, with SPT N value is a very profitable approach since most field parameters are based on SPT N values and CPT tip resistance.

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1 DOI 0.007/s x Soil Mechanics and Foundation Engineering, Vol. 5, No. 6, January, 205 (Russian Original No. 6, NovemberDecember, 204) CORRELATION OF SPTCPT DATA FROM THE SUBSIDENCE AREA IN GOLCUK, TURKEY M. Asci, C. Kurtulus, I. Kaplanvural, and M. O. Mataracioglu 2 Kocaeli University, Engineering Faculty, Department of Geophysics, Umuttepe Campus Kocaeli, Turkey. 2 Schlumberger, Geosolutions Geophysicists, Houston, USA. UDC : A correlation of standard penetration test (SPT) and cone penetration test (CPT) data was carried out by this study. The SPT provides information on the resistance and properties of soils and weathered rocks. In addition to the SPT, the CPT is widely used for site investigation and geotechnical design especially in alluvial areas, based on soil types. In order to determine the CPT values of the investigation areas, where only reliable SPT values are available, the SPT blow counts (N values) can be converted into CPT cone resistances ( values) by an SPTCPT correlation. The correlation of SPTCPT test results from the subsidence area was performed using statistical methods. The soils in this area are recent alluvial deposits, consisting mainly of silty clay, clayey silt, clay and sandy clay. The qc values are not increased when SPT values are increased as it is expected. Introduction In situ testing has traditionally been carried out in geotechnical engineering. In areas with suitable soils, the SPT and CPT soil investigation tools have gained popularity among geotechnical engineers. The SPT provides information about the resistance and properties of soils and weathered rocks. The CPT is a reliable and cost effective method for determining subsurface stratigraphy as well as obtaining many geotechnical parameters. Correlation of static cone tip resistance,, with SPT N value is a very profitable approach since most field parameters are based on SPT N values and CPT tip resistance. Previous correlative studies The relationship between SPT N values and cone tip resistance, n = ( /N) was analyzed by many authors. De Alencar Velloso [3] indicated ratios of SPT N values and cone tip resistance for different soil types and introduced 0.35 MPa for clay and silty clay, MPa for sandy clay and silty clay, 0.35 MPa for sandy silt, 0.6 MPa for fine grained sand, and.0 MPa for sand. Meigh and Nixon [6] indicated that this relation did not consider the effect of grain size and recommended nvalues as MPa for coarse grained sand and 0.3 MPa for gravelly sand. Schmertman [9] called attention to the conversion of SPT data to cone penetrometer values if only SPT data are available. He recommended MPa for silt, sandy silt, and slightly cohesive siltsand mixture, 0.3 MPa for clean, fine to medium sand and slightly silty sand, MPa for sandy gravel and gravel. He also suggested that the correlation of sleeve friction (f s ) with N values is better than that of and N value, especially for cohesive Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 6, p. 5, NovemberDecember, /5/ Springer Science+Business Media New York 268

2 soils. Sanglerat [8] cited Meyerhof [7] who suggested the relationship n = ( /N) = MPa. Robertson et al. [] demonstrated the ( /N) ratio as a function of main grain size, D 50. They indicated geology of the study area where over consolidation exists. They proposed a soil behaviortype classification zone based on cone penetration test with pore pressure measurement tests (CPTU, piezocone). Ismael and Jeragh [5], accomplished a correlation on calcareous desert sands in Kuwait and compared it with the results of Schmertmann [9], for clean, fine to medium sands and slightly silty sands. Their test result is higher than that of Schmertmann [9] for clean, fine to medium sands and slightly silty sands. Danziger and De Velloso [2], made a correlation between CPT and SPT for soils in Brazil. Their values were in the same range as Schmertmann [9], and Akca [] proposed a method to select and precede the data for SPTCPT comparison. He used the traditional and statistical methods for the correlation odd SPTCPT test results from the United Arab Emirates (UAE). His results showed that the traditional (arithmetic average) method gave a higher ratio than literature values, and statistical approaches gave almost similar results and a little higher results than the arithmetic average method. The nvalue (0.77) for sand corresponds well with the sand value (0.6.0) of De Alencar Velloso [3]. The other nvalues determined for silty sand and sandy silt are higher than the literature values. The SPT and CPT correlations performed in this study are based on the data collected from silty clay, sandy clay, clay and clayey silt soils. Geology of the study area The study area is located in the south coastlines of Izmit Gulf in Kocaeli (coordinates 40 o 0''' North and 29 o 0'27'' West) at 2 meters above sea level. The study area is located in the east of the depressions known as pullapart formed in Izmit Gulf by the northern branch of the North Anatolian Fault. The south of the study area is known as the Armutlu Peninsula consisting of Paleozoic and Mesozoic rocks, and the north of it is bordered with the Kocaeli Peninsula consisting of the OrdovicianEocene units. The depression areas are filled with the deposits carried by the streams from the ridge of the Armutlu Peninsula. As a result of this, several fan deltas developed along the coast line. The G ȯ lcu k delta developed by Hisar, Kazykla, Batak, and Yenikoy creeks carrying the fragments of metamorphic schist, gneiss, marble from the basement rocks, Eocene rocks, and CretaceousEocene volcanic rocks into the Izmit Gulf. The G ȯ lcu k delta had its present shape within the latest 6,000 7,000 years in the Holocene period. It is very important to study the geology of this delta in detail for the earthquake which caused liquefaction, collapsing, and lateral spread. These kinds of deformations were observed around Izmit Gulf, including G ȯ lcu k. The Hisar creek is one of the main creeks passing roughly in the middle of the study area and deposited the carried materials as layers. These layers forming lower units are deposited almost lateral towards open sea. The gravels and sands deposited by the creeks before reaching the sea are the upper layers. The coarsely grained materials in the bottom of the boreholes developed in the regression period in PreHolocene. The delta moved backward depending on the increase of the waters and the more coarse grained materials were deposited between the mountain foot and the delta. There is a composite stratigraphy with lateral and vertical gradations of fine grained deposits, marsh, and sand in coastal facies near the coastline. A sand band exists along the coastline [4], and a 2025 m thick clay layer overlying the sandygravely unit was determined in the offshore boreholes. The lateral and vertical gradations of sand, gravel, silt, and sand were observed locally in the boreholes. The shape of the coast line was changed during the 7 August 999 earthquake. The seawater inundated land by more than 500 m in some locations. Some extensive lateral displacements originated in the places where the streams reach to sea. Data selection and Interpretation Testing procedure. Begemann Cone Type was used for the CPT, and Pilcontype hammer and trip release system were used for SPT. The specimens were collected by using a splitbarrel (spoon) sampler. The N values measured were normalized to standard rod energy ratio (ERr) given by Skempton [0]. 269

3 TABLE Soil type Number of soil samples n value ( /N) Clayey silt Silty Clay Clay N value Fig.. Response of N values to for silty clay. N 60 = N(ERr/60), () where the ERr ratio is 60% and ERr/60 is. Hence, N 60 will not change. Therefore, measured N values were used directly. The n values ( /N) were calculated by applying the arithmetic average method. The maximum N values were obtained for sandy silt, and the minimum N values were calculated for clay (Table ). A total of 662 data values was used in statistical analysis for the study area soils. Data Selection. SPT values obtained from 23 boreholes and CPT values obtained from 9 boreholes constituted the SPT and CPT data sets. The boreholes are very close to each other within a 35 m distance range. Therefore, comparison of the test results could be performed within a reasonable distance range. Statistical Correlation. The CPT measurements were averaged over 0.5 m intervals for cone resistance values. The reading values of CPT were compared with the SPT N values located over the same depth range. The first step was plotting the depth versus the SPT blow count. In the second step, the cone resistance values were averaged over 0.5 m at the same level. The correlation n = /N was used, allowing the nvalue to be achieved for each 0.5 m, from which comparison could be made. The SPT and CPT correlations were accomplished for silty clay, sandy silt, clay and clayey silt in the study area using statistical analysis (Fig., Fig. 2, Fig. 3, Fig. 4). Correlation functions and coefficients were determined for each soil type. The correlation coefficient values provide a reasonably good correlation for all the soil types. The highest correlation (R 2 = ) was achieved for clayey silt and the lowest correlation (R 2 = 0.773) was accomplished for silty clay. Results of the SPT and CPT Both of the SPT and CPT results show that although there was an increase in the SPT blow counts with depth, the cone resistance ( ) did not indicate an increase at the same depths. This event 270

4 N value Fig. 2. Response of N values to for clayey silt N value Fig. 3. Response of N values to for clay N value Fig. 4. Response of N values to for sandy silt. 27

5 TABLE 2 Soil type Correlation equations Correlation coefficients Silty clay Clayey silt Clay = 233.2exp(.22N)+53exp( N) =.228exp( N)+0.393exp(0.0533N) = 233.2exp(.22N)+53exp( N) = 7.87exp(827N)+.938exp( N) TABLE 3. Soil type UAE De Alencar Velloso Schmertman Franki (from Akca []) Meigh and Nixon Mayerhof Golcuk Sand Silty sand can be explained by the increase of water content in any depth in the investigation area. As the water content values change between 4% and 7% in the range of 0 m from the surface, they vary between 24% and 27% below 0 m depth. Because the ground surface and near surface of the investigation area are in rather dry condition, low SPT values correspond to high cone resistance within 34 m below the surface. The resistances of the silty clay units and clayey silty units increase to depth up to 5 m and decrease below this level. The clay units have very low resistance values up to a depth of 20 m. The tip resistance of the sandy silty soils within 9 m also decreases with depth. Conclusion This study attempted to figure out correlations of SPT and CPT for silty clay, clayey silt, clay, and sandy silt. A statistical approach has been applied to find the best correlation results. The correlation functions were determined with the adaptation of exponential functions for the study area soils (Table 2). In the literature, the correlation coefficients were determined for sand, silty sand and sandy silt with adaptation of linear functions as shown in Table 3. The correlation coefficient of sandy silt determined in the G ȯ lcu k area is greater than that of others. On the other hand, the correlation could not be performed for silty clay, clayey silt, and clay because of different soil characteristics. REFERENCES. N. Akca, Correlation of SPTCPT data from the United Arab Emirates, Eng. Geol., 67, 2923 (2003). 2. B.R. Danziger and D.A. De Velloso, Correlations between the CPT and SPT for some Brazillian soils, Proc. of the International Symposium on Cone Penetration Testing, Swedish Geotechnical Society, Linkoping, Sweeden, 45 October, CPT'95, 2, 5559 (995). 3. D. De Alencar Velloso, O ensaio de diepsondeering e a determinacao da capacidade de carga do solo, Rodovia, 29 (959). 4. M. Eryilmaz, F. Y. Eryilmaz, Z. Kirca, and E. Dogan, Distribution of sediments in Gulf of Izmit and influencing factors In Quaternary Sequence in the Gulf of Izmit, Edited by E. Merich, 2744 (995). 5. N. F. Ismael and A. M. Jeragh, Static cone tesets and settlement of calcareous desert sand, Can. Geotech. J., 23(3), (986). 6. A. C. Meigh and I. K. Nixon, Comparison of insitu tests of granular soils, Proc. of 5th International Conf. on Soil Mechanics and Foundation Engineering, Paris, France (96). 7. G. G. Meyerhof, Shallow foundations, J. Soil Mech. Found. Div., ASCE, 9(SM2), 23 (965). 8. G. Sanglerat, The Penetrometer and Soil Exploration; Interpretation of Penetration DiagramsTheory and Practice, Elsevier, Amsterdam, 464 (972). 9. J. K. Schmertmann, Static settlement over sand, ASCEJSMFD 96 (SM3), 0043 (970). 0. A. W. Skempton, Standart penetration test procedures and the effects in sands of overbuden pressure, relative density, particle size, aging and overconsolidation, Geotechnique, 36(3), (986).. P. K. Robertson, R. G. Campanella, A. Wightman, SPTCPT correlations, J. Geotech. Eng., 09(7) (983). 272

Soil Behaviour Type from the CPT: an update

Soil Behaviour Type from the CPT: an update P.K. Robertson Gregg Drilling & Testing Inc., Signal Hill, California, USA ABSTRACT: One of the most common applications of CPT results is to evaluate soil type