Modulus Of Layer Research Articles

Sensitivity analysis of influencing factors of pile foundation stability based on field experiment

Based on the finite element analysis software ABAQUS, this paper establishes a three-dimensional finite element simulation model. According to the measured data of a project in Qingdao, the settlement obtained by static load test is selected as the index to measure the stability of the pile foundation. The Poisson ratio, elastic modulus, angle of internal friction, and friction coefficient of the pile-soil contact surface of each layer of soil are selected as the factors affecting the stability of the pile foundation. The experimental results of settlement at all levels are analyzed and compared through the variable control and orthogonal experiment. Finally, the main factors affecting the stability of the pile foundation are determined as follows: the elastic modulus, Poisson ratio, friction coefficient, angle of internal friction of pile end soil, and the elastic modulus of the fourth layer of soil, which provides a specific reference value for the subsequent research on the stability of pile foundation.

Study on anti-crack effect of semi-rigid base pavement with stress absorbing layer

For the characteristics of semi-rigid base asphalt pavement prone to cracking, various stress-absorption layers are applied widely by decreasing stress concentration, improving interlayer bonding and waterproofing. Existing studies on the anti-cracking effect of stress absorbing layers rarely consider top-down fatigue cracking on the outside of the boundary of the vehicle loading zone. Firstly, this paper proposes a finite element model setting a downward expansion of fatigue crack in pavement based on fracture mechanics. The influence law of modulus and thickness of stress absorbing layer on stress intensity factor of crack tip and the fatigue life of the pavement is analyzed furthermore. Numerical calculation results demonstrate that shearing stress intensity factor increases with stress absorbing layer thickness and decreases with stress absorbing layer modulus, while fatigue life of pavement grows with the modulus of the stress absorbing layer and decreases with its thickness. Sensitivity analysis indicates that the modulus of the stress absorbing layer has a greater effect on the fatigue life of the pavement relative to thickness, which offers reference for further promotion and application of stress absorbing layer.

Uncertainties in determining the responses of reinforced flexible pavements using in-situ tests

A 225m long full-scale testing lane was constructed at a local road in Australia to evaluate the performance of the flexible pavements over a weak soft subgrade. The pavements were reinforced with three types of geosynthetic products: High-density polyethylene (HDPE) geogrid, HDPE geocomposite and fibreglass geocomposite. The road was divided into 15 sections with different configurations such as the thickness of the base course, reinforcement types and locations, and base course materials. A series of in-situ tests were conducted on each section to compare the behaviour of the pavement structures, such as the moduli of the subgrade, base course and asphalt layer. The comparison shows that there is a large variation in the properties of the structures and great uncertainties in determining the properties even within the sections with the same configuration. When the base course is weaker, the FWD tests may be able to detect the effect of the reinforcements below the asphalt seal layer. Smaller plates are recommended when determining the modulus of thinner base course layers using FWD or LWD tests to minimize the influences from the subgrade.

A hybrid first/third-order plate theory for finite element analysis of sandwich plates with a transversely compressible core

Sandwich structures with thick soft cores subjected to transverse loads are usually resulting in deformations with various modes, including bending, twisting and compressing. In addition, the compression of the core results in a significant influence of the structural response. All classical plate theories are inadequate in predicting the behavior sandwich structures with thick soft core due to the assumption of no thickness change during deformation. To overcome this issue, a hybrid first/third-order shear deformation hypothesis with consideration of compressive effect is proposed for sandwich structures with thick soft cores. The first-order shear deformation theory is applied to both the top and bottom layers, while a refined third-order shear deformation theory that releases the assumption of no thickness change is developed for the thick soft cores. An eight-node quadrilateral plate element with twelve degrees of freedom including compressible displacements is created for finite element modeling. Based on the proposed refined hybrid first/third-order theory, a finite element model is developed using the Hamilton’s principle. The numerical model is first validated by the computational results of sandwich structures using commercial software. Then, the influences of various parameters on static displacements, vibrations and compressive deformations are systematically investigated, including e.g. boundary conditions, thickness of the core and face layers, elastic modulus of the core layer and the plate size. The present finite element modeling approach provides a powerful tool to accurately investigate the mechanical response of sandwich structures.

Evaluating pavement performance in bus rapid transit systems: Lessons from Seoul, South Korea

The proposed research aims to systematically investigate the condition of bus stops throughout Seoul, a densely populated metropolitan area. The study involves conducting a survey of multiple bus stops, taking into consideration traffic volume and pavement damage type. Field tests using the Falling Weight Deflectometer are conducted in heavily damaged bus stop sections to evaluate the performance of the surface, subbase, and subgrade layers. Additionally, this research proposes a polymer-modified stone matrix asphalt mixture with a nominal maximum size of 10 mm (10 mm PSMA) to enhance the rutting resistance of bus stop pavements while ensuring compliance with dynamic modulus acceptance values. Laboratory tests including Hamburg wheel tracking and dynamic modulus tests are conducted to achieve this objective. The results reveal that inadequate quality of the surface layer is the main cause of bus stop pavement failure in Seoul, with the average FWD modulus of the asphalt layer falling below the standard requirement of 725 ksi (28 % lower), indicating a 'low' structural condition based on evaluation standards. This can be attributed to inappropriate gradation and overload issues during rush hour. The dynamic modulus test results show that the PSMA 10 mm mixture outperforms the conventional 13 mm mixture in the low-frequency range and shows comparable performance in the high-frequency range. The Hamburg wheel tracking test indicates that all proposed mixtures have settlement values below 5.5 mm and do not exhibit the stripping point phenomenon, indicating excellent rutting resistance. Notably, the 10 mm PSMA mixture demonstrates superior permanent deformation resistance compared to the 13 mm PSMA and 13 mm PMA mixtures (1.26–185 times lower). Overall, the proposed mixtures exhibit promising performance in mitigating fast degradation at bus stops.

Lateral and longitudinal variations in dynamic modulus of asphalt pavement: Surface layer and base layer

The dynamic modulus of asphalt pavement is a significant factor used for predicting the pavement life. However, the service situations of asphalt pavement in lateral and longitudinal directions are different, which induces variation in the dynamic modulus of asphalt pavement. Given this background, this study aims to investigate the variations in dynamic modulus and phase angle in the longitudinal and lateral directions. Four road sections comprising surface layer and base layer were selected. For each road section, core samples were taken from three profiles along the longitudinal direction and four cores from different locations along the lateral direction were taken. The dynamic modulus and phase angle of specimen were characterised by indirect tensile test. The variations of dynamic modulus and phase angle in the lateral and longitudinal directions were analysed and compared with reference samples prepared in laboratory using master curve and coefficient of variation. The results show that the lateral and longitudinal differences induce more severe variations in dynamic modulus and phase angle compared with laboratory samples. Moreover, for the surface layer, the variation in the lateral direction is higher than in the longitudinal difference likely due to the inhomogeneity of asphalt mixture, variation in traffic loading, loading distribution, and the specific geometric structure of Norwegian pavement. In comparison with the surface layer, similar results caused by lateral and longitudinal differences are found for dynamic modulus and phase angle of the base layer because of its lower position and complicated stress distribution. Besides, a correlation between service life and the variations in dynamic modulus and phase angle is found for lateral samples.

Field implementation of enzyme-induced carbonate precipitation technology for reinforcing a bedding layer beneath an underground cable duct

A suitable bearing capacity of foundation is critical for the safety of civil structures. Sometimes foundation reinforcement is necessary and an effective and environmentally friendly method would be the preferred choice. In this study, the potential application of enzyme-induced carbonate precipitation (EICP) was investigated for reinforcing a 0.6 m bedding layer on top of clay to improve the bearing capacity of the foundation underneath an underground cable duct. Laboratory experiments were conducted to determine the optimal operational parameters for the extraction of crude urease liquid and optimal grain size range of sea sands to be used to construct the bedding layer. Field tests were planned based on orthogonal experimental design to study the factors that would significantly affect the bio-cementation effect on site. The dynamic deformation modulus, calcium carbonate content and long-term ground stress variations were used to evaluate the bio-cementation effect and the long-term performance of the EICP-treated bedding layer. The laboratory test results showed that the optimal duration for the extraction of crude urease liquid is 1 h and the optimal usage of soybean husk powder in urease extraction solution is 100 g/L. The calcium carbonate production rate decreases significantly when the concentration of cementation solution exceeds 0.5 mol/L. The results of site trial showed that the number of EICP treatments has the most significant impact on the effectiveness of EICP treatment and the highest dynamic deformation modulus ( E vd ) of EICP-treated bedding layer reached 50.55 MPa. The area with better bio-cementation effect was found to take higher ground stress which validates that the EICP treatment could improve the bearing capacity of foundation by reinforcing the bedding layer. The field trial described and the analysis introduced in this paper can provide a practical basis for applying EICP technology to the reinforcement of bedding layer in poor ground conditions.

Clothing Image Classification with DenseNet201 Network and Optimized Regularized Random Vector Functional Link

ABSTRACT To ameliorate the precision of clothing image classification, we proposed a clothing image classification method via the DenseNet201 network based on transfer learning and the optimized regularized random vector functional link (RVFL). First, the formula extracts weight’s parameters about DenseNet201 that is pre-trained on the ImageNet dataset for transfer learning, thereby obtaining an incipient network，after that trim this model parameters. The modified network is utilized to pick up the clothing image features output by the DenseNet201’s global average pooling layer. Second, regularization coefficient is introduced to control RVFL’s model complexity and solve the problem of over-fitting. Then, the generated solution vector of aquila optimizer (AO) is produced by marine predators algorithm (MPA). The input weights, biases of hidden layer and renormalization modulus of regularized RVFL are optimized using the improved AO algorithm. Finally, we use the optimized RVFL to assort abstracted fashion graphics traits. We use Accuracy, Macro-F1, Macro-R and Macro-P to assess the algorithm’s ability and compare this algorithm with ResNet50 network, ResNet101 network, DenseNet201 network, InceptionV3 network and different classifiers, which use DenseNet201 as the feature extractor to get the input. From the experimental results, this algorithm proposed has excellent classification power and generalization ability.

Field investigation of material layer properties for emulsion-treated base layer application in low-volume roads

ABSTRACT The study presents the determination of pavement design input parameters-structural layer coefficients and back-calculated layer moduli for Emulsion-Treated Base (ETB) layer materials in a Low-Volume Road (LVR) application. Seven test sections were constructed on a stretch of LVR with varying emulsion contents and 50% Recycled Asphalt Pavement (RAP) aggregate incorporation in ETB mixes. Structural performance of the test sections was periodically observed using a Benkelman Beam Deflectometer (BBD) and the data was used for the estimation of the structural layer coefficient of ETB, based on the effective structural number of the pavement. The deflection bowl data of the test sections were also captured using a Falling Weight Deflectometer (FWD) and the modulus of ETB layer was back-calculated using a back-calculation software. The study proposes a structural layer coefficient of 0.23–0.29 and back-calculated moduli of 578–919 MPa for ETB mixes characterised by Indirect Tensile Strength (ITS) values ranging between 140 kPa and 245 kPa. Traffic level-based ETB mix specifications are also proposed in the study, which enables a mix designer to proportion the mix for a selected design traffic level. For a design traffic level of 1 million standard axles, the target dry ITS specification was found to be 188 MPa.

Evaluation of ERAPave PP permanent deformation models using APT

Permanent deformation is one of the failure modes considered in the analysis and design of flexible pavements. ERAPave performance prediction (PP) which is a mechanistic empirical (ME) pavement design tool utilises two distinct models for the prediction of permanent deformation in the bound and unbound granular layers including subgrade. This paper aims to calibrate these models using pavement response and performance data from accelerated pavement testing (APT) structures. Material properties such as layer modulus were established through an optimisation that involves both falling weight deflectometer (FWD) and pavement response measurements. Based on the predicted performance results, a separate set of calibration was performed for permanent deformation development in moist and wet moisture conditions. The calibrated models have resulted in predictions that are in good agreement with observed performances. Furthermore, the model parameters successfully captured the initial densification behaviour and the associated sensitivity with axle load level.

An alternative method for determination of compaction level for the pavement granular layers

The performance and bearing capacity of the flexible pavement structure is ensured by providing necessary foundation comprised of unbound granular material (UGM) layers and subgrade. Whin this paper the compaction level parameters and deformation modulus relations determined for UGM layers and subgrade in construction site. The experimental data were tested applied standardized and improved test methods, such as an alternative falling weight deflectometer (FWD) test method with repetitive load, the plate load tester, lightweight deflectometer, dynamic cone penetrometer, and density Proctor tests. The data were analyzed based on statistical comparison of the compaction parameters, pairwise multiple comparison of test methods, clustering procedure for setting a level of compaction evidence and variance determination. Results proved capabilities of the alternative FWD test method under repetitive load to assess the relative compactness rate and the resilient responses, and provided the regression models of the dynamic modulus of the UGM layers and subgrade.

Degraded Ballast Stiffness Characterization Using Bender Element Field Sensor and PANDA® Penetrometer

The progressive degradation of railway ballast over time increases the degree of ballast fouling and poses significant drainability concerns leading to frequent maintenance activities. To avoid such issues, an effective and continuous characterization of the physical properties of the ballast layer is deemed necessary. This paper introduces the combined use of a bender element (BE) piezoelectric field sensor and a PANDA® dynamic cone penetrometer for periodic evaluations of ballast condition over the traffic use. To simulate various levels of ballast degradation, box tests were conducted using a dolomitic ballast material compacted in a laboratory-sized testbed with fouling indices ranging from zero to 39%. BE sensor pairs were embedded in the ballast layer to calculate the small strain modulus behavior of the ballast assessed through shear wave velocity measurements under different confinement conditions. Strength profiles of the ballast at different fouling levels were also measured using the PANDA® penetrometer. Experimental findings from both test methods indicate the existence of a dense state of ballast linked to a certain fouling index that maximized stiffness and strength characteristics of the tested ballast in dry condition. Accordingly, the potential use of BE field sensors embedded within in-service ballasted track coupled with periodic penetration testing can be a viable approach to evaluate ballast layer degradation. Various void packing conditions associated with ballast fouling levels can be linked to important ballast layer modulus and strength behavior. Further, such smart sensing of ballasted track behavior can provide long-term performance monitoring solutions for ballast cleaning and maintenance scheduling.

The appropriacy of the analytical models for calculating the shear capacity of cross-laminated timber (CLT) under out-of-plane bending

Rolling shear, an inherent property of cross-laminated timber (CLT) due to the weak shear strength of cross layers, is always the determinant of load-bearing capacity for short-span CLT members subjected to out-of-plane bending. Many analytical models were developed to calculate the shear capacity of CLT members. Because of the difficulty to precisely model the complicated shear failure mechanisms, however, no model was universally accepted. This paper aims to study the appropriacy of the commonly used analytical models, namely, composite beam theory, shear analogy method, Gamma method, and simple beam theory, by tests and analytical calculations. A composite beam theory-based simplified method was proposed. Three-point loading tests for the short-span CLT panels with 3 and 5 layers were conducted, and the shear capacities of the test specimens were calculated using the above-mentioned analytical methods. Shear strength and modulus of cross layers of the test specimens, which were used as the inputs for calculating the shear capacities, were tested by modified planar shear method. By comparing the calculation results obtained from different analytical models and the test results as well, it can be concluded that: (1) composite beam theory, shear analogy method, and the proposed simplified method give almost the same calculation results, therefore, the proposed simplified method can be used as the replacement for the other models; (2) Gamma method is more appropriate for calculating the shear capacity in case the input shear strength is determined by planar shear test; (3) the simple beam theory that is used in CSA O86 provides significantly lower shear capacity predictions than those obtained by the other methods.

Sensitivity analysis of pavement response to subgrade moisture variations

Moisture has detrimental effects pavement structures. Moisture effects on different structures will vary depending on their dimensions and properties. In this study, sensitivity analysis of pavement response to moisture was conducted using multilayered elastic theory, based on arbitrarily assumed subgrade moduli and the moduli from literature sources, respectively. The selected simulation variables included elastic modulus and thickness of asphalt surface, base and subbase layers as well as axle load. The fatigue and rutting life as well as their sensitivity indexes were obtained for each scenario. The results show that the soil with a relatively higher plasticity generally resulted in a higher sensitivity, whilst this trend was not monotonic with the soil plasticity. Drainage implications were summarized to provide a reference for the pavement drainage design. A drainage design process was proposed by incorporating sensitivity analysis. This study will facilitate the understanding of pavement response under different subgrade moisture conditions and pavement drainage design.

Evaluation of Airport Pavement Base Layer Stiffness Characteristics via Embedded Field Sensors

Real-time stiffness monitoring of unbound aggregate layers using embedded field sensors is crucial for advanced airport pavement design and management. This paper describes research findings on monitoring base layer stiffness characteristics for airport pavements using an embedded bender element (BE) field sensor, inductive coil sensors, and pressure cells. A full-scale pavement test section was constructed at the Federal Aviation Administration (FAA)’s National Airport Pavement Test Facility (NAPTF). A BE field sensor, inductive coil sensor pairs, and pressure cells were installed in the unbound aggregate base to evaluate the layer stiffness, applied load stress, and deformation characteristics. A triple dual tandem gear loading module applied 58,000 lb per wheel to the tested section with a wander pattern consisting of 66 passes arranged in nine lateral wander positions. Dynamic responses of coil sensors and pressure cells were collected during the traffic test, whereas BE signals were collected after completing each wander pattern. Laboratory repeated load triaxial tests with BE instrumentation were also conducted to establish a correlation for converting BE field sensor readings to layer modulus properties. The in situ modulus characteristics of the aggregate base layer were evaluated during full-scale testing using two methods: shear wave velocities from a BE field sensor, and strain and stress measurements from coil sensors and pressure cells. The moduli estimated using both approaches fell into typical ranges of crushed aggregate bases and were highly comparable. The moduli from the dynamic sensor measurements clearly showed the effect of vehicle wander on aggregate base layer measured responses.

Subgrade resilient modulus variation in low-volume roads design in north-eastern Brazil

The current asphalt pavement design method instituted in Brazil, MeDiNa, requires tests to determine the parameters of resilient modulus and permanent deformation of the granular layers. As these tests have a long execution time and high cost, this study analysed the variation of the resilient modulus (using composite model tested and linear predicted values) of low-volume road subgrade and the impact on the pavement design. This study simulated four different subgrades considering the soils of the metropolitan region of Fortaleza, Ceara, north-eastern Brazil and three predefined pavement structures. Total and subgrade rutting provided by the MeDiNa software were used as evaluation parameters. The simulation results allowed the authors to verify that the calculated rutting values are very close despite the resilient modulus adopted. In conclusion, road designers can consider any predicted linear value of the resilient modulus or composite models in the design of these highways, even with forecast errors greater than 20%. The study also proposes a low-volume road design catalogue considering the subgrades analysed.

Characteristics of inverse dispersion curve of Rayleigh wave in pavement shallow structure with engineering application

The inverse dispersion curve depicts the dispersion characteristics of inverse layered models, in the layer velocity decreases with depth. To reveal the inverse dispersion characteristics of Rayleigh-wave propagation in pavement, we established a method to determine the dispersion curve of Rayleigh-wave multimodal coupling superposition in pavement structure by decomposing the contribution of multi-mode phase velocity to the vertical displacement of road surface, which was verified by the velocity-stress finite difference scheme. On this basis, further comparative calculations found that the generalized reflection and transmission coefficient method for solving the Rayleigh wave fundamental dispersion curve can fully demonstrate the dispersion characteristics of the coupling superposition of multi-mode dispersion curves of Rayleigh wave in pavement structure, which is suitable for the calculation of Rayleigh-wave inverse dispersion characteristics. Meanwhile, the analysis of dispersion characteristics shows that when the frequency is higher than 5000 Hz, the phase velocities are determined by surface materials. In the low frequency band with frequency <10 Hz, the phase velocities are determined by soil-based deepest materials. And with the increase of the thickness of the intermediate layer, the phase velocity range of dispersion curve moves to the low frequency. In this regard, through sensitivity calculation, an optimization method for Rayleigh wave testing and inversion of elastic modulus of pavement structural layers was established by combining Levenberg-Marquardt and adaptive genetic algorithm. Through the comparative test on the scale model of three-layer pavement structure in laboratory, the results show that the elastic modulus of each layer of pavement structure can be successfully evaluated from the inverse dispersion characteristics of Rayleigh wave in pavement structure.

Modulus attenuation of semi-rigid asphalt pavement layer in accelerated pavement testing with MLS66

This research aimed to investigate the attenuation mode of the layer modulus of asphalt pavement in accelerated pavement testing (APT). A full-scale experimental section was constructed and tested using the APT facility. Two non-destructive testing (NDT) methods, named falling weight deflectometer (FWD) technique and portable seismic property analyzer (PSPA) test, were used to obtain the layer moduli of asphalt pavement during the APT test. The variation patterns of layer moduli obtained by FWD and PSPA tests were calculated and compared after the temperature was corrected to 20 ℃. It was found that the variation pattern of surface layer modulus based on field FWD measurements was consistent with the one measured from PSPA tests. That is the modulus of the surface layer increases with the APT load repetitions firstly and then decreases with the rise of the repetitions. The modulus values of the surface layer measured from PSPA tests are obviously larger than those backcalculated based on deflection basins. The ratio of the measured surface layer modulus based on the PSPA test to the backcalculated one based on the FWD test ranges between 2.06 and 2.71. The backcalculated base layer modulus always declines with the increasing loading repetitions. The attenuation patterns of the surface layer modulus and the base layer modulus in the damage stage are described as Ea=421100*N-0.6119 and Eb=128000*N-0.1096, respectively.

Modulus Estimation of Composites with High Porosity, High Particle Volume Fraction, and Particle Eigenstrain: Application to the LIB Active Layer with a Bridged-Particle Mesostructure

Due to the complex mesostructure and components of composite active layers in lithium-ion battery (LIB) electrodes, coupled with the concentration-dependent material properties and eigenstrains, efficiently estimating the effective modulus of the active layers remains a great challenge. In this work, the classic Mori–Tanaka method is found to be unable to estimate the modulus of the active layer. By realizing the importance of the mesostructure feature, a rod-rod model is proposed. The resulting modulus is expressed analytically. It is shown that the rod-rod model can accurately estimate the modulus evolution of the active layer if the material properties of the components and the evolution of volume fractions are known in advance. Moreover, a simplified rod-rod model is also developed to reduce the complexity of the proposed method. By knowing the volume fractions at two arbitrary states of charge and subsequently determining two constants, the simplified model can estimate the modulus efficiently. Considering both its accuracy and its simplicity, the simplified rod-rod model is the most suitable for the estimation. Thus, the methods developed in this work provide a new perspective for analyzing the material properties of composite active layers in LIB electrodes.

Stress dependent behaviour of unbound layers of unselected construction and demolition waste aggregates by lightweight deflectometer tests

The use of construction and demolition waste (CDW) aggregates in unbound road pavement layers is increasing. However, the lack of data on performance in the field has spurred this investigation into their in-situ properties. A lightweight deflectometer (LWD) is a fast and simulative testing device for estimating the elastic modulus of unbound pavement layers. A field test pit was built to run LWD measurements on an unbound subbase layer containing CDW aggregates compacted at different energy levels. To assess their stress-strain non-linear behaviour, several LWD drops were performed on the same location by varying (i) the loading mass, (ii) the drop height, and (iii) the plate diameter. A stress-hardening behaviour of in-situ CDW aggregates was observed, consistent with the stress dependent evolution of resilient modulus of granular material commonly recorded in laboratory tests. The LWD modulus was found to be dependent on the level of compaction energy but also sensitive to the mechanical response of the layer below. The outcomes at this test pit suggest it would be wise to consider the rational evaluation of the in-field stress dependent behaviour of unbound CDW granular materials at both the design stage and when devising quality acceptance procedures. Nonetheless, to have a comprehensive interpretation of LWD results a greater uniformity of material properties and a stronger control of construction procedures will be desired, especially when heterogenous materials such as CDW aggregates are investigated.