Добірка наукової літератури з теми "Rolling dynamic compaction"

Through established the simulation model for the engine and the traction host powertrain of rolling impact compaction machine, Simulated the working load with time history with the simulation parameters of rolling impact compaction machine. The simulation accuracy was verified by compared between the test speed and the simulation speed. The speed, turbine torque, torque converter efficiency, torque converter, gear ratios, fuel consumption, engine power, torque are dynamic changes follow with the alternating load and slope load so as to adapt to the dynamic drag torque fluctuations. Traction host power must be equipped with a full host transmission of the internal combustion engine. Driveline should be hydraulic transmission fluid or hydraulic machinery.

Although both mix variables and environmental variables are known to affect the fatigue response of asphalt-aggregate mixes, other factors—including specimen fabrication procedure and test equipment and procedures—are equally important. The development of a dynamic flexural beam fatigue test system is described, and the effects of specimen compaction method and equipment type on the precision of in situ fatigue lives of asphalt-aggregate mixes predicted by using laboratory strain-life relationships are discussed. Results indicate a coefficient of variation of 41 percent in fatigue life for the new fatigue equipment compared with one of 93 percent for an earlier electropneumatic version. The specimen compaction method was also found to influence significantly the precision of the predicted fatigue life. A 33 percent difference in coefficients of variation between the fatigue response of rolling wheel–compacted specimens and kneading-compacted specimens was observed. Consequently, twice as many specimens are required to achieve a given level of precision in in situ predicted fatigue life if kneading compaction is used instead of rolling wheel compaction. Similarly, if a pneumatic system and associated test procedure are used, approximately 12 times as many specimens are required to achieve similar precision in predicted fatigue life compared with the new servohydraulic fatigue test system.

This article verifies the feasibility to impact rolling technology instead of dynamic consolidation in soil areas soil region reinforcement processing by impact rolling soil base reinforcement experiments .In this essay, high soil areas embankment large area of reinforcement processing has opened up a new way.

Compaction quality of railroad subgrade relates directly to the stability and safety of train operation, and the core problem of the Intelligent Compaction of railroads is the transmission and evolution characteristics of vibration wave. Aiming at the shortages in exploring the transmission and evolution characteristics of the vibration signal, the typical subgrade compaction project of Jingxiong Intercity Railway Gu’an Station was selected to carry out the field prototypes tests, and the dynamic response from the vibratory roller to filling materials was monitored in the whole compaction process, and some efficient field tests data will be obtained. Based on this, the transmission and evolution characteristics of the vibration wave from the vibratory roller to filling materials in the compaction process are studied from the time domain, frequency domain, jointed time–frequency domain and energy domain by using one new signal analysis technology—Hilbert–Huang Transform. Some conclusions are shown as follows: first, the vibration acceleration peak gradually decreases with the increase of buried depth, and when the buried depth reaches 1.8 m, the vibration acceleration peak is closed to zero. At the same time, when the vibration wave propagates from the wheel to the surface of filling, the attenuation rate of acceleration gradually increases with the increase of rolling compaction times, while the attenuation rate of other layers in different buried depths gradually decreases. Second, the vibration wave contains fundamental wave and multiple harmonics, and the dominant frequency of the fundamental wave is nearly 21 Hz. With the increase of buried depth, the amplitude of fundamental, primary, secondary, until fifth harmonics decreases exponentially and the concrete functional relationship among different amplitudes of harmonics can be summarized as y = Ae−BX. Third, the vibration energy focuses on the fundamental wave and primary wave, which can increase with the increase of rolling compaction times, and when the rolling compaction time reaches five, their energy reaches maximum. However, when the filling reaches a dense situation, the energy of the primary wave gradually decreases. Therefore, the maximum rolling compaction time is five in the practical engineering applications, which will be helpful for optimizing the compaction quality control models and providing some support for the development of the Intelligent Compaction theory of railway subgrade.

Affected by the site construction conditions, the measurement passes of the Taihang Expressway K8 + 105 ∼ K8 + 341 (K8 worksite) in the Taihang Expressway did not meet the requirements of data analysis, and the quantity of the control points was insufficient so that the linear correlation between the dynamic deformation modulus () and the vibratory compaction value (VCV) was not strong. Therefore, the target value of VCV cannot be used to diagnose the E v d compaction quality of soil-rock filler. This paper analyzes the roller measurement VCV value and in situ measurements E v d value separately. Results reveal the difference between the VCV mean measured in the last two passes and the standard deviation of the measured VCV mean in the last pass are used as the main basis for the actual compaction quality. In addition, the E v d mean in the last rolling can be used as an auxiliary judgment basis for the quality control of the compaction.

Rolling dynamic compaction (RDC) consists of a non-circular module of 3, 4 or 5 sides, that rotates as it is towed, causing it to fall to the ground and compact it dynamically. There is currently little guidance available for geotechnical practitioners regarding the depths of improvement that are possible in varying soil conditions. Current practice dictates that practitioners rely on personal experiences or available published project case studies that are limited in scope and applicability as they are typically aimed at achieving a project specification. There is a reluctance to adopt RDC as a ground improvement technique as there is uncertainty regarding its limitations and capabilities. The underlying objective of this research is to quantify the ground response of the 8-tonne 4-sided impact roller. This research has used full-scale field trials and bespoke instrumentation to capture the ground response due to dynamic loading in homogeneous soil conditions. It was found that towing speed quantifiably influenced the energy imparted into the ground, with towing speeds of 10-12 km/h found to be optimal. Targeted full-scale field trials were undertaken to quantify the depth of improvement that can be achieved using RDC. Field results were compared to a number of published case studies that have used the 8-tonne 4-sided roller. Significantly, separate equations have been developed to allow practitioners to predict the depths that can be improved for the two major applications of RDC: improving ground in situ and compacting soil in thick layers. Finally, the in-ground response of RDC was measured using buried earth pressure cells (EPCs) and accelerometers. Force was determined from the measured change in stress recorded by EPCs whereas displacement was inferred from the double integration of acceleration-time data to give real-time load-displacement behaviour resulting from a single impact. The energy delivered to the soil by RDC is quantified in terms of the work done, defined as the area under the force versus displacement curve. Quantifying the energy imparted into the ground in terms of the work done is a key difference from past studies. Previous estimates of the energy delivered by impact roller at the ground surface has traditionally been predicted based on either gravitational potential energy (12 kJ) or kinetic energy (30 kJ to 54 kJ for typical towing speeds of 9 to 12 km/h). The two different values have caused confusion amongst practitioners. This research has determined that the maximum energy per impact that the 8-tonne 4-sided impact roller is capable of imparting to the ground is between 22 kJ to 30 kJ for typical towing speeds of 9 to 12 km/h. Quantifying the effectiveness of the 8-tonne 4-sided impact roller in terms of towing speed, depth of influence, and soil response measured via real-time measurements will lead to a greater understanding of the practical applications and limitations of RDC. Significantly, more accurate assessments of RDC will reduce design conservatism and construction costs, reduce instances where the predicted ground improvement does not occur and enable RDC to be used and applied with greater confidence.
Thesis (Ph.D.) -- University of Adelaide, School of Civil, Environmental and Mining Engineering, 2020

Rolling dynamic compaction (RDC) is a ground improvement technique, which involves towing heavy (typically 6–15 tonnes) non-circular modules (3-, 4- and 5-sided) behind a towing unit to achieve soil compaction. RDC has gained increased popularity in recent years since it has a greater influence depth and it can be operated at a higher speed. Although RDC has been successfully applied to many construction projects, there is currently very limited understanding of the behaviour of soil beneath the ground during the RDC process. In addition, the relationships between soil response and the effectiveness of RDC are still not well understood. These often results in the use of RDC being based on intuition or experience obtained from previous projects with similar soils and site conditions. To address the current knowledge gap, this research aims to quantify the soil response during the RDC process and then investigate the relationships between the mechanism of soil movement and the effects of RDC. This research focusses solely on the 4-sided impact roller. A series of physical scale model tests with the use of transparent soils, high speed photography and the image correlation technique were conducted to capture soil internal displacements subjected to RDC in real-time. The soil displacement field during the RDC process was measured and quantified. The loading and unloading response of soil subjected to a single roller impact was investigated and reported. In addition, the effects of operating speed and module mass on the internal displacements of the soil were determined. It was found that operating speed influenced soil displacements and the depth of improvement of the roller, and speeds between 12–14 km/h were recommended as the optimum operating speed. Soil displacements and improvement depth increased as speed rose to the optimal operating speed. After that, both soil displacements and improvement depth showed no further improvement and may even decrease due to the changes in the kinematics of the roller. In addition, the heavier roller induced greater soil displacements at each operating speed. A numerical scale model was developed and validated against physical scale model tests using the combined finite element method (FEM) and discrete element method (DEM) approach to simulate ground improvement induced by RDC. The numerical results were in good agreement with laboratory results. Relationships between porosity variations, soil movement and the motion of the roller were assessed using the developed numerical model. Porosities were also plotted against the number of passes, with the number of passes of approximately 35 found to be optimum. The numerical scale model was also modified, upscaled and compared against field measurements. It was found that the numerical scale model was able to provide reasonable predictions of ground improvement due to RDC, which offered the potential of obtaining an estimation of the performance of RDC before its application in practice. Finally, a numerical parametric study was performed to evaluate the effects of module mass, operating speed and various ground conditions on the effectiveness of RDC based on some aspects that are difficult to be measured in field tests. The results show that a heavier roller and a faster operating speed deliver greater compactive energies to the ground. The modelling results suggest that soil with a higher initial Young’s modulus and a higher internal angle of friction decreases the magnitude of soil displacements, which confirms that the impact roller is less able to significantly improve soils that are stiff or have a high initial shear strength. It is concluded that the proposed physical scale model captures the internal soil response during the RDC process, which provides greater insight into the mechanisms of soil movement due to RDC. This work expands the current knowledge of RDC theory and improves the confidence of RDC applications. The developed numerical model has demonstrated abilities in predicting ground improvement induced by RDC, which indicates the potential of applying the numerical model in predicting the performance of RDC and planning RDC-related ground improvement projects. In addition, the numerical model further evaluates the ground response subjected to RDC, which allows the effectiveness of RDC to be assessed from several aspects that are difficult to be measured using conventional investigation methods. In general, the results of this research provide a better understanding of the effectiveness of RDC, which are likely to reduce design conservatism, such as, excessive compaction requirements and overestimated costs, and also accelerate the adoption of RDC in ground improvement projects worldwide.
Thesis (Ph.D.) -- University of Adelaide, School of Civil, Environmental and Mining Engineering, 2022