Hani H. Titi

MINIATURE CONE PENETRATION TESTS IN SOFT AND STIFF CLAYS

An electric continuous intrusion miniature cone penetration test system was recently developed for roadway design and construction control of embankments. The system continuously advances a 2 sq cm electric miniature cone penetrometer by uncoiling a stainless steel push rod. Cone penetration testing advances a cylindrical probe into a soil sample and electronically measures the tip and sleeve resistance due to the intrusion. These resistance parameters are used to classify penetrated sediments and to estimate strength and deformation characteristics of soils. Field and laboratory testing programs were conducted on overconsolidated, normally consolidated, and compacted Louisiana clays. The field testing program consisted of cone penetration tests using both 2 and 15 sq cm electric cone penetrometers in conjunction with soil sampling, while laboratory tests included physical properties and strength characteristics of the investigated soils. Analyses of cone penetration tests were conducted to assess the repeatability and reliability, as well as confirming that the electric miniature friction cone (2 sq cm) output complies with the output of the 15 sq cm cone. The test data will provide the means to calibrate the miniature cone with respect to the commonly used cone penetrometers. It will be used to establish correlations between the miniature cone penetration test results and soil parameters determined in the laboratory and utilize them for roadway design and construction control of highway embankments.

Evaluation of resilient modulus of subgrade soil by cone penetration test

Pavement design based on the resilient modulus of subgrade soil has been adopted by many transportation agencies following the recommendations of the AASHTO guide for design of pavement structures. Laboratory and field nondestructive tests are generally used to evaluate the resilient modulus of subgrade soil. These methods have shortcomings and limitations and are considered laborious, time-consuming, and expensive. The difficulties associated with the existing methods signify the need for a popular in situ technology for evaluating the resilient modulus of subgrade soil. Among other methods, the cone penetration test (CPT) is fast, simple, and economical and provides repeatable and reliable results. The results of a pilot investigation to assess the possibility of predicting the resilient modulus of subgrade soil from the CPT soundings are presented here. Field and laboratory testing programs were carried out on two types of cohesive soils at the Louisiana Transportation Research Center/Pavement Research Facility. Field tests consisted of CPT soundings using the 15-cm2 friction cone penetrometer and the 2-cm2 miniature friction cone penetrometer. Laboratory tests included the resilient modulus and physical properties of the investigated soils. The results of the miniature CPT were evaluated and compared with the soundings of the 15-cm2 cone at the same site. Both laboratory and field tests were analyzed. Based on statistical analyses, a model was proposed to estimate the resilient modulus from the CPT data and basic soil properties. Predicted values of the resilient modulus are consistent with laboratory measurements.

Probabilistic CPT method for estimating the ultimate capacity of friction piles

This paper presents a probabilistic CPT method to estimate the ultimate capacity of driven friction piles utilizing CPT data. A database of 35 square PPC piles that were loaded to failure and their adjacent CPT were used to develop this method. Backcalculation was carried out to calibrate the correlation factors needed to determine the unit end bearing (qb) and unit skin friction (f) of the pile from CPT data (qc, fs) based on the probability of having each soil type. The ultimate pile capacities (QP) of the investigated piles estimated by the proposed method, three other CPT methods, and static α and β methods were compared with the measured pile capacities obtained from pile load tests. Statistical analyses were carried out to evaluate the reliability of the probabilistic CPT method and the results showed that the proposed method can predict the ultimate capacity of the piles with good accuracy. The capability of the proposed method was further verified by predicting the capacities of an additional 17 pile load tests. The probabilistic CPT method, in addition to Schmertmann, α, and β methods were calibrated to evaluate the resistance factors needed for the design of single driven piles based on the LRFD method.

Evaluation of Resilient Modulus Model Parameters for Mechanistic–Empirical Pavement Design

Correlations were developed to estimate the resilient modulus of various Wisconsin subgrade soils from basic soil properties. A laboratory testing program was conducted on common subgrade soils to evaluate their physical and compaction properties. The resilient modulus of the investigated soils was determined from repeated load triaxial testing according to the AASHTO T 307 procedure. The laboratory testing program produced consistent results and a high-quality database. The resilient modulus constitutive equation adopted by NCHRP Project 1-37A was selected for this study. Comprehensive statistical analysis was performed to develop correlations between basic soil properties and the resilient modulus model parameters ki. The analysis did not yield good results when the whole test database was used. However, good results were obtained when fine-grained and coarse-grained soils were analyzed separately. The correlations developed were able to estimate the resilient modulus of the compacted subgrade soils wit...

Prediction of bearing capacity of friction piles in soft Louisiana soils by cone penetration test

A comparison of four different methods for predicting the axial compression capacity of single piles using cone penetration test (CPT) results is presented. Nineteen pile load tests and parallel CPT soundings conducted close to the piles were identified and documented from the Louisiana Department of Transportation and Development archives. Piles with different sizes and lengths were investigated. The four prediction methods selected were the Schmertmann method, the de Ruiter and Beringen method, the French Central Bridge and Pavement Laboratory (LCPC) method, and the Tumay and Fakhroo method. An evaluation scheme was performed using these methods to assess their capability to reliably predict the axial compression capacity of piles installed in soft Louisiana soils. The predicted pile capacities obtained by the different methods were compared with the measured pile capacities obtained from pile load tests. Analysis of the results showed that the Schmertmann, de Ruiter and Beringen, and Tumay and Fakhroo methods predicted the ultimate compression capacities of piles installed in soft Louisiana soils with a reasonable accuracy. The LCPC method underpredicted the measured capacities of these piles.

Mapping Overweight Vehicle Permits for Pavement Engineering Applications

AbstractOversize-overweight (OSOW) permit programs allow carriers to move large, heavy, and often high-value freight on state and federal highways. This study analyzed six years of Wisconsin single-trip overweight permits and two years of Iowa single-trip overweight permits to visualize routing trends, identify heavily travelled highway segments, and provide support for mechanistic-empirical pavement design guide (MEPDG) analyses and pavement reliability research. The methodology used custom visual basic for applications (VBA) scripts for text parsing and route processing with results linked to a geographic information system (GIS) database. The results allowed for visualization of permit traffic, geospatial queries of permit routes, origin-destination analyses, and identification of heavily-used permit vehicle corridors. These results have numerous applications for highway design, bridge engineering, freight trend analysis, and highway system planning. Additionally, the methodology supports the generatio...

EVALUATION OF CPT METHODS FOR LOAD AND RESISTANCE FACTOR DESIGN OF DRIVEN PILES

This paper presents an evaluation of eight cone penetration test (CPT) methods and the static method to determine the load and resistance factor design (LRFD) input parameters for single driven piles. Evaluation of these methods was conducted based on load test database of thirty-four square precast prestressed concrete (PPC) driven friction piles tested to failure. Resistance factors for the investigated CPT methods and the static method were determined using reliability-based analysis. Other design input parameters were determined based on the AASHTO LRFD design specifications for bridge substructure. Based on the results of the analysis, the Penpile method showed the highest values of resistance factors while Tumay and Fakhroo and Schmertmann methods showed the lowest values of resistance factors.

Characterization of Overweight Permitted Truck Routes and Loads in Wisconsin

This study analyzed 95,000 overweight (OW) single-trip truck permits issued in Wisconsin between May 2007 and June 2013. A geographic information system and relational databases were used to conduct a statewide routing analysis to identify highways that are heavily used by OW permitted trucks, such as WI-140. Field studies at WI-140 confirmed a high proportion of OW trucks. In addition, pavement damage and deterioration caused by heavy truck traffic were investigated by conducting a visual distress survey and determination of the pavement condition index (PCI). The pavement of WI-140 was heavily distressed, with a PCI description of very poor. The Mechanistic–Empirical Pavement Design Guide (MEPDG) was used on WI-140 to evaluate the performance of the pavement under OW truck traffic. The results of the MEPDG analysis showed that the pavement was heavily distressed and deteriorated, a condition that was consistent with field measurements and observations. A primary application of the routing and pavement analyses is to assist the Wisconsin Department of Transportation in developing rehabilitation strategies for deteriorated pavements.

IMPLEMENTING HIGHWAY PREVENTIVE MAINTENANCE: COMPARING CHALLENGES, PROCESSES, AND SOLUTIONS IN THREE STATES

One of the central challenges facing todays state transportation policymakers is how to incorporate preventive maintenance concepts and strategies into existing asset-management systems. Seven unique challenges to implementing preventive maintenance are identified in the literature and elsewhere, and a discussion covers the ways states have addressed those challenges through various implementation strategies. Then, case studies provide examples of how that incorporation has occurred in the departments of transportation in Michigan, Kansas, and Nebraska. The three case studies are presented in an effort to demonstrate the advantages and disadvantages of these three unique approaches, herein labeled the top-down approach, for Michigan; the bottom-up approach, for Kansas; and the inclusive approach, for Nebraska. In particular, an examination is presented of how preventive maintenance concepts were integrated into the planning, budgeting, and technical needs-assessment for state highways.

Implementation of Miniature Cone Penetrometer in Roadway Design and Construction

A continuous-intrusion miniature cone penetration test (CIMCPT) system was developed, calibrated, and implemented by the Louisiana Transportation Research Center. The cone-penetration technology is fast, reliable, and cost-effective, especially when compared with the traditional site-characterization methods such as borings and laboratory and field tests. The implementation phase of the CIMCPT system in roadway design and construction in Louisiana is presented. The CIMCPT was used to evaluate the structural capacity of pavement shoulders to support diverted traffic during the I-10 rehabilitation near Rayne, to redesign and construct a stone base-course layer for State Route LA-182 in Franklin, and to evaluate the failure surface of the I-20/Missouri Pacific Railroad overpass embankment near Tallulah. The CIMCPT system was successfully implemented by the Louisiana Department of Transportation and Development (LA DOTD). Implementation of the CIMCPT technology in roadway design and construction has saved LADOTD money and time compared with traditional subsurface exploration techniques.