Papers by Murad Abufarsakh
In the state of Louisiana, roadways often have to be built over a weak subgrade due to the soft n... more In the state of Louisiana, roadways often have to be built over a weak subgrade due to the soft nature of Louisiana soil, which generates many design and construction difficulties. As an alternative to the traditional method of treating the soft soil with lime or cement, two geosynthetic products, a triaxial geogrid and a high-strength woven geotextile were evaluated for reinforcing unpaved roads constructed over natural soft subgrade. A total of six full-scale unpaved test sections were constructed, among which two sections were reinforced by one and two layers of triaxial geogrids respectively while high strength geotextiles were used to reinforce two of other sections with different base thicknesses. The rest of the two sections were left as control, of which one was constructed over sand embankments as the common practice in Southern Louisiana. The test sections were subjected to a full-scale moving wheel load applied by the Accelerated Loading Facility (ALF). A variety of instrumentation was used to measure the load-associated and environment-associated pavement responses and performance. Results of the full-scale testing demonstrate the benefits of geosynthetics in reducing the permanent deformation in the pavement structure.
This research project presents the calibration of resistance factors for the Load and Resistance ... more This research project presents the calibration of resistance factors for the Load and Resistance Factor Design (LRFD) method of driven piles driven into Louisiana soils based on reliability theory. Fifty-three square Precast-Prestressed-Concrete (PPC) piles that were tested to failure were included in this investigation. The predictions of pile resistances were based on static analysis (-method for clay and Nordlund method for sand), three direct CPT methods [Schmertmann method, De Ruiter and Beringen method, and Bustamante and Gianeselli (LCPC) method], and the average of the three CPT methods. Also, dynamic measurements with signal matching analysis of pile resistances using the Case Pile Wave Analysis Program (CAPWAP), which is based on the measured force and velocity signals obtained near the pile top during driving, were calibrated. The Davisson and modified Davisson interpretation methods were used to determine measured ultimate load carrying resistances from pile load tests. The predicted ultimate pile resistances obtained using the different prediction methods were compared with measured resistances determined from pile load tests. Statistical analyses were carried out to evaluate the capability of the prediction design methods to estimate measured ultimate pile resistance of driven piles. The results showed that the static method over-predicts pile resistance, while the dynamic measurement with signal matching analysis [CAPWAP-EOD (end of drive) and 14 days BOR (beginning of restrike)] under-predicts pile resistance. Among the three direct CPT methods, the De Ruiter and Beringen method was the most consistent prediction method with the lowest COV. Reliability based analyses using the First Order Second Moment (FOSM) method, the First Order Reliability Method (FORM), and the Monte Carlo (MC) simulation method were also conducted to calibrate the resistance factors () for the investigated pile design methods. The resistance factors with the target reliability ( Ｔ )of 2.33 for the different design methods were determined and compared with American Association of State Highway and Transportation Officials (AASHTO) recommendation values. In addition, the evaluation of different design methods was performed.
Japanese Geotechnical Society Special Publication, 2016
The Load Resistance Factor Design (LRFD) was introduced in Korea about a decade ago. However, the... more The Load Resistance Factor Design (LRFD) was introduced in Korea about a decade ago. However, the resistance factors suggested by AASHTO (2007, 2010) represent the characteristics of bedrocks in the US that may differ from those in Korea. There is also a general belief that the calculated probabilities of failure from conventional reliability analyses are not realistic because of the conservative bias used when predicting resistance and tails of probability distributions for load and resistance. The existence of a lower bound of resistance affects the reliability and resistance factors even though the lower bound of resistance is small. Thus, it is important to determine accurate resistance factors for drilled shafts based on reliable load test results and to calibrate the resistance factors considering lower-bound resistance. In this paper, an accurate resistance factor for drilled shafts was determined based on 13 sets of drilled shaft bi-directional load test data with strain gauges. Using a new log-normal distribution with lower bound of resistance, reliability analysis and resistance factor was performed using the advanced first order second moment (AFOSM) method. The target reliability indices were determined as 2.5, 3.0, and 3.5. For the target reliability index of 3.0 (AASHTO recommended value), the resistance factors were determined in the range of 0.13-0.32 for shaft resistance, 0.19-0.29 for base resistance. The lower bounds of resistance for each resistance (shaft and base) were determined, to be applied in the various bearing capacity equations, based on the Hoek-Brown failure criteria (2002) and the downgraded GSI values. Considering the lower-bound resistance, resistance factors were increased by up to 8% for the shaft resistance factor and 13% for the base resistance factor.
These papers will be of interest to practitioners, researchers, students, and policymakers workin... more These papers will be of interest to practitioners, researchers, students, and policymakers working to address sustainability in the area of geotechnical and geoenvironmental engineering.
Problematic Soils and Rocks and In Situ Characterization, 2007
The purpose of this paper is to evaluate the capability of existing interpretation methods and de... more The purpose of this paper is to evaluate the capability of existing interpretation methods and develop new methods to reasonably predict the overconsolidation ratio (OCR) of clayey soils utilizing the piezocone penetration test (PCPT) data. These existing methods include the Schmertmann method, Kulhawy and Mayne method, and the Chen and Mayne methods using pore pressure measurements either at the cone tip (u1) or at the cone base (u2). Seven sites in Louisiana were used for this study. At each site, in-situ PCPT tests were performed and soundings of cone tip resistance, qc, sleeve friction, fs, and pore pressures at different locations (u1 and u2) were recorded. High quality Shelby tube samples were collected close to the PCPT tests and used to conduct laboratory oedometer consolidation tests to evaluate the reference OCR values. The predicted OCR values from different methods were compared with the laboratory OCR values. The results showed that all the investigated PCPT methods overpredict the laboratory calculated OCR. The collected data were further used to develop two new PCPT methods that can estimate the OCR reasonably.
Journal of Environmental Engineering, 1987
ABSTRACT
Applied Mechanics and Materials, 2014
Cement-Treated Base (CTB) is a non-conventional method used in road bases materials to improve it... more Cement-Treated Base (CTB) is a non-conventional method used in road bases materials to improve its engineering properties due to the hardening of cement when moisture is present and extends the period of curing times. This study investigates the effects of cement additive on properties of base layer using laboratory mechanistic evaluation of stabilized soil mixtures. Laboratory tests conducted were Unconfined Compressive Strength (UCS), Indirect Tension test for Resilient Modulus (ITRM) and Flexure Strength (FS) tests. The results revealed that by adding Portland cement, the mechanical properties of the mixture have improved where the UCS is found to be an important quality indicator. In addition, the variables that influenced these tests, which are cement content, curing time, moisture content, and dry density, play important role to determine the performance of CTB. This paper presents the finding of a correlation conducted to analyse the influences of these variables using regres...
… Board 89th Annual …, 2010
The new I-10 Twin Span Bridge over Lake Pontchartrain is being constructed to replace the existin... more The new I-10 Twin Span Bridge over Lake Pontchartrain is being constructed to replace the existing bridge, which was damaged by Hurricane Katrina in 2005. The new bridge was designed to be higher and stronger than the existing bridge. The new bridge will be supported by ...
The contents of this report reflect the views of the authors who are responsible for the facts an... more The contents of this report reflect the views of the authors who are responsible for the facts and the accuracy of the data presented herein. The contents do not necessarily reflect the views or policies of the Louisiana Department of Transportation and Development or the Louisiana Transportation Research Center. This report does not constitute a standard, specification, or regulation.
TECHNICAL REPORT STÄNDARD PAGE 1. Report no. FHWA/LA.04/389 " 2. Government Accession No. 3.... more TECHNICAL REPORT STÄNDARD PAGE 1. Report no. FHWA/LA.04/389 " 2. Government Accession No. 3. Recipient's Catalog No. 4. Title and Subtitle ASSESSMENT OF IN-SITU TEST TECHNOLOGY FOR CONSTRUCTION CONTROL OF BASE COURSES AND EMBANKMENTS S. Report ...
Transportation Research Board 85th …, 2006
This paper describes how geosynthetics have increasingly been used to reinforce many earth struct... more This paper describes how geosynthetics have increasingly been used to reinforce many earth structures and are now a well-accepted means of improving engineering properties of marginal soils. However, most of past studies and applications of geosynthetics stabilization are ...
Transportation Research Record: Journal of the Transportation Research Board, 2005
A comprehensive testing program was conducted to evaluate the potential use of the dynamic cone p... more A comprehensive testing program was conducted to evaluate the potential use of the dynamic cone penetrometer (DCP) in the quality control–quality assurance procedure during the construction of pavement layers and embankments. The laboratory tests were conducted on different materials prepared inside two test boxes measuring 1.5 m x 0.9 m x 0.9 m (5 ft x 3 ft x 3 ft) located at the Louisiana Transportation Research Center (LTRC). The field tests were performed on different highway sections in Louisiana. In addition, nine test sections were constructed and tested at the pavement research facility site of the LTRC. In all laboratory and field tests, DCP tests were carried out in conjunction with the plate load test (PLT). Also, falling weight deflectometer (FWD) tests were carried out on the field sections. California bearing ratio (CBR) laboratory tests were performed on samples collected from the tested sections. Regression analysis was carried out on the collected data to correlate ...
Transportation Research Record: Journal of the Transportation Research Board, 2015
Moisture content and stress state, which includes the effects of matric suction for unsaturated s... more Moisture content and stress state, which includes the effects of matric suction for unsaturated soil, exert a significant effect on the resilient modulus (MR) values of fine-grained subgrade soils. The moisture content and, consequently, matric suction vary periodically in subgrades in response to seasonal variation. The relationship between MR and matric suction is investigated through repeated load triaxial testing on fine-grained soils to obtain MR values and evaluation of the soil–water characteristic curves (SWCCs). The SWCCs, which represent the relationship between suction and degree of saturation, were evaluated with a combination of axis-translation and chilled-mirror hygrometer techniques to allow SWCC representation across the entire range of saturation. The plasticity index (PI) had a significant impact on the matric suction–water content relationship such that the SWCC shifted to the left as the soil PI decreased. The test results indicated a significant relationship be...
Text =5,305 words Figures = 6 × 250 = 1,500 words Tables = 4 × 250 = 1,000 words Total = 7,805 wo... more Text =5,305 words Figures = 6 × 250 = 1,500 words Tables = 4 × 250 = 1,000 words Total = 7,805 words TRB 2008 Annual Meeting CD-ROM Paper revised from original submittal.
This paper presents the computerized MS-Windows visual basic CPT (Cone Penetration Test) soil cla... more This paper presents the computerized MS-Windows visual basic CPT (Cone Penetration Test) soil classification software that was developed as part of an extensive effort to facilitate the implementation of CPT technology in many geotechnical engineering applications. Five CPT soil engineering classification systems were implemented into handy tool software for friendly use by geotechnical engineers. These include the probabilistic region estimation and fuzzy classification CPT methods developed by Zhang and Tumay, Schmertmann, Douglas and Olsen, and Robertson et al. CPT classification methods. In the probabilistic region estimation and fuzzy classification methods, a conformal transformation is first applied to determine the profile of soil classification index (U) with depth from cone tip resistance (q c) and friction ratio (R f). A statistical correlation was established in the probabilistic region estimation method between the U index and the compositional soil type given by the Unified Soil Classification System (USCS). The CPT fuzzy classification on the other hand emphasizes on the certainty of soil behavior. Schmertmann and Douglas and Olsen methods provide soil classification charts based on cone tip resistance and friction ratio. However, Robertson et al. proposed a three-dimensional classification system that is presented in two charts: one chart uses corrected tip resistance (q t) and friction ratio (R f); while the other chart uses q t and pore pressure parameter (B q), as input data. Five sites in Louisiana were selected for this study. For each site, CPT tests and the corresponding soil boring results were correlated. The soil classification results obtained using the five different CPT soil classification methods were compared.
International Journal of Pavement Engineering, 2015
ABSTRACT This study evaluates the performance of geosynthetic-reinforced unpaved road sections ov... more ABSTRACT This study evaluates the performance of geosynthetic-reinforced unpaved road sections over soft subgrade using plate load test. The parameters investigated included the location and tensile modulus of geosynthetics, and the number of geosynthetic layers. Stress distribution on top of the subgrade layer and strain distribution along the geosynthetic reinforcements were also investigated. The test results indicated that geosynthetic reinforcement resulted in appreciable reduction of surface deformation and increase of bearing capacity. The test results also demonstrated the effects of geogrid arrangement/location on the performance of unpaved test sections, with double reinforcement location consistently yielded the best improvement. The definite trend of increasing Bearing Capacity Ratio (BCR) and reloading elastic modulus with increasing tensile modulus of geosynthetics was observed when geosynthetics were grouped according to aperture shape and polymer type. The BCR is defined as the ratio of the bearing capacity of reinforced unpaved sections to that of unreinforced unpaved section.
Contemporary Topics in In Situ Testing, Analysis, and Reliability of Foundations, 2009
This paper presents the evaluation of axial load resistance of drilled shafts installed in Louisi... more This paper presents the evaluation of axial load resistance of drilled shafts installed in Louisiana soils based on reliability analysis. Twelve drilled shafts that were tested using the Osterberg cell method or the static load test method were analyzed in this investigation. The predictions of axial shaft resistance were conducted using α method (total stress analysis) for cohesive soils and β method (effective stress analysis) for cohesionless soils as proposed by Reese and O’Neill, which are based on soil characteristics obtained from soil borings and laboratory tests. A short-term loadsettlement relationship was also estimated using the FHWA approach. The objective of this study is to calibrate the resistance factors (φ) for drilled shafts based on Louisiana experiences. In this research, the serviceability limit state is considered, because it has higher probability of occurrence than the ultimate limit state in Louisiana soils. Statistical data, validated by the Reese and O'Neill design method, was used to obtain the LRFD resistance factor (φ) for the serviceability limit state of drilled shafts by means of the First Order Second Moment (FOSM) method.
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Papers by Murad Abufarsakh