Seismic Modulus Research Articles

Suitability of Nondestructive Testing of Asphalt Concrete for Detecting the Impact of Moisture Damage

Asphalt pavement susceptibility to moisture damage is considered as a major issue in the durability and service life of the roadway. Quick and nondestructive testing of asphalt concrete pavement are the major concern for predicting its suitability for evaluation. In the present investigation, nondestructive test has been implemented to detect the moisture damage issue of asphalt concrete mixture. Asphalt concrete specimens were prepared using Marshall method. Aggregates gradation of wearing, binder and base course was implemented for the preparation of the specimens. Specimens were tested for ultrasonic pulse velocity before and after practicing the moisture damage procedure. The variations of seismic modulus among various gradation before and after the moisture damage were considered as a criterion for moisture damage and related to tensile strength ratio TSR. It was observed that the pulse velocity decline by a range of (11 to 16) for asphalt concrete after moisture damage. It was concluded that the Seismic modulus as calculated from the ultrasonic pulse velocity test was effective in distinguishing the impact of moisture damage. The seismic modulus at optimum asphalt content decline by (34.7, 46.7, and 52.6) % after moisture damage for wearing, binder, and base course mixtures respectively. The ultrasonic pulse velocity test is recommended for assessing the susceptibility of asphalt concrete mixture to moisture damage.

Frequency adjustment method for in-situ seismic modulus of asphalt concrete

ABSTRACT In a mechanistic-empirical (ME) pavement design method, the modulus of asphalt concrete (AC) is essential. The in-situ AC modulus can be obtained by the surface wave method (SWM). However, the measured modulus needs to be adjusted to the design frequency values. This study aimed to propose a frequency adjustment method for the in-situ AC seismic modulus. For this purpose, coring and dynamic modulus tests, FWD (Falling Weight Deflectometer) tests, and PSPA (Portable Seismic Pavement Analyzer) tests were carried out in the accelerated pavement test (APT). The master curves generated by the dynamic modulus results correlated well with the moduli determined from the other tests. Based on this relationship, a frequency adjustment factor was developed for the seismic modulus of the undamaged AC layer. For the damaged AC layer, the proposed factor was modified by incorporating the effect of the damage. Finally, to validate the frequency adjustment factor, the measured maximum tensile strains in the APT were compared with the values determined from the adjusted seismic moduli. The results prove that the frequency adjustment factor is appropriate to obtain the design modulus from the surface wave test. The PSPA test is also recommended to obtain the in-situ AC seismic modulus.

Verifying Moisture Damage Impact in Asphalt Concrete with the Aid of Nondestructive Test NDT

One of the major concerns of pavement durability is its susceptibility to moisture damage. In this investigation, non-destructive test NDT has been implemented to detect the moisture damage issue. Asphalt concrete specimens were prepared using the traditional Marshall method for wearing, binder and asphalt stabilized base course. Specimens were traversed by ultrasound pulse velocity before and after practicing the moisture damage procedure. The variation of dynamic and elastic modulus before and after the moisture damage was considered and related to tensile strength ratio TSR. It was noted that the pulse velocity decline by (11, 11.2 and 16.4) % and the dynamic modulus declines by (28, 6.6 and 28.5) % for asphalt concrete wearing, binder and base courses respectively after moisture damage. The elastic modulus exhibits no significant variation after moisture damage for wearing course while it declines by (9 and 11.7) % for binder and base courses respectively after moisture damage. It was concluded that the elastic and dynamic moduli were unable to clearly distinguish the impact of moisture damage, whereas the Seismic modulus calculated from the Ultrasonic Pulse Velocity test was effective in distinguishing such impact. The linear equation obtained with good coefficient of determination can explain 74 % of the variation in the seismic modulus after moisture damage.

Hot mix asphalt (HMA) moisture susceptibility analysis: material loss to mechanical properties

Numerous studies have been conducted to identify moisture sensitive mixes during mix design by simulating various mechanisms of moisture damage. These methods involve the determination of changes in strength or stiffness of asphalt mixes due to moisture conditioning. The objective of this study is to understand the coupled problem of moisture induced material loss and change in strength/stiffness of the mix. Moisture Induced Stress Tester was used for conditioning samples of a poor and a good performing mixes. This test applies cyclic pressures in the asphalt mix samples through repeated pulses of water. The effluent containing aggregates and binder that were dislodged from the samples during the moisture conditioning process were collected for testing. Both coated and uncoated/fractured aggregates were found in the effluent. The results indicated that the samples with a higher loss of asphalt binder compared to other samples in the investigation during conditioning may exhibit higher tensile strengths, and those with a loss of finer materials, which is indicative of aggregate breakdown, show a lower tensile strength. Both seismic modulus and indirect tensile strength tests were found to be able to differentiate the poor and good performing mixes. For the mixes used in this study, the rate of change in indirect tensile strength during moisture conditioning was found to be strongly correlated to the pre-conditioning modulus of the mix, and a method is suggested for using the threshold values of properties of pre-conditioning mixes for different durations of moisture conditioning during mix design to screen poor mixes in a fast and nondestructive manner.

Correlation of Elastic Moduli and Serpentine Content in Ultramafic Rocks

Understanding the physical properties of ultramafic rocks is important for evaluating a wide variety of petrologic models of the oceanic lithosphere, particularly upper mantle and lower crust. Hydration of oceanic peridotites results in increasing serpentine content, which affects lithospheric physical properties and the global bio/geochemical cycles of various elements. In understanding tectonic, magmatic, and metamorphic history of the oceanic crust, interpreting seismic velocities, rock composition, and elastic moduli are of fundamental importance. In this study, we show that as serpentine content increases, density decreases linearly with a slope of 7.85. Porosity of the samples does not show any systematic correlation with serpentine content, as it is more strongly affected by local weathering and erosional processes. We also correlate increase in serpentine content with a linear decline in shear, bulk, and Young’s moduli with slopes of 0.48, 0.77, and 0.45, respectively. Our results show that increase in serpentine content of mantle wedge and forearc mantle contributes to their brittle behavior and result in break-offs, obduction, and overthrusting. Therefore, serpentine content strongly affects tectonic processes at subduction zones, particularly serpentinization may be responsible for formation of weak fault zones. Also, serpentinization of fresh oceanic peridotite in slow and ultra-slow spreading ridges may be responsible for observed discontinuities in thin crust.

Estimation of the Mechanical Properties of Igneous Rocks in Consideration of Seismic Effects

It is not widely accepted that the dynamic strain rate experienced by a rock mass during an earthquake is lower than that during a high strain rate scenario such as an explosion or a rock burst. The present study investigated the problem of determining the mechanical properties of rock considering earthquake effects using experimental tests and empirical formulas. First, to obtain the most concentrated frequency band of earthquake energy, a statistical analysis was conducted to obtain the response spectra of ground motion records near the example projects. The mean response spectrum was then fitted with a design response spectrum formula. The most concentrated frequency band of earthquake energy was then determined with the flat segment of the design response spectrum. Based on this frequency range, cyclic loading-unloading testing that simulated the earthquake effect was conducted on rock samples. The strain rate range experienced by rocks during an earthquake was then obtained. This strain rate range is between the quasi-static and intermediate strain rate ranges and is significantly lower than the high strain rate range. Based on this strain rate range, dynamic triaxial compression tests were conducted on igneous rock specimens from the case study areas. It is confirmed that the fit of the dynamic compression test results with the Hoek-Brown (HB) criterion is more accurate than that with the Mohr-Coulomb criterion. The HB strength envelope under static conditions can be used to predict the seismic strength behaviors, requiring an update of only the intercept of the envelope. Thus, the HB strength criterion considering the seismic effect was obtained. Moreover, the seismic modulus of the intact rock can be estimated with the values of the uniaxial compressive strength (UCS) under different strain rates and the modulus ratio, which was found to be independent of the strain rate. Hence, it is practical to estimate the mechanical properties of rock masses in consideration of seismic effects with the seismic HB strength criterion and the Hoek and Diederichs equation based on the UCSs under various strain rates. Ultimately, the rock mechanical properties in consideration of seismic effects were estimated via the proposed approach for the Baihetan hydropower plant project as an example.

Low‐Frequency Measurements of Seismic Moduli and Attenuation in Antigorite Serpentinite

AbstractLaboratory measurements of seismic moduli and attenuation in antigorite serpentinite at a confining pressure of 200 MPa and temperatures up to 550 °C provide new results relevant to the interpretation of geophysical data in subduction zones. A polycrystalline antigorite specimen was tested via forced oscillations at small strain amplitudes and seismic frequencies (millihertz to hertz). The shear modulus has a temperature sensitivity, ∂G/∂T, averaging −0.017 GPa/K. Increasing temperature above 500 °C results in more intensive shear attenuation ( ) and associated modulus dispersion, with increasing monotonically with increasing oscillation period and temperature. This “background” relaxation is adequately captured by a Burgers model for viscoelasticity and possibly results from intergranular mechanisms. Attenuation is higher in antigorite ( at 550 °C and 0.01 Hz) than in olivine ( below 800 °C), but such contrast does not appear to be strong enough to allow robust identification of antigorite from seismic models of attenuation only.

Effect of coarse aggregate morphology on the mechanical properties of stone matrix asphalt

The aim of this study is to examine the effects of morphological characteristics of coarse aggregates on the rutting and fatigue performance of stone matrix asphalt (SMA). A total of twenty-two coarse aggregate fractions were analyzed, and different aggregate blends were used to prepare different SMA mixtures following the job-mix formula in Virginia State. Specimens from eight types of SMA mixtures, with three replicates each, were tested for rutting resistance with an asphalt pavement analyzer (APA). Six types of the SMA mixtures were tested for fatigue resistance with a modal mobile load simulator (MMLS) in conjunction with a portable seismic pavement analyzer (PSPA). Rut depth obtained from the APA and seismic modulus difference obtained during MMLS trafficking were linked to morphological characteristics of coarse aggregates. Statistical analysis showed that flatness ratio and elongation ratio had no measurable influence on rut depth. The regression analysis demonstrated that rut depth increased with the increase of sphericity, angularity and texture, which indicates that rutting resistance of SMA can be improved by using more equi-dimensional and angular coarse aggregates with rougher texture. However, angularity and texture were found to have little influence on seismic modulus difference. Sphericity was shown to have a negative influence on seismic modulus difference, and flatness ratio was shown to have a positive effect on seismic modulus difference, which indicated that using more spherical and less flaky coarse aggregates reduces the degradation of stiffness, resulting in improved fatigue performance of SMA mixtures. The performance results suggest that flat and elongated aggregates should be used only in limited amounts.

Damage Assessment of Tunnel Lining by Mobile Laser Scanning: Pittsburgh, Pennsylvania, Implementation Phase of FHWA SHRP 2 R06G Project

This paper presents the results of a nondestructive (NDT) laser scanner investigation that was conducted in one night by using the SPACETEC TS3 laser scanner in one tube of each of the Liberty and Armstrong Tunnels in Pittsburgh, Pennsylvania. A portable seismic property analyzer (PSPA), a hand-held NDT ultrasonic seismic device, was used to investigate a 200-ft-long segment of the lining of the Liberty Tunnel, for which results are also presented. The investigation was complemented with a limited inspection with traditional techniques (e.g., hammer sounding, coring) to validate NDT findings. This work was funded by FHWA under the auspices of Round 4 of the Implementation Assistance Program of the SHRP 2 R06G project. Both technologies incorporated in this study were also used and reviewed in the original SHRP 2 R06G project. With the use of the SPACETEC TS3 scanner and the supporting suite of software, the study obtained high-resolution imagery, thermal imagery, and three-dimensional profiles for the full length of the tunnels. The deliverables included complete mapping and inventory of distresses and moisture intrusion behind the lining. In the Armstrong Tunnel, SPACETEC technology was successful at detecting cold anomalies (tile debonding, water intrusion, etc.). However, in the Liberty Tunnel, detection of debonding or delamination was less effective as a result of the insufficient temperature gradient at the time of scanning within this particular tunnel. The PSPA results correlated well with results obtained from traditional techniques. Areas with a lower seismic modulus correlated well with areas showing debonding or delamination. Areas of severe debonding were also clearly identified with the PSPA device.

InSAR observations of lake loading at Yangzhuoyong Lake, Tibet: Constraints on crustal elasticity

We use Envisat 2003–2010 InSAR imagery over Yangzhuoyong Lake in southeastern Tibet to study the elastic response of the Earth's crust to variations in lake level. The net lake level drop during our study period is ∼3 m with seasonal variations of more than 1 m. The time-series close to the lake center shows a high correlation with the lake level history. Near the lake center the unit response with respect to lake level change is 2.5 mm/m in radar line-of-sight direction, or ∼2.7 mm/yr in vertical direction, corresponding to a vertical response of ∼4.3 mm/Gt load change. We show that the observations are most sensitive to the elastic properties of the crust in the 5–15 km depth range and explain them with a layered elastic half-space model with a Young's modulus of 50±9GPa Young's modulus in the top 15 km of the crust and using moduli inferred from seismology at greater depth. The inferred Young's modulus is ∼25% smaller than the seismic modulus, which we attribute to damaged rock and the presence of fluids.

Evaluating feasibility of modified drilling waste materials in flexible base course construction

The study focuses on the evaluation of the engineering properties of modified drilling waste materials (MDWMs) as base course materials in roadway construction. This goal was accomplished by two main laboratory test evaluations of the MDWMs which are the basic material characterization and the performance evaluation of base course material. Material characterization results of the MDWMs indicate that they are relatively high pH, low plastic, and clay sand materials, mainly consisting of quartz and barite and belonging to Grade 4 category in Texas Department of Transportation (TxDOT) Item 247 Flexible Base Aggregate. The unconfined compressive strength (UCS), triaxial compressive strength, indirect tensile strength, moisture susceptibility, and seismic modulus test data show that the untreated MDWM is lower than many of these requirements and is not a granular base material when compared with the typical base course requirements identified in the Item 247. However, evaluation of the MDWMs with 3% cement treatment in the laboratory showed good performance without sacrificing their abilities as proper base course materials and satisfied the requirements of Class M base as per TxDOT Item 276. However, it may be necessary that the quality control of this material be monitored in order to achieve consistent moisture content and gradation. Moreover, further work to establish optimum stabilizer content and type would be recommended for this material.

Seismic Modulus Maturity Function for Lime and Lime–Cement Stabilized Clay

AbstractStabilization via lime and/or cement is commonly used to improve poor subgrade soil. The key design parameters for lime stabilized soils and lime–cement stabilized soils (LSS/L-CSS) are strength and stiffness, the growth of which are dependent on both time and temperature. It is generally understood that increased curing temperature will result in increased LSS/L-CSS strength/stiffness; however, there is no quantitative framework for predicting this behavior. This paper proposes a modulus maturity function for LSS/L-CSS that estimates low-strain modulus as a function of the curing duration and the average curing temperature over that duration. To develop the maturity function, nondestructive seismic modulus tests were performed on cylinders cured at varying temperature regimes from three LSS/L-CSS construction sites. Variations in curing behavior were compared within and across sites and least-squares regression analysis was performed to assess the functional behavior of the data. Results indicate...

Strain response of a semi-rigid base asphalt pavement based on heavy-load full-scale accelerated pavement testing with fibre Bragg grating sensors

Full-scale accelerated pavement testing with a mobile load simulator 66 (MLS66) was conducted on a semi-rigid base asphalt pavement on a highway in Chongming Island, Shanghai, China. The goal was to investigate performance behaviour of an asphalt pavement with fine-sand subgrade in the river bed. Chongming is the terminal of G40 highway where fine sand is abundant. Although commonly found, there are little published data on its performance in a pavement structure. If found reliable in the accelerated test, the design would be used for the construction of G40 highway, which can lower the construction costs greatly and provide an engineering practice for follow-up research. Performance of the pavement structure was evaluated under high-frequency heavy trafficking while being subject to high-temperature and ambient environmental impact. This included monitoring of strains, temperature, modulus, rutting deformation, pavement depth and water level. This paper discusses the cumulative and instantaneous three-dimensional strain at the bottom of each layer in the semi-rigid base asphalt pavement. Generally good agreement was reached between the measured and calculated strains with back-calculation resilient modulus considering modulus reduction of asphalt layers because of temperature. A fatigue equation of the asphalt layer was established between loading applications, strain and seismic modulus, a small-strain value of Young's modulus. Conclusions regarding the spatial distribution, time-history change of three-dimensional dynamic strain response and the relationships between influencing factors and strains are presented.

Modulus evolution of asphalt pavement based on full-scale accelerated pavement testing with Mobile Load Simulator 66

A full-scale accelerated pavement testing was conducted with Mobile Load Simulator 66 in Chongming Island, Shanghai, to study the performance response of a semi-rigid base asphalt pavement with fine-sand subgrade designed for the G40 construction. As an index sensitive to temperature and load, three different moduli including the seismic modulus, field falling weight deflectometer back-calculation modulus and interior material testing system resilient modulus were all measured during and after the test. The modulus evolution of asphalt pavement with the loading applications, rutting, strain and temperature, and the comparison of three methods for measuring modulus were analysed. There exists a modulus gradient from top to bottom, which can be considered in the pavement design or fatigue life prediction. Because of the strain level differences, the seismic modulus was the largest, followed by back-calculation and resilient modulus; the development of seismic and back-calculation modulus better reflected the anti-deformation changes.

Comparing Linear Viscoelastic Properties of Asphalt Concrete Measured by Laboratory Seismic and Tension–Compression Tests

Seismic measurements and conventional cyclic loading have been applied to a cylindrical asphalt concrete specimen to compare the complex modulus and complex Poisson’s ratio between the two testing methods. The seismic moduli and Poisson’s ratio have been characterized by optimizing finite element calculated frequency response functions to measurements performed at different temperatures. An impact hammer and an accelerometer were used to measure the frequency response functions of the specimen which was placed on soft foam for free boundary conditions. The cyclic loading was performed by applying both tension and compression to the specimen while measuring the displacements in the axial and radial direction. The Havriliak–Negami and the 2S2P1D model have been used to estimate master curves of the complex modulus and complex Poisson’s ratio from the seismic and the tension–compression tests. The seismic measurements performed at a lower strain level than the tension–compression test give a higher absolute value of the complex moduli (e.g. \({\sim }12\,\%\) at 100 Hz) and a lower phase angle compared to the tension–compression results.

Free–Free Resonance Testing of In Situ Deep Mixed Soils

Abstract This paper focuses on the use of free–free resonance testing (FFR testing) applied to the characterization of stabilized silt and sand specimens treated in situ by deep soil mixing. The aim of FFR testing is to measure the natural frequencies of free vibration of the tested specimen. Compression and shear wave velocities, seismic moduli and Poisson’s ratio can be determined from these frequencies. Block samples were taken from soil–cement columns installed at a test site near Paris, France. Specimens of 100 by 50 mm (height to diameter ratio of 2) were cored from these blocks and submitted to FFR testing in the laboratory. The measured resonant frequencies were very repeatable for all specimens tested, validating the use of free–free resonance as a rapid testing method for the characterization of fairly heterogeneous stabilized soil specimens. It was found that both P-wave and S-wave velocities increase nonlinearly with unconfined compressive strength. A linear correlation between strength and dynamic stiffness was observed. Free–free resonance test results can be correlated with index parameters such as density and porosity and used for preliminary assessments of static stiffness as all these parameters varied linearly with measured wave velocities.

Seismic modulus growth of lime-stabilised soil during curing

This paper presents a study conducted to characterise seismic modulus growth in lime-stabilised soil (LSS) throughout 28-day curing using free-free resonance testing. The motivation for this study is to explore the prediction of 28-day modulus and strength from seismic modulus data collected during early curing, and in general to investigate the efficacy of seismic testing as a method of quality assessment for LSS. Measured E and G growth ranged from 250% to 900% during curing for the three soils. Modulus values and growth in modulus were significantly influenced by mineralogy and soil processing. The growth in seismic modulus for each soil exhibited a power law relationship with curing time. The 28-day modulus was estimated within 8% error for two soils using early curing modulus data, that is, through 7 days. Seismic modulus was found to correlate linearly with unconfined compressive strength (qu) throughout curing. The proportionality of E and qu remained constant during curing for each soil beyond day 3. The study shows that early curing seismic data – that is, through 7, 8 or 9 days – is capable of providing a good estimate of 28-day E and qu if the variability is reasonable (here, range/mean < 0·5).

Effectiveness of Cement Kiln Dust in Stabilizing Recycled Base Materials

AbstractEffectiveness of cement kiln dust (CKD) in improving the stiffness of recycled base course materials was studied using both seismic modulus and bench-scale resilient modulus tests. Recycled materials included road surface gravel (RSG) and recycled pavement material (RPM). The modulus of RPM and RSG specimens mixed with CKD increased 5–30 times compared with untreated materials; however, the improvement was not as high as cement stabilization. Modulus generally increased with curing time with more hydration; however, decrease in the modulus of the RPM mixed with 15% CKD during curing is attributed to swelling potential of the CKD. Lower rate of increase in modulus of CKD mixtures compared with cement mixtures with curing time was attributable to the chemical composition of CKD, i.e., high free lime and sulfate contents. Freeze-thaw durability tests resulted in modulus reduction on the order of 0.5 to 0.8 for CKD mixtures and 0.5 for cement mixtures. Attributable to the combined effects of stiffness...

Correlation of Asphalt Concrete Layer Moduli Determined from Laboratory and Nondestructive Field Tests

The falling weight deflectometer (FWD) is widely used for in situ nondestructive assessment of pavement layer moduli. For this purpose, FWD deflections are used with a number of back-calculation methodologies to come up with layer moduli. Back-calculating layer moduli from FWD deflections collected on thin asphalt concrete (AC) pavements is a challenge because the predicted deflection basin is not sensitive to the AC modulus. This study utilizes the portable seismic pavement analyzer (PSPA) to improve the reliability of back-calculated thin AC layer moduli. Compared with the FWD, the PSPA provides a direct measurement of seismic modulus at a higher load frequency level relative to the frequencies associated with typical truck traffic. Thus, the seismic modulus determined from PSPA tests needs to be corrected with the load frequencies typically used for pavement design. This paper compares AC moduli determined from laboratory dynamic modulus tests with corresponding values determined from FWD and PSPA measurements. The results exhibited favorable correlation between the AC moduli determined from laboratory and field tests at corresponding load frequencies and temperatures. The paper also proposes a methodology to obtain a composite modulus from mixture properties determined from laboratory tests of individual AC lifts for the purpose of comparing the composite modulus with corresponding values determined from field tests. The authors generated master curves of individual AC lifts on the basis of corresponding binder temperature–viscosity relationships and volumetric properties obtained from laboratory tests. A procedure was proposed for correcting PSPA AC seismic modulus at corresponding load frequencies and temperatures by using the master curves with Odemark’s assumption. This evaluation showed a promising correlation between the corrected PSPA modulus and FWD back-calculated AC modulus. From this, the authors provide a simple equation as an alternative method for correcting PSPA modulus when the material properties of individual layer are not readily available to employ the proposed methodology.

Effects of Warm-Mix Asphalt Additives on Workability and Mechanical Properties of Reclaimed Asphalt Pavement Material

The soaring cost of liquid asphalt binder and anticipated stricter environmental regulations have driven highway agencies to maximize the amount of reclaimed asphalt pavement (RAP) used for pavement construction. However, because of already aged and stiffened asphalt binder in RAP, the use of high percentages of RAP in hot-mix asphalt (HMA) presents many challenges. Problems with workability and compactability during construction need to be resolved first. This study investigated the feasibility of using 100% RAP HMA as a base course with warm-mix asphalt (WMA) additives (Sasobit H8 or Advera zeolite) at a lower temperature (125°C). Mix samples (control set with 100% RAP; a set with 100% RAP plus Sasobit H8 at 1.5%, 2.0%, and 5.0%; and a set with 100% RAP plus Advera zeolite at 0.3%, 0.5%, and 0.7%) were compacted with 50 gyrations. Their workability, bulk specific gravity, indirect tensile strength at 0°C, and moduli at 0°C, 26.7°C, and 50°C were determined. The effects of different amounts of WMA additives were compared. The results showed that workability of the 100% RAP HMA improved with the addition of Sasobit H8 or Advera zeolite at temperatures as low as 110°C. At temperatures less than 80°C, the addition of Sasobit H8 or Advera zeolite tended to stiffen the mix, as also reflected in increased seismic moduli and indirect tensile strength. Seismic modulus of the mixes was also found to be dependent on bulk specific gravity. The addition of Sasobit H8 proportionally increased bulk specific gravity of the mixes. The effect of amounts of Advera zeolite on bulk specific gravity was less well defined. It seemed that stiff asphalt binder in the RAP also affected compaction by preventing asphalt foam from fully forming, as it would when Advera zeolite was mixed with a virgin asphalt binder.