Correlation Of Undrained Shear Strength Research Articles

Evaluation of Empirical Formulas to Estimate Axial Capacity of Bored Pile in West Java, Indonesia

Pile foundation is part of the substructure that plays an important role in carrying and supporting the load acting on it. Therefore, a proper foundation design by estimating the bearing capacity of pile foundation is needed to ensure the safety of the building foundation. To achieve better estimation of pile capacity, analysis of the axial bearing capacity should be verified by pile test results such as Static Loading Test or dynamic test with a Pile Driving Analyzer. Based on the pile test data, the values of the skin friction and end bearing resistance can be back calculated, and hence it can be used in the calculation of pile bearing capacity using empirical methods. In this study, bearing capacity analysis was performed for drilled pile foundations, which had been tested using Static Loading Test and Pile Driving Analyzer. The analysis was carried out by comparing the results of empirical calculations for each test pile with the results of field tests. The calculation results were then compared to the empirical adhesion factor (alpha) method, which is commonly used by practicing engineers in Indonesia, according to the methods proposed by Kulhawy (1984), Reese & Wright (1977), and Reese & O'Neil (1988). Based on the 104 test piles data, the results are more in good agreement with the adhesion factor proposed by Kulhawy (1984) with a correlation of undrained shear strength, cu of 8 NSPT, a correlation of unit skin friction for sandy soils of 2.2 NSPT, and a correlation of unit end bearing for sandy soils of 70 NSPT-ave.

Correlation of Undrained Shear Strength and Liquidity Index of Fine-Grained Soils in West Java, Indonesia

The undrained shear strength of fine-grained soils is an important property in geotechnical engineering. However, the process of determining undrained shear strength can be challenging. Hence, the correlation of undrained shear strength with other soil properties needs to be established. Several studies have estimated undrained shear strength using the liquidity index. In the current study, we aim to find the best correlation of undrained shear strength and liquidity index of fine-grained soils in West Java, Indonesia at various water contents using the form of correlation of undrained shear strength and liquidity index and also factors influencing the undrained shear strength. The values of undrained shear strength and liquidity index are obtained by laboratory test and data collection from previous studies of soils in West Java. Results show a good linear relationship between the logarithmic value of undrained shear strength and liquidity index for 173 variations of soil samples. We also can conclude that the undrained shear strength of fine-grained soils is controlled by the proportion of finer grains presence and also the plasticity of the soils.

Reply to the discussion by Mesri and Wang on “Correlations for undrained shear strength of Finnish soft clays”

Reply to the discussion by Mesri and Wang on “Correlations for undrained shear strength of Finnish soft clays”

Discussion of “Correlations for undrained shear strength of Finnish soft clays”

Discussion of “Correlations for undrained shear strength of Finnish soft clays”

Correlation of JKR Probe with Undrained Shear Strength

The JKR probe test is a popular field test in Malaysia, and is especially used in soft soil areas to determine bearing capacity. However the correlation of undrained shear strength (Su) and the JKR probe test is not available at this moment. This study was performed to develop an empirical correlation of JKR probe and undrained shear strength of soft to stiff soil. In order to produce the correlation, the JKR probe test and the vane shear test have been performed at Universiti Tun Hussein Onn Malaysia (UTHM). Six JKR probe tests and 12 field vane shear tests were performed in close proximity to obtain good correlation. The results show that undrained shear strength and JKR probe can be correlated as Su=18J0.3. The proposed correlations will serve as a reference for engineers in estimating undrained shear strength, especially in low-risk construction design.

Correlations for undrained shear strength of Finnish soft clays

The study focuses on the derivation of transformation models for undrained shear strength (su) of Finnish soft sensitive clays. Specific correlation equations for suof Finnish clays are presented in this work for the first time. Field and laboratory measurements from 24 test sites in Finland are exploited for this purpose and a multivariate database is constructed. The multivariate data consist of sufrom the field vane test, preconsolidation stress, vertical effective stress, liquid limit, plastic limit, natural water content, and sensitivity. The main objective is to evaluate the interdependence of su, consolidation stresses, and index parameters and provide a consistent framework for practical use. The new correlations are established through regression analyses. The constructed framework is further validated by another independent multivariate database of clays from Sweden and Norway as well as by empirical equations for Swedish and Norwegian clays. Existing correlations are evaluated for Finnish and Scandinavian clays. Finally, bias and uncertainties of the new correlations are presented.

Reliability-Based Analysis of Bearing Capacity of Strip Footings Considering Anisotropic Correlation of Spatially Varying Undrained Shear Strength

AbstractA reliability-based analysis of the bearing capacity of strip footings considering the spatial variability of undrained shear strength of clay was performed using the random FEM. The effect of anisotropic correlation of spatially varying undrained shear strength on the mean and standard deviation of bearing capacity was obtained using the random FEM. It was found that the anisotropic correlation of undrained shear strength significantly affects the bearing capacity. The mean bearing capacity was found to be minimal for a specific combination of horizontal and vertical scales of fluctuation. The coefficient of variation of the bearing capacity increased with increases in horizontal or vertical scales of fluctuation, or both. The factor of safety required to achieve a specified target failure probability for different scales of fluctuation and coefficients of variation of the undrained shear strength of clay is presented.

Discussion of “Multivariate distribution for undrained shear strengths under various test procedures”

Care needs to be exercised when examining the empirical correlations for undrained shear strength proposed by Ching and Phoon (2013) because the manuscript does not adequately define the overconsolidation ratio (OCR), and the data in Table 2 that were used to develop the empirical correlations include values of OCR, as small as 1.1, 2.2, and 3.3 and as large as 50, 60, and 80. A clear distinction needs to be made among (i) OCR = p ′ / vo ′ , where for a natural soil deposit sublayer p ′ is the preconsolidation pressure and vo ′ is preconstruction effective vertical pressure; (ii) OCR = p ′ / vc ′ , where vc ′ is a consolidation pressure in the recompression range of a natural soil deposit sublayer with a preconsolidation pressure p ′ ; and (iii) OCR = vm ′ / vc ′ , where vm ′ , for a soil sublayer in the field or in the laboratory, is the maximum effective vertical pressure after loading and primary consolidation, and vc ′ is a consolidation pressure after unloading and primary rebound. In addition, the data in Table 2 include natural soil deposits as well as specimens reconstituted in the laboratory. In geotechnical engineering, there is a separate body of empirical literature on undrained shear strength of soft clay and silt deposits with values of p ′ / vo ′ typically less than 3 and rarely greater than 6 (Terzaghi et al. 1996, Arts. 20.1 to 20.7), and on undrained shear strength of stiff clays and shales (Terzaghi et al. 1996, Art. 20.8). This discussion only concerns soft clay and silt deposits because for these soils exists an adequate body of laboratory andfield undrained shear strengthdata as a functionof composition (e.g., expressed in termsof plasticity index, Ip), mode of shear (e.g., field vane (FV), direct simple shear (DSS), triaxial compression and extension (TC and TE, respectively), unconfined compression (UC), and mobilized in full scale construction), and rateof shearor time to failure (e.g., FVandUC fast, and field construction much slower).

Correlation of undrained shear strength and CPT resistance

The correlation of CPT resistance and undrained shear strength of soft Holocene clays is discussed in this paper. This soil type, covering significant part of Hungary is frequently involved in different geotechnical engineering problems such as building of highway embankments. Soil samples of eight different sites have been studied, samples were taken at each site and cone penetration tests were performed. The samples were tested by means of unconfined compression and consolidatedundrained triaxial compression tests. The correlation of the determined undrained shear strength and the experienced CPT results was evaluated and the empirical cone factors ( N k , N kt , N ke , N Δu ) were determined for each tests. The back-calculated cone factors have been compared with the values suggested by earlier works in this field. The possible correlations between cone factors and different soil properties (such as index of plasticity, pore pressure coefficient etc.) are also discussed in the paper and recommendations are given for estimation of undrained shear strength of Holocene clays.

Response of Vertically Loaded Pile in Clay: A Probabilistic Study

This study presents the response of a vertically loaded pile in undrained clay considering spatially distributed undrained shear strength. The probabilistic study is performed considering undrained shear strength as random variable and the analysis is conducted using random field theory. The inherent soil variability is considered as source of variability and the field is modeled as two dimensional non-Gaussian homogeneous random field. Random field is simulated using Cholesky decomposition technique within the finite difference program and Monte Carlo simulation approach is considered for the probabilistic analysis. The influence of variance and spatial correlation of undrained shear strength on the ultimate capacity as summation of ultimate skin friction and end bearing resistance of pile are examined. It is observed that the coefficient of variation and spatial correlation distance are the most important parameters that affect the pile ultimate capacity.

Assessment of undrained shear strength based on Cone Penetration Test (CPT) for clayey soils

This paper presents a rational way of developing the correlation of undrained shear strength based on the cone resistance from the Cone Penetration Test (CPT) for clayey soils. The field cone penetration test program included CPT, the index test, the one dimensional test and the triaxial test. The cone factor, which is most important for reliable estimation of undrained shear strength from cone resistance, has been evaluated considering the plasticity index of soils. The cone factor is influenced by the test methods that are used for obtaining the undrained shear strength. The isotropic Consolidated Undrained Compression Test (CIUC) for shear strength assessment has been used to effectively reflect in-situ strength. Following the field cone penetration test program, clayey soils from nine sites in Indiana have been investigated. Based on the results from the test program, the cone factor ranges from 8.0 at plasticity index of 7.9 to 12.1 at plasticity of 20.0 for Over Consolidated (OC) clays. This result parallels the increasing trend of the cone factor as the plasticity index increases, which was reported by some researchers, while other researchers showed the decreasing trends. An equation for estimating the cone factor is suggested for better geotechnical design.