Spatial Correlation of Cone Tip Resistance for Soil in Nasiriyah

Abstract

Background:Quantification of soil property spatial variations is an important step in any reliability-based design. Little stochastic parameter information about the soil in Nasiriyah, which is in southern Iraq, is available.Methods:In this paper, the Scale Of Fluctuation (SOF) for the site soil is examined, which is suggested for construction of the refinery fuel station project as no random parametric quantity has been studied in this region. A Cone Penetration Test (CPT) was performed as part of the site investigation to a depth of 20 m in the vertical direction, and 24 CPTs were analyzed within the site. The spatial correlation was computed using four methods, including Single Exponent (SNE), Square Exponent (SQE), Cosine Exponent (CSE) and Second-Order Markov (SOM). Identification of the soil type depended on the most recent classification chart, which is based on CPT results. The spatial correlation was evaluated for the vertical direction considering the cone tip resistance (qc) component. Three trend functions were applied to all CPT soundings, including linear, quadratic and cubic polynomials, which were utilized to transform the non-stationary data to stationary data. Three modes of soil were employed, including the eight-meter soil layer, a twelve-meter soil layer and the entire twenty meters of soil, which includes both layers.Results and Discussion:The mean values of SOF were 0.54 m, 0.53 m, and 1.73 m for soil layers 8 m, 12 m, and 20 m, respectively. The high value of the last mean is attributed to the 20 m of stratification in the ground. This study also indicates that the SOF decreases as the polynomial degree increases, which is due to enhanced fitting. The coefficient of variation (COV) for the SOF shows little variability for most of the studied soil cases.

Uncertainty Characterization for Soil Cohesion in a Project Site in Nasiriyah Using Bayesian Methods

“…The soil in this region is a floodplain formation consisting of clay, silt, and sand, where the silt forms 60% of the deposits. The silt soil and sand settle in the swamps, the mud runs below the Shatt al-Arab, and one million tons of sediments are dried up annually (12,000 years) in these rivers that flow from the northwest to the southeast of Turkey through this basin [9][10][11]. The soil in this region's shallow depth belongs to the Holocene epoch.…”

“…Figure 3B shows the results of C u estimated based on SPTN, according to Decourt (1990). Number of cohesion values used at various depths vary, for example at depths of (1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,22,23,24,25) The collected data were presented in histograms to be more reliable and to provide a means to reduce the high uncertainty. It is noted in Figure 4 that 95% of the cohesion rate in most projects ranges from (50-150) kPa, which was estimated through the equations of the corrected values for SPT N according to Decourt [17].…”

“…Figure3Bshows the results of C u estimated based on SPTN, according toDecourt (1990). Number of cohesion values used at various depths vary, for example at depths of(1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,22,23,24,25) m the number of calculated values of cohesion were respectively (2, 5, 9, 4, 7, 7, 7, 4, 11, 1, 5, 7, 5, 1, 10, 5, 3, 4, 4, 4, 2, 4, 2, 3).…”