In order to improve the quality of the project, we adopt the intelligent compaction control system and collect CMV values through experiments. In the experiment using finite element simulation software to simulate and analyze. From the simulation results to analyze the road surface displacement and stress trends, derived from the displacement of the pressed material in the fifth pass, the sixth pass is almost the same, the rate of change close to 0, can be considered pressed material has the desired pressure . The actual degree is in good agreement with the actual compaction of sand filling, indicating that the compaction state of the pressed material can also be verified from the stress angle of the pressed material. The stress change from the weak vibration to the strong vibration load increases first and then decreases rapidly, and the reduction of strong vibration is more obvious. Therefore, the simulation result also shows that the strong vibration has the better compaction effect than the weak vibration.
In the process of engineering construction, the compaction effect is directly related to the quality, safety performance and durability of the project, and is closely related to the safety of people’s life and property [
However, the emergence of intelligent compaction technology solves this practical problem well. Intelligent compaction [
In the theoretical experimental stage of subgrade, the CMV index controlled by intelligent compaction system reflects the change of resistance of the soil to the vibration wheel and indirectly reflects the degree of soil compaction. With the aid of finite element simulation analysis software [
The use of COMSOL Mulyiphysics software simulation analysis, through the analysis found that the compaction of the pressed material can be achieved through the intelligent compaction system indirectly collected resistance values and pressure material stress and displacement changes are reflected in both [
This experiment uses COMSOL Mulyiphysics software to analyze the compaction process used. And the compaction process is static pressure once, weak vibration one time, strong vibration four times, the model is a two-dimensional silty soil layer, a length of 50 meters, a thickness of 30 cm. Model shown in
The grid adopts the mapping method, and the total number of units is 22,992, and the local enlargement is shown in
The test road project is located in the Baoding area of the North China Plain, the area belongs to the key grain-producing area, along the flat terrain, there is no protruding hills and ridge, can be used as a borrow site. The soil quality along the project is mostly silt and some silty clay. The shaping index is about 10 and can be used as roadbed filler after drying. The maximum particle size of the filler should be less than 150 mm. In order to bring the original layer of soil on the influence factors of CMV value, to achieve the ideal test, decided to choose after the roadbed filling height to 2 m, subgrade compaction to using intelligent system for static pressure 1 time, weak vibration 1 times, strong vibration 4 times.
The software actually considers the elasto-plastic constitutive model of soil. Due to the fact that the external load of the actual simulation is small and the concentrated load simplified by the compactor is only obvious to the local, the soil actually only undergoes the elastic deformation process and has not yet reached the plastic deformation stage.
average displacement rate of change to specify, the software to extract the fifth pass and the sixth pass the average displacement of 2.51e−8m, 2.505e−8m, the
average rate of change of displacement is ( 2.51 − 2.505 ) e − 8 6 − 5 = 5 × 10 − 3 e − 8 ≈ 0 . In
dicating that the material being pressed against the external load capacity to strengthen and continue to vibrate compaction no effect, we can think that the soil has reached a strong state of compaction. Therefore, it can be concluded from the comparison of the above figure that the effect of strong vibration is better than the effect of weak vibration.
1) The first compaction of the end (t = 62.5 s)
As shown in
2) The second compaction of the last (t = 125 s)
As shown in
the roller is the last moment of the weak vibration stage, that is, the load moves from the end position of the static pressure to the left end. At this time, the displacement in most areas of the road is still relatively uniform, and the road surface stress is uneven. The displacement is only in the center of the road and near
the right half of the area, and the displacement direction is vertical upward, and the road in this position will have a slight bulge or warping phenomenon. At this time, the maximum displacement value is 0.7 microns, while the maximum stress value is 140 Pa. Compared with the static pressure phase, the maximum displacement and maximum stress of the road are reduced. The displacement and stress are still small in the vibration end of the roller and the surrounding area.
3) The third compaction of the last (t = 187.5 s)
As shown in
4) The fourth compaction of the last (t = 250 s)
As shown in
5) The fifth compaction of the last (t = 321.5 s)
As shown in
the road along the center of large displacement, vertical displacement in a third position near the place down, near the center of vertical displacement direction, and at this point, the maximal displacement value of 0.5 microns, and the second time compared to the strong vibration phase, the road of the maximal displacement almost remain the same, and the maximum stress of 1100 pa. The displacement and stress are still small in the vibration end of the roller.
6) The sixth compaction of the last (t = 375 s)
As shown in
third time strong vibration phase, compared to the road of the maximal displacement change is small, and the road surface the maximum stress of lower. The displacement is still small in the vibration end of the roller and the surrounding area. The maximum strength of pavement structure.
By more than six times the compaction, the results show that with the increase of compaction times, the displacement and stress of pavement present nonlinear immediately after the first increases, decreases, which embodies the road good compaction effect, which is consistent with the results of pavement compaction test. On this basis, analyzed the pavement compaction of displacement and stress under different position in the process of dynamic change process, and found that the road in the compaction process of displacement and stress appears asymmetric distribution form, this may be due to the road of internal moisture content and pore water seepage effects lead to the spread of the internal stress and displacement of soil development of heterogeneous characteristics.
At the end of each compaction, the stress and displacement of the road have similar distribution pattern, and the maximum stress is located near the middle of the middle, and there is a large peak in many places.
From Figures 16-21, it can be more intuitively reflected that the displacement along the length distribution of the road at the end of each time pressure is consistent with the result of cloud image. It can be seen from the figure that the displacement of the road surface is small, and the maximum displacement is all near the center near the middle, and the distribution of the multi-peak asymmetrical curve occurs. For example, when t = 62.5 s moment, roller is static pressure phase at the moment, at this point, the road in most regions of the displacement from the point of view of value are smaller, the maximal displacement of only 1.4 microns, and near the road along the length of a third and two-thirds. When to time t = 375 s, the road in most regions of the displacement is relatively uniform, just near the road along the center of large displacement, the maximal displacement value of 0.16 microns, compared to before several stages, the road of the maximal displacement decrease significantly. Therefore, it can be proved that after experiencing the vibration compaction, the displacement of pavement structure gradually becomes smaller and the final area is flat, so the pavement structure becomes dense.
Based on analysis, this article through the establishment of two-dimensional finite element model of porous elastic medium road, the simulation calculation under the working condition of vibration compaction displacement and stress distribution of the pavement, road surface is analyzed under different compaction times mechanical properties, the results showed that:
1) With the increase of the number of compaction passes, the displacement and stress of the pavement exhibit a nonlinear change, which increases first and then decreases rapidly. When the number of rolling passes reaches six times, the
average displacement change rate between the fifth pass and the sixth pass is close to 0. From the change of the overall average displacement curve, it can be seen that the average displacement of the first pass compaction is significantly lower than that of the sixth pass, and the actual test results also show that the soil has met the compaction degree. This shows that simulation of subgrade compaction test is relatively accurate.
2) Through simulation curve, the average displacement curve, and average stress from static pressure to the weak vibration and transition to strong vibration, the load is increased, and the weak to strong vibration change when there is a change of vibration, so in the third time in real time, displacement and stress will be recovered, because the outside of the load increase, but with the increase of compaction times, displacement and stress and decrease rapidly, reduce the size of the weaker than static pressure and vibration reducing effect is more apparent, this is also reflected the strong vibration effect than the weak vibration effect is good.
3) By analyzing the pavement compaction of displacement and stress under different positions in the process of dynamic change process, found the road surface displacement and stress in the compaction process appears asymmetric distribution form, this may be due to the road the influence of the internal moisture content and pore water infiltration due to leading to the spread of the internal stress of soil.
Yang, C.M., Wei, R.N., Yao, Y.F. and Wang, Q.L. (2018) Finite Element Simulation Analysis of Compressed Material in Intelligent Compaction. Engineering, 10, 173-186. https://doi.org/10.4236/eng.2018.104012