Isolation type soft soil foundation widening roadbed differential settlement control structure and method

Abstract

The invention discloses an isolation type soft soil foundation widening roadbed differential settlement control structure and method, and the structure comprises a pavement structure layer excavated on the shoulder side of old road roadbed filling, multiple steps formed by roadbed filling, new road roadbed filling formed by layered filling on the outer sides of the steps, and a new road pavement structure layer at the top of the new road roadbed filling. Geogrids and multi-foot anchoring components are laid on the tops of all stages of steps, U-shaped nails of the multi-foot anchoring components are inserted into step filling soil to be connected with the geogrids, multiple rows of capped piles are arranged on the lower portion of new roadbed filling soil at equal intervals to form a composite foundation, a row of lifting anti-slide piles are arranged on the inner sides of the capped piles, and the tops of the lifting anti-slide piles are arranged on the tops of the steps. Isolation steel sheet piles are arranged in the middle of the topmost step and connected through L-shaped connecting grooves, and the bottoms of the isolation steel sheet piles penetrate through a soft soil layer to penetrate into a supporting layer. The method has the beneficial effects that the additional settlement of the old road foundation caused by the filling load of the new road subgrade of the isolation widening section is solved, and the differential settlement of the new and old subgrade is effectively controlled.

Description

Technical Field

[0001] This invention belongs to the field of civil engineering technology, specifically relating to a structure and method for controlling differential settlement of roadbed widening in isolated soft soil foundations. Background Technology

[0002] The number of existing highway reconstruction and expansion projects is gradually increasing. The main method of highway reconstruction and expansion projects is to widen the existing highway. While maintaining traffic flow on one side of the existing highway, the pavement and ancillary structures at the edge of the existing roadbed are demolished. Then, steps are excavated on the slope of the existing roadbed, and the foundation beneath the widened section is treated. After the foundation treatment, the new roadbed of the widened section is filled in layers to the design elevation. Finally, the pavement structure layer of the widened section is constructed to complete the splicing of the old and new roadbeds. Because the stress history of the roadbed fill and the foundation soil beneath the old and new roadbeds are different, there are significant differences in the strength, deformation, and other mechanical properties between the old and new roadbed fill and the foundation soil. In addition, the foundation treatment methods of the old and new roadbeds are often different. Therefore, after the roadbed is widened, differential settlement between the old and new roadbeds will inevitably occur with the extension of service time, leading to the appearance of longitudinal cracks in the pavement, reducing the serviceability of the roadbed, and in severe cases, even causing local collapse of the roadbed. Furthermore, since highway reconstruction and expansion projects are mainly located in developed coastal areas of my country, these areas generally have continuous and deep soft soil layers. The long-term settlement of soft soil foundations further exacerbates the differential settlement problem of the reconstruction and expansion roadbeds. Therefore, how to develop an effective technology for controlling differential settlement of roadbeds widened on soft soil foundations is a pressing technical challenge facing highway reconstruction and expansion projects in my country.

[0003] Existing differential settlement control technologies for widened roadbeds are mainly divided into three types. The first type controls differential settlement by increasing the integrity of the spliced ​​roadbed. This is achieved by excavating steps on the existing roadbed and installing geogrids at the splice of the old and new roadbeds and in the pavement structure layer to increase the integrity and tensile strength of the spliced ​​roadbed and pavement. The second type controls differential settlement by coordinating the foundation stiffness of the old and new roadbeds. This involves adjusting the foundation treatment method according to the settlement distribution of the old and new roadbeds after widening construction to coordinate the foundation stiffness of the old and new roadbeds. The third type controls differential settlement by reducing the additional load on the widened roadbed. This involves using lightweight fillers such as foamed concrete to reduce the additional load and thus reduce the differential settlement between the old and new roadbeds.

[0004] The existing roadbed settlement technology for reconstruction and expansion has the following problems: 1. Although excavation steps and geogrid reinforcement can enhance the integrity of the new and old roadbeds, the improvement is limited. When the old roadbed experiences significant settlement under the additional load of the new roadbed in the widened section, or when the new roadbed experiences cumulative settlement over time due to the time effect of soft soil foundation, measures such as excavation steps and geogrid reinforcement cannot effectively control the differential settlement between the new and old roadbeds.

[0005] 2. The stiffness coordination method for new and old roadbed foundations has high requirements for the settlement calculation of the foundation under additional loads. Since the distribution of additional loads on widened roadbeds is more complex, and the foundation treatment methods of old roads are often different from those of new roads, the complexity of load distribution and the difference in foundation treatment methods make it difficult to accurately estimate the settlement distribution of the foundations of new and old roadbeds. Therefore, the foundation stiffness coordination method is also difficult to achieve ideal results.

[0006] 3. Lightweight subgrade filler can effectively reduce the additional load of widened subgrade, reduce the long-term settlement of new roadbed and the additional settlement caused by the additional load of widened subgrade on old roadbed. However, lightweight subgrade filler often uses foamed lightweight soil, which requires high construction level and maintenance conditions, and is prone to cracking and other problems that affect the integrity of the subgrade. In addition, the cost of this material is currently high, and it is usually only used in bridge abutment and culvert transition sections and road sections where settlement needs to be strictly controlled.

[0007] 4. Currently, the widened roadbed generally adopts a pile-supported reinforced embankment structure system consisting of a capped pile composite foundation, a reinforced crushed stone cushion layer, and embankment fill. This structure can effectively reduce the construction settlement and post-construction settlement of the widened roadbed, but it still cannot effectively control the additional settlement impact of the widened embankment load on the foundation below the old road. This is the main problem currently faced in the construction of widened roadbeds on soft soil foundations. Summary of the Invention

[0008] To address the shortcomings of existing technologies, this invention provides an isolated differential settlement control structure and method for widened roadbeds in soft soil foundations. It effectively controls the settlement and deformation of the widened roadbed, while simultaneously increasing the integrity of the new and old roadbeds and reducing the impact of the additional load from the widened section on the settlement of the underlying foundation, thereby effectively controlling the differential settlement between the new and old roadbeds.

[0009] This invention is achieved through the following technical solution: This invention provides an isolated differential settlement control structure for widened roadbeds in soft soil foundations. It includes a pavement structure layer excavated on the shoulder side of the old roadbed fill and multiple steps formed by the roadbed fill; new roadbed fill formed by layered filling outside the steps; and a new pavement structure layer on top of the new roadbed fill. Geogrids and multi-legged anchoring components are laid on top of each step. The multi-legged anchoring components are composed of multiple U-shaped nails, which are inserted into the step fill and connected to the geogrid. The geogrid is permeable... Multiple anchoring components are fixed to the inner end of each step. Multiple rows of capped piles are set at equal intervals in the lower part of the new roadbed fill to form a composite foundation. The bottom of the capped piles penetrates the soft soil layer to reach the bearing layer. A row of raised anti-slide piles is set inside the capped piles. The top of the raised anti-slide piles is set at the top of the step. The bottom of the raised anti-slide piles penetrates the soft soil layer to reach the bearing layer. Isolation steel sheet piles are set in the middle of the top step. The isolation steel sheet piles are connected by L-shaped connecting grooves. The bottom of the isolation steel sheet piles penetrates the soft soil layer to reach the bearing layer.

[0010] In the above technical solution, the new road surface structure layer is located at the top of the top step and is connected to the excavated part of the old road surface structure layer; In the above technical solution, the new roadbed fill is laid from the excavation step of the old road to the edge of the new roadbed fill; In the above technical solution, the geogrid is installed at the top of each step, and the geogrid is connected to the multi-legged anchoring member on the inner side of the top of the step.

[0011] In the above technical solution, the isolation sheet piles are arranged in the middle of the top step, with the top of the isolation sheet piles located on the surface of the top step and the bottom of the isolation sheet piles located in the bearing layer of the foundation; the isolation sheet piles are continuously arranged along the length of the roadbed at the splice of the new and old roadbeds, and the edges of the isolation sheet piles are connected by L-shaped connecting grooves.

[0012] In the above technical solution, the multi-legged anchoring member is inserted into the soil through the mesh gaps of the geogrid to fix and connect the geogrid; the multi-legged anchoring member includes multiple locations, and all multi-legged anchoring members are set along the inner ends of each level of step to ensure anchoring connection with the ends of the geogrid; the geogrid is fully laid in layers on each level of excavation step and the corresponding new roadbed fill, and is fixed at the inner ends of the steps by the multi-legged anchoring member, and the geogrid is fully laid to the edge of the new roadbed fill.

[0013] In the above technical solution, the multi-legged anchoring component includes multiple components, which are continuously arranged at a certain interval on the inner end of each step to fix the geogrid laid along the roadbed length; the multi-legged anchoring component includes U-shaped nails and connectors, and each multi-legged anchoring component consists of 4 U-shaped nails, with the top of the U-shaped nails connected by connectors.

[0014] In the above technical solution, the capped piles are set at equal intervals at the bottom of the newly filled roadbed to form a capped pile composite foundation. The pile cap size is 100~120cm and the pile cap height is 30~50cm. The top of the capped pile is set at the bottom of the newly filled roadbed and the top extends into the bearing layer of the foundation.

[0015] In the above technical solution, the raised anti-slide piles are continuously arranged along the length of the roadbed next to the innermost capped piles. The raised anti-slide piles are spaced at the same distance from the capped piles. The top of the raised anti-slide piles is located on the top surface of the corresponding step, and the bottom penetrates into the bearing layer of the foundation. The raised anti-slide piles are set at the bottommost step or the top of the second to last step, and the pile caps are arranged on the top surface of the step.

[0016] This invention also provides a construction method for an isolated soft soil foundation roadbed widening differential settlement control structure, including the following: At the shoulder of the old road, the old road pavement structure layer and the old roadbed fill are excavated in layers down to the ground surface. A certain width and height are reserved for each layer of the old roadbed fill to form a stepped structure. Within the widened roadbed area, capped piles are typically arranged at certain intervals along the roadbed length. The pile body is pressed in by static pressure construction, and the pile cap is made by on-site casting. Elevation anti-slide piles are installed at the bottom or the second to last step. The pile caps of the elevation anti-slide piles are placed on the top surface of the step. The bottom of the elevation anti-slide piles is inserted into the bearing layer of the foundation. The pile body of the elevation anti-slide piles is pressed in by static pressure, and the pile caps are made by cast-in-place. After the construction of capped piles and raised anti-slide piles is completed, the new roadbed fill will be filled in layers, starting from the lowest step and compacted to form the new roadbed fill. While carrying out the layered filling construction of the new roadbed, geogrids are laid. Geogrids are placed at the inner end of the steps and fixed with multi-foot anchor nails. The new roadbed fill is then filled and compacted on the surface of the laid geogrids. After the new roadbed is filled in layers, isolation steel sheet piles are driven into the middle of the top step using static pressure or vibratory hammer. The isolation steel sheet piles are arranged in the middle of the top step, with the bottom penetrating into the bearing layer of the foundation. They are connected by L-shaped connecting grooves and are arranged continuously along the length of the roadbed. After the isolation sheet piles and top geogrid are completed, a new road surface structure layer is laid on the surface of the top geogrid.

[0017] In the above technical solution, the construction of the isolation steel sheet piles includes setting out and positioning the pile holes on the top step surface of the old roadbed fill, and using static pressure or vibratory hammer to carry out the pile penetration construction.

[0018] The advantages and beneficial effects of this invention are as follows: 1. This invention, by setting isolation sheet piles at the top steps of the old road, with the bottom of the isolation sheet piles extending into the bearing layer of the foundation, and the two ends of the isolation sheet piles connected by L-shaped connecting grooves to form a continuous sheet pile isolation wall, can isolate the additional load of the new roadbed fill in the widened section, avoid additional settlement of the foundation below the old roadbed, and at the same time control the lateral displacement of the old roadbed fill, effectively controlling the differential settlement between the new and old roadbeds.

[0019] 2. This invention involves installing geogrids at the top of each level of excavation steps, laying the geogrids on the inner end of each step, and fixing them with multi-legged anchoring components. After fixing, new roadbed fill is filled on the surface of the geogrids. The geogrids reinforce the old and new roadbed fills, connecting the old and new roadbed fills into a whole, controlling the lateral displacement of the new roadbed fills, and coordinating the differential settlement between the old and new roadbeds.

[0020] 3. In this invention, the multi-legged anchoring component is used to fix the geogrid in each level of fill. It is inserted into the soil at certain intervals to firmly fix the geogrid to the inside of the step. The multi-legged anchoring component is composed of multiple U-shaped nails. The top of the U-shaped nails is connected into a whole by a connector. Compared with the traditional single U-shaped nail, the multi-legged anchoring component has a better anchoring effect on the geogrid and prevents the geogrid from sliding out with the lateral displacement of the soil.

[0021] 4. In this invention, capped piles are installed below the fill of the new roadbed in the widened section. The capped piles are arranged at certain intervals along the length of the roadbed to form a composite foundation. The pile caps are set below the fill of the new roadbed to provide support. The pile bodies penetrate into the bearing layer of the foundation to transfer the vertical load of the upper fill of the new roadbed. The capped piles and the fill of the new roadbed constitute a pile-supported reinforced embankment structure, which effectively bears the load of the fill of the new roadbed, reduces the settlement of the new roadbed, and can effectively control the cumulative settlement of the soft soil foundation over time.

[0022] 5. In this invention, raised anti-slide piles are installed at the top of the bottom step or the second-to-last step. The pile caps of the raised anti-slide piles are placed on the top surface of the step, and the bottom of the raised anti-slide piles penetrates into the bearing layer of the foundation. The raised anti-slide piles are arranged along the length of the roadbed at the same spacing as the capped piles. In addition to bearing the load of the new roadbed fill and reducing the settlement of the new road, the raised anti-slide piles can effectively control the lateral displacement of the old road slope under the load, and further reduce the differential settlement between the new and old roadbeds. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of an isolated soft soil foundation roadbed widening differential settlement control structure according to one or more embodiments of the present invention.

[0024] Figure 2This is a schematic diagram of the connection between the geogrid and the multi-legged anchoring member in the pavement structure layer of an isolated soft soil foundation roadbed differential settlement control structure according to one or more embodiments of the present invention.

[0025] Figure 3 This is a cross-sectional schematic diagram of capped piles and isolation sheet piles in an isolated soft soil foundation roadbed widening differential settlement control structure according to one or more embodiments of the present invention.

[0026] Figure 4 This is a schematic diagram of the location of the anti-slide piles in an isolated soft soil foundation widening roadbed differential settlement control structure according to one or more embodiments of the present invention.

[0027] Figure 5 This is a schematic diagram of the connection of isolation sheet piles in an isolation soft soil foundation widening roadbed differential settlement control structure according to one or more embodiments of the present invention.

[0028] Figure 6 This is a schematic diagram of the cross-section of the isolation steel sheet pile in an isolation soft soil foundation widening roadbed differential settlement control structure according to one or more embodiments of the present invention.

[0029] Figure 7 This is a schematic diagram of the connection between the geogrid and the multi-legged anchoring member inside the widened roadbed in an isolated soft soil foundation roadbed differential settlement control structure according to one or more embodiments of the present invention.

[0030] Figure 8 This is a detailed schematic diagram of a multi-legged anchoring component in an isolated soft soil foundation roadbed widening differential settlement control structure according to one or more embodiments of the present invention.

[0031] The diagram exaggerates the spacing or dimensions between parts to show their positions; the diagram is for illustrative purposes only.

[0032] Among them: 1-1, new road surface structure layer; 1-2, old roadbed fill; 1-3, new roadbed fill; 2-1, bidirectional geogrid; 2-2, multi-legged anchoring component; 3-1, capped pile; 3-2, isolation steel sheet pile; 4-1, raised anti-slide pile; 5-1, L-shaped connecting groove; 6-1, U-shaped nail; 6-2, connector.

[0033] For those skilled in the art, other related figures can be obtained from the above figures without any creative effort. Detailed Implementation

[0034] To enable those skilled in the art to better understand the present invention, the technical solution of the present invention will be further described below with reference to specific embodiments.

[0035] This invention proposes an isolated differential settlement control structure for widening roadbeds on soft soil foundations. Please refer to [link / reference]. Figure 1 , Figure 2 , Figure 3 and Figure 4 The project includes the excavation of the pavement structure layer on the shoulder side of the old roadbed fill 1-2 and the multi-level steps formed by the roadbed fill, the new roadbed fill 1-3 formed by layered filling on the outer side of the steps, and the new road pavement structure layer 1-1 on top of the new roadbed fill 1-3. Geogrid 2-1 and multi-legged anchoring components 2-2 are laid on top of each level of step. The multi-legged anchoring components 2-2 are composed of multiple U-shaped nails 6-1. The U-shaped nails 6-1 of the multi-legged anchoring components are inserted into the step fill and connected to the geogrid 2-1. The geogrid 2-1 is fixed to each level by the multi-legged anchoring components 2-2. At the inner end of the step, multiple rows of capped piles 3-1 are evenly spaced at the bottom of the new roadbed fill 1-3 to form a composite foundation. The bottom of the capped piles 3-1 penetrates the soft soil layer to reach the bearing layer. A row of raised anti-slide piles 4-1 is set inside the capped piles 3-1. The top of the raised anti-slide piles 4-1 is set at the top of the step. The bottom of the raised anti-slide piles 4-1 penetrates the soft soil layer to reach the bearing layer. Isolation steel sheet piles 3-2 are set in the middle of the top step. The isolation steel sheet piles 3-2 are connected by L-shaped connecting grooves 5-1. The bottom of the isolation steel sheet piles 3-2 penetrates the soft soil layer to reach the bearing layer.

[0036] Please see Figure 1 , Figure 2 and Figure 3 The old roadbed fill 1-2 is the existing roadbed. Steps are excavated in stages at the old road shoulder. The number of steps is determined according to the roadbed height. The step length is 120cm and the step height is 80cm. The height of the top step is determined according to the actual situation. After the old roadbed fill 1-2 is excavated in stages, it can be closely integrated with the new roadbed fill 1-3 to improve the integrity of the old and new roadbeds.

[0037] Please see Figure 3 Capped piles 3-1 are evenly spaced along the length of the roadbed in the foundation below the fill 1-3 of the new roadbed. The top of the pile is located at the bottom of the fill 1-3 of the new roadbed, and the bottom of the pile penetrates into the bearing layer of the foundation. Capped piles 3-1 are usually PHC pipe piles or CFG piles with a diameter of 40-60cm. The pile body is driven into the soil by static pressure or vibratory hammer. The pile cap is square and made by cast-in-place method. The side length of the pile cap is 100-120cm and the height of the pile cap is 30-50cm. C30-C40 concrete is used. After the construction of the capped piles is completed and the pile cap has reached the concrete curing age, the soil is backfilled and compacted.

[0038] Please see Figure 3 and Figure 4The raised anti-slide pile 4-1 is arranged at the bottom step or the top of the second to last step. The pile body is the same as the capped pile, using PHC pipe pile or CFG pile. The pile cap is made of C30 or C40 concrete cast in place. The raised anti-slide pile 4-1 has the same pile spacing and arrangement position as the capped pile 3-1. The pile bottom penetrates into the bearing layer of the foundation. The raised anti-slide pile 4-1 and the capped pile 3-1 adopt the same structural form and arrangement. In addition to bearing the vertical load of the new roadbed fill 1-3, they also play a role in reinforcing the slope of the old roadbed fill. They can control the lateral displacement of the old roadbed fill 1-2, improve the slope stability of the old roadbed, and effectively control the differential settlement between the new and old roadbeds.

[0039] Please see Figure 3 and Figure 4 Geogrid 2-1 is placed at the inner end of each step during the layered filling of the new roadbed 1-3 and fixed by multi-legged anchoring components 2-2. After the geogrid 2-1 is laid and fixed, the new roadbed 1-3 is filled on top of the geogrid 2-1 and compacted in layers. Geogrid 2-1 plays a role in increasing the tensile strength of the pavement in the new road surface structure layer 1-1 and in enhancing the integrity of the new and old roadbeds at each step below the pavement, thereby reducing differential settlement caused by asynchronous settlement and lateral displacement of the new and old roadbeds.

[0040] Please see Figure 2 and Figure 7 The geogrid 2-1 and the multi-legged anchoring member 2-2 are fixedly connected at the inner ends of each step. The multi-legged anchoring member 2-2 is embedded in the soil at a certain interval to fix the geogrid 2-1, ensuring the effective fixation of the geogrid 2-1. The multi-legged anchoring member 2-2 and the geogrid 2-1 are continuously arranged along the length of the roadbed to ensure the effective reinforcement of the old roadbed fill 1-2 and the new roadbed fill 1-3 by the geogrid 2-1.

[0041] Please see Figure 8 The multi-legged anchoring component 2-2 includes four U-shaped nails 6-1 and a connector 6-2. When in use, the U-shaped nails are inserted into the old roadbed fill 1-2 through the mesh gaps of the geogrid 2-1 to achieve a embedding effect. The connector 6-2 connects the four U-shaped nails 6-1 into a whole, which improves the embedding effect of the geogrid 2-1. Compared with traditional U-shaped nails, the multi-legged anchoring component 2-2 has a better fixing effect on the geogrid and improves the reinforcement effect of the geogrid 2-1 on the old roadbed fill 1-2 and the new roadbed fill 1-3.

[0042] Please see Figure 3 and Figure 4The isolation sheet piles 3-2 are continuously arranged along the length of the roadbed in the middle of the top step. The bottom of the isolation sheet piles 3-2 penetrates into the bearing layer of the foundation and is located at the same depth as the capped piles 3-1 and the raised anti-slide piles 4-1. The isolation sheet piles 3-2 isolate the additional settlement of the old road foundation caused by the load of the new roadbed fill 1-3, and can limit the lateral displacement of the old roadbed fill 1-2, thereby improving the stability of the old roadbed and effectively reducing the differential settlement between the new and old roadbeds.

[0043] Please see Figure 5 and Figure 6 The isolation sheet piles 3-2 are U-shaped Larssen sheet piles with L-shaped connecting grooves 5-1 at both ends. The purpose is to turn the direction of two adjacent isolation sheet piles 3-2 and connect them with the L-shaped connecting grooves 5-1, so that the adjacent isolation sheet piles 3-2 are connected to form a continuous isolation wall, which can isolate the additional load of the new roadbed filling.

[0044] Please see Figure 1 and Figure 2 The new road pavement structure layer 1-1 is laid on the top surface of the top step and the new roadbed fill 1-3. Geogrid 1-2 is laid at the bottom of the new road pavement structure layer 1-1. Geogrid 1-2 enhances the tensile strength of the new road pavement structure layer 1-1 and reduces the risk of longitudinal cracking of the pavement.

[0045] This embodiment also provides a construction method for an isolated soft soil foundation roadbed widening differential settlement control structure, including the following: The old road surface structure layer and the old roadbed fill 1-2 are excavated in layers to the foundation surface. The steps are excavated in stages starting from the old road shoulder. The step length is 120cm and the step height is 80cm. The height of the top step is determined by combining the design elevation of the pavement structure layer and the actual height of the roadbed.

[0046] After the old roadbed is filled with soil in stages 1-2 and the steps are excavated, the capped pile 3-1 is constructed. The location of the capped pile is determined by setting out the line in the foundation of the new road in the widened section. The capped pile 3-1 is driven into the foundation to the specified depth along the location by static pressure or vibratory hammer construction. The formwork is tied on site and the pile cap is cast in place.

[0047] The anti-slide pile 4-1 is constructed after the innermost row of capped piles 3-1 is completed. The anti-slide pile 4-1 is set at a certain interval along the length of the roadbed at the bottom or the top of the second to last step. The pile cap is placed on the top surface of the step. The anti-slide pile 4-1 is driven into the roadbed by static pressure, and the pile cap is made by on-site casting.

[0048] After the construction of the capped piles 3-1 and the raised anti-slide piles is completed, the new roadbed fill 1-3 is constructed from the foundation surface to the top of the roadbed in layers. During the layered filling, the compaction degree of the new roadbed fill should be not less than 92%~95%.

[0049] While the new roadbed fill is being constructed in layers 1-3, geogrid 2-1 is laid. Geogrid 2-1 is laid along the length of the roadbed and fixed with multi-legged anchoring members 2-2. Adjacent sections of geogrid 2-1 are also connected and fixed with multi-legged anchoring members 2-2. Geogrid 2-1 is fully laid during the construction of the new roadbed fill layers 1-3, which reinforces the new roadbed fill layers 1-3 and the old roadbed fill layers 1-2 and improves the overall integrity.

[0050] After the new roadbed filling is completed, the isolation steel sheet piles 3-2 are driven. The positioning is laid out in the middle of the top step. The isolation steel sheet piles 3-2 are driven into the roadbed by static pressure or vibratory hammer. The isolation steel sheet piles 3-2 are connected to each other in the roadbed through L-shaped connecting grooves and are continuously driven and arranged along the length of the roadbed.

[0051] After the isolation sheet piles 3-2 and the top geogrid 2-1 are completed, the new road surface structure layer 1-1 is laid on the surface of the top geogrid.

[0052] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A differential settlement control structure for widening roadbeds on isolated soft soil foundations, characterized in that: The project includes the excavation of the pavement structure layer on the shoulder side of the old roadbed fill and the multi-level steps formed by the roadbed fill, the new roadbed fill formed by layered filling on the outside of the steps, and the new road pavement structure layer on top of the new roadbed fill. Geogrids and multi-legged anchoring components are laid on the top of each step. The multi-legged anchoring components are composed of multiple U-shaped nails. The U-shaped nails of the multi-legged anchoring components are inserted into the step fill and connected to the geogrid. The geogrid is fixed to the inner end of each step through the multi-legged anchoring components. Multiple rows of capped piles are set at equal intervals at the bottom of the new roadbed fill to form a composite foundation. The bottom of the capped piles penetrates the weak soil layer to reach the bearing layer. A row of raised anti-slide piles is set inside the capped piles. The top of the raised anti-slide piles is set at the top of the step. The bottom of the raised anti-slide piles penetrates the weak soil layer to reach the bearing layer. Isolation steel sheet piles are set in the middle of the top step. The isolation steel sheet piles are connected by L-shaped connecting grooves. The bottom of the isolation steel sheet piles penetrates the weak soil layer to reach the bearing layer.

2. The isolated soft soil foundation roadbed widening differential settlement control structure according to claim 1, characterized in that: The new road surface structure layer is located at the top of the top step and is connected to the excavated part of the old road surface structure layer. The new roadbed fill is laid from the excavation steps of the old road to the edge of the new roadbed fill. The geogrid is installed at the top of each step, and the geogrid is connected to the multi-legged anchoring member on the inner side of the top of the step.

3. The isolated soft soil foundation roadbed widening differential settlement control structure according to claim 1, characterized in that: The isolation sheet piles are arranged in the middle of the top step, with the top of the isolation sheet piles located on the surface of the top step and the bottom of the isolation sheet piles located in the bearing layer of the foundation. The isolation sheet piles are continuously arranged along the length of the roadbed at the splice of the old and new roadbeds, and the edges of the isolation sheet piles are connected by L-shaped connecting grooves.

4. The isolated soft soil foundation roadbed widening differential settlement control structure according to claim 1, characterized in that: The multi-legged anchoring components are inserted into the soil through the mesh gaps of the geogrid to fix and connect the geogrid; the multi-legged anchoring components include multiple locations, and all multi-legged anchoring components are set along the inner ends of each level of step to ensure anchoring connection with the ends of the geogrid; the geogrid is fully laid in layers on each level of excavation step and the corresponding new roadbed fill, and is fixed at the inner ends of the steps by multi-legged anchoring components, and the geogrid is fully laid to the edge of the new roadbed fill.

5. The isolated soft soil foundation roadbed widening differential settlement control structure according to claim 1, characterized in that: The multi-legged anchoring component includes multiple components, which are continuously arranged at a certain interval on the inner end of each step to fix the geogrid laid along the roadbed length; the multi-legged anchoring component includes U-shaped nails and connectors, and each multi-legged anchoring component consists of 4 U-shaped nails, with the top of the U-shaped nails connected by connectors.

6. The isolated soft soil foundation roadbed widening differential settlement control structure according to claim 1, characterized in that: The capped piles are set at equal intervals at the bottom of the newly filled roadbed to form a capped pile composite foundation. The pile cap size is 100~120cm and the pile cap height is 30~50cm. The top of the capped pile is set at the bottom of the newly filled roadbed and extends into the bearing layer of the foundation.

7. The isolated soft soil foundation roadbed widening differential settlement control structure according to claim 1, characterized in that: The raised anti-slide piles are continuously arranged along the length of the roadbed next to the innermost capped piles. The raised anti-slide piles are spaced at the same distance from the capped piles. The top of the raised anti-slide piles is located on the top surface of the corresponding step, and the bottom penetrates into the bearing layer of the foundation. The raised anti-slide piles are set at the bottommost step or the top of the second to last step, and the pile caps are arranged on the top surface of the step.

8. The construction method of the isolated soft soil foundation roadbed differential settlement control structure according to any one of claims 1-7, characterized in that, Includes the following: At the shoulder of the old road, the old road pavement structure layer and the old roadbed fill are excavated in layers down to the ground surface. A certain width and height are reserved for each layer of the old roadbed fill to form a stepped structure. Within the widened roadbed area, capped piles are typically arranged at certain intervals along the roadbed length. The pile body is pressed in by static pressure construction, and the pile cap is made by on-site casting. Elevation anti-slide piles are installed at the bottom or the second to last step. The pile caps of the elevation anti-slide piles are placed on the top surface of the step. The bottom of the elevation anti-slide piles is inserted into the bearing layer of the foundation. The pile body of the elevation anti-slide piles is pressed in by static pressure, and the pile caps are made by cast-in-place. After the construction of capped piles and raised anti-slide piles is completed, the new roadbed fill will be filled in layers, starting from the lowest step and compacted to form the new roadbed fill. While carrying out the layered filling construction of the new roadbed, geogrids are laid. Geogrids are placed at the inner end of the steps and fixed with multi-foot anchor nails. The new roadbed fill is then filled and compacted on the surface of the laid geogrids. After the new roadbed is filled in layers, isolation steel sheet piles are driven into the middle of the top step using static pressure or vibratory hammer. The isolation steel sheet piles are arranged in the middle of the top step, with the bottom penetrating into the bearing layer of the foundation. They are connected by L-shaped connecting grooves and are arranged continuously along the length of the roadbed. After the isolation sheet piles and top geogrid are completed, a new road surface structure layer is laid on the surface of the top geogrid.

9. The construction method of the isolated soft soil foundation roadbed widening differential settlement control structure according to claim 8, characterized in that: The construction of the isolation steel sheet piles includes setting out and positioning the pile holes on the top step surface of the old roadbed fill, and using static pressure or vibratory hammers to drive the piles into the ground.

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