Revised Test Plan for Seasonal Monitoring Program using HWD Testing

Transcription

1 April 2005 Revised Test Plan for Seasonal Monitoring Program using HWD Testing Partnered Pavement Research Prepared for: California Department of Transportation Prepared by: University of California Berkeley Pavement Research Center Dynatest

2 TABLE OF CONTENTS Table of Contents... i List of Figures... ii 1.0 Introduction Objectives and Scope Experiment Design Pavement Deflection Measurements Using the HWD Pavement Test Sections Testing Procedure Flexible Pavements Rigid Pavements Load Level Time of Testing Geometry of Loaded Area and Deflection Sensor Additional Instrumentation and Monitoring Tests Thermocouples Coring Dynamic Cone Penetrometer Ground Penetrating Radar Weather Station Data Collection Lane closure Schedule for HWD Testing References i

3 LIST OF FIGURES Figure 1 HWD Loading Plate and Geophone Locations... 9 ii

4 1.0 INTRODUCTION Temperature and moisture seasonal variations have a profound impact upon pavement response and performance. Currently, Caltrans pavement design procedures do not account for climatic differences. Reports prepared for Caltrans (1, 2) have identified at least six unique climate regions for California, determined based on rainfall and air temperature data. The effects of pavement temperatures and rainfall on distress mechanisms for rigid, flexible, and composite pavements were identified and compared for each of the regions. Recommendations were made to incorporate those factors that have a large impact on pavement performance into design procedures. Seasonal temperature and precipitation variations are known to strongly affect the strength and stiffness of bound and unbound pavement layers and the subgrade. Critical low or high temperatures and substantial precipitation regimes can lead to a rapid rate of pavement distress. Therefore, knowledge of the effect of seasonal trends on the pavement response and performance is an important component of a mechanistic-based design procedure because it permits the proper characterization of the pavement materials across the entire year. For flexible pavements, development of relationships between temperature and asphalt concrete (AC) stiffness, and the effect of moisture content on aggregate base, subgrade strength, and modulus are important climatic functions to be considered in a mechanistic-based design method. In rigid pavements, temperature gradients are estimated in order to determine curling stresses in the slab. Shrinkage is calculated to determine warping stresses. Water inputs are used to design drainage systems to remove free water between the slab and the subbase. The majority of the design work performed by Caltrans is for rehabilitation. Deflections collected using non-destructive equipment is the primary means of characterizing pavements for 3

5 rehabilitation. Deflections essentially provide a snapshot of conditions at the time of testing, and must be extrapolated across the year using seasonal factors. 2.0 OBJECTIVES AND SCOPE The objective of the Heavy Weight Deflectometer (HWD) Seasonal Monitoring Program is to develop seasonal factors for design for the six climate regions in the California. This effort will require measurement of the effects of temperature and precipitation variations on the stiffness as measured using deflections of existing California pavement structures. Monitoring of the seasonal effects on pavement response will be accomplished with the use of the HWD, a non-destructive deflection measuring device. Most regions of California experience significant changes in pavement surface temperature and subgrade moisture content under rigid and flexible pavements. A temperature increase tends to soften the asphalt concrete, thereby increasing the deflections measured with the HWD, while a temperature decrease tends to stiffen the asphalt concrete, thereby decreasing the deflections measured with the HWD. Increases in moisture content in the granular layers and subgrade reduce their stiffness, thereby increasing the deflections measured with the HWD. In spite of these variations, Caltrans currently makes no corrections for seasonal variations except to limit test temperatures to the range of 7ºC to 54ºC. Temperature changes also affect the aggregate interlock at rigid pavement transverse joints, which in turn affects their load transfer efficiency (LTE). This surface deflection study will provide Caltrans with an understanding of the magnitude and impact of seasonal variations (temperature and moisture content) on the pavement response and material properties of typical California pavement structures. Specific goals of the HWD seasonal monitoring program are: 4

6 Evaluate the effect of seasonal variation on the surface deflection response. This information can be used with current and future design methods. Evaluate and characterize each pavement layer based on HWD testing and complementary non-destructive tests. Determine the response (stress, strain, deflection) of each pavement component. Establish a framework to support the activities for the development of the California Mechanistic-Empirical method. To accomplish these goals, a series of HWD tests will be programmed based on the six climate regions for California. 3.0 EXPERIMENT DESIGN A factorial combination approach will be used for the development of the experimental design. Two factors will be considered: 1) Pavement structure (flexible or rigid) and 2) Environmental (six total, based on the climate regions for California). Using this factorial, a total of 12 pavement structures will be tested under this program. The section locations will be selected so that there is little damage expected the duration of the experiment. Each section will be tested at two to four different times of the year to capture different seasons and in each season one in the cool time of the day and again in the hot time of the day to capture the temperature effects. 4.0 PAVEMENT DEFLECTION MEASUREMENTS USING THE HWD 4.1 Pavement Test Sections Table 1 summarizes relevant physical and environmental characteristics of the pavement sections to be tested. 5

7 Table1 Originally Proposed Pavement Test Sections Test Location Pavement Section Road Near Town Type Climate Region F01 I-5 Cottonwood, TIF PCC Valley F Red Bluff AC Valley F Ukiah PCC Bay Area F04 20 East of Ukiah AC Bay Area F Fortuna AC North Coast F Arcata PCC North Coast F07 I-5 Dunsmuir TIF PCC Mountain/High Desert F08 20 Dunsmuir TIF AC Mountain/ High Desert F09 40 Newberry AC Desert F10 58 Between Kramer and Barstow PCC Desert F11 1 Port Hueneme AC South Coast F Solvang PCC South Coast 6 Table 2 Actual Pavement Test Sections, January 2005 Location Test Road Near Town Caltrans County Pavement Climate Region F01 I-5 Cottonwood, TIF 2 Tehama PCC Valley F02 I-5 Red Bluff 2 Tehama AC Valley F03 US-101 Ukiah 2 Mendocino PCC Bay Area F04 Lark Dr Richmond 4 Contra Costa AC Bay Area F05 US-101 Fortuna 1 Humboldt AC North Coast F06 None Unavailable in Region 1 PCC North Coast F07 I-5 Dunsmuir TIF 2 Siskiyou PCC Mountain/High Desert F08 I-5 Dunsmuir TIF 2 Siskiyou AC Mountain/ High Desert F08b I-5 Dunsmuir TIF 2 Siskiyou AC/PCC Mountain/ High Desert F09 I-40 Newberry 8 San Bernardino AC Desert F10 I-40 Ludlow 8 San Bernardino PCC Desert F11 I-5 Oceanside 11 San Diego AC South Coast F12 I-5 Oceanside 11 San Diego PCC South Coast

8 The total length of each test section is 200 m (660 ft.). Testing will be conducted along one of the lanes. Criteria for selection include pavements located along straight sections, with low traffic hazards, and that are likely to have minimal traffic delays. Also it is desirable that the sections have an appropriate nearby location for installing a weather station close to the test sections. Testing is planned to be conducted twice a year [one series of tests during the summer months (July-September) and the other series during the winter months (January-March)] for a period of two to three years. Additional seasons may be added. It is estimated that the selected lane should be closed from 6:00 a.m. until 5:00 p.m. for the first set of HWD tests, and for 3 hours in the early morning and 3 hours in the afternoon hours for subsequent HWD tests. 4.2 Testing Procedure Flexible Pavements For the flexible sections, testing will be performed at 10-m intervals, with coverage of 20 tests per section along one testing line. Testing will be carried out in both wheel paths (two testing lines) for a total of 40 tests. Additional testing will be performed on the centerline at 25-m intervals for a total of 8 tests along the centerline Rigid Pavements For jointed rigid pavements, testing will be performed along the truck lane on 20 slab panels per test section along two testing lines for a total of 40 tests. One testing line will be along the centerline of slabs and the other one will be along the edge between the slab and the shoulder. Each slab will be tested at the center and at the joints and corners for the purposes of load transfer evaluation or void detection and calculation of build in shrinkage warping. 7

9 4.2.3 Load Level Three load levels will be applied on the pavements and each load level will be repeated two times. Only the last repetition for each of the three levels will be stored and used for analysis. Target loads for flexible pavements are 22.2 kn, 40 kn, and 53.4 kn. Target loads for rigid pavements are 40 kn, 53.4 kn, and 71.1 kn. Table 3 shows the combination of drop weights and heights to reach the target loads. Table 3 HWD Drop Weights and Heights for Testing Target Load, kn Height, mm Weight, kg Flexible Pavements Rigid Pavements Time of Testing HWD testing will be conducted at approximately 4 a.m. and 3 p.m. for each test section Geometry of Loaded Area and Deflection Sensor The locations of the loading plate and the seven transducers are shown in Figure 1. The sensor spacing with the 300-mm load plate for both flexible and rigid pavements are: Sensor mm ,524 8

10 300mm 203mm 102mm 152mm 153mm 304mm 610mm Loading Plate Area Geophone Figure 1. HWD loading plate and relative geophone locations. 5.0 ADDITIONAL INSTRUMENTATION AND MONITORING TESTS Additional tests conducted at each test location are described in the following sections. 5.1 Thermocouples Thermocouple wires will be installed in the test sections to measure surface and in-depth pavement temperatures. 5.2 Coring measurements. A few core samples (about four cores) of the bound layers will be obtained for thickness 9

11 5.3 Dynamic Cone Penetrometer DCP testing will be used to characterize and estimate thicknesses of the unbound layers and the subgrades. This test will be conducted where the cores are obtained. 5.4 Ground Penetrating Radar GPR testing will be conducted to estimate thicknesses of the pavement layers. 5.5 Weather Station A Davis weather station will be installed out of the right-of-way near the test section to measure air temperature, rainfall, relative humidity, wind speed and direction, and solar radiation. 6.0 DATA COLLECTION The HWD program will collect the following information: Inventory data: These correspond to basic pavement structure information: pavement thicknesses and components will be determined from construction data, GPR, soil survey reports, and limited coring. Climate data: These correspond to information collected from nearby weather stations and the installed weather stations. Monitoring data: These data correspond to information collected from pavement measurements repeated at selected time intervals. These include Heavy Weight Deflectometer (HWD) tests, and distress data collection. 10

12 7.0 LANE CLOSURE SCHEDULE FOR HWD TESTING The original schedule is shown below: Summer 2001 Winter 2001 Summer 2002 Winter 2002 One lane closure from 6:00 am to 5:00 pm One lane closure from 3 to 6 am and 1 to 4 pm One lane closure from 3 to 6 am and 1 to 4 pm One lane closure from 3 to 6 am and 1 to 4 pm This schedule was not precisely followed because of delays in instrumenting test sections and obtaining lane closure permits. The remaining testing schedule is: Winter (January March 15) 2005 Summer (May-June) 2005 Summer (August 1-Sept 15) 2005 Fall (October-November) 2005 Winter (January March 15) 2005 Summer (May-June) 2005 Summer (August 1-Sept 15) 2005 Fall (October-November) 2005 One lane closure from 6 to 10 AM and 12 to 2 PM One lane closure from 4 to 8 AM and 10 AM to 2 PM One lane closure from 4 to 8 AM and 10 AM to 2 PM One lane closure from 4 to 8 AM and 10 AM to 2 PM One lane closure from 6 to 10 AM and 12 to 2 PM One lane closure from 4 to 8 AM and 10 AM to 2 PM One lane closure from 4 to 8 AM and 10 AM to 2 PM One lane closure from 4 to 8 AM and 10 AM to 2 PM 8.0 REFERENCES 1. Harvey, J., A. Chong, and J. Roesler. Climate Regions for Mechanistic-Empirical Pavement Design in California and Expected Effects on Performance. CAL/APT Program, Pavement Research Center, Institute of Transportation Studies, University of California, Berkeley, June, Ongel, A. and J. T. Harvey. Analysis of 30 Years of Pavement Temperatures using the Enhanced Integrated Climate Model (EICM). Draft report prepared for the California Department of Transportation. Pavement Research Center, Institute of Transportation Studies, University of California Berkeley, University of California Davis. August