Highway embankment slope support reinforcement?

Highway embankment slope support reinforcement is very important to understand the original intention of reinforcement in order to better combine the actual situation, each detail of the treatment is very critical. Zhongda consulting on the highway embankment slope support reinforcement and we explain.

Retaining wall is to resist soil pressure, prevent soil collapse structures, widely used in civil engineering construction, water conservancy and hydropower, railway transportation and other engineering construction. In recent years, with the development of railroads, highways and urban rail transit, often need to set up retaining walls in extremely narrow sites, dense building groups or high fill areas, and the use of a single traditional gravity, cantilevered or retaining wall, usually unable to meet the engineering requirements. In this case, consider setting up joists and piles under the retaining wall, and use the joists to transfer the force on the retaining wall to the piles, so as to meet the requirements for the bearing capacity of the foundation.

1 Project Overview

The proposed project is located in Zizhong Economic Development Zone, Neijiang, Sichuan Province, near the Chengdu-Chongqing Expressway and the railroad branch line, in the construction of the northern section of the expressway from 0+500 to the south side of 0+700, it was found that there is a 20~24m high man-made pile of slopes, the slope gradient of the slopes is about 11 or so.

The pile of the slope is mainly composed of loose vegetative fill, and in the event of flooding or pile loading, the slope may be destabilized, resulting in landslides, avalanches, or even mudslides and other undesirable geological conditions. Therefore, in order to ensure the normal operation of the nearby Chengdu-Chongqing expressway and railroad, it is necessary to carry out slope remediation before the construction of the northern branch of the expressway.

2 engineering geological conditions

2.1 terrain and geological structure

The proposed construction project terrain for the original terrain, geomorphology is a shallow hill erosion geomorphology, the distribution of round and elliptical erosion hills, hills are caught in the gully. The measured ground elevation of each exploration borehole is 356.40~377.40m, with a relative height difference of about 21m. The geological structure of the construction site is located in the east wing of the Weiyuan dorsal slope, showing monoclinic rock output, rock production: dip angle of 3~50, the site bedrock buried shallow, tectonic fissure is not developed.

2.2 Geology of the site

The drilling found that the soil layer in the construction site is made up of miscellaneous fill, plain fill, and powdery clay of the residual slope deposits of the Holocene system of the fourth system, and the bedrock underneath is made up of mudstone of the Shaximiao group of the middle Jurassic system. The situation of each stratum of soil from top to bottom is as follows:

1) Plain fill soil (Q4ml). Brown, dry~wet, composition is mainly composed of clay and sandy mudstone blocks, with a small amount of domestic garbage; loose structure, thickness 0.3~11.8m.

2) Powdery clay (Q4dl+el). Brownish-yellow and yellowish-gray, wet, plastic, with composition dominated by clay and powder grains, containing ferromanganese oxides and nodules, layer thickness 0~7.0m.

3) Mudstone (J2s). Purple-red and dark brown, sandy mud structure, thick laminated structure, the mineral composition is mainly clay minerals, the local section is sandstone lenticular body, the rock quality is soft, the rock layer dip angle is nearly horizontal. Strong weathering zone rock body is more broken, there are vertical cracks in the rock body, but not too developed, the rock core is mostly fragmented, short columnar, the rock quality is very soft, the rock core has the characteristics of water loss and pressure loss cracking, very easy to be softened, ROD value of 10%~50%; the middle weathering zone is muddy rock, the rock core is mostly columnar and long columnar, the rock core node length of 10~50cm, the rock quality is a little bit hard, the ROD value of 70%~95%, the sandy quality is increased. The section of representative stratigraphic geology is shown in Figure 2.

2.3 Site hydrology

Surface water bodies are abundant in the area of the construction site, and the main recharge water source is atmospheric precipitation. Groundwater is mainly pore water and bedrock fissure water in the fourth system soil layer, relying on atmospheric precipitation recharge. Due to the large thickness of the loose layer of the fourth system, large voids and large groundwater catchment area, the groundwater in the site is well endowed with water, and the amount of water is abundant in the flooding period. However, during the survey period for the dry season, the survey of the groundwater level buried depth of 10m below.

3 Program Selection and Design

3.1 Program Selection

Since the project is adjacent to the highway and railroad its safety importance level is high, and the proposed road side line from the red line is only 5m, there is no space for sloping. In addition, the highest difference between the topography of the construction area is about 20~24m, and the slope is mainly man-made pile of fill, the physical and mechanical parameters of the soil and the self-stabilizing ability are poor. Once the slope is destabilized, the consequences are unimaginable.

In order to ensure the stability of the permanent slope, to ensure the operation safety of the proposed road, highway and railroad, must strictly control the deformation of the supporting structure. Due to the limited scope of the construction site, the slope release can not be carried out, and this slope is mainly artificial fill, the anchor can not play its effective role, and with the traditional cantilever pile or retaining wall, its lateral displacement is difficult to control. In view of the actual situation of this project, combined with the engineering experience in this region, and considering all the factors, the slope project is proposed to adopt the program of pile foundation joist cantilever retaining wall.

3.2 Program design

Based on the topography and geomorphology of the project site, the slope support is divided into AB section and BC section. Among them, the difference in ground elevation of AB section is below 10m, the railroad line is far away from the edge of the proposed road, and the piles of the lower part of the designed retaining wall are buried in the soil; the difference in ground elevation of BC section is about 20m, adjacent to the railroad line, and the piles of the lower part of the designed retaining wall are partly exposed above the ground. At the same time, the pile foundation of AB section and BC section is considered as the utility of anti-slip pile. The schematic design of slope support and the design scheme of BC section are shown in Fig. 3 and Fig. 4.

Scheme design points:

(1) When the piles are exposed to the ground, the baffle plate (C30) is used after the anti-slip piles to block the soil between the piles. When the height of pile exposed to the ground is below 1.5m, only baffle plate A is used; if the height of pile exposed to the ground is in the range of 1.5~5m, baffle plate A+baffle plate B is used. The reinforcement of plate is determined by the height of plate Anti-slip Pile (1.5m diameter)

(2) The end of the pile is embedded in the middle-weathered rock for more than 5m and the value of the length should be greater than the distance value from the bottom of retaining wall to the top of the strong weathering rock, and the expected average length of the pile is about 25m.

4 Pile joist retaining wall construction process requirements

4.1 Construction process

Pile joist retaining wall construction process is: pile positioning manual digging hole retaining wall installation of reinforcing steel cage pouring pile body concrete pile check side joist construction retaining wall construction maintenance.

4.2 construction precautions

In the construction of retaining wall, should pay attention to the following matters: retaining wall backfill should be compacted in layers, compaction coefficient of not less than 0.90. Wall along the length of every 15~20m to set up a settlement joints (expansion joints) of 20mm wide, the joints stuffed with asphalt waterproofing, or embedded in the asphalt-coated wooden boards. The strength of the wall concrete body reaches 70% of the design strength before backfilling, and tamping in layers.

5 Deformation Monitoring

During the construction of the slope support, 10 observation points were deployed for deformation monitoring. At present, the slope support project has been completed for 1 year, the monitoring results show that the retaining wall and the soil behind the wall displacement and settlement are located in the specification allowable changes in the range, the slope is in a stable state. This also proves that the slope project support program is reliable.

6 Conclusion

The characteristics of pile foundation joist retaining wall is to expand the scope of use of general retaining wall. In the actual project, due to the limitation of surrounding land condition, excavation condition and geological condition, the use of pile foundation joist retaining wall can place the foundation in the stable stratum, in order to save the upper retaining wall cross section, reduce the project cost, and at the same time, reduce the interference to the slope. In the complex surrounding environment of the slope, a combination of methods can be used to ensure its stable characterization. At the same time, a sound monitoring system should be established during the construction so as to grasp and adjust the construction program in time to ensure construction safety. In this project, the composite program of pile-based joist retaining wall is selected, and the slope reinforcement effect is good, which is a reference for the treatment of similar slopes.

"Highway embankment slope support reinforcement" detailed information in the Zhongda Consulting construction pass, want to have all the relevant building construction information.

More about the engineering/service/procurement category of the tender writing production, enhance the winning rate, you can click on the bottom of the official website customer service free consultation:/#/?source=bdzd