settlement trough associated with diaphragm wall construction in greater cairo

8/12/2019 Settlement Trough Associated With Diaphragm Wall Construction in Greater Cairo

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S O I L M E C H N I CSND

FOUND TIONSWTrntrm

Volume 12 Pt. 2December 2001

HOUSING AND BUILDING RESEARCH CENTRETHE EGYPTIAN GEOTECHNICAL SOCIETY


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PR F C ESOIL MECHANICS AND FOUNDATIONS is a half year book ofThe Egyptian Geotechnical Society which is part of the InternationalSociety for Soil Mechanics and Geotechnical Engineering

hanks to Prof Dr Omaima Ahmed Salah El DinChainnan of th Board of th Housing and building research centre

The Editor

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SOIL MECHANICS AND FOUNDATIONS

Volume 12 - Part 2Scientific Advisory BoardProf. Dr. Abdel-Rahman EI-RamlyFaculty of Engineering.Cairo Univ Giza. Egypt.Prof. Dr. Abdel-Fanah AbouleidFaculty of Engineering.Cairo Univ Giza. Egypt.Prof. Dr. Mohamed EI-SohbyFaculty of Enginee:ing.AI-Azhar Univ C ~ i r o Egypt.Prof. Dr. Abdel-Rahrnan BazaraaFaculty o EngineeringCuiro Univ Giza. Egypt.Prof. Dr. Mostafa EI-DemeryHousing and Building Research CentreDokki. Giza. Egypt. .Prof. Dr. Mohsen .YlashhourFaculty of Engineering.Zagazig Univ Zagazig. Egypt.Prof. Dr. Nadia GirgisHousing and Building Research CentreDokki. Giza. Egypt.

December 2001Scientific Editorial BoardProf. Dr. mr RadwanFaculty of Engineering at Mararia.Helwan Univ Cairo. Egypt.Prof. Dr. Amira Abdel-RahmanHousing and Building Research CentreDokki. Giza. Egypt.

onnerlyProf. Dr. Mohamed EI-SohbyFaculty of Engineering.AI-Azhar Univ Cairo. Egypt.Prof. Dr. Osama MazenHousing and Building Research CentreDokki. Giza. Egypt.

Soil MechC ics nd Foundations represents one o the scientific activities oThe Egyptim Geotechnical Society which is registered at the Ministry o SocialAffairs. Registration No. 1162/1993Address: : EI-Tahri i Street. Rm. 422. Dokki. Giza. Egypt. Tel. 1,:02)3369418

The Egyptian Geotechnical Societ is part ofThe Intem:?tional Society for Soil Mechanics and Geotechnic:ti Engineering


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SOIL MECHANICS AND FOUNDATIONS

Volume 12 - Part 2 December 2001

O N T E N T SEffect of Ground Anchors on the Behavior of iaphram Walls.

Mohamed E EI-Kilany and Tarek N Salem 1Validation of a New Method for Calculating the Edge MoistureVariation Distance.Basuony EI-Garhy and Abdel-Fattah Youssef 13Settlcmcnt Trough Associatcd with Diaph.-am WallCOllstructiouiu GI catcr Cairo.

A A Abdel Rahman aud S.M. EI-Sayed 29Evaluation of thc Performance of the Dilatometer in CohesiveSoils.

M M. AbdeI Rahman, M. A Elkhouly. O Ezzeldine and A FElhakim 41A New Method for Investigating Compressibility fromOedometer Tests.F ~ B ~ ~ ~Possible Correlation Between Some Engineering andElectro-Chemical Properties of Fine Grained Soils.Nagwa R EI-Sakhawy 71


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Jurnal o the Egyptian Geotechnical Society Vol 12 P:: rt 2 December 2001

Settlement Trough Associated with Diaphram \VallConstruction in Greater CairoA. A. Abdel RahmanS.M. EI-Sayed

ABSTRACT

Ass. Prof., Civil Engng. Dept., Engng. Res. Div .Nat. Res. Centre, EgyptAss. Prof., Struct. Engng. Dept., Fac. of Engng., - loin Shams Univ.

Deep excavation with the use of concrete diaphragm walls, as side supports, haveht cn increasingly applied in Greater Cairo for several purposes such as basements,IInderground garages, cut-and-cover tunnels, and subway stations. The wide use of concretediaphragm walls is attributed to the development of powerfi.il trenching equipment, theIItilization of bentonite sluITv as a support to the sides of trenches, Iii:: incorporation of wallsinto permanent structures, and the relative simplicity of their COllstrurnon compared withotiler traditional methods for vertical cut-off purposes. The most challenging task to)l.t otechnical engineers is to estimate the settlement associated with the trenching process,especially if the diaphragm wall is constructed near existing structures. Computationalcomplexities to obtain an acceptable estimate for the settlement field associated withtrenching, comprise the sequence of panel construction of the wall, the wall alignment, thepanel dimensions, the local soil formation of the site, the presence ofgromdwater the rate of~ ) n s t r u c t i o n , the presence of neighboring buildings, and the workmanship quality. Theobjective of this paper is to present observed settlements of buildings founded on differenttypes of foundations while constructing nearby continuos diaphragm wail panels. The fielddata were utilized to empirically estimate a generic settlement trough :0 be used for futureprojects. Also, the data were back analyzed using a widely practiced two-dimensional plane,;train finite element model to verity its reliability.Keywords: Diaphragm wal : trenching; excavation; settlement monitoring; structuraldamage; nonlinear analysis: twC'dimensional, and finite element.

I INTRODUCTIONDiaphragm wall construction imposes many engineering challenges regarding the;Iability of the excavated pands and the hazardous effect of the resulting deformation field onadjacent structures. The stability of the wall is preserved by the. iiquid support of thebentonite slurry. The most important property of the stabilizing slurry is its ability to establishalmost instantaneously a quasi-impermeable membrane or mudcakc at the soil-liquidi erface which contributes to the stabilization of the trench. Another significant factor intrench stability is the limited penetration of the bentonite into the soil (Sliwiniski and Fleming

1'17'); Fuchsberger, 1975).

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It has been proven that settlement troughs are usually associated with the process ofdiaphragm wall construction (poh and Wong, 1998). It was typically assumed thatdeformations will be small if there is an adequate factor of safety against overall instability ofthe trench (Goldenberg et aI. 1976). However, building settlements of more than 2 incheswere recorded during a trenching process in Hong Kong (Cowland and Thorley, 1985).Settlement damage to buildings is usually estimated using the angular distortioncriterion presented by Skempton and MacDonald (1956) or the tensile strain criterionintroduced by Burland and Wroth (1975). These common criteria necessitate assessing thesettlement profile or the settlement envelope emerging below buildiI)gs and buried pipelines.To estimate the settlement trough associated with the construction of diaphragm walls,different profiles have been recommended in the literature (Kutmen, 1986; Clough andO'Rourke, 1990; Thompson 1991; Gunn and Clayton, 1992; De Moor, 1994; Ng et. ai 1995;Gourvenec et. aJ 1998). Figure (1) presents widely accepted settlement distributionssuggested by Clough and O'Rourke (1990) and Tompson (1991). Clough and O'Rourke(1990), after ploning data from well documented case histories performed in alluvial soilconditions, recommended an upper limit of settlement equivalent to 0.15% of the trench

depth at the wall location, while the settlement trough is extended to about twice the trenchdepth, as shown in Figure I). On the other hand, Tompson (1991) recommended a settlementtrough, for over-consolidated clays, that has a maximum settlement value of 0.04% of thetrench depth, and extends to a maximum distance of about 3 times the excavation depth.Figure (2) presents the associated settlement trough with the trench excavation recommendedby Cowland and Thorley (1985), in silty sand deposits, which has a maximum settlementordinate of about 0.15% of the trench depth, and vanishes after about twice of the trenchdepth. The shortcoming ofgenerally applying these criteria tor any project is that they mightbe suitable only for a specific subsurface soil condition and trenching technique. Therefore,they can not be totally applicable when applying for projects located within differentgeotechnical conditions.The subsurface soil conditions throughout Greater Cairo are typically alluvial soils,especially around the river Nile and its branches, with relatively shallow groundwater level.These conditions are classified as problematic in case of diaphragm wall trenching due to therelatively expected higher values of settlement (Clough and O'Rourke, 1990). The escalatingneeds for an acceptable estimate of the deformations associated with the trenching process inGreater Cairo call for monitoring and back analyzing many projects in order to gain moreperception on the behavior of slurry trenching and their effect on nearby buildings. Estimatesof ground movements for ,future projects, having similar conditions, can be made using theempirical relationships developt d from these studies.This paper presents a c,'8e history where buildings' settlements were monitored whileexecuting diaphragm wall panels for a multistory building located in Dokki, Giza, Egypt.Back-analyses were performed on the monitored data to recommend a generic settlementdistribution to be associated with diaphragm wall construction, and verify the reliability ofawidely used plane-strain model.

2. THE SITE A ,;j) SUBSURFACE SOIL GEOTECHNIC L CONDITIONSThe case history of this paper presents the settlement data monitored during theconstruction of a diaphragm wall of a basement of a multistory building in Dokki, Giza,Greater Cairo during the year 2001. The site is located at nearly 1.0 km away from the river

Nile. The diaphragm wall is located as near as 1.80 m to existing buildings founded on deep30

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(piles) and shallow foundations. The diaphragm wall depth was 21.00 m with a thickness of0.60 m, and a steel reinforcement from top to tip. A grab-bucket machine with the use ofbentonite suspension, as a drilling fluid, was used to excavate the trenches.

The project area lies totally within the geomorphic unit known as the young alluvialplain representing the majority of the lowland portion of the Nile Valley in the Greater Cairoarea. Generally, the geology of Greater Cairo is characterized by tertiary sedimentary soilsand rocks and quaternary ;;oils, both underlain by older basement rocks. The Nile Riverdeposits govern the subsurface


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The maximum settlement for buildings founded on shallow foundation was about4.5mm, recorded at the locations of points 25, and point 22 on buildings D and E,respectively, located on the same distance from the diaphragm wall boundary. The minimumsettlement was recorded at point 24, building B , and point 31, building D located also atthe same distance from the diaphragm wall boundary: Figure (6) shows the plot of thesettlement of all points with distance away from the diaphragm waIl boundary.Generally, the settlements of all buildings can be expressed with one enveloperegardless of their foundation type. However, different settlement values were recorded atsimilar distances away from the diaphragm wall, which could be related to the effect ofdifferent buildings' stiffnesses or change in the mechanical properties of the foundation soilunderneath each building. It is worth noting that settlement of the buildings founded on deepfoundation occurred due to the fact that the depth ofdiaphragm wall panels was deeper thanthe depth of the piles of buildings A, B, and C .No form of structural cracks was observed in any building adjacent to the wall afterfinishing the diaphragm wall installation.A proposed general envelope of the settlement is shown in Figure (6). It can be seenthat the maximum observed settlement at the wall location is about 9.5 mm and extends to a

lateral distance of about 35.0 m. The maximum settlement represents a ratio of about 0.045%of the trench depth, and the lateral extent of the settlement trough goes to a maximum of 1.67of he trench depth.Therefore, we could reasonably recommend a settlement trough envelope where themaximum settlement is equivalent to 0.045% of the diaphragm wall trench depth, while itsextent away from the wall reaches to twice the same trench depth. The proposed distributionof the settlement trough can be expressed by the following equation:

S =s [ d - XJma x d

Where, S is the settlement at a distance x from the trench, Sma< is the maximumsettlement at the wall location, and d is trench depth. Figure (6) also presents a comparisonbetween the proposed settlement trough distribution, the envelopes recommended by Cloughand O'Rourke (1990), and Thompson (1991). The recommended maximum settlement byThompson (1991) was in a good agreement with the measured maximum value, whereasClough and O'Rourke's maximum settlement was much higher. Both envelopes showedwider and higher settlement trough distributions than the measured values.

4 NUlVIERICAL MODELING OF TRENCHING . , .Empirical formulas based on previous observations are commonly used to describe

the induced deformation due to the trenching required for diaphragm walls installation.However, they might not be regarded as a reliable basis of analysis even under the sameground conditions. This is because different installation and construction procedures andvarious boundary conditions are not deliberated in these empirical formulas. Plane-strainmodels are the most common among engineers to analyze walls. Plane-strain modeling of thetrenching process could be considered as an appropriate tool for estimating the maximumsettlement. However, the trough resulting from the plane-strain models are always wider thanthe actual profile due to the three-dimensional nature of the profile and the demerits of thewidely implemented classical constitutive relations.A two-dimensional plane-strain model was employed in this paper to back analyze thefield 'data and confirm its validity.

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III

The Hardening-Soil constitutive model of Plaxis vel' 7.2 (Brinkgreve and Vermeer,I J'IH) was used to simulate the behavior of different types of soils in which a decreasingIii I f l l cs,; is exhibited when subjected to primary deviatoric loading. That stems from a yieldI\lllcl;on (fJ of the form:

1 q 2q pf = . 2e l50 1 - R;CJ CJ 0;,

(I)ill which the model parameters q, qt; E5Q, and Eu are defined in Figure (7-a); Rr is the failure111111 which equals to q/qa, and et is the principal plastic strair:. Figure (7-b) presents thebhllPC of the yield func:ion (f) for cohesionless soils in the pI incipal stress s p a ~ e TheIl l',ociative flow rule is adopted so that the outward normal vector to the yield surface (f)I rplcsents the plastic strain vectof. The parameter 50 is the stiffness modulus for primaryIl"ldilig and is given by the equation:( )E = cef CCO lO - u ;0 E JO reiC C 0 { 9 ' P ~ (2)where Fj if is a reference stiffness modulus corresponding to the reference atmospheric1.'""lIning pressure (p"I), and m is an exponent number dominates the equation degree. Thehe:lI parameters c,


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s s [2d XJ6' 2d

Plane-strain finite element modeling can be used to predict settlement distributionassociated with diaphragm wall construction. However, due to the numerical limitation ofthat type of modeling, the settlement distribution is expected to be wider than the real on-sitebehavior although the maximum expected settlement at the wall location can be predicted.

6. REFERENCESL Brinkgreve, R. and Vermeer, P., 1998, Plaxis Ver 7.2: Material Models Manual , A.

A. Balkema, Rotterdam.2. Burland, J. B. and Wroth, C. P., 1975, Settlement of Btiildings and AssociatedDalUage , Build. Res. Establishment Current Paper, 33(75), Building ResearchEstablishment, Watford, England.3. Clough, G. and O'Rourke, T., 1990, Construction Inquced Movements ofInsituWalls , Design and Performance ofEarth Retaining Structures, ASCE GeotechnicalSpecial Publications 25, pp. 439-470.4. Cowland, J. W. and Thorley, C. B. B., 1985, Ground and Building SettlementAssociated with Adjacent Slurry Trench Excavation. Ground Movements andStructures - Proc., Third Int. Conf, University of Wales Institute of Science andTechnology, J. D. Geddes, ed., Pentech Press, London, England, 723-738.5. De Moor, E. K. 1994, "An Analysis of Bored PilelDiaphragm Wall InstallationEffects , Geotechnique, London, England, 44(2), 341-347.6. EDECON, 200 I, Geotechnical Report for Administrative Building Located in EIDokki, Giza, Egypt..7. Fuchsberger, M., 1975, "Some Practical Aspects of Diaphragm Wall Construction ,Proc. ofDiaphragm Walls Anchorages, Institution of Civil Engineers,London, pp.75-79.8. Goldberg, D. T. Jaworski, W. E. and Gordon, M. D., 1971\ Lateral Support andUnderpinning - Vol. III. Construction Methods , Report No. FHWA-RD-75-130,prepared for Federal Highway Administration, Office of Research Development,Washington D.C., p. 465.9. Gourvenec, S., and Powrie, W., 1998, Three-Dimensional Finite Element AnalysisofDiaphragm Wall Installation , Geotechnique (1999), Vol. 49, No.6, PP 801-823.10. Gunn, M. J. and Clayton, R. 1. 1992 Installation Effects and Their Importance in theDesign of Earth Retaining Structures , Geotechnique, London, England, 42(1), 137-142.

II. Kutmen, G., 1986, The Influence of the Construction Process on Bored Piles andDiaphragm Walls: A Numerical Study , Master's of Philosophy thesis, Univ. ofSurrey, England. .12. Ng, W. W., and Lings, M. L., 1995. Effects ofModeling Soil Nonlinearity and WallInstallation on Back-Analysis ofDeep Excavation in Stiff Clay , J. Geotech. Engrg.,ASCE, 121(10),687-695.13. Ng, C. W. W. Rigby, G. H Lie, G. H. and Ng, S. W. L., 1999, ObservedPerformance ofa Short Wall Panel , Geotechnique, Vol. 49, No.5, pp. 681-694.14.' Poh, T. Y. and Wong, . H. (1998). Effects of Construction ofDiaphragrn WallPanels on Adjacent Ground: Field TriaL Journal of Geotechnical and Geoenvironmental Engineering., Vol. 124, No.8, ASCE, 749-756.

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' \ f l l " * J I T g r g ; ~ 4 ; r : j % i i i i i f i i i j i i l l \ ; r ) 1 \ . . \ j ; a ; i ; , 2 ; ; , 6 ' ; . I j ; ' , ; h ;, m H , ~ ....... ; ; ; ; ' ; ~ l

I Salem, A M., 1997, Geotechnical Report for Administrative Building Located in El 'Dokki, Giza, Egypt.1 \ Schmertmann, J H, 1970, Static Cone to Compute Settlement Over Sand , Journalof the Soil Mech. And Found., ASCE, VoL 96, SM3, pp. 1011-1042.Ir Shata, A. A, 1988, Geology of Cairo, Egypt , Bulletin of the Association ofEngineering Geologists, VoL XXV, No.2, pp. 149-183.III. Skempton, A. W. and MacDonald, D. H., 1956, The Allowable Settlements ofBuildings , Proc., Inst. of Civil Engrs., Part III, The Institution of Civil Engrs.,London, pp. 727-768.

I'), Skempton, A W., 1986, Standard Penetration Test Procedures and Effect in Sands ofOverburden Pressqre, Relative Density, Particle Size, Aging and Over-consolidation ,Geotechnique, VoL 36, No.3, pp. 425-447.)0, Sliwiniski, Z. and Fleming, W. G. K, 1975, Practical Considerations Affecting theConstruction of Diaphragm Walls , Proc. of Diaphragm Walls & Anchorage,Institution ofCivil Engineers, London, pp. 1-10.11 Thompson, P., 1991, A Review of Retaining Wall Behavior in OverconsolidatedClay during Early Stages ofConstruction , Mphil Thesis, Univ. ofLondon, London,England.l.2. Wolf, T E, 1989, Pile Capacity Predication UsingPar meterFunctions , ASCEGeotechnical Special Publication No. 23, pp. 96-106

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Table (1): Geotechnical properties of strataDepth .Cohesion Unit Weight E r t l PoissfjLayer ~ o 50(m) . (kPa) kN m (MPa) ratiFill 0.00- 0 17 29 6 0.42.00

SILT-SAND 2.00- 0 18 31 10 0.35.00 .'Fine SAND, 5.00- 0 19 33.5 16 0.3some silt 11.00Graded 11.00-SAND,some 25.00 0 20 36 20 0.3aravel

Distance f rom TranchITrench Deptho 0.5 1.5 2 2.5 3a r ~ ~ _ ~ ~ ~

I0.02

0.04 .

0.00

o.oa0.1 .

0.12 .

0.14 .

0.16

------- --------------

I - Clough and O Rourke, 1990---Tompl >o:l. 1991

Fig. (I): Settlements envelopes associated with in-situ walls trenching

,

Dll,I.lanCG om Trench )(6f1Pth of Troneh D

.. , 0,o I 'I ... ., . . ':.. .... .:

I . .IlIa 0.06 .. I':: ...... _ cO .:..

0.10 :.:;:oo

, .

Fig. (2): Building settlements due to slurry trench excavation(after Cowland and Thorley, 1985)

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W

k .. 0 h ~ 0- , : X4 S i $. ,

S?T f i?-:t:, S?T ( i ~ " f " 4: ,,0' '

5 0 ,"' 'OJ ,

I .. .... .- 1 5 f 101 .. '0 _. .I ... ...15 ... '5 .. ... 20 .... 20 .... 25 5

~ - - - - - - - - - - - - - - - - ~ I u

~ ~ = = = ~ .

'50 28 3() " 34 36 38 0o , 0

5 5 0 . 10.. + ...5 15 ... 20 .... 20

25 25

oW

Eli15 (kN/m )10000 20000

.. .. ... ....

~w

30000

I

30LI________________ 2 ~ L I ______________ 30LI__________________ ~ L I ________________ J

Fig. 3): Site characterization

~w

~ [:::::1

1:>1

~ l i

o:

FILL

-:;... '". '' =

S I L T ~ N D

FINE SAND,SOME SILT

GRADEDSAND,SOME

GRAVEL


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oxSettlement painl

3m

6

20 Z 1312 8Diaphragm wall panels

3 \ 6

2310 5 .,'. E4 2 22 -.74I ) 1 > L = I = : : r : : ~ : : : r : : : S r ~12 8m : 35 1 8 ( 1005 )

Fig. -\): Layout of the wall and the settlement pointsConstruction sequence ofpanels is indicated by numbers)

38


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Lj",,,

' j t

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j

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,,


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Ohslanoo f r o m tho t rcmoh em ,. 15 20 2S 30 35

.. i ~a _ ~ - - - ~ - - - - - - - - ~ - : : - - ~ - - - - - - - - ----- -- ----------t ------I I, "- - - - - - - - - - - - - - ~ - - - - - - ~ - - ~ - - - - - - - - - ~ - - - - - - ~ - - - - - - - ~ - - - - - -I I I;iE

: 2

I I I1 , I I--------------r--- ~ -------r------,-------r------I l I I II Measured- - ~ - - - - - - : - _-1 - - ~ . -Proposed Envolope

I J I - - F E25 I I J _Tompson C1991_. t - --- --- - - - - - . : - - -.-----j-. _Clough & O Rouke (1990)I I I I II I I I i30 I I i I I I- - - - - - - - - - - - - r - - - - - - ~ - - - - - - - T - - - - - - - r - - - - - - - - - - - - - r - - - - - - -

J I I I I II I J I I I, ,35

Fig. (6): Comparison between measured settlements andmticipated profiles,la __ __ ______ E . . ~ ~ 2

- q,0Ce"0I;1"

___ ---- failure lin ..

i

(a)

s h e a \ : r , I ' . " d " S ' u ' r t a ' c ' 1 ~ ~ ~ ~ ~ ~ ~ ~ :.... -0',shear leld surface

(b)Fig. (7): Hardening soil model : (a) hyperbolic stress-strain relation;

(b) yield surface forcohesionless soil (after Brinkgreve and Vermeer, 1998)

Fig. (8): Finite element mesh

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settlement trough associated with diaphragm wall construction in greater cairo

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