Analysis of Engineering Properties and Sensitivity Factors of Geocell Retaining Wall Based on FLAC3D
Abstract: Based on the geogrid flexible retaining wall project of the base slope of the expressway highway, the engineering properties and sensitivity factors of the gravel geocell factory price retaining wall are studied. Through the FLAC3D finite difference software, the interaction between the cell unit and the fill is simulated, and the force and deformation law of the retaining wall is studied, and the physical engineering is used for comparison verification. At the same time, based on the FLAC3D strength reduction method, the sensitivity analysis of the factors affecting the stability of the retaining wall was carried out. The results show that under the overlying load of the high quality gravel geocell retaining wall, the back stress of the wall increases first along the wall back, then decreases, and then increases the wave shape distribution, and decreases from the wall back to the wall; the displacement curve of the retaining wall The slope of the wall decreases with the height of the wall and is in the form of a “net pocket”; the numerical calculation is consistent with the curve of the field test, indicating that the numerical model used is reasonable; in addition, the calculation indicates that the stability of the high quality gravel geocell retaining wall is correct for the internal friction of the fill The corner is the most sensitive. The research results have important reference value and guiding significance for the design and construction of the gravel geocell factory price retaining wall.
Keywords: gravel geocell for sale retaining wall; FLAC3D software; engineering traits; field test; sensitivity factor
The gravel geocell for sale is a three-dimensional network structure made of high-strength HDPE sheet by high-strength welding. It is widely used in water conservancy and highway because of its good adaptability, economy, stability, and ecological environment. , railways and other fields, but its theoretical research lags far behind engineering practice [1-3]. At present, the research on high quality gravel geocell mainly focuses on the horizontal laying of reinforced foundations and the protection of embankment slopes in gravel geocell factory price [4-7]. A few scholars have also studied the use of gravel geocell for sale as ecological materials for retaining walls. Some results have been achieved. Qu Zhanhui  used ANSYS software to analyze the elastoplastic simulation of the engineering behavior of the gravel geocell for sale retaining wall. Song et al.  used Plaxis software to study the effects of different aspect ratios, slopes and subgrade surface loads on the denaturing behavior of high quality gravel geocell retaining walls. Wang Gen et al  used the ADINA finite element numerical simulation analysis to consider the coupling relationship between wall and subgrade soil and studied the multi-stage flexible retaining wall of gravel geocell for sale. The force mechanism compares the force of the multi-stage retaining wall under various working conditions. However, the research on the engineering characteristics of the high quality gravel geocell retaining wall is still not perfect, and there is no systematic on-site measured data support. The research on the sensitive factors of geogrid retaining wall stability is rare. The only research is mainly on the influence of the size and slope of the retaining wall on the force and deformation of the retaining wall. The stability of the gravel geocell for sale retaining wall is sensitive. The effects of sexual factors are rarely mentioned, so further research is needed.
Based on the K126+880-K126+920 section of the expressway from Zhumadian to Xinyang (Yu’an), this paper uses the finite element analysis software FLAC3D of geotechnical engineering to calculate the stress and deformation characteristics of the gravel geocell factory price flexible retaining wall. The comparison with the measured data verifies the rationality of the numerical simulation. On this basis, the effects of high quality gravel geocell unit size, retaining wall aspect ratio, average slope ratio, fill weight, cohesion and internal friction angle on the stability of gravel geocell for sale retaining wall are studied. factor. It has certain reference significance for engineering design.
1. Project Overview
A geogrid ecological retaining wall is the latest development of reinforced soil technology. Compared with traditional supporting structures, it has the advantages of high strength, less amount of work, beautiful appearance and good ecological performance . In order to reduce land occupation, save project cost and create an ecological and environmentally friendly highway environment, the K126+880-K126+920 section of the Zhixin Expressway adopts the geogrid ecological retaining wall support scheme. Figure 1 is a schematic cross-sectional view of the retaining wall with a depth of 0.4 m and a base of 2.6 m high. The wall is made up of 13 layers of high quality gravel geocell. Each floor is 20 cm high and each compartment is 2 cm. The outer side is connected with a 40 cm high baffle and the total height of the retaining wall is 1 m. The top is the pavement structure, 1 m high. In order to study the stress and deformation characteristics of a geogrid ecological retaining wall and guide the engineering construction, this paper takes this gravel geocell factory price retaining wall as an example for numerical simulation analysis.
Figure 1 Schematic diagram of the geotechnical compartment ecological retaining wall
2. Establishment and parameter selection of FLAC3D model for geocell retaining wall
In this paper, the finite difference software FLAC3D of Itasca Company of USA is used as the simulation analysis software, and the simulation analysis model is established according to Figure 1 . Since FLAC3D does not have a unit for simulating the high quality gravel geocell, and the geogrid performance is very similar to that of the cell, the cell can be approximated as being vertically stretched by a two-dimensional grid. Therefore, the gravel geocell for sale is FLAC3D since the calculation. The lateral and longitudinal layout of the Geogrid unit is simulated . This unit simulates the friction characteristics between the soil through the spring-slider system. The properties of the reinforcement are shown in Table 1. The Mohr-Coulomb model is used for foundation, grid fill, roadbed fill, and pavement structure. The parameters are shown in Table 2. The model is provided with contact surface units at the interface between the gravel geocell for sale structural layer, the cell, and the fill, and the foundation and the fill to simulate the mutual interaction between the cell layers, the cell and the fill, and the foundation and the fill. Function , the meshing is shown in Figure 2. This paper calculates the force and deformation performance of the gravel geocell factory price wall and wall back in the natural state.
Table 1 Mechanical parameters of the ribbed material and the reinforced soil interface
Table 2 Mechanical parameters of rock and soil
Figure 2 Schematic diagram of meshing
3. Numerical simulation of engineering properties
In order to study the stress and deformation laws of the wall, a total of 39 monitoring points were recorded to record the stress and deformation of the retaining wall. The monitoring points are arranged as shown in Figure 3.
Figure 3 Schematic diagram of monitoring point layout
Fig. 4 is a horizontal stress cloud diagram after the retaining wall is stabilized, and Fig. 5 is a horizontal displacement cloud map. As can be seen from Fig. 4 and Fig. 5, the force form of the high quality gravel geocell retaining wall is similar to that of the unreinforced side slope, and the gravel geocell factory price compartment is ecologically blocked. The wall merges with the slope to treat the retaining wall as a reinforced slope.
Figure 4 Horizontal stress cloud map
Figure 6 shows the force curve of the wall and wall back of the high quality gravel geocell retaining wall. Figure 6 shows that the active earth pressure on the monitoring surface of the retaining wall increases first, then decreases and then increases the distribution along the top of the wall. Taking the wall back as an example, the earth pressure from 0 to 0.4 m below the top of the wall gradually increases from 3.3 kPa to 4.6 kPa, the pressure from 0.4 m to 0.8 m gradually decreases to 3.9 kPa, and the pressure at the bottom of the wall gradually rises from 0.8 m to the bottom of the wall. At 5 kPa. The active earth pressure from the back of the wall to the wall is decreasing, and the pressure at the bottom of the wall is 5 kPa, 4.7 kPa, and 4.5 kPa, respectively.
Figure 5 Horizontal displacement cloud map
Figure 6 Horizontal stress calculation curve of retaining wall
Fig. 7 is the strain curve of the wall and wall back of the gravel geocell factory price retaining wall. It can be seen from Fig. 7 that the deformation from the back of the wall to the wall gradually becomes obvious and the displacement is nonlinearly distributed along with the wall height, showing the form of “net pocket”. The displacement increases first and then decreases along the top of the wall to the wall. The displacement from 0 to 1.8 m gradually increases to 1.7 cm, and the displacement from 1.8 m to the wall foot gradually decreases to 1.1 cm.
Figure 7 Horizontal displacement calculation curve of retaining wall
4. Comparison of numerical simulation results with field test results
During the on-site construction of the gravel geocell factory price retaining wall, the JXY-type earth pressure box produced by Dandong Liaodan Instrument Co., Ltd. was buried at the monitoring point, and the observation data was completed after 150 days of construction. Figure 8 shows the comparison of measured values of lateral earth pressure and finite element calculations. In physical engineering, due to the limited number of pressure boxes buried, the measured pressure value can not continuously reflect the wall and wall back soil pressure changes, but from the wall back and the wall body measured point pressure connection can be seen, the earth pressure measured curve is two large, middle Small concave distribution, and the inflection point appears at 0.4 m, the maximum appears at the bottom of the wall, from the wall back to the wall are 4 kPa, 4.3 kPa, 5.6 kPa. Compared with the calculated curve, the measured curve also has a concave distribution with two large and small intermediate points. The position of the curve inversion point is consistent with the calculated curve, and the difference between each measuring point is less than 15%. Figure 9 is a comparison curve between the measured values of wall deformation and the calculated values of finite elements. In physical engineering, the RTS-822A infrared total station produced by Guangzhou Guide Instrument Co., Ltd. observes the deformation of the wall gravel geocell factory price. It can be seen from the observation curve that the deformation of the retaining wall increases first along the top of the wall and decreases after reaching a certain value. In the shape of a “net pocket”, the maximum displacement occurs at 0.6 m from the wall toe, reaching 15.8 mm. Compared with the calculated curve, the measured curve also shows the same trend distribution, and the maximum value also appears near 0.6 m. The difference between the measured value and the calculated value of each measuring point is less than 20%.
Figure 8 Comparison of calculated and measured values of retaining wall stress
Fig. 9 Comparison of calculated and measured values of horizontal displacement of retaining wall
It can be seen from the above results that the calculation results are basically consistent with the measured results gravel geocell factory price, which indicates that the FLAC3D calculation model can better simulate the working behavior of the high quality gravel geocell retaining wall and verify the reliability of the measured results.
5. Analysis of sensitive factors of geocell retaining wall stability
Based on the above research, this paper selects six factors that affect the stability of the gravel geocell factory price retaining wall, namely the size of the high quality gravel geocell unit, the aspect ratio of the retaining wall, the average slope ratio, the filling weight, the cohesion, and the internal The friction angle , each factor is taken at 8 different levels, with a single factor as the variable, the overall stability coefficient K is determined by FLAC3D calculation, and the multi-factor single-index calculation is analyzed with the stability safety factor as the index. The values of each factor are shown in Table 3. The relationship between the stability coefficient and related parameters is shown in Figure 10 to Figure 16.
Table 3 Table of factors affecting the stability
It can be seen from Fig. 10 that as the height of the cell unit increases, the K value of the stability coefficient increases little. When the height increases by a factor of 1, that is, from 100 mm to 200 mm, the stability factor K value increases by only 0.05. , an increase of 1.3%. It can be seen from Fig. 11 that as the cell gap increases, the K value of the stability coefficient decreases, but the amplitude is not large. When the welding distance increases from 100 mm to 400 mm, the K value decreases by 0.08, a decrease of 3.4. %, indicating that cell height and weld spacing have no significant effect on overall stability.
Figure 10 K-cell unit height relationship curve
Figure 12 shows that the overall stability factor is significantly affected by the aspect ratio. As the aspect ratio increases, the height H of the retaining wall increases, and the width B decrease. The stability is approximately linear and gradually decreases. The retaining wall increased from an aspect ratio of 1.0 to 4.5, and the K value decreased by 0.8, a reduction of 37%. Figure 13 shows the relationship between the slope ratio and the stability factor gravel geocell for sale. Figure 13 shows that the slope ratio has little effect on the stability factor. As the slope ratio decreases, the stability factor K increases more slowly. The retaining wall increased from an upright to a slope of 0.7, and the K value increased by only 0.3, an increase of 13.6%.
Figure 11 K-cell welding pitch curve
Figure 12 K-Aspect Ratio H/B Curve
Figure 13 K-slope ratio curve
Figure 14 K-γ relationship curve
Figure 14 shows that the stability coefficient K is not significantly affected by the weight γ of the fill. As the γ increases, the K value decreases less. The fill γ increased from 16 kN/m3 to 23 kN/m3, and the K value decreased by only 0.3, which was 12.5%. Figure 15 is the relationship between the internal friction angle φ and the stability coefficient K. Figure 15 shows that the stability coefficient is significantly affected by the internal friction angle of the fill gravel geocell for sale, that is, as the internal friction angle φ increases, the stability coefficient K is The linear relationship is gradually increasing. The internal friction angle increased from 20° to 34°, and the stability factor increased by 0.81, an increase of 74.3%.
Figure 15 K-φ relationship curve
It can be seen from Fig. 16 that as the cohesion c increases, the stability coefficient K increases little and is approximately horizontal. When the cohesion c value increases from 20 kPa to 36 kPa, the stability coefficient K increases only by about 0.09, and the growth rate is 4.5%, indicating that its stability is minimally affected by the cohesion c value.
Figure 16 K-c relationship curve
Through the sensitivity analysis of the six factors affecting stability, the following conclusions can be drawn: the internal friction angle is the most important sensitive factor affecting the stability of the retaining wall. As the value of φ increases, the linear relationship of stability increases. Large, and the rate of change is very fast; the aspect ratio H/B of the retaining wall has a significant effect on the stability. As the aspect ratio increases, the stability gradually decreases with a larger extent gravel geocell for sale; the slope of the retaining wall also has a certain stability. Influence, with the increase of the slope, the stability gradually increases with a small increase; while the soil compactness, cohesion c, and cell size are less sensitive to stability, with little effect. In summary, among the six influencing factors, the sensitivity is ranked from the largest to the smallest, the internal friction angle of the fill > the aspect ratio of the retaining wall > the slope > the filling weight > the filling cohesion > the cell unit size.
(1) The back stress of the high quality gravel geocell retaining wall increases first along the wall back, then decreases, and then increases the wave shape distribution, and decreases from the wall back to the wall. The slope of the displacement curve of the wall of the retaining wall decreases with the height of the wall and is in the form of a “net pocket”.
(2) The calculation result of FLAC3D numerical analysis is consistent with the trend of the field-measured curve. The calculated value is basically equal to the measured value, which indicates that it is reasonable to use FLAC3D to simulate the gravel geocell factory price retaining wall, which can better simulate the working behavior of high quality gravel geocell retaining wall.
(3) Factor sensitivity analysis shows that the stability of the gravel geocell for sale retaining wall is most sensitive to the internal friction angle of the fill. With the increase of the internal friction angle, the stability increases continuously; the aspect ratio of the retaining wall has a greater impact on stability. The rest is followed by slope, heavy soil filling, soil cohesion, and cell unit size. Therefore, in the actual project, the reasonable selection of the gravel geocell factory price filler is the key to ensure the stability of the gravel geocell for sale retaining wall.