A method for regulating and controlling the settlement of a widened roadbed based on a constraint isolation wall

Abstract

The application discloses a kind of based on constraint isolation wall's wide roadbed settlement regulation and control method, it is related to civil engineering technical field, including the following steps: S1, according to the width of wide roadbed of splicing, the horizontal position and vertical depth of constraint isolation wall are determined, so that the settlement curve after construction of the top of wide roadbed is most gentle;S2, according to the position of constraint isolation wall, design old roadbed step scheme, carry out step excavation;S3, according to the horizontal position of constraint isolation wall, from the surface of excavated step, constraint isolation wall construction is carried out;S4, new roadbed soil is filled and compacted, covers constraint isolation wall and excavated step, completes roadbed splicing and settlement control.The application discloses a kind of based on constraint isolation wall's wide roadbed settlement regulation and control method, can greatly improve the fatigue life of pavement, guarantee the long-term use performance of pavement, to realize the cost reduction and efficiency increase of road reconstruction and extension project, low-carbon life extension, reduce the cost of human resources and machine, also can shorten construction period.

Description

Technical Field

[0001] This invention relates to the field of civil engineering technology, and in particular to a method for controlling settlement of widened roadbeds based on constrained isolation walls. Background Technology

[0002] With economic development, existing expressways can no longer meet the ever-increasing traffic demand, leading to a surge in highway reconstruction and expansion projects in my country. Roadbed widening is a major form of highway reconstruction and expansion. When the embankment is high and the soil quality is poor, the old and new roadbeds will influence each other and cause uneven settlement. The widened pavement will be subjected to additional stress under the influence of this uneven settlement, often resulting in longitudinal cracks and other defects, severely affecting the durability of the reconstructed pavement.

[0003] To address the issue of differential settlement in roadbeds during reconstruction and expansion projects, numerous treatment measures have been proposed in practice, including enhanced compaction, rockfill displacement, partial replacement, lightweight fill, and geogrid reinforcement. When the fill is high and the soil quality is poor, composite pile foundation treatment is also necessary. Composite foundations can effectively reduce absolute settlement, but when the fill is high, the treatment area is large, resulting in low economic efficiency. Furthermore, it cannot effectively control the post-construction settlement curve morphology, and its effect on reducing additional stress on the pavement is not significant.

[0004] Isolation measures between new and old roadbeds can effectively reduce the impact of new roadbeds on old roadbeds, and some research has been conducted. However, some existing technologies only place isolation measures below the original ground surface, which cannot restrain the lateral deformation of the old roadbed and requires the excavation of steep slopes on the old road, making them difficult to implement in practice. Some isolation measures use pile treatment, which cannot limit the rheological properties of the foundation and extends beyond the top surface of the roadbed, easily causing uneven settlement of the pile-soil pavement and potentially causing pavement arching. Other combined retaining structures are too complex and cumbersome to implement. In addition, most treatment measures are introduced too late and cannot control settlement during the construction period.

[0005] Developing a settlement control method for widened roadbeds based on constrained isolation walls to efficiently control roadbed settlement, reduce additional stress on the pavement, and prevent longitudinal cracking in widened pavements after reconstruction and expansion has become a technical challenge that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] The purpose of this invention is to provide a method for controlling the settlement of widened roadbeds based on constrained isolation walls, thereby solving the problems listed in the background art.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0008] This invention discloses a method for controlling settlement of widened roadbeds based on constrained isolation walls, comprising the following steps:

[0009] S1. Determine the horizontal position and vertical depth of the confined retaining wall based on the width of the widened roadbed section, ensuring the smoothest settlement curve after construction of the top of the widened roadbed. The horizontal position of the confined retaining wall is located at the plumb line where the top of the widened roadbed is 1 / 4 of the width from the edge. The formula for determining the vertical depth h of the confined retaining wall is h = -0.0031H. 3 +0.1008H 2 +0.3761H+7.3-3W / 4n, where H is the embankment height, W is the widened width, and n is the slope ratio of the old roadbed.

[0010] S2. Based on the location of the confined isolation wall, design the old roadbed step scheme and excavate the steps. Project downwards from a point 1 / 4 of the width from the top of the widened roadbed and intersect the old roadbed slope at a point. Make this point the outer corner of the step. Based on this, design the old roadbed step excavation scheme. The step width is designed to be 1.3m to 1.8m and the height is designed to be 0.8m to 1m.

[0011] S3. Construct the confined isolation wall from the surface of the excavated steps according to its horizontal position;

[0012] S4. Fill and compact the new roadbed soil, cover the confinement isolation wall and the excavated steps, and complete the roadbed widening and settlement control.

[0013] Preferably, step S3 specifically includes the step where the outer corner of the step is located as the top position of the constraint isolation wall, and the construction of the constraint isolation wall is carried out from the top position downwards. The vertical depth of the constraint isolation wall is h, and the width of the constraint isolation wall is 50-80cm.

[0014] Preferably, the confining isolation wall is a cement-soil continuous wall or a channel-type cutting deep mixing underground cement-soil continuous wall.

[0015] Preferably, step S4 specifically includes completing the construction of the confined isolation wall, and after the monitoring is qualified, proceeding with the normal roadbed filling, covering the confined isolation wall and the excavated steps, and completing the roadbed widening and settlement control.

[0016] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0017] This invention discloses a method for controlling the settlement of widened roadbeds based on constrained isolation walls. Instead of controlling the total settlement of the roadbed and directly supporting the pavement structure, it allows the roadbed to undergo a certain amount of absolute settlement. Starting from controlling the additional stress on the pavement, it treats the situation with the simplest measures. At the same time, it limits the lateral deformation of the old embankment caused by the action of the new roadbed and the horizontal rheology of the subgrade after construction, thereby achieving the function of adjusting the settlement curves of the new and old roadbeds after construction.

[0018] The requirement that the top of the confined retaining wall not extend beyond the new roadbed but be on the slope steps of the old roadbed can avoid road surface heave caused by differential settlement of the soil wall, advance the construction time of the confined retaining wall, limit settlement during construction period, and thus shorten the overall construction period;

[0019] The confined isolation wall can achieve precise adjustment of the post-construction settlement curves of the new and old roadbeds, reducing differential settlement of the old road area by about 20% and reducing additional stress on the surface of the old road by about 40% throughout the process; it can almost eliminate the slope change at the splicing point of the new and old roadbeds, making the post-construction settlement curve smoother, and reducing the additional tensile stress at the bottom of the base layer at the splicing point by up to 70% and the additional shear stress on the surface layer by up to 60%;

[0020] It can also significantly improve the fatigue life of the road surface and ensure its long-term performance, which is of great significance for reducing costs, increasing efficiency, and extending the life of road reconstruction and expansion projects. Attached Figure Description

[0021] The present invention will be further described below with reference to the accompanying drawings.

[0022] Figure 1 This is a schematic diagram of the constraint isolation wall treatment of the present invention;

[0023] Figure 2 This is a flowchart of a method for controlling settlement of a widened roadbed based on a constrained isolation wall, according to the present invention.

[0024] Figure 3 This is a schematic diagram illustrating the determination of the location of the constraint isolation wall according to an embodiment of the present invention;

[0025] Figure 4 This is a graph showing the final total settlement curves of the old and new roadbed tops where the confined isolation wall measures were implemented according to this invention.

[0026] Figure 5 This is a graph showing the additional stress curve of the old pavement caused by the total differential settlement of the constraint isolation wall measures adopted in this invention;

[0027] Figure 6 This is a post-construction settlement curve of the top of the old and new roadbeds where the confined isolation wall measures are adopted according to the present invention;

[0028] Figure 7 This is a curve showing the additional stress at the base of the widened road surface caused by differential settlement after construction of the constrained isolation wall measures according to the present invention. Detailed Implementation

[0029] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0030] like Figure 1-7 As shown, a method for controlling settlement of widened roadbeds based on constrained isolation walls includes the following steps:

[0031] S1. Determine the horizontal position and vertical depth of the confined retaining wall based on the width of the widened section of the roadbed, ensuring the smoothest settlement curve after construction of the top of the widened roadbed. The horizontal position of the confined retaining wall is related to the widening width; the vertical plane located at 1 / 4 of the width from the edge of the top of the widened roadbed is the horizontal position of the confined retaining wall. Furthermore, the optimal vertical depth of the confined retaining wall is determined by the embankment height, the widening width, and the slope ratio of the old roadbed. The formula for determining the vertical depth h of the confined retaining wall is h = -0.0031H. 3 +0.1008H 2 +0.3761H+7.3-3W / 4n, where H is the embankment height, W is the widening width, and n is the slope ratio of the old roadbed. Setting up a constraint isolation wall with a depth determined by this formula can minimize the post-construction settlement of the new and old roadbeds. For deep soft soil conditions, the vertical depth is selected according to this formula. For underlying bedrock conditions, when the calculated wall depth has entered a strongly differentiated rock layer with a uniaxial compressive strength exceeding 1MPa, the location of this rock layer is taken as the required depth.

[0032] S2. Based on the location of the confined isolation wall, design the old roadbed step scheme and excavate the steps. Project downwards from a point 1 / 4 of the width from the top of the widened roadbed and intersect the old roadbed slope at a point. Make this point the outer corner of the step. Based on this, design the old roadbed step excavation scheme. The step width is designed to be 1.3m to 1.8m and the height is designed to be 0.8m to 1m.

[0033] S3. Construct the confined isolation wall from the surface of the excavated steps according to its horizontal position;

[0034] S4. Fill and compact the new roadbed soil, cover the confinement isolation wall and the excavated steps, and complete the roadbed widening and settlement control.

[0035] Specifically, step S3 includes the step at the outer corner of the step being the top position of the constraint isolation wall, and the construction of the constraint isolation wall proceeding downwards from this position. The vertical depth of the constraint isolation wall is h, the width of the constraint isolation wall is 50-80cm, and the modulus range is approximately 100MPa.

[0036] Specifically, the confined isolation wall is a cement-soil continuous wall or a channel-type cutting deep mixing underground cement-soil continuous wall.

[0037] Specifically, step S4 includes completing the construction of the confined isolation wall, ensuring it passes monitoring, and then proceeding with the normal roadbed filling, covering the confined isolation wall and the excavated steps, and completing the roadbed widening and settlement control.

[0038] Example

[0039] The reconstruction and expansion project of a highway in a coastal area has poor soil quality. The parameters are shown in Table 1. The road is widened on both sides, with a width of 15 + 7.5m and a fill height of 10m. The slope ratio of the new and old roadbeds is 1:1.5.

[0040] According to the aforementioned design method and construction scheme for a confined retaining wall to precisely control differential settlement of high-fill widening roadbeds, a schematic diagram of the confined retaining wall is shown below. Figure 1 As shown, the flowchart is as follows Figure 2 As shown, the specific implementation is as follows:

[0041] Table 1 Soil parameters in this area

[0042]

[0043] 1) such as Figure 3 As shown, first determine the location of the isolation wall. First, take a point on the new roadbed surface that is 1 / 4 × 7.5 = 1.875m away from the edge of the roadbed, and project this point downwards to a point on the slope of the old roadbed.

[0044] 2) Then determine the depth of the isolation wall. In this example, H=10m, W=7.5m, n=1.5. According to the formula h=-0.0031H 3 +0.1008H 2 +0.3761H+7.3-3W / 4n, the optimal total depth is determined to be 13.25m, of which 5.25m is above ground and 8m is below the wall;

[0045] 3) Finally, the width and modulus of the isolation wall were determined. This project is a deep soft soil condition, but the fill is not too high. According to the requirements of this invention, the thickness is 50cm and the modulus is 100MPa.

[0046] 4) Based on the previously determined location of the confined isolation wall, and according to the requirement that the external corner of a certain step roughly coincides with the projection point of the old roadbed slope, design the old roadbed step scheme and carry out step excavation. In this example, the step size above the projection point is approximately 1.4m × 0.95m (width × height), with a total of five levels; the step size below the projection point is approximately 1.55m × 1.05m (width × height), with a total of five levels, which meets the requirements.

[0047] 5) Construct the confinement wall. The height of the top of the wall is the step where the outer corner of the above-mentioned steps is located. Take 50cm inward from the corner of the steps to find the specific top of the wall. Then, construct the wall to a total depth of 13.25m.

[0048] The construction method can be either a cement-soil continuous wall or a channel-type cutting deep mixing underground cement-soil continuous wall method (TRD method). The isolation wall can be constructed before the roadbed is filled, or the roadbed can be filled to the level of the top step of the wall, a TRD equipment working platform can be built, and then the isolation wall can be constructed.

[0049] After surveying and setting out and trenching, once the equipment is in place, vertical cutting is carried out along the designated wall site, and the process is advanced in sections. Depending on the target treatment modulus and the foundation soil, different cement admixtures are used in the stages above and below the original surface.

[0050] For this work condition, the embankment compression modulus is 30 MPa, the soft soil compression modulus is 3-4 MPa, the cement content above the original surface is 15%, and the cement content below the original surface is 25%. The horizontal advancing speed is 0.6 m / h, the cutter chain speed is 12-15 rpm, the water-cement ratio is 0.8-1.2 (adjusted according to fluidity), and the grouting pressure is 0.5-1.0 MPa to ensure the uniformity of the wall.

[0051] 6) After the wall construction monitoring is completed, the roadbed filling is carried out normally, covering the isolation wall and the excavated steps, and the roadbed widening and settlement control are completed. During the roadbed filling process after the wall construction is completed, the roadbed can be quickly filled to the predetermined elevation and the road surface can be paved to open traffic, without considering static placement or preloading.

[0052] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0053] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for controlling settlement of widened roadbeds based on constrained isolation walls, characterized in that: Includes the following steps: S1. Determine the horizontal position and vertical depth of the confined retaining wall based on the width of the widened roadbed section, ensuring the smoothest settlement curve after construction of the top of the widened roadbed. The horizontal position of the confined retaining wall is located at the plumb line where the top of the widened roadbed is 1 / 4 of the width from the edge. The formula for determining the vertical depth h of the confined retaining wall is h = -0.0031H. 3 +0.1008H 2 +0.3761H+7.3-3W / 4n, where H is the embankment height, W is the widened width, and n is the slope ratio of the old roadbed. S2. Based on the location of the confined isolation wall, design the old roadbed step scheme and excavate the steps. Project downwards from a point 1 / 4 of the width from the top of the widened roadbed and intersect the old roadbed slope at a point. Make this point the outer corner of the step. Based on this, design the old roadbed step excavation scheme. The step width is designed to be 1.3m to 1.8m and the height is designed to be 0.8m to 1m. S3. Construct the confined isolation wall from the surface of the excavated steps according to its horizontal position; S4. Fill and compact the new roadbed soil, cover the confinement isolation wall and the excavated steps, and complete the roadbed widening and settlement control.

2. The method for controlling settlement of widened roadbed based on constrained isolation walls according to claim 1, characterized in that: The S3 step specifically includes the step where the outer corner of the step is located as the top position of the constraint isolation wall, and the construction of the constraint isolation wall is carried out from the top position downwards. The vertical depth of the constraint isolation wall is h, and the width of the constraint isolation wall is 50-80cm.

3. The method for controlling settlement of widened roadbed based on constrained isolation walls according to claim 1, characterized in that: The confined isolation wall is a cement-soil continuous wall or a channel-type cutting deep mixing underground cement-soil continuous wall.

4. The method for controlling settlement of widened roadbed based on constrained isolation walls according to claim 1, characterized in that: The steps in S4 specifically include completing the construction of the confined isolation wall, ensuring it passes monitoring, and then proceeding with the normal roadbed filling, covering the confined isolation wall and the excavated steps, and completing the roadbed widening and settlement control.

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