Spliced widened roadbed settlement regulation and control method based on constraint separation wall

Abstract

The invention discloses a method for regulating and controlling the settlement of a widened roadbed based on a constraint separation wall, which relates to the technical field of civil engineering and comprises the following steps: S1, determining the horizontal position and the vertical depth of the constraint separation wall according to the width of a widened part roadbed, so that the settlement curve is the most smooth after the top of the widened roadbed is constructed; s2, an old roadbed step scheme is designed according to the position of the constraint separation wall, and step excavation is conducted; s3, according to the horizontal position of the constraint separation wall, construction of the constraint separation wall is conducted on the surface of the excavated step; and S4, new roadbed soil is filled and compacted, the constraint isolation wall and the excavated steps are covered, and roadbed widening and settlement control are completed. According to the method for regulating and controlling settlement of the widened roadbed based on the constraint separation wall, the fatigue life of the pavement can be greatly prolonged, the long-term use performance of the pavement can be guaranteed, cost reduction, efficiency improvement, low-carbon life extension and human-material-machine use cost reduction of road reconstruction and extension projects can be realized, and the construction period can be shortened.

Description

Technical Field

[0001] The present invention relates to the technical field of civil engineering, and in particular to a method for controlling settlement of a widened roadbed based on a constrained isolation wall. Background Art

[0002] With economic development, existing expressways are unable to meet growing traffic demands, leading to a rapid increase in highway reconstruction and expansion projects in my country. Roadbed widening is a common method of highway reconstruction and expansion. When the fill is high and the soil quality is poor, the new and old roadbeds will interact and cause uneven settlement. This uneven settlement can cause additional stress on the widened road surface, leading to longitudinal cracks and other defects, seriously compromising the durability of the reconstructed and expanded road surface.

[0003] To address differential subgrade settlement in roadbed renovation and expansion projects, numerous treatment measures have been proposed, including enhanced compaction, riprap to squeeze out silt, partial backfill replacement, lightweight fill, and geogrid reinforcement. When the fill is high and the soil quality is poor, pile-based composite foundation treatment is also necessary. Composite foundations can effectively reduce absolute settlement, but when the fill is high, the treatment area required is large, making them less economical. Furthermore, they cannot effectively control the shape of the post-construction settlement curve, and their effectiveness in reducing additional stress on the road surface is limited.

[0004] Isolation measures between the new and old roadbeds can effectively reduce the impact of the new roadbed on the old one, and some research has been conducted. However, some existing technologies place isolation measures only below the original surface, failing to constrain lateral deformation of the old roadbed and requiring steep excavation of the old roadside slope, making implementation difficult. Some isolation measures use pile treatment, which fails to limit ground rheology and extends beyond the top of the roadbed, easily causing uneven settlement of the pile-soil pavement and potentially causing road bulging. Other combined retaining structures are overly complex, with cumbersome procedures, making implementation difficult. Furthermore, most treatment measures are introduced too late, failing to control settlement during construction.

[0005] How to develop a method for controlling the settlement of a widened roadbed based on a constrained isolation wall, effectively controlling the settlement of the roadbed, reducing the additional stress on the road surface and preventing longitudinal cracks from occurring in the widened road surface after expansion and reconstruction, has become a technical problem that needs to be solved urgently by those skilled in the art. Summary of the Invention

[0006] The purpose of the present invention is to provide a method for controlling the settlement of a widened roadbed based on a constrained isolation wall, so as to solve the problems listed in the background technology.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions: The present invention provides a method for controlling settlement of a widened roadbed based on a constrained isolation wall, comprising the following steps: S1. Determine the horizontal position and vertical depth of the restraining isolation wall based on the width of the widened roadbed, so that the settlement curve of the top of the widened roadbed is the flattest after construction. The plumb line at the point where the top of the widened roadbed is 1 / 4 of the width from the edge is the horizontal position of the restraining isolation wall. The formula for determining the vertical depth h of the restraining isolation wall is h=-0.0031H. 3 +0.1008H 2 +0.3761H+7.3-3W / 4n, where H is the fill height, W is the widening width, and n is the slope of the old roadbed; S2. Based on the location of the restraining isolation wall, design a step plan for the old roadbed and excavate the steps. Project downward from a point 1 / 4 the width of the top of the widened section of the roadbed to the edge, and intersect it with the old roadbed slope at a point located at the outer corner of the step. Based on this, design the excavation plan for the old roadbed steps. The step width is designed to be 1.3m to 1.8m, and the height is designed to be 0.8m to 1m. S3. According to the horizontal position of the restraining isolation wall, the restraining isolation wall is constructed from the surface of the excavated step; S4. Fill the new roadbed soil and compact it to cover the restraining isolation wall and excavated steps, and complete the roadbed widening and settlement control.

[0008] Preferably, the step S3 specifically includes the step where the outer corner of the step is located being the top position of the constrained isolation wall, and the wall construction of the constrained isolation wall is carried out from the top position downward, the vertical depth of the constrained isolation wall is h, and the wall width of the constrained isolation wall is 50 to 80 cm.

[0009] Preferably, the constrained isolation wall is a cement soil continuous wall or a channel-cut deep mixing underground cement soil continuous wall.

[0010] Preferably, the step S4 specifically includes completing the construction of the restraining isolation wall and, after qualified monitoring, carrying out the roadbed filling normally, covering the restraining isolation wall and the excavated steps, and completing the roadbed widening and settlement control.

[0011] Compared with the prior art, the present invention has the following beneficial technical effects: The present invention discloses a method for controlling subgrade settlement during widening based on a constrained isolation wall. The method does not control the total subgrade settlement or directly support the pavement structure. Instead, it allows a certain absolute subgrade settlement to occur. By controlling the additional stress on the pavement, the method uses the simplest measures to treat the situation. The method also limits the lateral deformation of the old embankment caused by the new subgrade, as well as the horizontal rheology of the soil foundation after construction, thereby adjusting the post-construction settlement curves of the old and new subgrades. The top of the restraining wall is required to not extend beyond the new roadbed but to be on the slope steps of the old roadbed. This can avoid road surface uplift caused by differential settlement of the earth wall, advance the construction time of the restraining wall, limit settlement during the construction period, and thus shorten the overall construction period. The restrained isolation wall can achieve precise adjustment of the post-construction settlement curve of the new and old roadbeds, reducing the differential settlement of the old road by about 20% and the additional stress on the old road surface throughout the entire process by about 40%. It can almost eliminate the slope change at the junction of the new and old roadbeds after construction, making the post-construction settlement curve smoother, and reducing the additional tensile stress at the bottom of the base layer at the junction by 70% and the additional shear stress on the surface layer by 60%. It can also significantly improve the fatigue life of the road surface and ensure the long-term performance of the road surface, which is of great significance to achieving cost reduction, efficiency improvement, low-carbon and life extension of road reconstruction and expansion projects. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The present invention will be further described below with reference to the accompanying drawings.

[0013] Figure 1 This is a schematic diagram of the treatment of the constraint isolation wall of the present invention; Figure 2 This is a flow chart of a method for controlling settlement of a widened roadbed based on a constrained isolation wall according to the present invention; Figure 3 A schematic diagram illustrating the position determination of a constrained isolation wall according to an embodiment of the present invention; Figure 4 The final total settlement curve of the new and old roadbed tops with the restraining isolation wall measures adopted in the present invention; Figure 5 This is a graph showing additional stress on the old pavement caused by the total differential settlement when the restraining isolation wall measures are taken in the present invention; Figure 6 A post-construction settlement curve diagram of the top of the new and old roadbeds adopting the restraining isolation wall measures of the present invention; Figure 7 This is a curve diagram of additional stress at the base of the widened pavement caused by post-construction differential settlement when the restraining isolation wall measures are taken in the present invention. DETAILED DESCRIPTION

[0014] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is 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.

[0015] like Figure 1-7 As shown, a method for controlling settlement of a widened roadbed based on a constrained isolation wall includes the following steps: S1. Determine the horizontal position and vertical depth of the restraining isolation wall based on the width of the widened roadbed, so that the settlement curve of the top of the widened roadbed is the flattest after construction. The horizontal position of the restraining isolation wall is related to the widening width. The plumb line at the point where the top of the widened roadbed is 1 / 4 of the width from the edge is the horizontal position of the restraining isolation wall. Furthermore, the optimal vertical depth of the restraining isolation wall is determined by the fill height, widening width, and the slope of the old roadbed. The formula for determining the vertical depth h of the restraining isolation wall is h=-0.0031H. 3 +0.1008H 2 +0.3761H+7.3-3W / 4n, where H is the fill height, W is the widening width, and n is the slope of the old roadbed. Setting a restraining 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, if the calculated wall depth reaches a strongly differentiated rock stratum with a uniaxial compressive strength exceeding 1 MPa, the required depth is taken as the location of that rock stratum. S2. Based on the location of the restraining isolation wall, design a step plan for the old roadbed and excavate the steps. Project downward from a point 1 / 4 the width of the top of the widened section of the roadbed to the edge, and intersect it with the old roadbed slope at a point located at the outer corner of the step. Based on this, design the excavation plan for the old roadbed steps. The step width is designed to be 1.3m to 1.8m, and the height is designed to be 0.8m to 1m. S3. According to the horizontal position of the restraining isolation wall, the restraining isolation wall is constructed from the surface of the excavated step; S4. Fill the new roadbed soil and compact it to cover the restraining isolation wall and excavated steps, and complete the roadbed widening and settlement control.

[0016] Specifically, the step S3 includes the step where the outer corner of the step is located as the top position of the constrained isolation wall, and the wall construction of the constrained isolation wall is carried out from this position downward. The vertical depth of the constrained isolation wall is h, the wall width of the constrained isolation wall is 50 to 80 cm, and the modulus range is about 100 MPa.

[0017] Specifically, the constrained isolation wall is a cement soil continuous wall or a channel-cut deep mixing underground cement soil continuous wall.

[0018] Specifically, the step S4 includes completing the construction of the restraining isolation wall and, after qualified monitoring, carrying out the roadbed filling normally, covering the restraining isolation wall and the excavated steps, and completing the roadbed widening and settlement control.

[0019] Example

[0020] The soil quality of the highway reconstruction and expansion project in a coastal area is poor. The parameters are shown in Table 1. The widening width is 15 + 7.5m on both sides, the fill height is 10m, and the slope ratio of the new and old roadbeds is 1:1.5. According to the aforementioned design method and construction scheme of a restrained isolation wall for accurately controlling the differential settlement of a high fill and widened roadbed, the schematic diagram of the restrained isolation wall is as follows: Figure 1 As shown in the flow chart, Figure 2 As shown, the specific implementation is as follows: Table 1 Soil parameters in this area

[0021] 1) If 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 roadbed edge, and project this point downward to a point on the old roadbed slope. 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 the ground and 8m is below the wall; 3) Finally, determine the width and modulus of the isolation wall. This project is in deep soft soil conditions, but the fill is not too high. According to the requirements of this invention, the thickness is 50 cm and the modulus is 100 MPa. 4) Based on the previously determined position of the restraining isolation wall and the requirement that the outer corner of a step roughly coincide with the projection point of the old roadbed slope, a step plan for the old roadbed is designed and excavated. In this example, the steps above the projection point are approximately 1.4m × 0.95m (width × height), with a total of five steps; the steps below the projection point are approximately 1.55m × 1.05m (width × height), with a total of five steps, which meets the requirements; 5) Construction of the restrained isolation wall is carried out. The step where the outer corner of the step is located is the height position of the wall top. A width of 50cm is taken inward from the step corner to be the specific wall top position. The wall is then constructed to a total depth of 13.25m. The construction can be carried out in the form of a cement soil continuous wall or a channel cutting deep mixing underground cement soil continuous wall method (TRD method). The isolation wall can be constructed before the roadbed is filled. Alternatively, the roadbed can be filled to the same level as the wall top step, and the TRD equipment working platform can be built before the isolation wall is constructed. Carry out surveying and setting out and trench excavation. After the equipment is in place, cut vertically along the designated wall location and advance in sections. According to the target treatment modulus and foundation soil quality, different cement content is adopted in the stages above and below the original surface. For this working condition, the compression modulus of the embankment is 30MPa, the compression modulus of the soft soil is 3-4MPa, the cement content is 15% above the original surface, and 25% below the original surface. The horizontal advancement speed is 0.6m / h, the knife chain speed is 12-15rpm, the water-cement ratio is 0.8-1.2 (adjusted according to fluidity), and the grouting pressure is 0.5-1.0MPa to ensure the uniformity of the wall. 6) After monitoring the wall construction, the roadbed is filled as normal, covering the isolation wall and excavated steps, completing the roadbed widening and settlement control. This roadbed filling process, after the wall construction is complete, allows the roadbed to be quickly filled to the desired elevation, paved, and opened to traffic without requiring static or preloading.

[0022] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0023] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for controlling settlement of a widened roadbed based on a constrained isolation wall, characterized by: The steps include: S1. Determine the horizontal position and vertical depth of the restraining isolation wall based on the width of the widened roadbed, so that the settlement curve of the top of the widened roadbed is the flattest after construction. The plumb line at the point where the top of the widened roadbed is 1 / 4 of the width from the edge is the horizontal position of the restraining isolation wall. The formula for determining the vertical depth h of the restraining isolation wall is h=-0.0031H. 3 +0.1008H 2 +0.3761H+7.3-3W / 4n, where H is the fill height, W is the widening width, and n is the slope of the old roadbed; S2. Based on the location of the restraining isolation wall, design a step plan for the old roadbed and excavate the steps. Project downward from a point 1 / 4 the width of the top of the widened section of the roadbed to the edge, and intersect it with the old roadbed slope at a point located at the outer corner of the step. Based on this, design the excavation plan for the old roadbed steps. The step width is designed to be 1.3m to 1.8m, and the height is designed to be 0.8m to 1m. S3. According to the horizontal position of the restraining isolation wall, the restraining isolation wall is constructed from the surface of the excavated step; S4. Fill the new roadbed soil and compact it to cover the restraining isolation wall and excavated steps, and complete the roadbed widening and settlement control.

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

3. The method for controlling settlement of a widened roadbed based on a constrained isolation wall according to claim 1, characterized in that: The restrained 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 a widened roadbed based on a constrained isolation wall according to claim 1, characterized in that: The step S4 specifically includes completing the construction of the restraining isolation wall and, after qualified monitoring, carrying out the normal roadbed filling, covering the restraining isolation wall and the excavated steps, and completing the roadbed widening and settlement control.

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