Mark Morvant

Computerized Cone Penetration Test for Soil Classification: Development of MS-Windows Software

Computerized MS-Windows Visual Basic software of a cone penetration test (CPT) for soil classification 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 as a handy, user-friendly, software tool for geotechnical engineers. 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 (qc) and friction ratio (Rf). 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. Conversely, the CPT fuzzy classification emphasizes the certainty of soil behavior. The 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 (qt) and friction ratio (Rf); the other chart uses qt and pore pressure parameter (Bq) 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.

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.

IMPLEMENTATION OF CONE PENETRATION TEST TECHNOLOGY IN DESIGN AND ANALYSIS OF DRIVEN PILES

The design and analysis of pile foundations in Louisiana are based on traditional subsurface exploration methods. This procedure is expensive and time consuming, and it often results in a pile design that is too conservative. The Louisiana Department of Transportation and Development (LA DOTD) has recently adopted the cone penetration test (CPT) technology to design and analyze driven piles. A research effort was undertaken at the Louisiana Transportation Research Center to identify the most appropriate CPT methods for predicting the ultimate axial load carrying capacity of piles driven into Louisiana soils. An evaluation was conducted to rank the CPT methods based on their capability to predict the measured pile load carrying capacity. The top three performance methods were programmed into software, called Louisiana Pile Design by CPT, to facilitate their use in the design and analysis of driven piles by LA DOTD engineers. The current LA DOTD implementation plan is to use the CPT technology to supplement conventional subsurface exploration techniques and to reduce the number of soil borings and pile load tests. A plan for eliminating conventional subsurface exploration completely and replacing it with CPT is still under investigation. The best performing CPT methods were implemented in the design of driven piles on several highway bridges. In these projects, the CPT was capable of identifying the soil stratification at the pile bent location and predicting the pile load carrying capacity. The benefit of implementing the CPT technology in the design and analysis of driven piles over the conventional subsurface exploration methods was also demonstrated.

DEVELOPMENT OF DATABASE FOR LOUISIANA HIGHWAY BRIDGE-SCOUR DATA

Scour of highway bridges in Louisiana has been collected and monitored since 1970. Approximately 120 bridges are being monitored at a frequency of one to several times per year with an average of six cross sections for each bridge. Consequently, a tremendous amount of scour data in the format of traditional paper files already exists for these bridges. Manual and visual analysis of data has been tedious work, and there existed a need to develop a computer program and a database system to perform scour-data management. Database-management software has been developed for storage, retrieval, and analysis of scour data of Louisiana highway bridges. The system stores the data in a database system within the network. A computer program was developed as a front-end to allow the user to access the database, retrieve the data via several search routines, plot the scour data for analysis, and perform data updates. The program compiles the on-site data collected during scour survey and the bridge data relevant to scour properties. It can be used in (a) determining local scour at the piers and contraction scour at the bridge, (b) analyzing the long-term changes in riverbed elevations at various locations in the site, (c) providing the major parameters that are commonly used in bridgescour models for scour prediction, and (d) evaluating site conditions and soil properties for scour repair. The program tabulates and plots the bridge information, pier data, and coordinates of the river cross sections at the survey locations. It displays survey maps and soil-boring data. The analysis of the bridge-scour data is performed using plots of the cross sections, longitudinal sections, and contour lines of the scour data. The history of the scour at any specific location is plotted in time plots. Further implementations of the database system are suggested for more accurate determination of potential scours in highway bridges.