Agroch imic •. Vol. XXVIJ - N . 2-3 Aprile·Giu¡!JlO 1983

Soil properties and geotechllical .. haracteristirs uf m,han area 80ils in Sevilla, Spain

D. DE LA ROSA. J RUIZ and J L. PEREZ (enrro de Edafología y f\ iolog ía Apli cada (~el Cuano. c.s. l .e .. Se"il"!, Spain . Ucp'tflemento de Mec:inic t de Sucios. E.T.S J~ ArquitenurJ. Uni versidad de Se\·ill'l. Srain .

INTRODUCTION. - In basis ro soiJ surveys, it is very impor­tant to synthesize typical vertical profiles which represent the spa­tia] variability of soi1 characteristics. Statistic summary of data 1S an ;:¡ppropiate procedure as first approximation and whenever suflicient data are avai1able (WILDING et aL , 1964).

Currently, there are a]so a few papers that outline the existen­ce of stochastic modelling and tour rhe value of the technique in soi! variability studies (ALONSO and KRIZEK, 1975 ; VANMARCHE, 1977; DE LA ROSA and ALMoRzA, 1980). Severa! « canned com­puter programs» (e.g. BARR et aL , 1976) have spectra! anaJysis a­vailable as an option for that data examinatíon.

Simple conelation and regression analvses may be useful to es timate the contribution of soil analytica! properties to enginee­ring charactetÍstics (e.g. DE LA ROSA , 1979; McNABB, 1979). So, it is possible to formulate the numerical expresion which would better represent the studied phenomena for predicting engineering determinations.

Within soil general characterization, particle size distríbution , ca tion-exchange capacity, and acrivity of clay represent signíncant soi1 properties in re1ation to its engineering behaviour. P1asticity, shrink-swell properties , compressibílitv, and shear strength are a­mong the most important aspects of soi] investigation determining the suitability of soi1s for geotechnica! purposes.

In Sevilla soi1s , few analytical and geotechnica1 studies conduc­ted on individua! and grouped specimens (e.g. PEREZ et aL , 1981) have contributed to an increased understanding of properties of the­se soi1s. Ir then becomes desirab1e to ana!yse soi! data statistically. These analyses are suitable to summarize available data on Sevilla soils in order to provide a base-line for future investigations. In this respect , the application of a discriminant procedure to mathe-

1:'

174 D. DE LA ROSA , .r. RUIZ and J. L. PEREZ

matical1y distinguish among several groups of these soils , is now

under development by the authors. This paper was undertaken to (i) present central tendency and

variance statistics for selected soil analytical and geotechnical cha­racteristics of 83 s011s sampled in urban area from Sevilla City, (ii) explain geotechnical determinations upon soil analytical properties, and (Íií) interpred geotechnical dsta in basis to the relationships bet­

ween certain determinations .

MATERIALS AND METHODS. - Most of the investigated soils were classi­fied in pedological terms as Typic Xerofluvents (Soil Taxonomy System defineci by SOIL SURVEY STAFF, 1975). Tbese are brownish soi ls rhat formed in recent water-deposited sediments of Guadalquivir river. Strarification oí the materials is normal. Slopes are lower than 2 percent, and the drenage is well. The mean annual air temperature is about 17"C, and the precipitaríon is about 500 mm, mosr of it coming between October and Apri l.

Soil samples were taken from each one of the 83 test sires (Fig . 1), within of five depths: O to 1 m, 1 to 2 m, 2 to 3 m, 3 to 4 m, and 4 lO 5 m. These soil samples were collected witb a rotarion auger « Kraelius D-500 ».

Total sand ({raction 0.06 mm), silr (fracrion 0.06-0.002 mm ) and clay (fracrion ". 0.002 mm) contents were determined by the hydrometer method (BouyoucOS, 1962), after carbonate removal with sodium acetate. Carbonate content was measured by a volumetric method (SOIL SURVEY STAFF, 1972). Cation.exchange capacity (CEC) was derermined by methylene blue adsorpríon (NEVINS and WEINTRITT, 1967). C1ay activity was defined as the plasticity index to clay contenr ratio (UEHARA, 1978). This clay conrent in percentage was refered to total soil sample .

Liquid límit and plastic Emit were determined by methods Nos. D 423-66 and D 424-59 described in the ASTM Srandards (AMERICAN SOCIETY FOR TESTING AND MATERIJ\,LS , 1970) Porential volume change (PVC) was measured by LAMBE res t (LAMBE, 1960). The PROCTOR tesr determinarions: maximum demity and optimum moisrure were based on AASHO designations T 99-70 and T 180-70 (AMERICAN ASSOCIATION OF STATE HIGHWAY OFFICIALS , 1961). California bearing ratio (CBR), swell and absorption were determined by the ASTM procedures D 1883-73 (AMERICAN SOCIETY FOR TESTING AND MATERIALS , 1970).

The follow ing statistical variables were computed for each soil depth: mean (M) , coefficient of varÍation (CV = 1 O x 100 I M; e standard deviation) , range (max and min), and number of observations (n). In the simple correla tion and regression analyses, correlatian (r) and determination (R2) coefficients, intercept (a) , and coefficient of regc'ession (b) were derermined.

RESULTS AND DISCUSS !ON - Distribution ni soil properties and geotechnical characteristics. - The soil analytical properties: total sand, silt, clay and carbonate contents, cation exchange-capa­city (CEC) and activity index, and geotechnical determinations: Ji.

SOIL PROPERTIES AND GEOTECHNICAL CHARACTERISTICS 175

quid and plastic limits, plasticity index, potentíal volume change (~VC), maximum density, optimum moisture, California bearing ra­rJo (CBR), swell and absorptíon data for rhe soil samples investiga· ted are summarized in Tables 1 and 2.

Road

Train

Urban area

Test si te

/. \ I \

/ / \

/ \ -+--+- -1- -I-..,1~ ~-+a.. \ \ A '. \ /1 \ • ~~ • I \ ............ ~,

\ /GENTERle ~\ /'1 V \ e\ \ . \

'/r¡ \ • -\ , '1. '1 \ • '1 \

~<i; '/¡ í' • \ ~ /// MACARENA;

X, I • /

-...... •

~ / /

;t; //. /

~ e a. ..., a.

./. . //

===;~= GIRALDA / cY' ,/ ER N VION

~ l' ª \ •• .1' e ·1 ./ / .1 • \1/ l· ,

• ITABLADILL\ .~I ,. • \ • 7' / . .\. , / . . \ ~ /.

\ ,. I •• I -:: __ \0...--., /

~~--t / • • I

\ . \.. I

.~ I • \ / IF===:::::P--""

\ / O 2Km

• To Cadiz

F1G. 1. - Location oí test sites (83) in Sevi lla C ity.

176

~ ~ " ~ '" " .t

'" ~ " ';";

.!:

'" '" <.;. " "" '-~ ~

'" ~ " A. a "-A.

"' ~ ¿:' " '" " e c.;

>-~

~

'" " ,~

" ::: "-~ o

a ... " ~ " " " "" l'i " "" " " o:::

'"' --' :? r-

D. DE LA ROSA, J. RUIZ and J. L. PEREZ

¿ ~ o o ¡-.. r- ~ ...,. ...,. V\ '" E

'" r- ...,. o o "'. "9 '" 1'- ve· ":'

S o o o

...,. ..". ...,. '" "'

...,. lr\ V\ V\ "" "" '"

"' N ...,. O tr\ o: "9 "' "' V\ <;' ~ .,.¡. ~ 6 ~ ,;,

6

'" lr\ V\ "' '" tr\

..c "" "" "" 1'- ,- ~ o. v

-O ,, _ _ ~''' ___ u,,_

'0 V\ Vl "' ~

...,. '" ~ 3: "" r-~

N .,.¡. ~ N C>

o

;:::: ;:::: ;:::: r- r- ~ r- r- r-

~I ...,. ...,. ..,. '" r- '" ::: '0 r- ce ~ -e

S ,;, " ~ C> o::: o

-~-,-----_. ~--,,--

¿ ~ "" ~ '" "' -[)

'" '" '" "" -D '" E I 1- ~ __ ~uuu __ • _________

~

6 v ;?; N r- V\ '" '" "" e V\ -[) 00 N -" N ,.:. S ,A N 6

,o::: 6

--_._----- ._--------_ ..

te:

",0 ~ "' t' 6°

<U '" "' 8 x <U o v o. c

"' v ~] o " "' H ¿;

"' <U e H v o "' o " E ,.. v O v e u

:>. ii U :~ v e ..:s a ¡.¡.¡ v " ¿¡::; en U U U <1C

----_._--------"-

~ ~ " ;:o ~

" " ::;

'" §

" ';";

.:: '" "" <.;. " "" " ~ " ~ 'E ~

" ~ '" " "' .~

" '" " ~ '" " '"' '-

-.2

.:: '" " . .g " '" '-

'" ~ '" -a ... " ..t:;

§ " "" " "' " ""' " " o:::

N W ...r

'" -< f-<

..c o. v -O

'0 en

I~ 6

rr,rf\~r<'"'1Q'\0'\a-..0'C\ r- r- r-- r-- ....... ,......, ....... .-1 .-1

_'" o tr1t"-CIJ 0"'T ~6 '-.DNt"'\J'-NN'-DN-66¿6oo~¿~~~ ~..... :;~ 6~

NO o f"'\1--r-- c:a-: l06 '' 'ON«'\O'\NNOOrr'l ........ 6666N~N6.j. ..... ~ V;'O--: Ce

, , 1,1 f"'\f"'\r<"'\rt"'\ooooo ,c; '-..D'-D-o'-Df'I\~H\"""\1"I'\

""1"0 o NCO'-Ú o:a-: r-o '-..D N "" 0'\""";: N ce f"'\ ........ 666¿r':"oN6oo ,.....;:,.....;: :~ 66

SOIL PROPERTIES AND GEOTECHNICAL CHARACTERISTICS 177

As synthesized from the statistical data, a Sevilla soil has the following properties eX'pressed in mean values of the total depth analysed: medium texture (sand C"-l 28%, silt C"-l 33%, and clav C"-l 38%); a carbonate content of 25%; 14 meq/l00g is the CEe; activity index is about 0.8; a liquid Emit of 38%, a plastic Emit of 18%, and a plasticity index of 20; the PVC is 3.3; Proctor deter­minations, maximum density and optimum moisture content, are 1.74

SAI·m.o¡,

O 25 27 29 31

__ 61 /

/ /

/

/ /

ti 66 I I

E I I I

I .67 !-G.. I LU I o I

I I

-' .71 - \ .:J \ ú1 4 \

\ _81

CARBONATE. %

SILT, %

29 31 33

e 38 \ \ \ ,

\

35

t 35 I I 1 I I

4. 35 , \

\ \

\ 38.

/ I

/

/ /

I .41.

CE C, meq/100 9

I

35 38 ¿Q 42

ACTIVITY INDEX

O 22 24 26 28 130 132 134 136 ., 073 075 077

E 2 I 1-G.. LU o

-' o ú1

FIG.

4

5

2. of 01

.. 67 , , , " , ,

'e, 64 , , , , \ /'e 57

/

/ / f 48

I I I I .49

/ /

/ 4( 46

\ \ \ \

/ /

?/41 /

/ /

'. 52

/

36, I I I I

38 .­/

//

- Typica] prof!le of the soi!s investigated as synthesízed from the statistica] data soi] properties . Points represent mean values {M) and numbers indicate coefficient variatíon leV) in percentages

178 D. DE LA ROSA, J. RUIZ and J. L. PEREZ

g/cm3 and 17%, respectively; 4.0% is the CBR, 1.3% the swell, and 3.9% the absorption. Sand content was the most variable of the 15 properties investigated, while maximum density was the least variable.

When several soil depths are considered, the typical profiles of the soils investigated are shown in Figs. 2 and 3. The vertical axes of the graphs are divided lnto soil depths of one meter of tickness. Coefficient of variation are shown adjacent to the mean values which

L10UID L1MIT. % PLASTIC L1MIT, % PLASTICITY INDEX

o 37 21 38 39 17 18 19 19 20 I I

,28 .22 I I

f- I - I -I _ 29

/ / -/

I + 21 I I E 2

/ ~29

\ f- \ -\

I ~20

\

r \ \

'X. 1-o.. W o 3

\

>* 34 \ f22 == o

Vl / I /

/ /40

I I

'24

4

5 I I I I I I

FiG, 3 iPart 1)

PVC MAXIMUM DENSITY, g/cm 3 OPTIMUM MOISTURE, %

o 32 34 36 172 174 176 164 158 172

,62 .,6 1'22 \ , I

\ , , I \ , I \ , I \ , , I \ ,5 E .60 -.7

I I / I I / 'X.

I I / I 1- I I / o.. I I /

w ( 64 '5 ti 21 o , ,

3 , , , ,

o , Vl ,65

I I I I I

" 73

FlG, 3 (Part 2)

SOTL PROPERTIES AND GEOTECHNICAL CHARACTERISTICS 179

are placed at the mid-point of the soil depth and joined by disconti­nuallines.

Mean distribution of sand, silt and clay (Fig. 2) are reported on the basis of percent of the soil sample without carbonates. The

E 2

'X 1-o.. W o

== o Vl

e B R,

38 42

/ /

/ /

f35 /

/ /

,J 25

%

45

,. 35

f-

f-

SWELLING, % ABSORPTION. %

11 13 15 39 41 43 I I

• 71 4~ • /

.,..-<'" / / .,.."

/ " / ,,'" (70 .... 50 \ I \ I \ I '.59 .55

-

I L I I

FIG, 3 (Part 3)

FIG, 3, - Typícal profile of the soils investígated as synthesized from the statistical data of geotechnical characteristics. Points represent mean values (M) and numbers indicate coefficient of variation ¡CV) ín percentages,

50

x.. 50 \>~ 1>-"

>< 40 W 'b", O

SOIL DEPTH Z f5J o

O 0-1 m

> 30 '" 1':Zm

t- o Z-3m

U 3-4 m ¡:: 4-5m tf) 20 « ::En = 331 ...J .6 a. §'&e< ~

10 >() q..p

'. 0

0 10 20 30 40 50 60 70 80 90 lOO LlaUIO L1MIT. "/o

FIG, 4, - Relation hetween plastilcity índex and liquid límÍ! for typícal profile of the soíls investigated.

180 D. DE LA ROSA, J. RUIZ and J. L. PEREZ

distributions of these properties show that sand is concentrated in the surface and depther soil depths, while silt and clay present a more alternating pattern. CEC moderatelly parallel clay content in the depher horizons. Coefficients of variatíon increase clearly with depth in most of the analytical property distributions.

For geotechnical characteristics (Fig 3), there was nothíng u­nusual about the distribution of means by soil depth. The distribu­tion of plasticity index means display the increasing of plasticity with depth of investígated 50ils. The coefficient of varíation values, according to the elevate specimen number (83), indica te that these soíls have developed in relatively homogeneous materials although sorne geotechnical characteristícs, such as PVC (CV "'0 60%), range considerately from site to site.

Geotechnical characteristic vs. soil properties. - Regressions of geotechnical determinations upon physico-chemical soil properties were computed. It is reported only the best regressions for each geotechnical determination (Table 3). The best regressions have the highest coefficients of determination (R2-values).

In the majority of cases, there was nothing unusual arbout the influence of the selected soil properties on the geotechical characte­ristics. Clay content and CEC had the most important effects on the geotechnical determinatÍons of the soils studied. For plasticity index, the R2-value shows that the equation reported in Table 3, with CEC as independent variable, accounted for 81 % of the obser­ved variation. However for absorption index, the regression analy­sis shows that CEe had not important effect on this engineering cha­racteristic. Similar correlations were found by DE LA ROSA (1979),

TABLE 3. - Besl regressiol1s" lo explain geotechnical characteristics ¡rom Ibe se/eeted soil propertíes

Equation

, Liquid limit = -2...13 +0.42 (cation-exchange capacity) Plastic limit = 13.09+0.13 (day content) Plasticity ¡ndex = CU5+ 1.47 (cation-exchange capacity) PVC = -.53 +0.29 (cation-exchange capacity) Optimum moisture = 20.92--0.13 (sand content) Maximum density = 2.33-0.02 (cation-exchange capacity) CBR = 6.71--0.07 (day content) Swell = --0.55 +0.13 (cation-exchange capacíty) Absorption = 1.04+0.20 (cation-exchange capacity)

'e BeS! regressions are those thar have the highest R2.

0.77 0.30 o.S! 0.6~

0.79 0.46 0.37 0.49 0.31

0.88 0.55 O.9Cl 0.80 0.89 ObS 0.6! 0.70 0 .56

3.0

N

E u --Ol ~

lJJ ~ 20 (/) (/) lJJ o:: o..

(!) z j 10 lJJ

~

I

S01L DEPTH

o 0-1 m.

6 1-2 m

O 2 -3 m

. 3-4 m

+ 4 -5 m

~n = 281

+ Q

el + . • ~ + ~

¡;¡ ~ q •

~ t o ., • 'tf

• 11 G Ii!~ é tJ • 6

O . !11 ."* B O

Il. ~ 6 O • 5

O ~ O ~ (j>~ é .6 O @.

6 ~ JI$ é +

<:JI O -4 U

+ • > ~ LffI· 6 'é I'l, o..

• .ro~. O 3 @. • 4!J 11 é

míi!8 O liil ~ O 2 6 ~~ @ O tl!!

O • + ~ O LlJÁl

~ O ci> ~ Q • +~

+ - O

10 20 30 40 °O~----------~----------~~----------~----------~

PLASTICITY INDEX FIC. 5. - Relarion berween PVC and plasriciry index for rypical proíile oE the soils inve­

stigated.

30r------------r------------r-----------,,----------~

o O-

~ ::::> 10 ~ ~ o.. O

o

o

é

O

50lL DEPTH

O O-1m

6 ¡-2m

o 2 - 3 m

::En = 82

O~O------------7.10,-----------~2~O------------~30~----------~40

PlASTlCITY INDEX FIC; 6. - Relation between optimum moistue and plasticity index for typícal profile of the

soils investigated.

182 D. DE LA ROSA, J. RUIZ and J. L. PEREZ

between plastidty index and CEC, to relate data from a variety of Florida so11s.

Relatíons between geotecbnical characteristics. - The modera­tely high plasticity of the investigated soils is illustrated in Fig. 4, for a total of 331 pair of values for pIasticity index and liquid limito The degree of scatter on the chart shows the variability of mate­rials. This variability appears to be most1y influenced by the diffe­rentia! clay mineralogy (PEREZ et al., 1981). It is interesting to note that most of the poínts in the graph are Iocated upon A-line. In Fig. 5 is shown the poor correlatíon between PVC and plasticity indexo JUSTO and SAETERSDAL (1979) found similar correlation for a wide range of experimental values. Optimum moisture was hi­ghly correlated with plasticity index (Fíg. 6). This íntensity of as­sociation between pairs of values is equal1y high for aH the soil de­pth. Relation analysis for the 82 pairs of values between CBR and plasticity index Fig. 7) showed the lowest correlation among the four cases studíed.

8 é

SOIL DEPTH

7 O 0- 1 m

" 1 - 2m

6 O 2 - 3 ni 4!J ~ O O

:En = 82 5

O G. O

tl Gl; Ó

o ;;-

á ~ O o

" &l ~

a:: 4

al U

3

~ {'J O O

"~ Él

~ o " <tJ Ó O

.I!J é 4!J

2 é o 4')l

l o

10 20 30 40

PLASTlCITY INDEX FIG. 7. Relation between CBR and platicity index for typical profile of ihe soils inve-

stigated.

SOIL PROPERTIES AND GEOTECHNICAL CHARACTERISTICS 183

ACKNOWLEDGMENTS - The authors are grateful to J. L. de Justo, Pro­fes sor of Soil Mechanics and Foundations, University of Sevilla, for his con s­tructive suggestions and assistance in revision work. This research is a part of Ph. D. Thesis work, University of Sevilla, by the second author.

REFERENCES

ALONSO E. E. and KRIZFK R. J.: Srochastic formulation of soil properties. Prac. 2nd lnl. Cont. Appl. slat. Probo soil struct. Eng., Aachen (1975).

A.ERICAN ASSOCIATION OF STATE HIGIlWAY OFFICIALS: Standard specifictions for highway material s and methods of samplíng and testing, Ed. 2.2v. (1961).

AMERICAN SOCIETY FOR TESTII\G AND MATERIALS: Book of ASTM standards, pp. 212-219 (1970).

EARR A. J., GOODNIGIlT J. H., SALL ]. P. and HELWING J. T.: A user's guide to SAS-76. SAS Ins\. Inc., Raleigh (1976).

BouyoucOS G. ].: Hydrometer method improved for making particles size analyses of soils. Agronomy, 54, 464 (1962).

DE LA ROSA D.: Relation of several pedological characterislÍcs to engineering qualities of soiL r soiL scí, 30, 793 (1979).

DE LA ROSA D. and ALMORZA J.: Aplicación de la modelación probabilista en caracteriza­ción de suelos. An. Eda/ Agrob, 39, 1385 (1980).

JUSTO J. L. and SAETERSDAL R.: Design parameters fol' special soil conditions. VII Eurp. Con!. sait Mech. Fund. Eng. Proc., Brighton (1979).

LAMBE T. W.: The character ano identifIcation of expansive ,oils. Pedo Hous. Adm., Wa· shington (1960).

McNABB D. H.: Correlation of soil plasticity with amorphous clay constituents. Soil sci sac. Am. 1, 43, 613 (1979).

NEVINS M. S. and WEINTRITT D. ].: Determination of cation-exchange capaCÍty by methy­lene blue adsorption. ]. AfII. Ceram. Soco Bull., 46, 587 (1973).

PEREZ J. L., RUIZ J., DE LA ROSA D., 1L\QUEDA C. and GONZALEZ F.: Relationhip of clay mineralogy to engineering properties in Sevilla soils. 7th Int. Clay Con!., Bologna (1981).

SOIL SUERVEY STAFP: Soil survey laboratory methods and procedures for collecting soil samples. U.S. Govt. Prinr'ng Office. Washington (1972).

SOIL SURVEY STAFF: Soíl taxonomy, a basic system of soil classification for making and interpreting soil surveys. U.S. Govr. Printing Office, Washington (1975).

UEIlARA G.: The chemistry and physics of low activity clays. Embrapa, SNLCS Pub., Rio de Janeiro (]978).

VANMARCKE E.: Probabilistics modelling of soil profiles. IX Int. Con/. soil Mech. Found. Eng, Tokyo (1977).

WILDING L. P., SCIlAFER G. M. and lONES R. B.: A ,tatistical summary of ceftain physical and chemical properties of sorne selected profiles from Ohio. Soíl Sci. sac. Am. Prac. 28, 674 (1964).

SUMMARY. - Statistics including the mean, range and co~fl:!cient of variation are Téported for certain pedological and geotechnical properties for 83 soils sampled in urban area from Sevilla City. Maximum density was the least variable of the properties investigated, while total sand content was the most. Regressions of geotechnical determinations upon physico-chemical soil properties were computed. Clay content and cation-exchange capacity had the most important ef!ects on the geotechnical determinations. Finally, geotechnical data were interpreted on the basis of the relationships between several determina· tions. Optimum moisture was highly correlated with plasticity index, and Cali­fornia bearing ratio was the lowest.

184 D. DE LA ROSA, J. RUIZ and J. L. PEREZ

RBSUMB. - On a déterminé plusieurs parametres statistiques guí corrc­spondcnt a des proprietés pédologiques et géotechniques des echantillons de 83 sols de l'aire urbaíne de Séville. La propríété d'une plus grande variabilité est ccl­de la densité maxímum, tandis que la téneur en sable présente la plus basse dispersíon de valeurs. On a calculé aussí les régressions línéares entre les deux groupes de variables. La téneur en argüe et la capacité d'echange cationique sont les caractéristiques pédologiques d'un effect plus intense sur les détermina­tiones géotechniques. Finalement, on a réalisé une interprétation de l'information géotechnique sur la base des rclations entre plusieurs propriétés. Les caracterisri­ques qui ont une meílleure corrélation sont l'humídité oprime et ¡'indice de plasticité.

ZUSAMMENFASSUNG. - Verschiedene Statistiks entsprechend pedo 10-gische und geotechnísche Eigenschaften von 83 Baden lokalizierte in stadtische Areas von Sevilla wurden bestimmt. Maximale Dichte und Sandgehalt waren die Eigenschaften mit grassere und níedrige Datenzerstreuung. Auch die lineare Regressíonen zwischen beide Gruppen von Daten wurden bestimmt. Tongehalt und Kationenumstauchkapazitat waren die pedologische Eigenschaften mí, haheren Einfluss über die geotechnische Daten. Unter Berücksichtigung de, Beziehungen zwischen einige Eigenschaften wurde eine Interpretierung der geotechnischen Daten vorgeschlagen. Opptima Feuchtigkeit und Plasticitatindex waren die Eigenscaften mit der Besten Korrclation.

RESUMEN. - Se determinaron diversos parametros estadisticos correspon­dientes a propiedades edafológicas y geotécnicas, de 83 suelos muestreados en el área urbana de la ciudad de Sevilla. La densidad máxima resultó ser la propiedad de mayor variabilidad, mientras que el contenido en arena presentó la menor di­spersión de valores. Se calcularon tambinén las regresiones lineales entre ambos grupos de variables. Contenido en arcilla y cap:1Cidad de cambio catiónico fueron las características edafológicas de efecto más acusado sobre las determinacio­nes geotécnicas. Por último se llevó a cabo una interpretación de la informa­ción geotécnica, en base a las relaciones entre varias determinaciones. Las caracte­rísticas mejor correlacionadas fueron humedad óptima e índice de plasticidad.

RIASSUNTO. - Sono stati determinati datí statistici diversi, che cor­rispondono alle proprieta pedologiche e geotecniche, di 83 suoJi nei pressi deJ­¡'area urbana della citta di Siviglia. La densita massima e stata la propriera di piu ampia variabilira, mentre il contenuto di sabbia mostra la piu bassa di­spersione. Si sono anche calcolate le linee di regressione tra i due gruppi di variabili. Il contenuto in argilla e la capacita di scambio catíonico furono le caratteristiche pedologiche che piu influiscono sopra le determinazioni geotec­niche. Finalmente, e stata realizzata una interpretazione della informazione geotecnica, basata sulle relazioni tra le varie proprieta. Le caratteristiche corre­late meglio sono state l'umidira ottima e l'indice di plasticira.

Pervenuto in Redazione il 20 Luglio 1982