Behavior of Laterally Top-Loaded Deep Foundations in Highly ...

Behavior of Laterally Top-Loaded Deep Foundations inHighly Porous and Collapsible Soil

Paulo José Rocha de Albuquerque, D.Sc.1; David de Carvalho, D.Sc.2;Roberto Kassouf3; and Nelson L. Fonte Jr.4

Abstract: Problems associated with horizontal loading in foundation structures often occur when the surface soil has particular character-istics like the unsaturated, porous, and collapsible soils that are very common in Brazil. In the state of São Paulo, more precisely in the regionof Campinas, the occurrence of such soils is detected in several places. For this reason, this work was conceived for the purpose of assessing theperformance of four types of deep foundations subjected to horizontal loading via analysis of the load versus horizontal displacement curve anddetermination of the horizontal reaction coefficient of the soil (nh). To accomplish this, load tests were carried out with bored piles, continuousflight auger piles (CFA), steel piles, and belled caissons at the Experimental Site of Foundations at the StateUniversity of Campinas—Unicamp,Campinas, São Paulo, Brazil. The tests were performed under soil conditions of naturalmoisture and after 48 h of flooding. The results showed alarge drop in parameters of soil resistance due to flooding—an approximately 50% drop on average for the ultimate load and 70% for thehorizontal reaction coefficient of the soil. DOI: 10.1061/(ASCE)MT.1943-5533.0002582. © 2018 American Society of Civil Engineers.

Author keywords: Lateral load tests; Foundations; Highly porous soil; Collapsible soil.

Introduction

The soil and the foundation elements are critical parts to considerwhen analyzing the behavior of a structure. In some cases, deepfoundations are used because of the need to transmit loads in deepand resistant soil horizons. In general, this type of foundation can besubmitted to different simultaneous loads (vertical, horizontal, andbending moments) and to different types of loading (static, cyclic, ordynamic). Although these situations occur frequently, few cases arereviewed, particularly in porous, collapsible soils. In many cases,parameters used in other studies are adopted, ignoring the hetero-geneity and particular behavior of these types of soils. The calcu-lation of horizontally loaded piles is carried out with the use ofsimplified mathematical models that reduce the complexity of thereal problem. In the literature, one can review the classical modelspresented by Miche (1930), Matlock and Reese (1961), Broms(1964), Poulos (1971), and Poulos and David (1980).

The most commonly used concept is the theory of horizontalreaction of the soil (Terzaghi 1955; Palmer and Thompson 1948;Davisson and Gill 1963; Matlock and Reese 1960, 1961; Davisson1970). This theory enables estimation of the proportionality be-tween the reaction and soil displacement by means of a factorknown as the coefficient of horizontal reaction (nh). This parameter

is difficult to determine mathematically, but it can be calculated viaload tests. In the case of horizontal loading, the load is assessedaccording to a prefixed or limit displacement, because it is not easyto identify the geotechnical rupture load as observed in compressionand traction loadings. In this way, when sizing piled foundationsunder horizontal loading, the criterion for the project is not theultimate horizontal load capacity; the criterion is the maximum dis-placement or, in some cases, the prefixed displacement that the loadcan attain (Poulos and David 1980).

The critical parameter to be determined in a horizontal loadingtest is the coefficient of horizontal reaction (nh), which is defined asthe horizontal reaction of the soil along the pile shaft divided by itsdeflection in a determined position. In general, simplified hypoth-eses are used in foundation projects that involve horizontal loading,adopting proportionality between the soil reaction and the displace-ment of the deep foundation.

It must be pointed out that this parameter is not an intrinsic prop-erty of the soil, because it depends on the characteristics anddimensions of the piles and on the displacement to be imposed.Considering the difficulty of estimating its value theoretically, it iscommon to use the resource of load tests as a means to determinethis parameter more appropriately, because it is performed in theplace where the construction will occur.

In Brazil, the incidence of porous, collapsible soils in surfacelayers is high; such soils may represent more than half of the cover-age area in a determined region. Several studies have been performedin Brazil to analyze the behavior of deep foundations, particularly bymeans of piles in this type of soil (Cintra 1981; Cintra and Aoki2009; Del Pino 2003; Miguel and Cintra 1996; Miguel 1996). Thesestudies demonstrated the influence of these soils under the effect ofhorizontal loading, particularly when the moisture content varies,leading to excess decrease of horizontal reaction.

In the study of transversally loaded piles, a key aspect is thereaction of the soil, that is, how the soil reacts when it receives pileloads. Hence, the problem of laterally loaded piles is a problem ofsoil–structure interaction, which involves key characteristics suchas the type of soil, the physical and mechanical properties of the

1Associate Professor, School of Civil Engineering, Architecture andUrban Design, Univ. of Campinas, Campinas 13083-889, Brazil. Email:[email protected]

2Associate Professor, College of Agricultural Engineering, Univ. ofCampinas, Campinas 13083-875, Brazil. Email: [email protected]

3Professor, Dept. of Civil Engineering, DeVry Metrocamp, Campinas13035-500, Brazil (corresponding author). Email: [email protected]

4Director, Geoponto Engineering, Mogi das Cruzes 08773-530, Brazil.Email: [email protected]

Note. This manuscript was submitted on August 14, 2017; approvedon July 25, 2018; published online on November 26, 2018. Discussionperiod open until April 26, 2019; separate discussions must be submittedfor individual papers. This paper is part of the Journal of Materials inCivil Engineering, © ASCE, ISSN 0899-1561.

© ASCE 04018373-1 J. Mater. Civ. Eng.

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https://doi.org/10.1061/(ASCE)MT.1943-5533.0002582

mailto:[email protected]





soil, pile stiffness and geometry, and the type of loading (static,dynamic, cyclic).

In the study of piles subjected to horizontal loading, it is neces-sary to determine the variation of the modulus of the horizontalreaction of the soil with depth. The simplest hypotheses are thosethat take the modulus of horizontal reaction as constant or as grow-ing linearly with depth, a variation linked to the characteristicsof soil deformation.

The theory of soil horizontal reaction (Winkler’s hypothesis),which enables simulation of the behavior of soil submitted to hori-zontal stresses with a set of independent springs, it is possible toconsider the proportionality between the soil reaction and the dis-placement of the spot under analysis. This is how Terzaghi (1955),through Winkler’s hypothesis, defined the relationship betweenhorizontal stress and displacement with the concept of the coeffi-cient of horizontal reaction of the soil (K), which can be seen inEq. (1). This reaction is defined as the relationship between the soilreaction (in units of force applied along the pile length) and thecorresponding displacement [Eq. (1)] (Reese and Van Impe 2011):

K ¼ py

ð1Þ

whereK = modulus of horizontal reaction (FL−2); p = applied force(FL−1); and y = horizontal displacement (L).

This notation presents the advantage of being independent of thediameter of the foundation. Therefore, Eq. (1) can be rewritten as

K ¼ kh · D ð2Þwhere kh = horizontal reaction coefficient (FL−3); and D = diameterof the foundation (L).

For pure sand, the Young’s modulus increases (approximately)linearly with depth. Therefore, the soil reaction to the load appliedto the pile is assumed to increase linearly with depth [Eq. (3)]:

K ¼ py¼ nh · z ð3Þ

where nh = modulus of the horizontal reaction of the soil (FL−3);and z = depth (L).

Although the supposed behavior of the variation of the modulusof horizontal reaction is not precisely similar to the actual behavior,the approximations are considered effective because, according toTerzaghi (1955), refinements and sophistications in the reactionmodulus function are not justifiable due to the depth, because errorsin the results of the calculations are very small when compared tothose involved in the estimation of numerical values of soil reactionmoduli. Therefore, for most cases, fully satisfactory results can bederived by using laws of simple variation of the reaction moduluswith the depth. Matlock and Reese (1960) supplemented this affir-mation by stating that the use of results from practical cases, bymeans of load tests, is a common tool for such cases and a simpleway to get the modulus of horizontal reaction. The first studies onthe results of load tests in sandy soils were those produced byAlizadeh and Davisson (1970), showing a graph of the variationof the coefficient of horizontal reaction (nh) in the y-axis and hori-zontal displacement (yo) in the x-axis using equation Eq. (4) asproposed by Matlock and Reese (1961):

yo ¼�HT3

EI

�Δy ð4Þ

where T = relative stiffness between the pile and the soil; H =lateral load; E = Young’s modulus of the pile; I = inertia moment;and Δy = correction of the vertical displacement.

The relative stiffness (T) is defined by Eq. (5):

T ¼ffiffiffiffiffiffiEInh

5

sð5Þ

The modulus of the horizontal reaction (nh) is defined byEq. (6):

nh ¼4.42H5=3

y5=3o ðEIÞ2=3ð6Þ

This work was developed based on the results of horizontal load-ing tests in foundations executed locally. With the results, it waspossible to draw the load versus horizontal displacement curves foreach soil condition (natural and preflooded) as well as graphs of thecoefficient of horizontal reaction versus horizontal displacement.The displacements were measured at the tip of the pile at the samelevel as the application of the load. The nh values were obtained perthe proposal of Alizadeh and Davisson (1970).

Materials and Methods

This section presents the main geological and geotechnical charac-teristics of the experimental site and the characteristics of the pilesand belled caisson studied.

Geological and Geotechnical Characteristics

Diabase soils in the northwest region of Campinas surface as dark,reddish-brown porous soil. The subsoil of the experimental site iscomposed of a layer of diabase soil mostly composed of a sandy-silty clay surface layer with high porosity down to a depth of 6 m,followed by a sandy-clayey silt layer down to a depth of 19 m. Thewater table is found at a depth of 18 m (Cavalcante et al. 2007). Inorder to determine the geotechnical properties of the local subsoil,undisturbed samples were extracted down to 15 m deep in order tocarry out tests of characterization, resistance, and compressibility.Standard penetration tests with torque measurements (SPT-T) andcone penetration tests (CPT) were also performed (Fig. 1).

In order to assess the collapsible characteristics of the soil,oedometric tests were conducted at determined depths (0.75 m,5.00 m, and 8.00 m) Monacci (1995) (Table 1). From the resultsobtained, the proposal of Vargas (1978) was used, which considerspotentially collapsible soils as soils with a degree of structuralcollapse above 2% [Eq. (7)]:

i ¼ Δec1þ ei

ð7Þ

where Δec = variation in the void ratio due to collapse of the soilstructure; and ei is the index of voids before flooding.

In addition to the study carried out by Monacci (1995), anotherresearch study regarding collapsibility was conducted by Gon(2011), who performed oedometric tests with flooding at stressesof 100, 200, and 400 kPa. Table 2 shows the results of the collaps-ibility index (Vargas 1978). The results indicate that at prefloodingstress values of 200 kPa and 400 kPa, the soil indicates a potentialfor collapse at almost all depths. For a stress of 100 kPa, only thesamples at 1 m, 4 m, and 8 m indicate the potential for collapse(Table 2).


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Load Tests

The preparation of the tests followed the recommendations of theUS standard D3966 (ASTM 2013), which provides standard testmethods for deep foundations under lateral loads. The minimumtime of application for each load was 30 min, following the require-ments of the Brazilian standard NBR 12131 (ABNT 2006) forslowly maintained load tests (SMLT). The location tests are shownin Fig. 2.

Two load tests were performed for each type of foundation, thefirst with soil in a natural condition and the second with a soil in apreflooding condition. The tests followed the Brazilian standard

Typical profile based on SPT

Dep

th (

m)

0

2

4

6

8

10

12

14

16

18

20

22

Red poroussilty clay

(Colluvium Soil)

Concretion

Redclayey Silt

(ResidualDiabasic)

CL LG'

ML NG'

Siltyfine sand

(DecomposedDiabasic Rock)

GWL

Grain SizeDistribution (%)

0 25 50 75 100

Med

ium

san

d

Cla

y

Fine

san

d

Silt

qc (MPa)

0 1 2 3 4 5 6

Rf (%)

0 2 4 6 8 10

fs (MPa)

0.0 0.1 0.2 0.3

Nspt 60(blows/30 cm)

0 10 20 30 40

T/Nspt 60(N.m/blows/30 cm)

0 10 20 30 40

Fig. 1. Electrical and mechanical CPT and SPT-T test results. (Adapted from Giacheti et al. 2004.)

Table 1. Collapse coefficients according to the applied pressure and thedepth

Depth (m) σ (kPa) i (%)

0.75 5.0 5.09.8 11.119.4 7.4

5.00 9.8 2.419.4 3.8

8.00 38.7 3.177.3 5.3

Source: Data from Monacci (1995).

Table 2. Collapsibility index

Depth (m)

PC (%)

100 kPa 200 kPa 400 kPa

1 7.80a 27.0a 6.00a

2 1.30 0.65 23.0a

3 0.45 0.04 19.8a

4 9.90a 7.50a 26.8a

5 0.28 7.03a 7.24a

6 1.10 3.40a 9.20a

7 1.40 5.60a 10.7a

8 5.20a 6.60a 0.09

Source: Data from Vargas (1978).Note: PC = potential collapsibility.aPC > 2%.

Fig. 2. Pile test locations.


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NBR 12131 for slowly maintained loading tests; that is, the read-ings were acquired at times of 1, 2, 4, 8, 15, 30 min, and so forth.The minimum time before changing the load stage was 30 min.The load stages used were on the order of 10% of the maximumestimated load with a limit displacement of 25 mm for finalizing theloading.

Prior to the beginning of the preflooding process, a preexcava-tion with a depth of approximately 0.3 m and dimensions of 0.5 ×0.5 mwas constructed. From this well, it was possible to maintain aconstant water depth. The preflooding was maintained until the be-ginning of loading. Flooding was maintained for 48 h, and the flowrate was measured through a hydrometer; the flow averaged a watervolume of 52 m3, that is, 1.08 m3=h. Although the soil has a clayeytexture, its behavior is similar to sandy silt with a porous structure(63% average porosity and 1.8 × 10−5 m=s permeability coeffi-cient), which justifies the percolated volume.

The load tests were performed using a hydraulic jack witha 500 kN capacity and a pump and load cell with the samecapacity. For the belled caisson tested, there were two other cais-sons reacting against each other on the other side, as seen in themodels in Figs. 3 and 4.

After the tests, samples of the subsoil were obtained to verify theinfluence of flooding on the subsoil. The samples showed thatflooding changed the soil moisture to a depth of 3 m.

Tested Piles

The load tests were performed on four types of deep foundations.Table 3 shows the characteristics of the elements used.

Results and Analysis

Load versus Displacement

From the results of the load tests, it was possible to obtain theload versus displacement curves and their maximum values.Table 4 summarizes the values of the maximum load and maximumdisplacement, and Figs. 5–8 show the load versus displacementbehavior.

The loading end criterion was based on a minimum displacementof 12 mm, so that nh could be calculated for the predetermined in-terval (6–12 mm) or for a load that would guarantee the structuralintegrity of the pile, as was the case with the bored pile. In view of itsreinforcement rate, it was found that it would not be possible to addmore load to the structural element.

Table 4 shows that, in the case of the caisson, the maximumload was higher for flooded conditions than for the natural soil.However, it should be noted that the maximum displacement was9.5 times higher than that obtained in natural conditions. In theother foundation types, the loads obtained in flooded conditionswere lower, that is, less than half the values in natural conditions,showing the collapsible behavior of the subsoil. It is possible toverify the differences in the behavior of the load versus displace-ment curves for the analyzed conditions in Figs. 5–8.

Preflooding the topsoil caused a drastic reduction in soil resis-tance to horizontal loading. Taking a 5-mm displacement as a refer-ence for the steel pile in natural soil conditions, the supported load

Fig. 3. Belled caisson system setup.

Fig. 4. Assembly details of the belled caisson load test.

Table 3. Pile characteristics

Characteristic

Foundation type

Steel pile CFA pile Bored pile Belled caisson

Length (m) 12 12 12 9Section W ¼ 250 mm × 32.7 kg=m; S ¼ 42.1 cm2;

Iyy ¼ 473 cm4; Ixx ¼ 4,937 cm4

0.40 m 0.40 m Shaft = 0.8 m;base = 1.6 m

Reinforcement (mm) — 4ϕ16 4ϕ16 15ϕ25Young’s modulus (GPa) 205 21 20 20

Note: W = designation; S = area; Iyy = inertia moment (y − y); and Ixx = inertia moment (x − x).


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is approximately 50 kN, whereas in the preflooded soil at the samedisplacement the supported load is approximately 3 kN. For boredpiles in natural soil conditions and a 5-mm displacement, the sup-ported load is approximately 48 kN, while for preflooded soil at thesame displacement the supported load is approximately 8 kN. Forcontinuous flight auger (CFA) piles, the supported load is approx-imately 45 kN in natural soil conditions, whereas for prefloodedsoil with a 5-mm displacement the supported load is approximately

2 kN. For the belled caisson, the loss of strength was more evident.In natural soil conditions at a displacement of 5 mm, the load wason the order of 125 kN. However, the same load in floodedconditions represented a displacement of approximately 50 mm—10 times higher.

Horizontal Reaction Coefficient (nh) versusDisplacement

From the values obtained from the tests and by the Matlock andReese (1960, 1961) equation, the nh values were obtained for arange of 6–12 mm (Table 5).

The values of nh obtained for the bored piles, CFA piles, and thebelled caissons were on the same order, that is, with average valuesof 10.8 MN=m3 and coefficients of variation on the order of 15%.However, for the steel pile, the value of nh was 2.5 times higher,which may due to the high stiffness of the material (steel) due to itsYoung’s modulus being approximately 10 times greater than thoseof the concrete foundations analyzed.

For the values obtained in the flooded situation, a drastic reduc-tion was observed for both the bored and CFA piles. A repre-sentative result of only 3.5% of the value obtained in natural soilconditions was obtained. For the belled caissons, it was observedthat the reduction in the nh values, which was on the order of 27%,was not as evident as in the bored and CFA piles; in the steel pilesthe reduction was 70%. Fig. 9 shows the variation in the horizontal

Table 4. Values of horizontal maximum loads and maximumdisplacements

Foundationtype

Soilmoisturecontent

conditionsMaximumload (kN)

Maximumdisplacement

(mm) Qnat∶Qflooded

Steel pile Natural 70 12.74 0.44Flooded 30 34.79

Bored pile Natural 41 7.91 0.31Flooded 13 13.66

CFA pile Natural 41 12.02 0.31Flooded 13 13.69

Belled Caisson Natural 180 18.17 0.86Flooded 210 171.09

0

10

20

30

40

50

60

70

80

0 5 10 15 20 25 30 35

Lat

eral

load

(kN

)

Displacement (mm)

Natural ( SMLT)

Flooded (QLMT)

Fig. 5. Load versus horizontal displacement curves for steel piles.

0

10

20

30

40

50

60

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28

Lat

eral

Loa

d (k

N)

Displacement (mm)

NaturalFlooded

Fig. 6. Load versus horizontal displacement curves for bored piles.

0

10

20

30

40

50

60

0 5 10 15 20 25 30 35 40 45 50 55

Lat

eral

load

(kN

)

Displacement (mm)

Natural

Flooded

Fig. 7. Load versus horizontal displacement curves for CFA piles.

0

50

100

150

200

250

0 20 40 60 80 100 120 140 160 180

Lat

eral

Loa

d (k

N)

Displacement (mm)

Natural

Flooded

Fig. 8. Load versus horizontal displacement curves for belled caissons.


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reaction coefficient for natural soil conditions for all foundationstested.

Fig. 9 shows that the horizontal reactions of the concrete foun-dations were close, as previously observed by means of the valuesof nh. A higher stiffness of the steel pile is observed, which is re-lated to the material (steel) and its geometry. Note that the loadingwas done in the direction of greater inertia. Fig. 10 shows the varia-tion in the horizontal reaction coefficient for flooded conditions forall of the foundations tested.

In Fig. 10, the bored and CFA piles show similar behaviors, inthe same way as seen with the natural soil conditions; however, thisobservation does not hold true for the belled caissons. The belledcaissons were less influenced by the effects of the flood. In contrast,the steel piles presented anomalous behavior, with an increase inthe reaction up to a displacement of 10 mm and a decrease there-after. This behavior was associated with the noncontact area be-tween the soil and the pile originated by the first loading, whichwas on the same order of magnitude.

Displacement along the Depth: Belled Caissons

In the belled caisson load tests (natural soil conditions) it waspossible to use the inclinometer, which allowed the collection of dis-placement readings along the depth after each increment of load. Thereadings were taken every 0.5 m in depth using a torpedo sensor(Fig. 11). An inclinometer was utilized (OTR-OG310S, OTR-GEO,

Italy; scale� 30°; resolution 25,000; sinα; nonlinearity < �0.057°in full scale; misalignment between the two axes < 1.5°).

In Fig. 12, it is possible to check the displacements along thedepth for each load increment.

Based on Fig. 12, it can be observed that the belled caissonsshowed displacements up to a depth of 5.5 m, which demonstratesthe importance of assembling the reinforcement in this region inwhich there is greater influence of the load. Note that below thisdepth a small deflection in the direction opposite to that of the

0

10

20

30

40

50

60

70

80

0 5 10 15 20 25 30

n h(M

N/m

3 )

Displacement (mm)

Bored

CFA

Caisson

Steel

Fig. 9. Curves for nh versus horizontal displacement—natural soilconditions.

0

2

4

6

8

10

12

14

16

18

20

0 5 10 15 20 25 30

n h(M

N/m

3 )

Displacement (mm)

Bored

CFA

Caisson

Steel

Fig. 10. Curves for nh versus horizontal displacement—floodedconditions.

Table 5. Values of the horizontal reaction coefficients

Foundation typeSoil moisture

content conditions nh (MN=m3)a

Steel pile Natural 25.4Flooded 7.4b

Bored pile Natural 11.6Flooded 0.6

CFA pile Natural 11.9Flooded 0.2

Belled Caisson Natural 9.0Flooded 6.5

aAverage values from 6–12 mm displacements.bRange from 10–12 mm.

Fig. 11. Insertion of the equipment.


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loading is observed, with a maximum value of 0.2–6.5 m. It is alsofound that the displacements were representative of the 90 kN load(half of the maximum test load of 180 kN).

Estimation of Depth Displacements

Based on the results obtained by the inclinometer, it was possible toevaluate the proposed methodology that Miche (1930) developedfor long piles embedded in soil with linearly increasing coefficientsof horizontal reaction with depth, loaded at the top by a horizontalforce. In his proposal, Miche presents an equation for the determi-nation of depth displacement. Thus, considering the belled caissongeometry and a horizontal load of 180 kN with the soil reactionincreasing linearly with depth, the solution of the problem is givenin Eq. (8):

T ¼ffiffiffiffiffiffiEInh

5

rð8Þ

where T = relative stiffness of the pile/soil; E = Young’s modulusof the pile; I = moment of inertia of the structural element; andnh = horizontal reaction coefficient.

The horizontal displacement at the top of the pile (y0) is givenby Eq. (9):

y0 ¼ 2.40T3 · HE · I

ð9Þ

Using the values obtained through the methodology proposedby Miche (1930) and the displacement values obtained by the incli-nometer, it was possible to compare the results. Fig. 13 shows thevariation in the depth displacement obtained experimentally andtheoretically using the methodology. An agreement is observedin the results, showing the proximity between the graphs. For thehorizontal displacement, Miche’s method resulted in a value of18.44 mm; experimentally, the average value of the interval was17.15 mm. Another fact to be observed is the influence of loadingin depth. The theoretical data point at 2.64T ¼ 5.59 m is on thesame order as the experimental value. Such a value representsthe boundary depth at which the displacements are no longer influ-enced by the load.

Analysis of the Literature Values in Highly Porous Soil

In this section, some data collected from the Brazilian literaturefor tests performed on porous and collapsible soils are presented.Fig. 14 shows the variation in the horizontal reaction coefficientfor several types of deep foundations embedded in sands andclays.

In Fig. 14, most of the values of the horizontal reaction coef-ficient for natural soil conditions are between 4.1 and 12.3 MN=m3

(regardless of soil type and foundation), showing a maximum thatis approximately four times the minimum. Only the steel and dis-placement piles [full displacement pile (FDP)], both executed inthe same subsoil, provided values of nh higher than those in theobtained range (12.3 MN=m3).

As for the values obtained in flooded conditions, a greatervariation in the results is observed, with a minimum value of0.2 MN=m3 and a maximum of 7.4 MN=m3—a difference of 37times between the maximum and minimum values obtained.

Conclusions

The results obtained in the load tests showed low values of load,regardless of the moisture content of the soil (natural or prefloodedconditions). This demonstrated the need for previous assessment ofthe soil properties when submitted to horizontal loading.• Previous analyses of the local subsoil indicated 63% porosity

and a coefficient of hydraulic conductivity on the order of2 × 10−5 m=s. This demonstrates high potential for water infil-tration in the surface layer. These characteristics are criticalbecause they reduce load capacity and increase horizontal dis-placement when there is variation in the soil moisture content.Therefore, it is necessary to check water, rainwater, and sewagepiping for leakage, because they may cause severe problems tostructures supported on such terrain.

• The range obtained for values of nh in this study for thedeep foundations under investigation was between 9.0 and25.4 MN=m3 (natural moisture content). Such values are closeto those found in the Brazilian literature for soils with similar

-10

-9

-8

-7

-6

-5

-4

-3

-2

-1

0-1 1 3 5 7 9 11 13 15 17 19

Len

gth

(m)

Displacement (mm)

45 kN 60 kN

75 kN 90 kN

105 kN 120 kN

135 kN 150 kN

165 kN 180 kN

Caisson Axis

Fig. 12. Belled caissons—inclinometer readings. (Data from Kassouf2012.)

-9

-8

-7

-6

-5

-4

-3

-2

-1

0-2 0 2 4 6 8 10 12 14 16 18 20

Len

gth

(m)

Displacement (mm)

Miche (1930) Experimental

Depth = 3.96 T = 8.37 m

Depth = 2.64 T = 5.59 m

Depth = 1.32 T =2.79 m

Fig. 13. Theoretical and experimental curves.


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characteristics but different from those proposed by the interna-tional literature.

• Preflooding markedly impacted the characteristics of the subsoilby relevantly influencing the results of nh; with preflooded soil,nh was in the range of 0.2–7.4 MN=m3, which represents anapproximate decrease of 70% compared to the values obtainedwith natural moisture content.

• The inclinometer results from the top (17.15 mm) are close tothe dial gauge readings (18.18 mm), showing that the readingsin depth obtained from the inclinometer are reliable.

• The Miche (1930) method proved to be suitable for the calcula-tion of the horizontal displacement at the top of the belled cais-sons (18.40 mm) and the identification of the null displacementat depth, which was very close to that obtained by the inclin-ometer data (Z ¼ 2.64T or 5.59 m). This statement is valid pro-vided that the appropriate reaction coefficient is used for eachtype of soil. The load influenced the displacement of the foun-dation (belled caisson) up to seven times its diameter.

Acknowledgments

The authors thank the University of Campinas (Unicamp) and theSão Paulo Research Foundation (Fapesp).

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