CN203334154U - Embankment structure for preventing bearing platform of pile foundation from stretching in roadbed under viaduct - Google Patents

Abstract

The utility model relates to an embankment structure in which pile caps under viaducts extend into roadbeds. The structure is mainly composed of roadbed treatment piles, pile tops connecting vertically and horizontally to cover beams, light filler layers, solidified soil backfill layers, and transverse reinforcement layers. Composition; subgrade treatment piles are set in the subgrade, and the pile tops are preset with connecting steel bars; vertical and horizontal connecting cap beams are poured on the subgrade treatment pile tops, and the connection with the pile body is strengthened through the pile top connection reinforcement bars; the subgrade is composed of solidified soil and light filler. Layer backfill with transverse reinforcement layer inside. The utility model can effectively improve the integrity of the embankment structure under the viaduct, improve the performance of the roadbed filler, reduce the weight of the filler, and solve the longitudinal cracks and waves of the road surface caused by the uneven settlement of the roadbed caused by the extension of the cap into the roadbed. technical and economic benefits.

Description

An embankment structure in which the pile cap under the viaduct extends into the subgrade

technical field

The utility model belongs to the field of foundation treatment, and relates to a combination control structure for subgrade deformation under a viaduct, in particular to an embankment structure in which pile caps under a viaduct extend into the subgrade. It has multiple advantages such as integrity and reduced filler weight, and is suitable for subgrade treatment projects under viaducts in highways and municipal roads in soft soil areas, especially for subgrade treatment where viaduct caps extend into the subgrade and may cause cracks on the road surface. the

Background technique

With the increasing demand for urban traffic, the proportion of viaducts and overpasses in urban traffic planning is increasing. However, due to the small width of the central isolation green belt of urban roads, when the size of the designed pile cap is large, the bridge Pile caps often extend into the subgrade below the roadway under the viaduct, seriously affecting the integrity of the subgrade structure. At the same time, due to the wide distribution of soft soil in the coastal provinces of my country, it has the characteristics of high water content, high compressibility, poor permeability, high sensitivity, low strength and uneven thickness, etc., the roadbed structure is easy to be damaged under the upper traffic load. There is a more obvious post-construction settlement. the

A large number of projects have shown that for viaducts and overpass bridges built in soft soil areas, due to the small settlement of bridge pile foundations and large subgrade settlements, if there is no effective control measure and structure for the deformation of the subgrade under the viaduct, it will be difficult for road construction. Benefits and driving quality have many adverse effects or safety hazards. For example, the subgrade soil settlement will produce lateral friction resistance on bridge piles, which will change the mechanical performance of the pile body; the uneven settlement deformation of the subgrade will cause longitudinal cracks or cracks near the edge of the cap. Road surface rutting and other engineering diseases shorten the maintenance period of the road; the deformation of the subgrade structure will affect the performance of the pavement structure, which in turn will affect the driving comfort, reduce the road traffic capacity, and even cause driving safety hazards. the

At present, the measures to deal with the above problems in various regions mainly include overlaying, excavation and replacement of lightweight materials, and grouting. The overlay method is to add pavement materials above the surface of the original pavement. Although this method can quickly make up for the settlement difference between road sections and quickly improve the traffic conditions of the road, because it fails to improve the bearing performance of the underlying foundation, the overlay layer It will increase the weight of the pavement structure, which is not good for the settlement control of the soft foundation, and it is easy to appear a vicious circle of more overlays and more settlement, and the engineering cost of multiple overlays is also high. The grouting method is to press a certain amount of cement slurry into the reinforcement area through the grouting pipe, and improve the bearing capacity of the roadbed by solidifying the roadbed soil. However, this reinforcement measure is aimed at strengthening the shallow soft foundation or the upper roadbed. It is difficult to inject grout into the relatively hard soil layer when it is deep, and it is also difficult to inject grout into the center of the embankment for a wide section of the roadbed. The subgrade structure deforms unevenly under the overlying load. Light material replacement is to use light material instead of the original filler to fill the embankment. This method has a good pretreatment effect on reducing the overlying load of the subgrade and reducing the overall settlement of the road surface. However, when it is adopted on a large scale, the engineering cost will increase It is relatively high, and because the filler itself has low bearing capacity and poor shear resistance, it is insufficient to deal with the deformation of the pavement structure caused by the difference between the settlement of the viaduct pile foundation and the road surface, especially under the condition of soft soil foundation. Replacing the subgrade filler with lightweight materials can reduce the weight of the embankment load, but this method is difficult to improve the integrity of the soil in different areas within the subgrade range, and it is difficult to coordinate and control the uneven deformation of the subgrade, and it is also difficult for the soil to resist bending. The improvement effect of pulling performance is relatively limited. Therefore, if the embankment is filled with lightweight filler, it is necessary to improve the shear and bending resistance of the embankment. the

To sum up, at present, the treatment of road diseases and subgrade deformation problems under viaducts in the engineering field is mainly based on after-the-fact remedial methods, such as overlaying, excavation, replacement of light materials, and grouting. A more satisfactory treatment effect has also been obtained. However, generally speaking, since these methods do not involve the structural optimization of the embankment, their improvement effects are limited, and it is difficult to fundamentally solve the problem of deformation coordination of embankment filling under bridge piles, and even a vicious circle will appear in which the more the remedy is made, the more serious the problem will be. the

In view of the above-mentioned technical background, in order to better prevent and control the road disease problems that may be caused by the pile cap under the viaduct extending into the subgrade, and improve the construction efficiency of the road, it is urgent to invent a reasonable embankment structure under the bridge, so that it can be effectively Reduce the deformation of the subgrade soil under the viaduct, improve the performance of the subgrade filler, improve the integrity of the embankment filler, and reduce the weight of the filler. the

Contents of the invention

The purpose of this utility model is to invent a new type of subsidence that can effectively prevent the uneven settlement of the road under the viaduct and improve the performance of subgrade filling by combining the three settlement control measures of strengthening the subgrade, reducing the overlying load and enhancing the cooperative mechanical performance of the subgrade structure. The subgrade disease prevention and control structure under the viaduct. the

In order to achieve the above-mentioned technical purpose, the utility model adopts the following technical solutions:

An embankment structure in which pile caps under a viaduct extend into the subgrade, characterized in that the structure is mainly composed of subgrade treatment piles, pile top vertical and horizontal connection cover beams, lightweight filler layers, solidified soil backfill layers, and transverse reinforcement layers ; Set roadbed treatment piles in the roadbed, and the pile tops are preset with connecting steel bars; the vertical and horizontal connecting cap beams are poured on the tops of the roadbed treatment piles, and the connection with the pile body is strengthened through the pile top connecting steel bars; the roadbed is layered with solidified soil and light filler Backfilling with transverse reinforcement layer inside.

The subgrade treatment piles are weakly compacted soil piles and non-compacted soil piles. The pile body is 500mm~800mm away from the edge of the viaduct cap, penetrates the weak ground base, and is driven into the bearing layer by 500mm~2000mm. The pile spacing is 3000mm~4000mm. Arranged at equal intervals, the pile length is selectively reduced or kept constant according to the principle of smooth transition of settlement. the

The vertical and horizontal connecting cover beams at the top of the pile are cast-in-place reinforced concrete cover beams in the shape of a well, and the cover beams on the top of the edge piles extend 600-1000mm short-distance cantilever, and the width of the cover beams is 1-2 times the diameter of the foundation treatment piles; the cover beams The inner steel bar is connected with the top steel bar of the subgrade treatment pile by welding or binding. the

The solidified soil backfill layer is formed by mixing the excavated soil of the original roadbed with a solidifying agent, and is solidified to 600mm~1200mm below the bottom of the pile top vertically and horizontally connecting the cover beam, and its thickness is 1500~3000mm. The curing agent is cement, lime or Soil stabilizer. the

The light filler is light soil mixed with air bubbles, light soil mixed with foam beads or light soil mixed with EPS particles. the

The horizontal reinforcement layer is high-strength steel mesh or steel-plastic geogrid, and one or more layers are set according to the coordination requirements of filler deformation. the

The construction method of the embankment structure that the pile cap under the above-mentioned viaduct stretches into the subgrade comprises the following steps:

1) Preparation before construction: According to the design drawings, process the construction site, measure the pile position, and draw the outline of the pile position;

2) Take soil to form a hole: drill a hole to take soil, if necessary, it should be supplemented with mud wall or buried casing;

3) Construction of subgrade treatment piles: After clearing the holes, construct the foundation treatment piles in the holes, control the depth of the pile body into the soil according to the design requirements, and preset the steel bars connected to the vertical and horizontal connecting cover beams at the top of the piles;

4) Excavation and backfilling with solidified soil: After the strength of the subgrade treatment piles meets the design requirements, a combination of manual excavation and mechanical excavation is used to excavate the subgrade and fill soil to the design elevation below the pile top, and the excavated soil is solidified. Backfill layer by layer to the top of the pile;

5) Construction of pile top vertically and horizontally connected cover beams: After the backfill soil has a certain strength, a formwork is set on the pile tops of the subgrade treatment piles, and the preset steel bars on the pile tops are connected with the vertically and horizontally connected steel bars of the cover beams, and the pile tops are poured vertically and horizontally connecting cover beams;

6) Fill the solidified soil: After the vertical and horizontal connection cap beams at the top of the pile reach the design strength, remove the formwork and continue to fill the solidified backfill soil layer by layer;

7) Laying of the transverse reinforcement layer: After the solidified soil is laid, the transverse reinforcement layer is laid and stretched;

8) Pave light soil: After compacting and solidifying the backfill soil, pave the light filler layer;

9) Pavement structural layer construction: carry out pavement structure construction according to the design requirements.

The utility model has the following characteristics and beneficial effects:

(1) Using weakly compacted soil and non-compacted soil piles for subgrade treatment can reduce the impact of pile construction on the adjacent viaduct pile cap; the length of subgrade treatment piles is selectively reduced or kept constant according to the principle of smooth transition of settlement It can better coordinate the deformation of subgrade soil.

(2) The vertical and horizontal connecting cap beams are integrally cast in-situ, and are integrated with the weakly squeezed soil piles through the reserved steel bars at the top, which can not only effectively improve the integrity of the subgrade structure, but also reduce the load on the weak soil layer. the

(3) The embankment filler uses air bubbles to mix light soil and solidified soil, which can not only reduce the weight of the filler, but also increase the strength of the embankment filler, and can also reduce the amount of embankment earthwork handling. The use of air bubbles to mix light soil has higher strength, The characteristics of water resistance and durability can also save the construction of water stabilization layer in roadbed construction. the

(4) A transverse reinforcement layer is set between the air-bubble mixed light soil and the solidified soil and within the solidified soil layer to improve the shear resistance of the subgrade, which can simultaneously enhance the integrity of the filler, adjust the upper load distribution, and coordinate the deformation of the embankment . the

In a word, the utility model is characterized in that the load is transmitted to the bearing layer of the subgrade through weakly squeezed soil piles, the integrity and anti-settlement ability of the embankment structure are enhanced by setting vertical and horizontal connecting cover beams, and the filler is improved by backfilling solidified soil and light soil It has good technical and economic benefits by setting the transverse reinforcement layer to enhance the coordinated deformation ability of the filler. the

Description of drawings

Figure 1 is a schematic elevation view of the embankment structure where the pile cap under the viaduct extends into the subgrade;

Fig. 2 is a sectional view along line A-A of Fig. 1;

Fig. 3 is a sectional view along line B-B of Fig. 1;

Fig. 4 is a sectional view along line C-C of Fig. 1;

In the figure: 1—subgrade treatment pile, 2—reinforcing cage, 3—soft soil layer, 4—bearing layer, 5—pavement structure layer, 6—light soil layer, 7—transverse reinforcement layer, 8—cured backfill Soil layer, 9-pile top vertical and horizontal connection cover beam, 10-curb stone, 11-green belt, 12-isolation fence, 13-bridge pier, 14-pile foundation cap, 15-viaduct pile foundation.

Detailed ways

Design and construction technical requirements of bridge pile foundations and pile caps, design and construction technical requirements of weakly squeezed soil piles, steel bar stacking, hoisting, and binding construction technical requirements, concrete mix ratio design and construction technical requirements, etc., in this embodiment No more repetitions, emphatically explain the embodiment of the utility model related to the structure. the

Fig. 1 is a schematic elevation view of the embankment structure with pile caps extending into the subgrade under the viaduct; Fig. 2 is a sectional view of Fig. 1 along line A-A; Fig. 3 is a sectional view of Fig. 1 along line B-B; Fig. 4 is a sectional view of Fig. 1 along line C-C Sectional view. Referring to Figures 1 to 4, the embankment structure where the pile cap under the viaduct extends into the subgrade is mainly composed of subgrade treatment piles 1, light soil layer 6, transverse reinforcement layer 7, solidified soil backfill soil layer 8, pile top vertical and horizontal Connect the cover beam 9 and other parts to form. the

The foundation treatment pile 1 adopts bored cast-in-situ pile, the pile diameter is 400 mm, and the distance between the pile body and the pile cap 14 of the viaduct is 500 mm. The depth of the long piles driven into the bearing layer 4 is 1000mm, and the depth of the short piles driven into the bearing layer 4 is 500mm; the concrete strength grade of the pile body is C30, and the longitudinal reinforcement of the reinforcement cage 2 is HRB335 (diameter 16mm) threaded steel bar, and the spiral bar uses HPB300 (diameter 8mm) smooth steel bar. The length of the longitudinal reinforcement of the reinforcement cage 2 protruding from the top of the pile is 200 mm, which is used as the connecting reinforcement connecting the vertical and horizontal cover beams 9; the specific construction requirements of the subgrade treatment pile 1 comply with the current regulations, and the net height requirements of construction equipment are lower than those of viaducts height, avoid as much as possible the impact on the pile cap 14 and the viaduct pile foundation 15 when the construction foundation handles the pile. the

The vertical and horizontal connection cover beam 9 at the top of the pile is a reinforced concrete integral cast-in-place cover beam, the concrete strength grade is C30, the width of the cover beam in the subgrade filling area is 500mm, and the height is 400mm. The top extends 600mm short-distance cantilever; the longitudinal steel bar connecting the cover beam 9 vertically and horizontally adopts HRB335 (16mm in diameter) threaded steel bar, and the stirrup adopts HPB300 (8mm in diameter) smooth steel bar; the longitudinal steel bar connecting the cover beam 9 vertically and horizontally Binding connection with the longitudinal reinforcement of reinforcement cage 2. the

The solidified backfill soil layer 8 is formed by mixing and stirring the soil taken out from the borehole, excavated part of the soil, and waste soil when the site is leveled. The mixing ratio is 8% (mass ratio). The thickness of the solidified soil backfill layer is 2000mm, including the bottom 1000mm of the pile top vertically and horizontally connecting the cover beam and the 600mm from the bottom of the light soil layer 6 to the top surface of the pile top vertically and horizontally connecting the cover beam 9, and the gap between the pile top vertically and horizontally connecting the cover beam 9 Backfilling is also done, and a layer of transverse reinforcement layer 7 is laid on the top surface of the pile top vertically and horizontally connecting the cover beam 9, and the solidified backfill convex layer 8 extends to the surroundings of the pier 13. the

The transverse reinforcement layer 7 is made of steel-plastic geogrid, the tensile yield force per linear meter of steel-plastic geogrid is ≥80kN/m, and the yield elongation is ≤3%. Lay the grid slowly forward with a paving machine or manually, and manually straighten it every 10 meters long, and connect the overlapping parts of the geogrid along the horizontal direction of the roadbed with 8# iron wire every 1000mm, and then Use U-shaped nails to anchor every 1500mm on the laid grid. the

Lightweight soil layer 6 is made of light soil mixed with air bubbles, and is located under the pavement structure layer with a thickness of 500mm, and the embankment within the range under the viaduct is laid with the same thickness. The mix ratio of air-bubble mixed light soil should be selected according to the design strength, wet bulk density, fluidity and other requirements. The design wet bulk density of air-bubble mixed light soil is not greater than 6.5kN/m3, and the 28-day unconfined compressive strength is not low At 0.8MPa, 32.5# ordinary Portland cement is used for cement, and the proportion of air bubbles is not less than 65%; a layer of transverse reinforcement layer 7 is laid on the contact surface between the light soil layer 6 and the solidified backfill soil layer 8 . the

The main construction steps of the embankment structure where the pile foundation cap under the viaduct extends into the subgrade using bored piles as subgrade treatment piles are as follows:

1) Preparation before construction. According to the design drawings, process the construction site, measure the pile position, and draw the outline of the pile position.

2) Take soil to form a hole. Drilling for soil, if necessary, should be supplemented with mud retaining wall or buried casing, and the pile length shall be determined according to the design requirements. the

3) Construction of subgrade treatment piles. After clearing the hole, lower the reinforcement cage 2, the top surface of the reinforcement cage 2 is 400mm higher than the opening, after the reinforcement cage 2 is placed, pour concrete to form the subgrade treatment pile 1. the

4) Excavate and backfill with solidified soil. After the strength of the subgrade treatment pile 1 meets the design requirements, excavate the subgrade filling soil 3 to 1000mm below the top surface of the subgrade treatment pile 1 by combining manual excavation and mechanical excavation. Evenly pave and backfill to the top of the pile to form the lower solidified backfill soil layer 8 . the

5) Construction of pile top vertically and horizontally connected cover beams. After the solidified backfill soil layer 8 at the lower part of the subgrade treatment pile 1 reaches the design strength, a formwork is set up on the pile top of the subgrade treatment pile. The reinforced steel bars are poured into concrete to form pile top vertically and horizontally connecting cap beams 9. the

6) Fill the solidified soil. After the vertical and horizontal connecting cover beams 9 at the top of the pile reach the design strength, the formwork is removed, the first horizontal reinforcement layer 7 is laid, stretched and fixed, and then the solidified backfill soil layer 8 is filled layer by layer. the

7) Laying of transverse reinforcement layer. After the solidified backfill soil layer 8 is filled, the second layer of transverse reinforcement layer 7 is laid, stretched and fixed. the

8) Spread light soil. Pave an appropriate thickness of air-mixed light soil layer 6. the

9) Construction of pavement structure layer. Carry out the construction of pavement structure 5, curb stone 10, green belt 11, isolation fence 12, etc. according to the design requirements. the

Claims (5)

1. under a viaduct, pile foundation support table stretches into the embankment structure of roadbed, it is characterized in that described structure mainly processes stake, stake top by roadbed and form to connecting bent cap, light filler layer, solidified earth backfill layer, transversal reinforcement layer in length and breadth; Roadbed is set in roadbed and processes stake, the default connecting reinforcement in stake top; Build in roadbed processing stake stake top to connecting bent cap in length and breadth, strengthen being connected with pile body by stake top connecting reinforcement; Roadbed adopts solidified earth and light filler back-filling in layers, inside establishes the transversal reinforcement layer.

2. under viaduct according to claim 1, pile foundation support table stretches into the embankment structure of roadbed, it is characterized in that it is weak soil compaction, non-Squeezing Soil Pile that described roadbed is processed stake, pile body is apart from viaduct cushion cap edge 500mm ~ 800mm, penetrate flabbily basic unit, squeeze into bearing stratum 500mm ~ 2000mm, pile spacing is 3000mm ~ 4000mm, and in length and breadth to uniformly-spaced arranging, stake is long optionally to be reduced or remains unchanged according to the smooth-going transition principle of sedimentation.

3. under viaduct according to claim 1, pile foundation support table stretches into the embankment structure of roadbed, it is characterized in that described stake top is steel concrete integral cast-in-situ bent cap to connecting bent cap in length and breadth, be groined type, stake roof rail in edge is extended 600 ~ 1000mm short distance cantilever, and the bent cap width is 1 ~ 2 times that ground is processed stake stake footpath; In bent cap, reinforcing bar is connected with a roadbed processing stake top rebars, and connected mode is that welding or colligation connect.

4. under viaduct according to claim 1, pile foundation support table stretches into the embankment structure of roadbed, it is characterized in that described light filler is air bubble mix light-textured soil, foam beads mix light-textured soil or EPS particle light soil.

5. under viaduct according to claim 1, pile foundation support table stretches into the embankment structure of roadbed, it is characterized in that described transversal reinforcement layer is high strength reinforcement mesh sheet or steel plastic geogrid, according to the filler compatibility of deformation, requires one or more layers is set.

Images