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Influence of Support Conditions on Roller-Integrated Machine Drive Power Measurements for Granular Base
Abstract
A controlled field study was conducted to evaluate the influence of underlying layer support conditions on roller-integrated machine drive power (MDP) measurements. Multiple layers of granular base material were placed over a section of wet/soft subgrade and a section of concrete base for comparison. The material was compacted in layers using a 12-ton vibratory padfoot roller. MDP and in-situ spot test measurements were obtained on each layer and the results were statistically analyzed. Results indicate that compaction layer MDP measurements are strongly dependent on stiffness and heterogeneity of the supporting layer. If relatively stable and homogenous support conditions exist, the effect is not statistically detectable. Although the compaction layer properties (as measured by in-situ test measurements) are relatively uniform, the MDP measurements tend to capture the variability of the underlying layers. Post-construction tests by carefully excavating the compaction layers showed significant improvement in stiffness of the granular base layers compared to the initial compaction layer measurements. The reason is attributed to possible densification of underlying layers during compaction of the layers above and an increase in lateral stresses during compaction.
... This additional energy consumption is directly correlated with the strength of the subgrade, such that greater subgrade strength results in less penetration and additional energy consumption [7]. Essentially, energetic method ICMV is a promotion of the net power required for a compactor to pass through a compacted subgrade, without the need to obtain vertical vibration information from the roller [8]. This also makes energetic method ICMV suitable for various types of compactors [9]. ...
Intelligent compaction (IC) technology have been used for quality control and quality assurance (QC/QA) in subgrade construction. The effective regression correlations between Intelligent Compaction Measurement Values (ICMV) and In-situ Measurement Values (ISMV, including compaction degree and subgrade modulus ELWD) are the essential prerequisite of using IC technology for QC/QA. This paper presents the results from an experimental research study that was conducted from a practical subgrade project of China to explore the regression relationships between ICMV and ISMV. Three types of ICMV, including CMV, CCV and Evib, were collected along with the corresponding positions of the rollers. Two types of ISMV, containing compaction degree and ELWD, were measured by ring sampler method and light weight deflectometer (LWD) at specified test points, respectively. Based on these data, the influences of roller parameters and subgrade properties on the regression relationships of ICMV and ISMV were investigated. In addition, linear regression and 5 nonlinear regression algorithms were compared. The results suggest that ICMV reflect the stiffness of subgrade more than reflecting the density. In the regression of ICMV and ISMV, subgrade properties are more important than roller parameters while both of them should not be neglected. The influences of underlying stiffness and roller amplitude are linear while that of roller speed and moisture content are nonlinear. Nonlinear algorithms, especially the random forest, have the better performance compared to linear algorithm. Moreover, the combination of random forest and linear algorithm can further improve the accuracy of ISMV prediction.
... Detailed background information on the MDP system is provided by White et al. (2005). Controlled field studies documented by White and Thompson (2008) and Vennapusa et al. (2009) verified that MDP values are empirically related to granular soil compaction characteristics (e.g., density, stiffness, and strength). MDP is a relative value referencing the material properties of the calibration surface, which is generally a hard compacted surface (MDP = 0 kJ/s). ...
In this study, test sections were built to evaluate the long-term performance of portland cement (PC) stabilization with polymer fiber reinforcement in granular subbase layers by measuring in situ engineering properties (i.e., strength and stiffness) over time with special focus on freeze/thaw performance. Two different fibers—discrete fibrillated polypropylene (DF-PP) fiber and monofilament-polypropylene (MF-PP) micro-fiber—were used for reinforcement. A target 5% PC and target 0.4% fiber content was used for stabilization and reinforcement of the granular subbase layer. Within 1 to 3 days of curing, a 6 in. crushed limestone modified subbase layer was placed over the stabilized layer and compacted using a vibratory smooth drum roller. In situ testing involved testing the foundation layers immediately after construction, and after 1, 2, 3, and 7 days, and 3, 9, 10, and 21 months of curing. Spring-thaw occurred after 9 and 21 months of curing. Dynamic cone penetrometer (DCP), falling weight deflectometer (FWD), and roller-integrated compaction monitoring (RICM) tests were used for in situ testing. Laboratory tests were conducted to assess the freeze-thaw durability performance of the treated and untreated samples. Both laboratory and field testing indicated that strength and stiffness properties yielded the lowest values during thawing period, and that addition of PC and PC + fibers to the subbase material showed significant improvement in the strength and stiffness properties and freeze-thaw performance. Addition of fibers alone showed some improvement in the subbase layer laboratory freeze-thaw performance.
... This is primarily because of the differences in measurement influence depths. Accelerometer based roller measurements have measurement influence depths ranging from 0.8 m to 1.5 m depending on soil layering, drum mass, and excitation force [25,[39][40][41], while machine drive power based measurements range from 0.3 to 1.3 m depending on the heterogeneity in subsurface conditions [33]. On the other hand, most point-MVs have influence depths <0.5 m [41]. ...
Roller-integrated compaction monitoring (RICM) technologies provide virtually 100-percent coverage of compacted areas with real-time display of the compaction measurement values. Although a few countries have developed quality control (QC) and quality assurance (QA) specifications, broader implementation of these technologies into earthwork construction operations still requires a thorough understanding of relationships between RICM values and traditional in situ point test measurements. The purpose of this paper is to provide: (a) an overview of two technologies, namely, compaction meter value (CMV) and machine drive power (MDP); (b) a comprehensive review of field assessment studies, (c) an overview of factors influencing statistical correlations, (d) modeling for visualization and characterization of spatial nonuniformity; and (e) a brief review of the current specifications.
This paper describes the interpretation of intelligent compaction (IC) data from two layered soil test beds using center of gravity (CG) roller-measured soil stiffness. Conventional edge-mounted (EM) roller-measured soil stiffness values are interpreted from vertical accelerations measured by discrete, single-position accelerometers. However, these EM accelerometers are located at variable distances from the drum CG; the resulting vertical accelerations are thus affected by the rotation of the roller drum about the drum CG in the direction of roller travel. This leads to undesirable measurement artifacts, specifically multiple possible soil stiffness values for one soil location and an artificial dependence of the soil stiffness values on the direction of roller travel. In this study, left and right EM acceleration data from a vibratory roller are used to compute vertical accelerations at the CG of the roller drum. These vertical accelerations are used to compute CG stiffness values, which are not subject to the measurement artifacts associated with EM stiffness values. The resulting CG stiffness values are used to interpret IC data from two test beds with multiple 15-30 cm thick base-subbase-subgrade lifts. CG soil stiffness increases with the addition of subbase and base lifts, showing a desired sensitivity to changes in soil materials. CG stiffness also increases with the addition of multiple base lifts, showing a desired sensitivity to an increase in the overall thickness of the base material. This study demonstrates the efficacy of this unambiguous measure of soil stiffness for practical usage in IC of layered earthwork systems.
Recent developments for measurement and analysis of machine power response caused by changes in physical soil properties have the potential to change completely the future of earthwork construction. A technique in which a self-propelled sheepsfoot roller was used to compact cohesive soils was developed; field pilot studies were then conducted. Results from field tests using conventional testing techniques (nuclear moisture–density gauge, dynamic cone penetrometer, drive core, and Clegg impact hammer) showed strong correlations to machine power (r² > 0.9) when data were averaged over a 20-m test strip. These developments related to measurement and analysis of machine energy as a function of changes in physical soil properties and provide the benefit of 100% coverage combined with a differential Global Positioning System and ruggidized touchscreen computer monitor showing spatial information on cumulative number of passes and machine power output. Results can be transmitted in real time to an on-site computer for review via a wireless Internet system.
To evaluate roller-integrated machine drive power (MDP) technology for predicting the compaction parameters of cohesive soils considering the influences of soil type, moisture content, and lift thickness on machine power response, a field study was conducted with 15-m test strips using three cohesive soils and several nominal moisture contents. Test strips were compacted using a prototype CP-533 static padfoot roller with integrated MDP technology and tested using various in situ compaction measurement devices. To characterize the roller machine-soil interaction, soil testing focused on measuring compaction parameters for the compaction layer. Variation in both MDP and in situ measurements was observed and attributed to inherent variability of the compaction layer and measurement errors. Considering the controlled operations to create relatively uniform conditions of the test strips, measurement variability observed in this study establishes a baseline for acceptable variation in production operations using MDP technology in cohesive soils. Predictions of in situ compaction measurements from MDP were found to be highly correlated when moisture content and MDP-moisture interaction terms were incorporated into regression models.
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