Construction method for multi-layer three-dimensional tracking full replacement treatment of soft foundation

Abstract

The invention discloses a construction method for multi-layer three-dimensional tracking full replacement treatment of a soft foundation, and relates to the technical field of hydraulic engineering construction. The construction method comprises the following steps that a soft interlayer is decomposed into a plurality of soft rock stratums which are connected in sequence in the vertical direction; selecting a plurality of to-be-processed layers with processing conditions; processing is started from a certain to-be-processed layer with conditions, and the to-be-processed layer is decomposed into a plurality of replacement adits which are connected in sequence; when the replacement adit on the outermost edge is excavated to the preset depth, concrete backfilling is conducted on the excavated part; the remaining replacement adit is sequentially subjected to excavation and concrete backfilling; the next to-be-treated layer with the conditions is selected for excavation and concrete backfilling till concrete replacement of all the to-be-treated layers is completed; and finally, the remaining soft rock stratum is excavated, and concrete backfilling is carried out, so that concrete full replacement of the soft rock stratum is completed. The soft foundation can be completely replaced by a backfilled concrete structure, and potential safety hazards caused by replacement of part of the soft foundation are avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of hydraulic engineering construction, and particularly relates to a construction method for multi-layer three-dimensional tracking and full replacement treatment of soft foundations. Background Art

[0002] An arch dam is an arch-shaped water retaining structure that bulges upstream on a plane, and uses the action of the arch to transfer all or part of the water pressure to the bedrock on both sides of the river valley. Therefore, the arch dam has relatively high requirements for the shape of the river valley at the dam site and the foundation. The stability of the mountain body at the dam abutment is a necessary condition to ensure the safety of the arch dam. However, in actual projects, due to complex geological conditions, faults, joint fissures, extrusion dislocation zones, rock mass weathering, unloading, soft rock masses, etc. may exist in the rock mass at the dam abutment. To ensure the safety of the arch dam, the treatment plan for the soft foundation at the dam abutment has become a major technical problem in the design of many arch dams.

[0003] In the design scheme for treating the soft foundation at the arch dam abutment, to avoid the safety risks caused by excessive excavation span and height of the soft foundation, generally, shear resistance holes, anchoring holes, concrete frames, etc. are used for treatment. The essence of these treatment methods is to use the concrete structure to partially replace the soft foundation to form a force transmission body, so as to achieve the purpose of transmitting the force from the upstream mountain body to the downstream mountain body. However, since only part of the soft foundation is replaced, the stress condition of the formed concrete structure is relatively poor, and local tensile stress often occurs during the normal operation of the arch dam, leaving hidden dangers for the safe operation of the arch dam, causing problems such as non-convergent deformation of the slope near the dam after impoundment, and even tensile cracks may occur, affecting the force transmission effect. It is difficult to ensure the safety, reliability, and durability of the project. Moreover, when using shear resistance holes, anchoring holes, concrete frames, etc. for treatment, shaft or inclined shaft excavation is often required during the excavation process. For soft surrounding rocks, the construction safety risk is relatively large. Summary of the Invention

[0004] In order to solve the deficiencies of the prior art, the purpose of the present invention is to provide a construction method for multi-layer three-dimensional tracking and full replacement treatment of soft foundations, which can achieve full replacement of the soft foundation with a backfilled concrete structure, avoiding the safety hazards caused by partial replacement of the soft foundation; at the same time, it can also decompose the soft foundation into several replacement adits with relatively small excavation risks for treatment, reducing the safety risks of shaft or inclined shaft excavation such as shear resistance holes and frame excavation holes, and the excavation and concrete backfilling construction are also more convenient and fast.

[0005] The present invention is realized through the following technical solutions: A construction method for multi-layer three-dimensional tracking and full replacement treatment of soft foundations includes the following steps: S1: Obtain the soft interlayer to be treated, and decompose the soft interlayer into a number of soft rock layers that are sequentially connected in the vertical direction; S2: Among several said soft rock strata, select several strata to be treated that meet the treatment conditions, and start the treatment from a stratum to be treated that meets the conditions; S3: Decompose a stratum to be treated that starts first into several replacement adits connected in sequence from one side to the other side of itself, and first excavate the outermost replacement adit; S4: When the outermost replacement adit is excavated to a predetermined depth, backfill the excavated part with concrete; S5: After the concrete reaches the support strength, successively excavate and backfill the remaining said replacement adits until the concrete replacement of a stratum to be treated that starts first is completely completed; S6: Repeat steps S3 - S5, select the next stratum to be treated that meets the conditions for excavation and concrete backfilling until the concrete replacement of several strata to be treated is completely completed; S7: Finally, excavate the remaining soft rock strata and backfill with concrete, thus completing the full concrete replacement of the said soft interlayer.

[0006] Compared with the replacement of some soft foundations in the prior art, the formed concrete structure has relatively poor stress conditions, and local tensile stress often occurs during the normal operation of the arch dam, leaving hidden dangers for the safe operation of the arch dam, causing problems such as non - convergent deformation of the slope near the dam after impoundment. The present invention provides a construction method for treating soft foundations by multi - layer three - dimensional tracking full replacement, which can realize the full replacement of the soft foundation with a backfilled concrete structure, avoiding the potential safety hazards caused by the replacement of some soft foundations; at the same time, it can also decompose the soft foundation into several replacement adits with relatively small excavation risks for treatment, reducing the safety risks of the excavation of vertical shafts or inclined shafts such as shear - resistant holes and frame - excavated holes, and the excavation and concrete backfilling construction are also more convenient and fast. It is mainly applied to the treatment of the soft foundation of the arch dam shoulder, but for the soft foundation of the gravity dam and other soft foundations that need to be treated, this design scheme can also be used for treatment.

[0007] Further optimize, the boundary of the outermost said replacement adit is the demarcation line between the soft foundation and the hard foundation.

[0008] Further optimize, use the outermost replacement adit of each treatment layer as a detection hole for the soft foundation, so as to further confirm the boundary and shape of the soft foundation during the construction process.

[0009] Further optimize, during the process of excavating the said replacement adit, temporary support needs to be carried out by shotcrete with bolts and steel supports.

[0010] Further optimize, before pouring backfill concrete in the said replacement adit, several anchor bolts need to be embedded in the side wall of the replacement adit, one end of the anchor bolt extends into the hard bedrock or the already poured concrete, and the other end is located in the replacement adit.

[0011] For further optimization, step S5 further includes the following sub-steps: Before the remaining replacement adits are backfilled with concrete, the concrete that has been cast and backfilled on the peripheral sides needs to be roughened.

[0012] For further optimization, when excavating the remaining soft rock strata, all the remaining soft foundations at the crowns in the already backfilled and treated layers need to be dug out and backfilled with concrete.

[0013] For further optimization, during the excavation of the replacement adits, at least one original soft rock foundation for support needs to be reserved in the middle of the excavation area, and the replacement adits are excavated around the original soft rock foundation.

[0014] For further optimization, after the excavation of the replacement adits around the original soft rock foundation is completed, the circumferential area of the original soft rock foundation is backfilled with concrete, and an exit passage connected to the original soft rock foundation is reserved; After the concrete backfilling of the circumferential area of the original soft rock foundation is completed and the support strength is reached, the original soft rock foundation is excavated, and the area where the original soft rock foundation is located is backfilled with concrete; After the concrete backfilling of the area where the original soft rock foundation is located is completed, the exit passage is backfilled with concrete.

[0015] For further optimization, before the layer to be treated is excavated, a construction access road connected to the entrance of the layer to be treated or a construction branch tunnel connected to the exit of the layer to be treated is also excavated.

[0016] Compared with the prior art, the present invention has the following advantages and beneficial effects: The present invention provides a construction method for multi-layer three-dimensional tracking and full replacement treatment of soft foundations, which can realize the full replacement of soft foundations with backfilled concrete structures, avoiding potential safety hazards caused by partial replacement of soft foundations; at the same time, it can also decompose soft foundations into several replacement adits with relatively low excavation risks for treatment, reducing the safety risks of shaft or inclined shaft excavations such as shear resistance holes and frame excavation holes, and the excavation and concrete backfilling construction are also more convenient and fast. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the following will briefly introduce the drawings required for the embodiments. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings. In the drawings: Figure 1Construction flow chart of a multi - layer three - dimensional tracking full replacement method for treating soft foundation, which is disclosed by the present invention; Figure 2 Schematic plan view of the distribution of soft foundation at the downstream dam shoulder of a certain arch dam in Embodiment 1 disclosed by the present invention; Figure 3 Schematic elevation view of the treatment of soft foundation at the downstream dam shoulder of a certain arch dam in Embodiment 1 disclosed by the present invention; Figure 4 Three - dimensional schematic diagram of the distribution of soft rock at the downstream dam shoulder of a certain reservoir arch dam in Embodiment 2 disclosed by the present invention; Figure 5 Front elevation schematic diagram of the distribution of soft rock at the downstream dam shoulder of a certain reservoir arch dam in Embodiment 2 disclosed by the present invention; Figure 6 Backfill procedure diagram for the treatment of salt - dissolved breccia in the 5th replacement adit in Embodiment 2 disclosed by the present invention; Figure 7 Backfill procedure diagram for the treatment of salt - dissolved breccia in the 8th replacement adit in Embodiment 2 disclosed by the present invention; Figure 8 Backfill procedure diagram for the treatment of salt - dissolved breccia in the 11th replacement adit in Embodiment 2 disclosed by the present invention. Detailed implementation manners

[0018] To make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the embodiments and the accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0019] Embodiment 1: As shown in Embodiment 1 Figures 1-3 it provides a soft interlayer distributed at the downstream of a certain arch dam and its construction treatment procedures.

[0020] As shown in the attached Figure 2 drawings, there is a soft interlayer distributed at the downstream of a certain arch dam, and its width is B. Through the stress analysis and calculation of the arch dam, in the vertical direction as shown in Figure 3 the height that needs to be treated for this interlayer is H. If the soft interlayer is excavated and then backfilled with concrete at one time, a large height difference during the excavation of the soft interlayer will bring huge safety hazards; while if partial excavation is carried out by means of shear - resistant holes, anchor holes, concrete frames, etc., the poor stress conditions of the locally replaced concrete structure will bring safety hazards to the normal operation of the arch dam. The present invention proposes to adopt a method of setting multi - layer three - dimensional tunnels to track and excavate and backfill in time to achieve the full replacement treatment of the soft foundation, and replace the excavated soft rock mass with concrete that meets the stress requirements of the arch dam.

[0021] The specific construction method steps of the present invention are as follows: 1) Decompose the weak interlayer of the arch dam shoulder that needs to be treated into several weak rock layers in the vertical direction. The height can generally be 3 to 12 meters according to the actual situation of the project to avoid the safety risk caused by excavating too high a height of the weak interlayer at one time. Figure 3 As shown, in this example, the weak interlayer within the height H range needs to be dealt with in the downstream of a certain arch dam, and it is divided into 7 layers.

[0022] 2) Each layer needs to be completely connected from top to bottom to ensure that all vertical weak interlayers can be excavated and processed. Each weak rock layer can be divided into several replacement flat tunnels with excavation sections of 3-10m×3-12m (width×height). The specific section size can be determined comprehensively based on the distribution shape of the weak interlayer to be processed, the project progress requirements, the configuration of construction machinery, etc. Figure 3 The third layer is divided into two left and right displacement tunnels, and the remaining layers can also be decomposed into two small left and right displacement tunnels. The cross-section of each displacement tunnel can be a conventional city gate tunnel type.

[0023] 3) A replacement tunnel of a certain layer can be excavated when conditions are met, and its excavation section is 3~10m×3~12m (width×height). Taking the third layer as an example, assuming that its construction traffic conditions are relatively good and the excavation conditions can be met earlier, the replacement tunnel on the left or right side can be excavated first. In this example, it is assumed that the replacement tunnel on the right side is excavated first. Due to the uncertainty of underground engineering, the replacement tunnel on the right side that is excavated first can also be used as an exploration hole for soft foundations, and its right boundary can be the boundary between soft foundations and hard foundations, so as to further clarify the actual boundary distribution of soft foundations. The temporary stability of the replacement tunnel on the right side can be solved by conventional "anchor spraying + steel support" measures according to the surrounding rock type.

[0024] 4) After the third-layer right replacement tunnel is excavated to the designed depth, the excavated part can be backfilled with concrete to support the upper rock mass and avoid the safety risks caused by long-term exposure after tunnel excavation. In order to ensure the stability of the upper backfilled concrete during the lower excavation process, a part of the anchor rods can be embedded in the hard bedrock before the upper concrete is poured, and a part of the anchor rods can be embedded in the concrete to be poured, so that the anchor rods can stabilize the upper concrete after pouring.

[0025] 5) After the strength of the poured concrete in the right replacement tunnel of the third layer is strong enough to play a supporting role, the left replacement tunnel of the third layer that has not yet been excavated can be excavated. The weak surrounding rock of the arch can be supported by "anchor spraying + steel support" measures. For the hard foundation on the left boundary of the replacement tunnel and the poured concrete on the right boundary, the support measures can be appropriately simplified according to the safety monitoring data.

[0026] 6) After the left replacement adit of the third layer is excavated to the designed depth, the excavated part can be backfilled with concrete, and then the replacement of the soft foundation of the third layer with concrete is completely completed. To ensure the quality of the bond between the backfilled concrete on the left and right sides, the old concrete that has been poured should be roughened before the new concrete is poured. At the same time, some anchor bolts should be embedded in the hard bedrock and the poured concrete to enhance stability.

[0027] 7) Continue to process the replacement adits of other layers. Select a layer that meets the treatment conditions and repeat steps 3) to 6). Through the above excavation and backfilling treatment methods and steps, the entire soft foundation of the arch dam abutment that needs to be treated can be completely excavated and replaced with concrete. It should be noted that for the soft foundation that has been backfilled in the lower layer during excavation, such as when the fourth layer is excavated as previously assumed and the third layer has been backfilled with concrete, the remaining soft foundation at the top of the third layer should be excavated together during the excavation of the fourth layer to ensure that the entire soft foundation that needs to be treated is completely cleaned.

[0028] Through the above steps, it is possible to replace the entire soft foundation with backfilled concrete structure, avoiding potential safety hazards caused by partial replacement of the soft foundation. At the same time, it is also possible to decompose the soft foundation into several replacement adits with relatively low excavation risks for treatment, reducing the safety risks of shaft or inclined shaft excavations such as shear resistance holes and frame excavation holes. The excavation and concrete backfilling construction are also more convenient and fast.

[0029] Example 2: This Example 2 further optimizes on the basis of Example 1 to optimize the internal construction procedures of the replacement adit; as Figures 4-8 described, it is the soft interlayer distributed downstream of the arch dam of a certain reservoir and its construction treatment procedures.

[0030] A certain reservoir project is located in the upper reaches of the canyon section of Qianhe, a left tributary of a certain place. The water retaining dam is a 132m high roller compacted concrete double-curved arch dam. The elevation of the dam crest is 565.30m, and the elevation of the dam bottom is 433.30m. The lithology in the dam site area is mainly composed of unequal-thickness interbeds of limestone of the Lower Triassic Jialingjiang Formation (T 1j ) and salt solution breccia. The local span of the soft foundation is up to more than 30 meters, and the upper and lower displacements are irregularly distributed, as shown in Attachment Figure 4 and Attachment Figure 5 shown. After systematic calculation and analysis of the factors affecting the stability and deformation of the dam, such as the natural state, treatment scope, treatment plan, etc., the T 1j ⑤ layer of argillaceous cemented salt solution breccia in the range of elevation 433.3 - 510m on the downstream side of the left dam abutment adopts the full replacement scheme proposed by the present invention, that is, the soft foundation in the range of elevation 433.3 - 510m is completely excavated and backfilled tightly with C20 slightly expanded concrete. According to the on-site construction traffic conditions, the soft foundation that needs to be treated is divided into 11 layers of replacement adits from bottom to top, as shown in Table 1 for details.

[0031] Table 1: Stratified Characteristics Table of Treatment of Soft Rock at the Downstream Dam Shoulder of an Arch Dam in a Reservoir

[0032] In actual construction, the first replacement adit to be excavated is the 5th layer, followed by the 8th layer and the 11th layer. Taking the treatment methods of these three layers as an example, the construction steps in a specific case of the present invention will be further described. To better reflect the situation during the construction process, the time node selected for this case is October 2020, when each replacement adit was under excavation and backfilling treatment.

[0033] (1) Steps for clearing halokarst breccia and backfilling with concrete in the 5th layer replacement adit (EL466 - 473m): Using the temporary construction access road built during the foundation pit excavation, enter the adit directly from the exposed halokarst breccia part on the slope. The excavation section of the main adit is 6×7m. The excavation of halokarst breccia at EL466 - 473m is as shown in the appendix. Figure 6 As the distribution of halokarst breccia in this layer is relatively simple, the excavation and backfilling steps are also relatively simple. By October 2020, there was still uncleared halokarst breccia at the upstream end inside the adit. Its property was that the upper part had low strength and the lower part had relatively high strength. The treatment method was: to avoid safety risks caused by too long excavation time, directly backfill the excavated area of the 5th layer replacement adit with slightly expanded concrete; then, when excavating the halokarst breccia replacement adit at the upper layer EL473 - 480m, use the method of local under - excavation to remove the upper part with poor properties of the remaining halokarst breccia at EL466 - 473m and then backfill with concrete. The better - strength mixed - cemented halokarst breccia in the lower part can be retained, which can meet the requirements of force transfer between the upstream and downstream of the bedrock.

[0034] (2) Steps for clearing the halokarst breccia replacement adit and backfilling with concrete in the 8th layer replacement adit (EL486 - 493m): The excavation section of the main adit is 6×7m. In actual construction, it is carried out along the boundary where limestone intersects with halokarst breccia. First, complete the excavation around the halokarst breccia (as shown in areas C1, C2, C3, and C4 in the appendix), and retain the halokarst breccia in the middle as a support to ensure the stability of the chamber (as shown in areas B1 and B2 in the appendix). For the remaining soft halokarst breccia that has not been cleared (as shown in areas B1 and B2 in the appendix), adopt the method of backfilling with concrete in parts to form a support and then excavating in blocks. For details, see the appendix. Figure 7 (as shown in areas C1, C2, C3, and C4 in the appendix), retain the halokarst breccia in the middle as a support to ensure the stability of the chamber (as shown in areas B1 and B2 in the appendix). Figure 7 For the remaining soft halokarst breccia that has not been cleared (as shown in areas B1 and B2 in the appendix), Figure 7 adopt the method of backfilling with concrete in parts to form a support and then excavating in blocks. For details, see the appendix. Figure 7As shown, to more clearly reflect the excavation procedure of the middle argillaceous salt-solution breccia, this figure selects the period when the peripheral excavation was completed in October 2020 and the middle argillaceous salt-solution breccia had not been excavated yet. The replacement treatment steps of the salt-solution breccia in the 8th replacement adit (EL486 - 493m) are shown in Table 2 in detail.

[0035] Table 2: Table of replacement treatment steps for the salt-solution breccia in the 8th replacement adit (EL486 - 493m)

[0036] (3) Steps for excavation and concrete backfilling of the salt-solution breccia replacement adit in the 11th replacement adit (EL506 - 513m): The excavation cross-section of the main adit is 6×7m. Due to the limitation of the on-site terrain conditions, the actual construction starts from the 1# branch adit excavated from the 506 construction access road and proceeds along the boundary where the limestone intersects with the salt-solution breccia. First, the excavation around the salt-solution breccia is completed (as shown in areas C1, C2, and C3 in the attachment Figure 8 ), and the middle salt-solution breccia is reserved as a support to ensure the stability of the cavern (as shown in areas B1 and B2 in the attachment Figure 8 ). Later, since the 506 access road needs to be dug through for the dam foundation excavation, a 503 construction branch adit is added as a construction access road for the later excavation and backfilling to avoid affecting the dam construction period. To avoid potential safety hazards caused by too large an excavation span, for the remaining soft salt-solution breccia that has not been cleared (as shown in areas A1, B1, and B2 in the attachment Figure 8 ), the method of backfilling concrete in parts to form a support and then excavating in blocks is adopted. To more clearly reflect the excavation procedure of the middle argillaceous salt-solution breccia, this figure selects the period when the peripheral excavation was completed and the middle argillaceous salt-solution breccia had not been excavated yet. The replacement treatment steps of the salt-solution breccia in the 11th replacement adit (EL506 - 513m) are shown in Table 3 in detail.

[0037] Table 3: Table of replacement treatment steps for the salt-solution breccia in the 11th replacement adit (EL506 - 513m)

[0038] The treatment of the remaining layers is basically similar to the above three layers, and will not be elaborated in this article. As of the end of 2023, the excavation and backfilling treatment of the salt-solution breccia on the downstream side of the left dam shoulder of this reservoir has been completed. No production safety accidents occurred during the process, and the effect of the backfilled concrete is also good. No cracks or other situations were found, indicating the safety and reliability of the present invention.

[0039] The specific embodiments described above further elaborate on the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only the specific embodiments of the present invention and is not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A multi-layer three-dimensional tracking full replacement construction method for treating soft foundation, characterized in that: The following steps are involved: S1: obtaining a weak interlayer to be processed, and decomposing the weak interlayer into a plurality of soft rock layers connected in sequence in a vertical direction; S2: Selecting several layers to be treated that meet the treatment conditions from among the several soft rock layers, and starting the treatment from one of the layers to be treated that meets the conditions; S3: Decompose the first layer to be treated from one side to the other side into a number of replacement flat holes connected in sequence, and excavate the replacement flat hole at the edge first; S4: When the outermost replacement tunnel is excavated to a predetermined depth, the excavated part is backfilled with concrete; S5: When the concrete reaches the supporting strength, the remaining replacement holes are excavated and backfilled with concrete in sequence until the concrete replacement of the first layer to be treated is completed; S6: repeating steps S3 to S5, selecting the next qualified layer to be treated for excavation and concrete backfilling, until all the layers to be treated have completed concrete replacement; S7: Finally, the remaining soft rock layer is excavated and backfilled with concrete, thereby completing the full replacement of concrete in the soft interlayer.

2. A multi-layer three-dimensional tracking and full replacement construction method for treating soft foundation according to claim 1, characterized in that: The boundary of the outermost replacement adit is the dividing line between the soft foundation and the hard foundation.

3. The construction method of multi-layer stereoscopic tracking full replacement for treating soft foundation according to claim 1 is characterized in that: The replacement flat holes at the edge of each treatment layer are used as detection holes for the weak foundation to further confirm the boundaries and shapes of the soft foundation during the construction process.

4. The construction method of multi-layer stereoscopic tracking full replacement for treating soft foundation according to claim 1 is characterized in that: During the excavation of the replacement tunnel, anchor spraying and steel support are required for temporary support.

5. The construction method of multi-layer stereoscopic tracking full replacement for treating soft foundation according to claim 1 is characterized in that: Before pouring backfill concrete in the replacement flat tunnel, a number of anchor rods need to be pre-buried in the side wall of the replacement flat tunnel, one end of the anchor rod extends into the hard bedrock or the poured concrete, and the other end is located in the replacement flat tunnel.

6. The construction method of multi-layer stereoscopic tracking full replacement for treating soft foundation according to claim 1 is characterized in that: The step S5 further comprises the following sub-steps: Before backfilling the remaining replacement flat hole with concrete, the backfilled concrete on the surrounding side needs to be roughened.

7. The construction method of multi-layer stereoscopic tracking full replacement for treating soft foundation according to claim 1 is characterized in that: When excavating the remaining soft rock, the remaining soft foundation at all the vaults in the backfilled treated layer needs to be excavated and backfilled with concrete.

8. A multi-layer three-dimensional tracking and full replacement construction method for treating soft foundation according to any one of claims 1 to 6, characterized in that: During the excavation of the replacement tunnel, at least one original soft rock foundation for support needs to be retained in the middle of the excavation area, and the replacement tunnel is excavated around the original soft rock foundation.

9. The multi-layer three-dimensional tracking full replacement construction method for treating soft foundation according to claim 8 is characterized by: After the excavation of the replacement flat tunnel around the original soft rock foundation is completed, the circumferential area of ​​the original soft rock foundation is backfilled with concrete, and an exit passage connected to the original soft rock foundation is reserved; After the concrete pouring and backfilling in the peripheral area of ​​the original soft rock foundation is completed and the supporting strength is reached, the original soft rock foundation is excavated, and the area where the original soft rock foundation is located is poured and backfilled with concrete; After the concrete backfilling of the area where the original soft rock foundation is located is completed, the exit channel is backfilled with concrete.

10. The multi-layer three-dimensional tracking and full replacement construction method for treating soft foundation according to claim 1 is characterized in that: Before excavating the layer to be treated, a construction access road connected to the entrance of the layer to be treated or a construction branch hole connected to the exit of the layer to be treated is also excavated.

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