Subgrade Compaction Research Articles

利用激光图像技术检测路基压实度

利用激光图像技术检测路基压实度

利用激光图像技术检测路基压实度

利用激光图像技术检测路基压实度

Research of Impact Compaction Technology on Foundation and Subgrade in Yellow River Flooded Area

To study the feasibility of impact compaction on the foundation and subgrade compaction in Yellow River flooded area and explore construction process and control parameters that could ensure good compaction results, experiment was conduct on impact compaction. By way of detecting the influence of impact compaction on settlement, moisture content and degree of compaction in different construction technology to analysis the feasibility of impact compaction on the foundation and subgrade compaction in Yellow River flooded area. By evaluating the effect of compaction of different construction techniques, appropriate construction technology and control parameters of impact compaction on foundation and subgrade in the Yellow River flooded area was summarized. Research results showed that impact compaction had a good compaction effect on foundation and subgrade in Yellow River flooded area. For foundation compaction, discontinuous impaction construction should be adopted and control parameters should use degree of compaction and settlement and the best impaction times should be 12 -14 times. For subgrade compaction, the thickness of the loose layer should be 80cm and the best impaction times should be 25-30 times.

Study on Impact Compaction of Aeolian Sand Subgrade and its Effect Evaluation

In order to solve the problem of aeolian sand subgrade compaction, we studied the technology of impact compaction, applied it to the engineering practice and analyzed its effect with Rayleigh wave. The technology of impact compaction can combine the compaction of potential energy and kinetic energy and make it easier for the materials to reach their elastic stage. With the combined function of "knead-roll-impact", the impact compaction road roller can compact the soil body and offer 6～10 times impact force and 3～4 times the depth of influence more than the vibratory roller. The impact compaction methods of aeolian sand subgrade were put forward. The comparative field compaction tests between impact and vibratory compaction are carried through, which are detected by Rayleigh wave. The results show that the impact compaction can make the density of the aeolian sand subgrade 2～5% higher than the vibratory compaction, and reach the influence depth of 7 metres. To sum up, the impact compaction can clearly increases the strength and stiffness of aeolian sand subgrade with a dynamic elastic modulus of 202.63MPa.

Comparison Experimental Study on Subgrade Compaction Quality Test Methods

The principles of the continuous test methods for compaction degree is introduced based on subgrade engineering cases. The compaction parameter CMV associated with subgrade compaction is obtained through spectrum analysis on the response of a vibratory drum during compaction operations. Comparative analysis is conducted on CMV and the in situ test index Evd, which verifies that the continuous test index CMV has a high reliability and a good correlation with Evd and can objectively and comprehensively reflect the subgrade compaction quality and provides necessary basis for the application of the continuous quality test methods for subgrade.

Application of DCP to Evaluate Subgrade Compaction Quality

Although DCP (Dynamic Cone Penetrometer) cannot directly reflect the subgrade compaction degree, experience shows that the smaller DCP penetration rate is and the better the compaction quality will be. Tai-Ao highway in China is selected as an engineering example, some relationship curves are obtained by in-situ tests, such as total hammering number of DCP and penetration depth, and penetration ratio and penetration depth, and these curves reveal that DCP can reflect the compaction quality in some degree. And then a lot of FWD and DCP are in-situ tested on the same points of filled and excavated subgrade, and the back-calculated CBR and FWD (1 ton, 3 ton and 5 ton) are analyzed and they have better correlation, and DCP is approved to be a better manner to test and evaluate the compaction quality of highway subgrade.

The Potential Use of the Light Drop-Weight Deflectometer to Control Subgrade Compaction on Forest Roads

Abstract Improving subgrade strength can reduce a road's construction and maintenance costs. Additionally, it may lessen some of the environmental impacts from forest roads. However, most forest roads receive little effort to establish or control compaction because of the perceived increase in construction costs and potential delays in the flow of wood from the area. A light drop-weight deflectometer was tested on two forest roads in western Oregon to determine if this tool could aid with improving forest road construction by improving the quality of the road's subgrade. One road was built on a fine sand-silt soil and the other was constructed on a silt-clay soil. The goal was to correlate the easily collected subgrade values produced from the light drop-weight deflectometer and wet unit weight to the soaked and nonsoaked California bearing ratio (CBR) values for the subgrade, which are common design variables used to determine the minimum thickness of the aggregate surface. The light drop-weight deflectometer showed mixed results with regards to its ability to predict the values from the more expensive CBR laboratory test. The results from site 1, sand-silt soils, showed the potential of the light drop-weight deflectometer to aid in construction control as the values from light drop-weight deflectometer, when combined with the wet unit weight, explained a statistically significant amount of the variability in the soaked and nonsoaked laboratory CBR values. These variables explain approximately 60% of the variation in CBR values. The data from site 2, the silt-clay soils, were not able to significantly predict the subgrade strength variables, and the road will need to continue to use the traditional methods for establishing and controlling compaction.

Compaction of Forest Roads in Northwestern Oregon – Room for Improvement

Monitoring the construction and as-built conditions of a low volume aggregate surfaced forest road in Northwest Oregon coupled with detailed laboratory testing of the subgrade soils allowed an analysis of the potential benefits of improved structural road design and construction control. Specifically, subgrade compaction was found to be far below desirable levels that would achieve greater subgrade strength, and based on a common design equation, allow for the use of significantly less aggregate. It is inferred that a combination of inadequate compaction energy and failure to account for the detrimental influence of high field moisture content resulted in poor subgrade densities. This case study showed that a 34 percent saving in aggregate cost maybe possible.

Successful Application of CLSM on a Weak Pavement Base/Subgrade for Heavy Truck Traffic

Lack of proper pavement base and subgrade compaction leads to premature failures that account for millions of dollars in damages. Controlled low-strength material (CLSM) concrete was introduced in this study as pavement base material near a manhole where proper compaction is unachievable. Rut-resistant stone matrix asphalt was placed on top of the CLSM as a wearing surface layer. Dynamic cone penetrometer (DCP) testing was used to monitor CLSM construction. One day after placing, the CLSM gained sufficient strength to support construction traffic. Further, DCP results indicated that the CLSM possessed uniform characteristics of concrete that could improve the load-bearing capacity and serviceability of the pavement near the manhole. After 18 months of heavy truck traffic, maximum rutting was 5 mm, well below the failure criteria of 12.5 mm. Based on cost and performance, CLSM concrete has the potential to improve problematic areas in pavement.

A simple chart for the prediction of resilient modulus

Considerable effort has been put into the task of obtaining characterization of pavement materials, and the laboratory equipment necessary for this task is both expensive and complex. This note presents a method of overcoming this problem for partially saturated cohesive subgrades. An investigation was undertaken to see if a simple relationship could be obtained linking the resilient modulus to some standard laboratory test. It was suggested that the resilient properties would be reflected in the two parameters: relative compaction and relative moisture content. A series of field tests was performed to ascertain the effect of in situ compaction and moisture level on the resilient modulus of a road subgrade as indicated by the Benkelman beam surface deflexion. It was found that the deflexion was dependent on both moisture and compaction levels. The chart was constructed by interpolation of A number of results, and indicated that there was an optimum moisture level that would give minimum resilience for any particular sub-grade compaction level. The use of this method would allow the practising road engineer to make an estimate of resilient modulus without direct recourse to expensive repeated load triaxial tests. /TRRL/