
me
nt
(mm
)
horizontal
De/B=0.5
De/B=1.0
De/B=1.5
De/B=2.0
De/B=2.5
De/B=3.0 b
=30o
0
2
4
6
8
10
12
14
16
0 50 100 150Pressure (kPa)
Se
ttle
me
nt
(mm
)
horizontal
De/B=0.5
De/B=1.0
De/B=1.5
De/B=2.0
De/B=2.5
De/B=3.0 c
Fig. 6 Pressure - Settlement curve of the Cases Analysed
(DR = 72%)
a
Fig. 6 Pressure –settlement curve of the cases analyzed (DR= 72%)
(51-54) 51
6
Tikrit Journal of Eng. Sciences/Vol.13/No.4/December 2006
Fig. 8 Comparison of qu (present sudy) with qu
(Sud, 1984) for Strip Footing adjacent to Slpoes
0
20
40
60
80
100
120
140
0 20 40 60 80 100 120 140
qu, kPa (this study)
qu,k
Pa
(S
ud
1984)
45o
Fig. 7 Evaluation of Ultimate Bearing
Capacity(DR= 72%, =30o, De/B=2.5)
0
2
4
6
8
10
12
0 20 40 60 80 100 120
Pressure (kPa)
Sett
lem
en
t (m
m)
qu=83kPa
Fig. 7 Evaluation of ultimate bearing capacity DR= 72%, β=30
0,
De/B=2.5
Fig. 8 Comparison of qv (present study) with qv (Sud, 1984) for strip
footing adjacent to slopes
(52-54) 52
7
Tikrit Journal of Eng. Sciences/Vol.13/No.4/December 2006
y = 0.0974x + 0.5746
R2 = 0.9455
0.4
0.5
0.6
0.7
0.8
0.9
1
0 0.5 1 1.5 2 2.5 3 3.5
De/B
S/S
o
=30oa
y = 0.0947x + 0.6405
R2 = 0.9375
0.4
0.5
0.6
0.7
0.8
0.9
1
0 0.5 1 1.5 2 2.5 3 3.5
De/B
S/S
o
=26.6ob
y = 0.0853x + 0.7144
R2 = 0.932
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
0 0.5 1 1.5 2 2.5 3 3.5
De/B
S/S
o
=20oc
Fig. 9 Variation of (S/So) with (De/B) ratio
Fig. 9 Variation of (Sβ/S0) with (De/B) ratio
(53-54) 53
8
Tikrit Journal of Eng. Sciences/Vol.13/No.4/December 2006
حساب الهبوط للأسس الضحلة المقامة على التربة الرملية والقريبة من المنحدرات
د. عدنان جايد زيدان مدرس
جامعة تكريت -الهندسة المدنية قسم خلاصةال
الهدف من هذا البحث هو دراسة سلوك الاساسات الضحلة و القريبة من المنحدرات باستخدام طريقة العناصر المحددة. حيث تم تحليل اربع واربعين حالة لاساس
من خلال 1984عام Sudشريطي يستند على تربة رملية والتي تم دراستها )من قبل رب انموذجية(. تمت مناقشة العلاقة بين الضغط و الهطول من خلال النتائج التي تم تجا
الحصول عليها وتشير نتائج التحليل الى تقارب النتائج المستحصلة مع النتائج التي مختبريا. وكذلك تم احتساب مقدار اجهاد التحمل الأقصى 1984عام Sudحصل عليها
هطول( -اطع مماسي المنحني الخاص بالـ )ضغطللتربة تحت الاساس باستخدام تقالاساس والتي تم الحصول عليه لجميع الحالات في هذه الدراسة، و قد بينت النتائج بان
.1984عام Sudهذه القيم للأجهاد الاقصى للتربة مقاربة للنتائج التي حصل عليها هبوط للأساس تم كذلك ايجاد علاقة رياضية يمكن باستخدامها احتساب مقدار ال
القريب من المنحدرات اذا تمت معرفة مقدار الهبوط لنفس الاساس الذي يستند على ارض مستوية. و قد وجد ان بعد الاساس عن المنحدر و زاوية ميل المنحدر يؤثران في هذه
العلاقة، في حين لاتتأثر هذه العلاقة بعامل الامان والكثافة النسبية للتربة.
الكلمات الدالةهبوط، اجهاد التحمل، -العناصر المحددة، لاخطي، الأساسات الضحلة، المنحدر، ضغط