Journal of Engineering Geology

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The Alborz dam rock foundation is composed of marl and sandstone. With regard to the proposed plan for the grout curtain in marly rocks (relatively soft and plastic( which is significantly different from the hard and brittle rocks, the boreholes spacing (influence radius slurry), injection pressure (resistance rock), and even the composition and concentration of slurry are important. In the present paper, in order to evaluate the grout curtain of Alborz Dam, emphasis has been placed on two important parameters, namely, the coefficient of permeability and cement take. The results of cement take suggest that the distance between the primary boreholes is long and there is no proper connection between the primary and secondary boreholes. Moreover, grouting results of the fifth and sixth series of grout holes imply that the depth of some of the sixth series of grout holes has not been attained at the water tightening surface. A review of the rate of the cement take - time - pressure graphs and cement take - time graphs on the right abutment indicates that the injection pressure has not been applied in accordance to marly rocks leading to unfavorable phenomenon of opening and closing of joints (hydrojacking). Notably, the check holes results on the right abutment indicate that water tightening at this area has been provided a satisfactory and acceptable job.

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Marl rocks are from weak rocks which cause some problems due to high swelling and efflorescence capability, low resistance and durability in construction of engineering structures. Creation of these problems is due to inadequate recognition of engineering geology properties of these rocks. Hence, in this research for determination of the physical and mechanical parameters of marl rocks of Safa dam site, Aterberg limits, density, porosity and moisture percent, uniaxial compressive strength (UCS), direct shear, swelling and three axial compressive strength tests and X-ray diffraction (XRD) and X-ray fluorescence (XRF) analyses were performed on available samples from excavated bores. Results of experiments indicate that the type and contents of minerals and percentage of calcium carbonate in marl rocks, especially clay minerals are effective factors on engineering geology properties of these rocks

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Marly rocks of Abtalkh formation were classified by Q, RMR, RSR and RQD rock mass classification systems using 222 meters logs from exploratory boreholes in Doosti dam site. The results show that the RMR is the most suitable method for classification of studied rock masses and has highest correlation coefficient with RQD. The validity of different Q-RMR equations was studied using error ratio (ER). Cameron et al. (1981) and Morno (1982) equations have lowest ER and highest validity for studied marlstones. Bieniawski (1989) and Cameron (1981) relationships are lower and higher limits of equations for marly rocks respectively. 

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Introduction
The standard penetration test (SPT) is one of the most common tests in geotechnical investigations. The results of this test are known as a simple, inexpensive, and tangible criterion in geological and geotechnical engineering. Many computational methods and engineering judgments depend on the results of this test. In this research, estimation of physical and engineering properties of clay soils was carried out using statistical methods based on standard penetration test results. The scope of this case study is related to a variety of clayey soils in Tabriz (the northwest of Iran). The existing relationships were confirmed based on database of this study. After statistical analysis of the database, eight relationships including single and two-variable associations have been proposed to estimate the physical and engineering properties with better performance using nonlinear regression.
Material and Methods
Different types of clayey silt and marl layers spread in Tabriz were included for the purpose of this study. The geological age of these layers dates back to the Miocene and Pliocene era. This research was conducted in two sections of the field and analysis. Two machine boreholes were drilled, and, based on ASTM, a standard penetration test with other laboratory tests were performed on the soil specimens in order to determine the physical and plasticity properties. According to the results of this study and the existing data, a total of 107 series were prepared. Based on the soil properties, 11 variables were selected including the fine grain percentage (FGP), liquid limit (LL), plastic limit (PL), percentage of clay particles (C), plastic index (PI), consistency index (CI), activity (A), dry unit weight (γ_d), natural moisture content (w_n), initial void ratio (e_o), and effective vertical stress (σ'_v). The standard penetration tests were run for each meter in drilled boreholes. The results of this test were corrected according to NCEER method. The correlation between the variables and corrected standardized penetration test results (N₆₀) were studied by Spearman ranking coefficient. Verifications of the existing eight experimental relationships between  standard penetration and other soil properties, proposed by Kayabasi (2015) and Hoshmand et al., (2012), were checked out using the findings and data of the present study. The linear, exponential, logarithmic, and exponential regressions between each variable and N₆₀ were investigated using SPSS software, version 16. The best regression with the highest R² for each variable was selected. Eight new relationships were proposed. Performance of the suggested relationships was compared with the existing relationships.
Results and Discussion
The findings of the current study could be summarized as:
1. The clay soils of the studied area in Tabriz were classified into four categories including CH, MH, CL, and ML according to USCS classification. The range of changes in plastic index and liquid limits of the samples were 9.19 ~ 45% and 29 ~ 77%, respectively. The corrected standard penetration test results (N₆₀) changed from 9 to 28 showing that soil compression was low to high.
2. The highest positive and negative Spearman correlation coefficients were related to the consistency index (+0.772) and moisture content (-0.759), respectively.
3. The existing empirical relationships, based on the database of this study, were found to have better statistical coefficients in terms of consistency index, activity, moisture percentage, and fine grained percentage. In term of sample depth, the experimental relationship, showed the lowest statistical coefficient.
4. Four single-variable and two-variable relationships were proposed by nonlinear regression analysis. Using these relationships, clay soil properties including activity, moisture content, fine grain percentage, and consistency index were estimated based on N_60. In addition, two relations were proposed between sample depth (D) and vertical effective stress (σ'_v) with N₆₀. The statistical coefficients of the suggested relationships were better than the existing empirical relationships. The proposed relationship of estimating the consistency index with coefficient (R²) of 0.673 and regression line slope of about 1 had the best performance.
Conclusion
In general, the main objective of this study was to investigate the correlation between physical and plasticity properties of clay soils and N₆₀ on Tabriz clayey soils. Clay soils of the present study included various silty and marl layers. Sufficient correlation was observed between the physical and engineering properties of clay soils and N₆₀. The validation of the existing experimental relationships based on A, w_n, FGP, and D resulted in weak statistical coefficients (R² <5) employing the database of the current study. Six new experimental relationships were proposed to estimate A, FGP, w_n, and CI as well as two correlations of N₆₀ with effective stress and sample depth. Generally, the results have been revealed that the statistical coefficients of the proposed relationships were improved compared with the existing relationships. The most suitable relationship was the estimation of soil consistency index (R²~70) and root mean square error (RMSE=129). Finally, due to the novelty of this research topic, verification and development of the proposed relationships for the soils has been recommended in other areas.

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