Field Study of In Situ Subgrade Soil Response Under Flexible Pavements

1998 ◽  
Vol 1639 (1) ◽  
pp. 23-35 ◽  
Author(s):  
Shongtao Dai ◽  
Dave Van Deusen
Keyword(s):  
Resilient Modulus ◽  
Soil Pressure ◽  
Vertical Pressure ◽  
Soil Response ◽  
Subgrade Soils ◽  
Linear Elastic ◽  
Subgrade Soil ◽  
In Situ Sensors ◽  
Falling Weight

Falling weight deflectometer (FWD) and truck tests were performed on three instrumented flexible pavement sections at the Minnesota Road Research project. The purposes of the study were (1) to investigate sub-grade soil response under FWD and moving truck loads and (2) to estimate in situ resilient modulus of the subgrade soil. The truck tests were performed at various speeds ranging from 16 to 78 km/h. The subgrade deformations and the vertical pressures on the top of the subgrade soils were measured from in situ displacement and soil pressure gauges. The experimental results showed that the deformations and the vertical pressures, in general, did not show significant dependency of truck speed within the above speed range. However, a slight decrease of the vertical pressure with increase of speed was observed for a thin conventional pavement section, while the vertical pressure in a relatively thick pavement section appeared to be less sensitive to speed. The results from FWD tests indicated that the subgrade deformation was linearly related to the FWD loads up to approximately 40 kN. Furthermore, a method is presented to estimate in situ subgrade modulus using the linear elastic theory and the measurements from the in situ sensors. The estimated modulus is comparable with the laboratory results at a low deviator stress level and is lower than modulus obtained from the backcalculation using FWD deflection basins.

scholarly journals Evaluation of Resilient Modulus of Subgrade and Base Materials in Indiana and Its Implementation in MEPDG

2014 ◽  
Vol 2014 ◽  
pp. 1-14 ◽  
Author(s):  
Richard Ji ◽  
Nayyarzia Siddiki ◽  
Tommy Nantung ◽  
Daehyeon Kim
Keyword(s):  
Resilient Modulus ◽  
Falling Weight Deflectometer ◽  
Statistical Tool ◽  
Material Constants ◽  
Analysis And Evaluation ◽  
Subgrade Soils ◽  
Base Materials ◽  
Subgrade Soil ◽  
Different Seasons ◽  
Falling Weight

In order to implement MEPDG hierarchical inputs for unbound and subgrade soil, a database containing subgradeMR, index properties, standard proctor, and laboratoryMRfor 140 undisturbed roadbed soil samples from six different districts in Indiana was created. TheMRdata were categorized in accordance with the AASHTO soil classifications and divided into several groups. Based on each group, this study develops statistical analysis and evaluation datasets to validate these models. Stress-based regression models were evaluated using a statistical tool (analysis of variance (ANOVA)) andZ-test, and pertinent material constants (k1,k2andk3) were determined for different soil types. The reasonably good correlations of material constants along withMRwith routine soil properties were established. Furthermore, FWD tests were conducted on several Indiana highways in different seasons, and laboratory resilient modulus tests were performed on the subgrade soils that were collected from the falling weight deflectometer (FWD) test sites. A comparison was made of the resilient moduli obtained from the laboratory resilient modulus tests with those from the FWD tests. Correlations between the laboratory resilient modulus and the FWD modulus were developed and are discussed in this paper.

scholarly journals Alternate Method of Pavement Assessment Using Geophones and Accelerometers for Measuring the Pavement Response

2020 ◽  
Vol 5 (3) ◽  
pp. 25
Author(s):  
Natasha Bahrani ◽  
Juliette Blanc ◽  
Pierre Hornych ◽  
Fabien Menant
Keyword(s):  
Full Scale ◽  
Displacement Sensor ◽  
Traffic Loading ◽  
Pavement Monitoring ◽  
In Situ Sensors ◽  
Vibrating Table ◽  
Processing Techniques ◽  
Falling Weight ◽  
Pavement Instrumentation

Pavement instrumentation with embeddable in-situ sensors has been a feasible approach to determine pavement deteriorations. Determining pavement deflections during the passage of the load is a promising strategy to determine the overall performance of the pavement. There are different devices that apply loads to the pavements and measure the deflection basin, these include static, vibratory, or impulse loadings. Most commonly used are the static loading like Benkelman beam and impulse loading like the Falling Weight Deflectometer (FWD). However, these techniques are costly and the measurements are recorded infrequently, i.e., once per year or two years. This study focuses on the use of geophones and accelerometers to measure the surface deflections under traffic loading. To develop a method to measure pavement deflections, the sensors were submitted first to laboratory tests, and then tested in situ, in a full scale accelerated pavement test. In the laboratory, the sensors were submitted to different types of loading using a vibrating table. These tests were used to determine the noise and sensitivity of the sensors, and then to evaluate their response to signals simulating pavement deflections under heavy vehicles. The sensor response was compared with measurements of a reference displacement sensor. Different processing techniques were proposed to correct the measurements from geophones and accelerometers, in order to obtain reliable deflection values. Then, the sensors were evaluated in a full scale accelerated test, under real heavy axle loads. Tests were performed at different loads and speeds, and the deflection measurements were compared with a reference anchored deflection sensor. The main advantage of using accelerometers or geophones embedded in the pavement is to enable continuous pavement monitoring, under real traffic. The sensor measurements could also be used to determine the type of vehicles and their corresponding speeds. The study describes in detail the signal analysis needed to measure the pavement deflections accurately. The measurements of pavement deflection can be then used to analyze the pavement behavior in the field, and its evolution with time, and to back-calculate pavement layer properties.

Relationship Between Backcalculated and Laboratory-Measured Resilient Moduli of Unbound Materials

2003 ◽  
Vol 1849 (1) ◽  
pp. 177-182 ◽  
Author(s):  
Gerardo W. Flintsch ◽  
Imad L. Al-Qadi ◽  
Youngjin Park ◽  
Thomas L. Brandon ◽  
Alexander Appea
Keyword(s):  
Resilient Modulus ◽  
Shift Factor ◽  
Falling Weight Deflectometer ◽  
Test Results ◽  
Structural Capacity ◽  
Bulk Stress ◽  
Stress Dependent ◽  
Falling Weight ◽  
Virginia Smart Road

The resilient moduli of an unbound granular subbase (used at the Virginia Smart Road) obtained from laboratory testing were compared with those backcalculated from in situ falling weight deflectometer deflection measurements. Testing was performed on the surface of the finished subgrade and granular subbase layer shortly after construction. The structural capacity of the constructed subgrade and the depth to a stiff layer were computed for 12 experimental sections. The in situ resilient modulus of the granular subbase layer (21-B) was then back-calculated from the deflections measured on top of that layer. The back-calculated layer moduli were clearly stress-dependent, showing an exponential behavior with the bulk stress in the center of the layer. Resilient modulus test results of laboratory-compacted specimens confirmed the stress dependence of the subbase material modulus. Three resilient modulus models were fitted to the data. Although all three models showed good coefficients of determination ( R2 > 90%), the K-θ model was selected because of its simplicity. The correlation between field-backcalculated and laboratory-measured resilient moduli was found to be strong. However, when the stress in the middle of the layer was used in the K-θ model, a shift in the resilient modulus, θ, was observed. This finding suggests that a simple shift factor could be used for the range of stress values considered.

scholarly journals Studi Literatur Korelasi Hasil Uji Berdasarkan Uji Plate Bearing dan Uji Dynamic Cone Penetrometer

2020 ◽  
Vol 3 (4) ◽  
pp. 1157
Author(s):  
Steven Lius ◽  
Inda Sumarli ◽  
Ali Iskandar
Keyword(s):  
Soil Samples ◽  
Cone Penetrometer ◽  
Clayey Soils ◽  
In Situ Test ◽  
Subgrade Soils ◽  
Testing Method ◽  
Dynamic Cone Penetrometer ◽  
Subgrade Soil

The subgrade soils must be able to withstand the load that is transferred. The quality of the subgrade soil is important because if it is sturdy, the construction above it can also be sturdy as well. Therefore, in designing a construction, soil investigation, such as plate bearing test and dynamic cone penetrometer test, must be conducted. However, one method may be superior compared to others, that the author will analyze the correlation between them. Plate bearing test is an in-situ test used for determining the ultimate bearing capacity of soil by only applying pressure to it. Whereas, dynamic cone penetrometer test is a testing method to measure the thickness and strength of soil. In this research, the collected data will be analyzed and correlated. The result of correlation between ks and CBR from DCP test is the determinant coefficient value. The value for clayey soils is 0.6198 which means that the correlation value is strong. Meanwhile, for sandy soils, the values are 0.9841 and 0.9878 which means both of the correlation values are very strong. Furthermore, the correlation of Su values from both tests cannot be determined because the soil samples have not reached the fracture condition. Lapisan subgrade merupakan lapisan yang menahan seluruh beban di atasnya. Kualitas dari lapisan ini sangat penting, karena jika lapisan subgrade tersebut kokoh, maka konstruksi di atasnya juga akan kokoh. Oleh karena itu, dalam merencanakan sebuah konstruksi, penyelidikan tanah, seperti uji plate bearing dan uji dynamic cone penetrometer, di lokasi suatu bangunan yang akan dibangun itu sangat penting. Namun, setiap metode penyelidikan tanah tentunya memiliki kelebihan dan kekurangan masing-masing, sehingga penulis akan menganalisa korelasi antara kedua pengujian. Uji plate bearing merupakan metode pengujian untuk menentukan nilai daya dukung tanah dengan hanya memberikan tekanan pada tanah. Sedangkan, uji dynamic cone penetrometer merupakan metode pengujian untuk mengetahui nilai ketebalan dan kekuatan suatu lapisan tanah. Pada penelitian ini, data yang sudah dikumpulkan akan dianalisa dan dikorelasikan. Hasil korelasi antara nilai modulus reaksi tanah dasar dan CBR dari uji DCP untuk jenis tanah lempung menghasilkan koefisien determinan sebesar 0.6198 yang artinya nilai korelasi tersebut kuat. Sedangkan, untuk jenis tanah pasir, didapatkan koefisien determinan sebesar 0.9841 dan 0.9878 yang artinya nilai korelasi tersebut sangat kuat. Kemudian, untuk korelasi nilai kuat geser tanah dari masing-masing pengujian belum bisa dijelaskan karena sampel tanah yang digunakan belum mencapai kondisi fracture.

Resilient modulus of unsaturated subgrade soil: experimental and theoretical investigations

2013 ◽  
Vol 50 (2) ◽  
pp. 223-232 ◽  
Author(s):  
C.W.W. Ng ◽  
C. Zhou ◽  
Q. Yuan ◽  
J. Xu
Keyword(s):  
Resilient Modulus ◽  
Fatigue Cracking ◽  
Cyclic Stress ◽  
Radial Deformation ◽  
Soil Response ◽  
Triaxial Apparatus ◽  
Subgrade Soil ◽  
Concrete Layer ◽  
Accuracy Of Measurements ◽  
Water Tension

The resilient modulus, MR, of subgrade soil is an important stiffness parameter for analysing fatigue cracking in either the asphalt or concrete layer of a pavement. Although subgrade soil is often unsaturated and subject to seasonal variations of moisture content and hence suction in the field, effects of soil suction on the resilient modulus are generally not accounted for in existing testing methods. In this study, MR values of a subgrade soil under various stress and suction conditions were investigated using a suction-controlled cyclic triaxial apparatus. To enhance the accuracy of measurements, Hall-effect transducers were employed to monitor the local axial and radial deformation of each specimen. It was found that MR increases with number of load applications when a soil contracts, but decreases slightly when a soil dilates. When suction increases, the soil response tends to change from contractive to dilative due to suction-induced dilatancy. Moreover, the measured MR is highly dependent on the stress state. It decreases with cyclic stress due to the nonlinearity of the soil stress–strain behaviour, but increases significantly with suction due to the presence of water tension. At the same stress and suction conditions, MR measured along the wetting path is generally larger than that measured along the drying path. A new semi-empirical equation representing the stress-dependency of MR is proposed and was verified using experimental results of four different soils.

Evaluation of Resilient Modulus Test Protocols for New Mexico Subgrade Soil

2013 ◽  
Vol 742 ◽  
pp. 109-115 ◽  
Author(s):  
Md Tahmidur Rahman ◽  
Anthony S. Cabrera ◽  
A. Tarefder Rafiqul
Keyword(s):  
New Mexico ◽  
Laboratory Testing ◽  
Resilient Modulus ◽  
Measurement Methods ◽  
Subgrade Soils ◽  
Subgrade Soil ◽  
Design Guide ◽  
Internal Deformation ◽  
Testing Protocols ◽  
Important Design

Resilient modulus (MR) is a laboratory determined parameter of pavement subgrade soil which is an important design input for the Mechanistic Empirical Pavement Design Guide (MEPDG). There are two accepted laboratory testing protocols for determining MR, namely AASHTO T307 and NCHRP 1-28A. AASHTO method is more popular because of its simplicity in positioning the load and deformation transducers. This study is undertaken to examine the available test protocols for New Mexico subgrade soil by varying the location of deformation transducers and effects of sample size. AASHTO A-6 subgrade soils have been collected from the state of New Mexico, USA. Specimens of 2.8 inch and 4 inch diameters are reconstituted using modified proctor compaction.Resilient modulus values aredetermined using external and internal deformation techniques. Comparative analyses are performed and amount of extraneous large deformation (lower MR) measured by the AASHTO recommended external deformation transducers is measured.In addition, appropriate internal deformation measurement methods are recommended to obtain most consistent MR values. 2.8 inch and 4 inch diameter sample generate almost similar MR values.

Variation of Resilient Modulus with Soil Suction for Compacted Subgrade Soils

2005 ◽  
Vol 1913 (1) ◽  
pp. 99-106 ◽  
Author(s):  
Shu-Rong Yang ◽  
Wei-Hsing Huang ◽  
Yu-Tsung Tai
Keyword(s):  
Moisture Content ◽  
Resilient Modulus ◽  
Matric Suction ◽  
Soil Suction ◽  
Subgrade Soils ◽  
Subgrade Soil ◽  
Relative Compaction ◽  
Service Conditions ◽  
Paper Method ◽  
Key Parameter

The variations of resilient modulus with the postconstruction moisture content and soil suction for cohesive subgrade soils were evaluated. In particular, the effects of relative compaction of the subgrade on the suction and resilient modulus were investigated. To simulate subgrade soils at in-service conditions, soil specimens were compacted at various relative compactions and optimum moisture content and then saturated to equilibrium moisture content to test for resilient modulus and soil suction. The filter paper method was used to measure the total and matric suctions of two cohesive soils. Test findings demonstrated that resilient modulus correlated better with the matric suction than with total suction. Matric suction was found to be a key parameter for predicting the resilient modulus of cohesive subgrade soils. A prediction model incorporating deviator stress and matric suction for subgrade soil resilient modulus was established.

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