A method for designing and constructing a continuous trenching process trench wall stability

Abstract

The application provides a continuous trenching process trench wall stability design and construction method, which is used for determining the width of the reinforcing area in the trench wall reinforcing and maintaining step, scientifically decomposes the total lateral earth pressure load acting on the trench wall into the load borne by the reinforcing area and clearly reveals the collaborative working mechanism of the reinforcing area and the undisturbed soil by establishing a load proportion distribution model; the reinforcing area is simplified as a vertical stress component mechanical model bearing lateral load, which not only ensures the rigor of the theory, but also makes the calculation process simple and practical, and is convenient for engineering application; the minimum width of the reinforcing area can be quantitatively determined by checking the bending and shearing strength of the reinforcing area, and the blindness of the traditional experience method is avoided; meanwhile, the interface is checked for the anti-sliding stability, so that the interface is ensured not to be damaged by sliding, and a complete safety guarantee system is formed.

Description

Technical Field

[0001] This invention relates to the field of deep foundation pit and diaphragm wall construction technology in geotechnical engineering, specifically to a design and construction method for ensuring the stability of narrow and deep trench sections during trenching (before the pre-support structure is put into use) in the "trenching and supporting" process. Background Technology

[0002] In the construction of deep foundation pits and diaphragm walls, the stability of the trench walls during the excavation process is a key technical challenge, especially for narrow trench sections with large depths and relatively small widths. Traditional methods mainly rely on engineering experience or general strength reduction theories for trench wall reinforcement design, which has significant shortcomings: 1) Incomplete design theories often lead to overly conservative reinforcement schemes, resulting in wasted costs and difficulties in subsequent excavation, or insufficient reinforcement causing safety risks; 2) The mechanical mechanism of the collaborative work between the reinforced area and the undisturbed soil is not clearly revealed, especially the key load transfer effect of the reinforced area-undisturbed soil interface is ignored; 3) No specific analysis method has been established for the stress characteristics along the long side of narrow trenches.

[0003] Furthermore, existing methods typically do not specify the number of measuring points, their locations, sampling frequency, and stability criteria for the load reduction factor η. They also lack verification paths after rounding the candidate width, return conditions after the four verifications fail, and engineering calculation examples that include ground parameters, reinforced zone dimensions, complete calculation processes, field monitoring results, and comparisons with traditional empirical methods under the same working conditions. Consequently, it is difficult to verify the accuracy of the calculation model and to quantitatively evaluate the amount of reinforcement work and the safety reserve of the trench wall.

[0004] As can be seen from the above, the existing technology lacks a systematic approach that is theoretically clear, computationally simple, and can accurately guide the design of trench wall reinforcement to ensure the stability of the trench. Summary of the Invention

[0005] This invention aims to overcome the shortcomings of existing technologies and provide a theoretically rigorous and computationally simple method for designing and constructing the stability of deep and narrow trench walls. Based on an innovative load ratio distribution, this method can scientifically determine the width of the reinforcement zone, thereby determining the grouting reinforcement parameters. This ensures the self-stability of the trench section after excavation and before the pre-support system is activated, providing a safe foundation for the subsequent "support before excavation" process.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0007] A method for designing and constructing the stability of trench walls under continuous trenching technology, used to determine the width of the reinforced zone in the trench wall reinforcement and curing process. The method includes the following steps:

[0008] Step 1: Establish a load distribution model, including the total lateral earth pressure load acting on the trench wall. Decomposed into the load borne by the reinforced area Loads transferred between the reinforced zone and the undisturbed soil interface And determine the load reduction factor for the reinforced zone. ,0< <1, load reduction factor for reinforced zone Distribution coefficient characterizing the proportion of load borne by the reinforced zone;

[0009] Step 2: Simplify the reinforced area into a vertical load-bearing member that bears lateral loads, and calculate the total lateral earth pressure pa(z) at the depth z of the trench wall. The value of z ranges from 0 to H, where H is the distance from the bottom to the top of the reinforced area.

[0010] Step 3: Distribute the total lateral earth pressure on the trench wall according to the load reduction factor η to obtain the net distributed load acting on the reinforced area at depth z, and calculate the maximum bending moment and maximum shear force of the reinforced area based on the net distributed load acting on the reinforced area at depth z.

[0011] Step 4: Determine the minimum width of the reinforced zone based on both the bending strength condition and the shear strength condition, and take the larger of the two values ​​as the width of the reinforced zone. ;

[0012] Step 5: Perform anti-sliding stability calculation at the interface between the reinforced zone and the undisturbed soil. This calculation includes calculating the interfacial shear stress at depth z of the reinforced zone of the trench wall. The overall stability of the interface meets the safety requirements, and the local stability of the most dangerous part of the interface also meets the safety requirements. If the verification passes, proceed to step 7; if the verification fails, proceed to step 6.

[0013] Step 6: Adjust the interface strength parameters or increase the width of the reinforced area. Return to step 5, where the interface strength parameters include the interface cohesion ci and the interface internal friction angle Φi.

[0014] Step 7: Based on the width of the reinforced area and the interface stability calculation results determined above, implement the following steps in sequence: trench wall reinforcement and maintenance, deep trench excavation, hoisting and placing the pre-support structure, axial force loading of the pre-support structure, and trench backfilling, so as to ensure that the trench wall can be self-stabilized in the unsupported exposed stage after the deep trench excavation is completed and before the axial force loading of the pre-support structure.

[0015] Preferably, in the above-mentioned continuous trenching process for designing and constructing trench wall stability, the load reduction factor of the reinforced zone is... Based on field tests, n strain gauges were arranged at intervals along the depth direction in the reinforced area of ​​the trench wall, forming n measuring points. These n measuring points were located within the monitoring section at the middle of the long side of the trench wall, within a depth range of 0.2H to 0.9H, where n is a natural number greater than 1 and not less than 6. Additional measuring points were added at the stratum boundaries. Each strain gauge underwent temperature compensation and zero-point calibration after installation, and continuous data collection was performed for at least 30 minutes before excavation. During the unsupported exposure stage after trench excavation, the strain distribution at different depths in the reinforced area was measured, with a sampling interval of no more than 60 seconds. When the strain change rate of three adjacent sampling periods was no greater than 5%, the corresponding measured value was taken as stable data. When the coefficient of variation of the load reduction factor η of multiple monitoring sections was greater than 10%, additional monitoring sections were added and measurements were repeated. Based on the measured strain of each strain gauge and the elastic modulus of the reinforced area material, the load at each measuring point in the reinforced area was calculated. :

[0016]

[0017] In the formula: Let i be the load at the i-th measuring point; Let be the strain at the i-th measuring point; Let be the elastic modulus at the i-th measuring point, where n is a natural number greater than or equal to 1; i is the number of the measuring point, which is a positive integer greater than or equal to 1 and less than or equal to n.

[0018] The final value of η is the sum of the loads at each measuring point in the reinforced area. Summation of earth pressure at each measuring point in the reinforced area The ratio is determined as follows:

[0019]

[0020] In the formula: η is the load reduction factor of the reinforced zone; P 加固 (i) represents the equivalent load borne by the reinforced area at the i-th measuring point; p a (z i ) represents the lateral earth pressure at the depth of the i-th measuring point; z i Let be the depth of the i-th measuring point; n be the total number of measuring points; and i be the measuring point number.

[0021] Preferably, in the above-mentioned continuous trenching process for designing and constructing trench wall stability, in step 2, the total lateral earth pressure pa(z) at the trench wall depth z is calculated as active earth pressure, and the calculation formula is: ,

[0022] in: Active earth pressure coefficient, γ is the soil weight; z is the depth of the trench wall reinforcement zone; q is the ground surcharge.

[0023] Preferably, in the above-mentioned continuous trenching process for trench wall stability design and construction method, in step 3, the total lateral earth pressure on the trench wall is distributed according to the load reduction factor η to obtain the net distributed load acting on the reinforced area at depth z:

[0024] ;

[0025] In the formula: p 加固 (z) represents the net distributed load acting on the reinforced zone at depth z; η is the load reduction factor for the reinforced zone; p a (z) represents the total lateral earth pressure at a trench wall depth z;

[0026] Calculate the maximum bending moment of reinforced zone 2 based on the net distributed load acting on the reinforced zone at depth z: Maximum bending moment of reinforced zone Located at the bottom of the reinforced zone, at this point z=H:

[0027]

[0028] In the formula: η is the maximum bending moment in the reinforced zone; η is the load reduction factor for the reinforced zone; K a γ is the active earth pressure coefficient; H is the soil weight; H is the height of the reinforced zone; q is the equivalent uniformly distributed ground surcharge.

[0029] Calculate the maximum shear force of reinforced zone 2 based on the net distributed load acting on the reinforced zone at depth z: Maximum shear force of reinforced zone Located at the bottom of the reinforced zone, at this point z=H:

[0030] .

[0031] Preferably, in the above-mentioned continuous trenching process for designing and constructing trench wall stability, step 4, determining the minimum width of the reinforcement zone based on the bending strength condition as a bending strength verification, includes:

[0032] Calculate the section modulus of the reinforced zone :

[0033] = 2 / 6;

[0034] Meeting the bending strength requirement: the maximum bending stress in the reinforced zone. Tensile strength of reinforced area :

[0035]

[0036] In the formula: The maximum bending stress in the reinforced area; This represents the maximum bending moment in the reinforced area. B is the section modulus of the reinforced zone; B is the width of the reinforced zone. The tensile strength of the reinforced area;

[0037] To obtain the minimum width of the reinforced zone :

[0038]

[0039] In the formula: B is the minimum width of the reinforced zone required to meet the bending strength condition; f is the maximum bending moment in the reinforced zone. t This represents the tensile strength of the reinforced area.

[0040] Preferably, in the above-mentioned continuous trenching process for designing and constructing trench wall stability, in step 4, the tensile strength of the reinforced zone... =0.1q u q u This represents the unconfined compressive strength of the reinforced zone.

[0041] Preferably, in the above-mentioned continuous trenching process for designing and constructing trench wall stability, step 4, determining the minimum width of the reinforced zone based on shear strength conditions as a shear strength verification, includes:

[0042] Satisfying the shear strength condition: mean shear stress The shear strength of the reinforced zone must be less than or equal to that of the reinforced zone. :

[0043]

[0044] In the formula: The average shear stress of the reinforced section; B is the maximum shear force in the reinforced zone; B is the width of the reinforced zone. The shear strength of the reinforced zone;

[0045] Considering a stress non-uniformity coefficient of 1.5:

[0046]

[0047] In the formula: The maximum shear stress in the reinforced zone after considering the uneven distribution of shear stress; 1.5 is the shear stress unevenness coefficient; The average shear stress of the reinforced section; The shear strength of the reinforced zone;

[0048] have to: ;

[0049] In the formula: B is the minimum width of the reinforced zone required to meet the shear strength condition; f is the maximum shear force in the reinforced zone. v 1.5 represents the shear strength of the reinforced zone; 1.5 represents the shear stress non-uniformity coefficient.

[0050] Preferably, in the above-mentioned continuous trenching process for designing and constructing trench wall stability, in step 4, taking the larger of the two values ​​as the width of the reinforced zone means obtaining the width of the reinforced zone while simultaneously satisfying the bending strength and shear strength conditions. :

[0051] =MAX

[0052] In the formula: B is the width of the final reinforced area; This represents the maximum bending moment in the reinforced area. This represents the maximum shear force in the reinforced area. The tensile strength of the reinforced area; This represents the shear strength of the reinforced zone.

[0053] Preferably, in the above-described continuous trenching process for designing and constructing trench wall stability, in step 5,

[0054] Calculate the interfacial shear stress at depth z of the reinforced zone of the trench wall. :

[0055]

[0056] In the formula: η is the interfacial shear stress at depth z; η is the load reduction factor of the reinforced zone; p a (z) represents the total lateral earth pressure at depth z of the trench wall; (1-η) represents the proportion of load transferred through the interface;

[0057] Calculate the interfacial shear strength at depth z of the reinforced zone of the trench wall.

[0058]

[0059] In the formula: τ f (z) represents the interfacial shear strength at depth z, and c i For interfacial cohesion; Let Φ be the normal stress at depth z of the interface. i The angle of friction within the interface.

[0060] Preferably, in the above-mentioned continuous trenching process, the design and construction method for trench wall stability is as follows: the normal stress at the interface at depth z... =K0γz, where K0 is the static earth pressure coefficient, γ is the soil weight, and z is the depth of the trench wall reinforcement zone, with pore water pressure negligible.

[0061] Preferably, in the above-mentioned continuous trenching process for designing and constructing the trench wall stability, step 5, ensuring that the overall stability of the interface meets safety requirements, means that the overall safety factor of the interface...

[0062]

[0063] In the formula: F s整体 c is the overall safety factor along the entire depth of the interface; i γ is the interfacial cohesion; H is the height of the reinforced zone; K0 is the coefficient of earth pressure at rest; γ is the soil weight; Φ i η is the internal friction angle of the interface; η is the load reduction factor of the reinforced zone; K a 1 is the active earth pressure coefficient; q is the equivalent uniformly distributed ground surcharge; 2.0 is the safety factor limit for the overall stability of the interface.

[0064] Preferably, in the above-mentioned continuous trenching process for designing and constructing the trench wall stability, step 5, ensuring that the local stability of the most dangerous locations at the interface meets safety requirements, refers to the local safety factor of the interface.

[0065] ,

[0066] In the formula: F s (z) represents the local safety factor of the interface at depth z; For interfacial shear strength; c represents the interfacial shear stress. i γ is the interfacial cohesion; K0 is the coefficient of earth pressure at rest; γ is the soil weight; z is the depth of the reinforced trench wall; Φ i η is the internal friction angle of the interface; η is the load reduction factor of the reinforced zone; p a (z) represents the total lateral earth pressure at depth z of the trench wall; 1.8 represents the safety factor limit for the local stability of interface 3;

[0067] The most dangerous position on the interface occurs at the top or bottom of the reinforced area. When the most dangerous position occurs at the top of the reinforced area, z=0, and the local safety factor of the interface is [value missing]. F

[0068] F ,

[0069] In the formula: F s(0) is the local safety factor at the top of the interface where z=0; c i η is the interfacial cohesion; η is the load reduction factor of the reinforced zone; q is the equivalent uniformly distributed ground surcharge; K a 1.8 represents the active earth pressure coefficient; 1.8 represents the local safety factor limit.

[0070] When the most dangerous location on the interface appears at the bottom of the reinforced area, z=H, and the local safety factor of the interface is...

[0071]

[0072] This ensures that the local stability of the most unfavorable position of the interface meets the safety requirements.

[0073] In the formula: F s (H) is the local safety factor at z=H at the bottom of interface 3; c i γ is the interfacial cohesion; K0 is the coefficient of earth pressure at rest; γ is the soil weight; H is the height of the reinforced zone; Φ i η is the internal friction angle of the interface; η is the load reduction factor of the reinforced zone; K a 1.8 represents the active earth pressure coefficient; q represents the equivalent uniformly distributed ground surcharge; and 1.8 represents the local safety factor limit.

[0074] Preferably, in the above-mentioned continuous trenching process for designing and constructing trench wall stability, in step 6, when the bending strength or shear strength conditions are not met, the width of the reinforcement zone 2 is increased. And return to step 5; when the overall security factor of interface 3 is... If the local safety factor Fs(z) of interface 3 is less than 2.0 or less than 1.8, increase the interfacial cohesion ci and / or the interfacial internal friction angle Φi, and return to step 5.

[0075] Preferably, in the above-described continuous trenching process for designing and constructing trench wall stability, after returning from step 6 to step 5, if the width of the reinforced area 2 is increased... If the interfacial cohesion ci and / or the interfacial internal friction angle Φi increase, causing the change in the remeasured load reduction factor η to exceed 5%, return to step 1 to redetermine the load reduction factor of the reinforced area. .

[0076] As can be seen from the above-disclosed technical solutions, the beneficial effects of the present invention compared with the prior art are as follows:

[0077] In summary, the present invention provides a method for designing and constructing the stability of trench walls under continuous trenching technology. By establishing a load distribution model, the total lateral earth pressure load acting on the trench walls is... Scientifically decompose the load borne by the reinforced area and Through the interface transfer section, the collaborative working mechanism between the reinforced zone and the undisturbed soil is clearly revealed; the reinforced zone is simplified into a mechanical model of a vertically stressed member bearing lateral loads, which ensures both theoretical rigor and makes the calculation process simple, practical, and easy to apply in engineering; by verifying the bending and shear strength of the reinforced zone, the minimum width of the reinforced zone can be quantitatively determined, avoiding the blindness of traditional empirical methods; at the same time, by verifying the anti-slip stability of the interface, it is ensured that the interface will not slip and fail, forming a complete safety assurance system. Attached Figure Description

[0078] Figure 1 This is a schematic diagram showing the plan layout and main dimensions of the tank wall reinforcement under continuous troughing process.

[0079] Figure 2 This is a schematic diagram of the vertical stress model of the reinforced area, the distribution of the total lateral earth pressure pa(z) at the trench wall depth z, and its main parameters.

[0080] Figure 3 A schematic diagram showing the arrangement of strain measurement points along the depth in the reinforced area and the data acquisition (i.e.) Figure 1 (AA cross-section diagram).

[0081] Figure 4 For lateral earth pressure loads in and A schematic diagram showing the force distribution between them.

[0082] Figure 5 This is a schematic diagram of the direct shear test of the interface for undisturbed soil, reinforced zone, and interface combination specimens.

[0083] In the diagram: 1 is the original soil, 2 is the reinforced area, 3 is the interface, 4 is the pre-supported structure, 5 is the strain gauge, and 6 is the data acquisition device. Detailed Implementation

[0084] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The technical content and features of the present invention will be described in detail below with reference to the listed embodiments and the accompanying drawings. It should be noted that the drawings are all in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of the present invention. For ease of description, the terms "upper" and "lower" used below are consistent with the upper and lower directions in the accompanying drawings, but this should not be construed as a limitation of the technical solution of the present invention.

[0085] Please see Figures 1 to 5 This embodiment discloses a design and construction method for the stability of the tank wall under a continuous trenching process, used to determine the width of the reinforced zone 2 in the tank wall reinforcement and curing step. The method includes the following steps:

[0086] Step 1: Establish a load distribution model, including the total lateral earth pressure load acting on the trench wall. Decomposed into the load borne by the reinforced area and the load transmitted through the interface 3 between the reinforced zone 2 and the undisturbed soil 1 , And determine the load reduction factor for the reinforced area. ,0< <1, load reduction factor for reinforced zone The distribution coefficient characterizes the proportion of load borne by the reinforced zone; that is, the total lateral earth pressure load acting on the trench wall is denoted as... The load borne by the reinforced area is denoted as The load passed through the interface is denoted as and satisfy = + The total lateral earth pressure at depth z of the trench wall is denoted as pa(z). The trench wall refers to the interface between the reinforced zone and the undisturbed soil. The maximum bending moment and maximum shear force of the reinforced zone are still denoted as... and .

[0087] Step 2: Simplify the reinforced area 2 into a vertical load-bearing member that bears lateral loads, and calculate the total lateral earth pressure pa(z) at the depth z of the trench wall. The value of z ranges from 0 to H, where H is the distance from the bottom to the top of the reinforced area of ​​the trench wall.

[0088] Step 3: Distribute the total lateral earth pressure on the trench wall according to the load reduction factor η to obtain the net distributed load acting on the reinforced area at depth z, and calculate the maximum bending moment and maximum shear force of the reinforced area based on the net distributed load acting on the reinforced area at depth z.

[0089] Step 4: Determine the minimum width of the reinforced zone based on both the bending strength condition and the shear strength condition, and take the larger of the two values ​​as the width of the reinforced zone. ;

[0090] Step 5: Perform anti-sliding stability calculation of the interface 3 between the reinforced zone 2 and the undisturbed soil 1. The anti-sliding stability calculation of the interface between the reinforced zone and the undisturbed soil includes calculating the interface shear stress at the depth z of the reinforced zone of the trench wall. The overall stability of the interface meets the safety requirements, and the local stability of the most dangerous part of the interface also meets the safety requirements. If the verification passes, proceed to step 7; if the verification fails, proceed to step 6.

[0091] Step 6: Adjust the interface strength parameters or increase the width of the reinforced area. Returning to step 5, the interface strength parameters include the interface cohesion ci and the interface internal friction angle Φi; adjusting the interface strength parameters can improve the interface strength parameters ci and the interface internal friction angle Φi measured by direct shear test at the interface between the reinforced zone and the undisturbed soil by improving the grouting process, adding admixtures or adopting different reinforcement methods, thereby increasing the interface shear stress τf(z).

[0092] Step 7: Based on the width of the reinforced area and the interface stability calculation results determined above, implement the following steps in sequence: trench wall reinforcement and maintenance, deep trench excavation, hoisting and placing pre-support structure 4, axial force loading of pre-support structure 4, and trench backfilling, so as to ensure that the trench wall can be self-stabilized in the unsupported exposed stage after the deep trench excavation is completed and before the axial force loading of pre-support structure 4.

[0093] As a preferred option, step 7 is carried out in the original sequence of trench wall reinforcement and curing, deep trench excavation, hoisting and placing pre-support structure 4, axial force loading of pre-support structure 4, and trench backfilling. Excavation can only begin after the reinforced area 2 has reached the design strength and the width, uniformity, and interface 3 strength have been inspected. After the deep trench reaches the design depth, the pre-support structure 4 is hoisted and placed in a timely manner, and the axial force of the pre-support structure 4 is applied in stages according to the special construction plan.

[0094] During the unsupported exposure phase, the strain, horizontal displacement of the trench wall, and surface settlement of reinforced zone 2 were monitored simultaneously. An early warning was issued and the sampling interval was shortened when the monitored value reached 80% of the control value; when the control value was reached, excavation was stopped and the pre-support structure 4 was immediately hoisted or loaded. The unconfined compressive strength q of reinforced zone 2 was measured. u The width of the reinforced area did not meet the design value. If the negative deviation is greater than 50mm or the difference between two consecutive load reduction factor η retest results is greater than 10%, the next construction step shall not be carried out.

[0095] This invention provides a method for designing and constructing the stability of trench walls under continuous trenching technology. By establishing a load distribution model, the total lateral earth pressure load acting on the trench walls is... Scientifically decompose the load borne by the reinforced area and Through the interface transfer section, the collaborative working mechanism between the reinforced zone and the undisturbed soil is clearly revealed; the reinforced zone is simplified into a mechanical model of a vertically stressed member bearing lateral loads, which ensures both theoretical rigor and makes the calculation process simple, practical, and easy to apply in engineering; by verifying the bending and shear strength of the reinforced zone, the minimum width of the reinforced zone can be quantitatively determined, avoiding the blindness of traditional empirical methods; at the same time, by verifying the anti-slip stability of the interface, it is ensured that the interface will not slip and fail, forming a complete safety assurance system.

[0096] Preferably, in the above-mentioned continuous trenching process for designing and constructing trench wall stability, the load reduction factor of the reinforced zone is... The reinforced area is considered as a vertical cantilever beam fixed to the bottom.

[0097]

[0098] In the formula: η is the load reduction factor for reinforced zone 2, 0 < <1; P 加固 (z) represents the equivalent load borne by reinforced zone 2 at depth z; p a (z) represents the total lateral earth pressure at depth z of the trench wall; z is the depth calculated downwards from the top of reinforced zone 2; H is the height of reinforced zone 2;

[0099] The above is a theoretical calculation method. For ease of calculation, the following method is used in actual engineering: load reduction factor of the reinforced zone. Based on field tests, n strain gauges 5 are arranged at intervals along the depth direction in the reinforced area of ​​the trench wall, forming n measuring points. These n measuring points are located in the monitoring section at the middle of the long side of the trench wall and are arranged within a depth range of 0.2H to 0.9H, where n is a natural number greater than 1 and not less than 6. The strain gauges 5 collect monitoring data through a data acquisition device 6. Additional measuring points are added at the stratum boundary. After installation, each strain gauge undergoes temperature compensation and zero-point calibration, and continuous data collection is performed for no less than 30 minutes before excavation. During the unsupported exposure stage after trench excavation, the strain distribution at different depths in the reinforced area is measured, with a sampling interval of no more than 60 seconds. When the strain change rate of three adjacent sampling periods is no greater than 5%, the corresponding measured value is taken as stable data. When the coefficient of variation of the load reduction factor η of multiple monitoring sections is greater than 10%, additional monitoring sections are added and the measurement is repeated. Based on the measured strain of each strain gauge and the elastic modulus of the reinforced area material, the load at each measuring point in the reinforced area is calculated. :

[0100]

[0101] In the formula: Let i be the load at the i-th measuring point; Let be the strain at the i-th measuring point; Let be the elastic modulus at the i-th measuring point, where n is a natural number greater than or equal to 1; and i is the number of the measuring point, which is a positive integer greater than or equal to 1 and less than or equal to n.

[0102] Because the total earth pressure is difficult to measure accurately and directly, it is calculated using a well-established theoretical formula. The final value of η is the sum of the loads at each measuring point in the reinforced area. Summation of earth pressure at each measuring point in the reinforced area The ratio is determined as follows:

[0103]

[0104] In the formula: n is the number of measuring points; Let i be the load at the i-th measuring point; It is the depth of the reinforced zone where measuring point i is located; The depth of the reinforced zone where measuring point i is located. Earth pressure at the location;

[0105] like Figure 3 As shown, to ensure the repeatability of the load reduction factor η measurement results, at least one monitoring section is set at the middle of the long side of each trench wall; when the trench section length is greater than 20m, an additional monitoring section is set every 10m from the middle of the trench section to both ends. Each monitoring section has no less than 6 measuring points in the depth range of 0.2H to 0.9H, and additional measuring points are set at the stratigraphic boundary; after the strain gauges are installed, temperature compensation and zero-point calibration are performed, and continuous sampling is performed for no less than 30min before excavation, with a sampling interval of no more than 60s during the unsupported exposure stage.

[0106] When the strain change rate of three adjacent sampling periods is no greater than 5%, the corresponding measured value is taken as stable data. When the coefficient of variation of the load reduction factor η of multiple monitoring sections is greater than 10%, additional monitoring sections are added and the uniformity of reinforced zone 2 is verified. The bending strength verification and shear strength verification adopt the design value of the load reduction factor η that is unfavorable to reinforced zone 2, and the anti-slip stability verification of interface 3 adopts the design value of the load reduction factor η that is unfavorable to interface 3. Both are still uniformly referred to as load reduction factor η, and no separate name for load or force is given.

[0107] Preferably, in the above-mentioned continuous trenching process, the design and construction method for trench wall stability must satisfy the following relationship to ensure the stability of the trench wall:

[0108]

[0109] In the formula: R 加固 To enhance the flexural or shear bearing capacity of reinforced zone 2; R 界面 P represents the shear bearing capacity of interface 3. 总 The total lateral earth pressure load acting on the trench wall is η; the load reduction factor for the reinforced zone is F. s1 and F s2 These are the safety factors for reinforced zone 2 and interface 3, respectively.

[0110] Preferably, in the above-mentioned continuous trenching process for designing and constructing trench wall stability, the load reduction factor of the reinforced zone is... The reinforced zone is considered as a vertical cantilever beam fixed at the bottom. The reinforced zone itself has sufficient strength and stiffness to withstand η times the total earth pressure, and the interface between the reinforced zone and the undisturbed soil has sufficient shear strength to withstand (1-η) times the total earth pressure.

[0111]

[0112] In the formula: R 加固 η is the flexural or shear bearing capacity of reinforced zone 2; η is the load reduction factor for the reinforced zone; P 总 R is the total lateral earth pressure load acting on the trench wall; 界面 F represents the shear bearing capacity of interface 3. s1 and F s2 These are the safety factors for reinforced zone 2 and interface 3, respectively.

[0113] Load reduction factor for reinforced zone Field tests determined that the load borne by the reinforced area was obtained by embedding strain gauges at the reinforced area and the interface. ,

[0114] .

[0115] In the formula: η is the load reduction factor for reinforced zone 2; P 加固 (z) represents the load distribution borne by reinforced zone 2; P 界面 The load distribution transmitted to interface 3; B represents the load borne by the reinforced zone, and B is the width of the reinforced zone 2; z is the integral variable; dz is the differential element in the integration direction.

[0116] This invention simplifies the reinforced zone into a mechanical model of a vertically stressed member bearing lateral loads. Under lateral earth pressure, the reinforced zone undergoes bending and shear deformation, ensuring both theoretical rigor and a simple and practical calculation process, making it convenient for engineering applications.

[0117] Preferably, in the above-mentioned continuous trenching process for designing and constructing trench wall stability, in step 2, the total lateral earth pressure pa(z) at the trench wall depth z is calculated as active earth pressure, and the calculation formula is:

[0118] ,

[0119] Where: p a (z) represents the total lateral earth pressure at depth z of the trench wall, in kPa. =tan 2 (45 ° -Φ s / 2); Φ s γ is the internal friction angle of the soil; γ is the soil weight, in kN / m³. 3z represents the depth of the reinforced trench wall, ranging from 0 to H in meters (m), where H is the distance from the bottom to the top of the reinforced trench wall. q represents the ground surcharge in kPa. When calculating the lateral earth pressure distribution acting on the trench wall, the active earth pressure theory is used, and the lateral earth pressure pa increases linearly with depth z. The reason for the increase in earth pressure with depth is that the static earth pressure generated by the self-weight of the deeper soil is greater, while the additional earth pressure generated by the ground surcharge remains constant at all depths.

[0120] Preferably, in the above-mentioned continuous trenching process, the design and construction method for trench wall stability,

[0121] In step 3, the total lateral earth pressure on the trench wall is distributed according to the load reduction factor η to obtain the net distributed load acting on the reinforced area at depth z:

[0122] ;

[0123] In the formula: p 加固 (z) represents the net distributed load acting on the reinforced zone at depth z; η is the load reduction factor for the reinforced zone; p a (z) represents the total lateral earth pressure at a trench wall depth z;

[0124] Calculate the maximum bending moment of reinforced zone 2 based on the net distributed load acting on the reinforced zone at depth z: Maximum bending moment of reinforced zone Located at the bottom of the reinforced zone, at this point z=H:

[0125]

[0126] In the formula: η is the maximum bending moment in the reinforced zone; η is the load reduction factor for the reinforced zone; K a γ is the active earth pressure coefficient; H is the soil weight; H is the height of the reinforced zone; q is the equivalent uniformly distributed ground surcharge.

[0127] Calculate the maximum shear force of reinforced zone 2 based on the net distributed load acting on the reinforced zone at depth z: Maximum shear force of reinforced zone Located at the bottom of the reinforced zone, at this point z=H:

[0128] .

[0129] In the formula: η is the maximum shear force in reinforced zone 2; η is the load reduction factor for the reinforced zone; γ is the active earth pressure coefficient; H is the soil weight; H is the height of reinforced zone 2; q is the equivalent uniformly distributed ground surcharge.

[0130] Preferably, in the above-mentioned continuous trenching process for designing and constructing trench wall stability, step 4, determining the minimum width of the reinforcement zone based on the bending strength condition as a bending strength verification, includes:

[0131] Calculate the section modulus of the reinforced zone :

[0132] = 2 / 6;

[0133] In the formula: W is the section modulus of the reinforced zone 2 calculated per unit trench length, in m²; B is the width of the reinforced zone 2, in m.

[0134] Meeting the bending strength requirement: Maximum bending stress in reinforced zone 2 Tensile strength of reinforced area :

[0135]

[0136] In the formula: This represents the maximum bending stress in reinforced zone 2. is the maximum bending moment of reinforced zone 2; W is the section modulus of reinforced zone 2; B is the width of reinforced zone 2; The tensile strength of reinforced zone 2; =0.1q u q u 0.1 represents the unconfined compressive strength of reinforced zone 2; 0.1 is the conversion factor between tensile strength and unconfined compressive strength in this embodiment.

[0137] To obtain the minimum width of the reinforced zone :

[0138] .

[0139] In the formula: B is the minimum width of the reinforced zone 2 required to meet the bending strength condition; This represents the maximum bending moment in reinforced zone 2. This represents the tensile strength of reinforced zone 2.

[0140] Preferably, in the above-mentioned continuous trenching process for designing and constructing trench wall stability, step 4, determining the minimum width of the reinforced zone based on shear strength conditions as a shear strength verification, includes:

[0141] Satisfying the shear strength condition: mean shear stress The shear strength of the reinforced zone must be less than or equal to that of the reinforced zone. :

[0142]

[0143] In the formula: The average shear stress at section 2 of the reinforced zone; B is the maximum shear force in reinforced zone 2; B is the width of reinforced zone 2. To enhance the shear strength of reinforced zone 2, It is determined based on the cohesion C of the reinforced zone and the internal friction angle φ of the reinforced zone.

[0144] Considering a stress non-uniformity coefficient of 1.5:

[0145]

[0146] In the formula: The maximum shear stress in reinforced zone 2 is calculated after considering the uneven distribution of shear stress; 1.5 is the shear stress unevenness coefficient. The average shear stress; This represents the shear strength of reinforced zone 2.

[0147] have to: .

[0148] In the formula: B is the minimum width of the reinforced zone 2 required to meet the shear strength condition; This represents the maximum shear force in reinforced zone 2. 1.5 represents the shear strength of reinforced zone 2; 1.5 represents the shear stress non-uniformity coefficient.

[0149] Preferably, in the above-mentioned continuous trenching process for designing and constructing trench wall stability, in step 4, taking the larger of the two values ​​as the width of the reinforced zone means that, under the condition of simultaneously satisfying the bending strength and shear strength requirements, the following values ​​are obtained:

[0150] Width of reinforced area =MAX

[0151] In the formula: B is the final width of the reinforced area 2; This represents the maximum bending moment in the reinforced area. This represents the maximum shear force in the reinforced area. The tensile strength of the reinforced area; This represents the shear strength of the reinforced zone.

[0152] The width of the reinforced zone obtained in this way meets the bending strength and shear strength requirements, ensuring that the reinforced zone will not experience bending or shear failure under lateral earth pressure. The width of the reinforced zone... The determination of the value is based on rigorous mechanical calculations, and the design is more accurate and reasonable compared with the traditional empirical method.

[0153] After obtaining the width of reinforced zone 2 (as a candidate width) based on the flexural strength and shear strength conditions, it should be rounded up according to the width modulus achievable by the construction equipment, and the rounded actual width of the reinforced zone should be calculated. Resubstitute the original bending strength and shear strength conditions for verification; during verification, the maximum bending moment and maximum shear force in the reinforced zone should still be calculated using the original conditions. and .

[0154] Preferably, in the above-described continuous trenching process for designing and constructing trench wall stability, in step 5,

[0155] Calculate the interfacial shear stress at depth z of the reinforced zone of the trench wall. :

[0156]

[0157] In the formula: η is the interfacial shear stress at depth z of interface 3; η is the load reduction factor of reinforced zone 2; p a (z) represents the total lateral earth pressure at depth z of the trench wall; (1-η) represents the proportion of load transmitted through interface 3.

[0158] Calculate the interfacial shear strength at depth z of the reinforced zone of the trench wall.

[0159]

[0160] In the formula: Let z be the interfacial shear strength of interface 3 at depth z; Let z be the normal stress at interface 3 at depth z. =K0γz, pore water pressure is negligible; c i For interfacial cohesion; Φ i γ is the internal friction angle of the interface; K0 is the coefficient of earth pressure at rest, K0=1-sinΦi; γ is the soil weight; z is the depth of the reinforced zone of the trench wall; η is the load reduction factor of the reinforced zone; p a (z) represents the total lateral earth pressure at depth z of the trench wall. The interfacial cohesion ci and the interfacial internal friction angle Φi were determined by in-situ direct shear tests on the engineering test section.

[0161] like Figure 5 As shown, the interfacial cohesion ci and the interfacial internal friction angle Φi were determined by on-site interfacial direct shear test: combined specimens of the original soil 1, the reinforced zone 2 and the interface 3 were obtained at depths of approximately H / 3 and 2H / 3, respectively, with no less than 3 sets of parallel specimens at each depth, and sheared under no less than 3 levels of normal stress; the strength envelope was fitted according to the test results, and the lower value or statistical characteristic value of the test results was used as the design value of ci and Φi.

[0162] When the strata are clearly layered, the groundwater level is located in the unsupported exposed area, or mud slurry is used for wall protection in the trench, the total lateral earth pressure pa(z) at depth z of the trench wall should take into account the effective unit weight of each soil layer, the ground surcharge, and the water pressure difference between the inside and outside of the trench, and should be calculated in segments at the stratigraphic boundaries, groundwater level, and process change locations. , , And Fs(z).

[0163] Preferably, in the above-mentioned continuous trenching process for designing and constructing the trench wall stability, step 5, ensuring that the overall stability of the interface meets safety requirements, means that the overall safety factor of the interface... .

[0164] In the formula: F s整体 c is the overall safety factor along the entire depth of interface 3; i γ is the interfacial cohesion; H is the height of reinforced zone 2; K0 is the coefficient of earth pressure at rest; γ is the soil weight; Φ i η is the internal friction angle of the interface; η is the load reduction factor of the reinforced zone; 1 is the active earth pressure coefficient; q is the equivalent uniformly distributed ground surcharge; 2.0 is the safety factor limit for the overall stability of interface 3.

[0165] Overall safety factor (average along depth):

[0166] =

[0167] In the formula: F s整体 c is the overall safety factor along the entire depth of interface 3; i γ is the interfacial cohesion; H is the height of reinforced zone 2; K0 is the coefficient of earth pressure at rest; γ is the soil weight; Φ i η is the internal friction angle of the interface; η is the load reduction factor of the reinforced zone; 1 is the active earth pressure coefficient; q is the equivalent uniformly distributed ground surcharge; 2.0 is the safety factor limit for the overall stability of interface 3.

[0168] Substituting into the calculation, we get (i.e., calculating the interfacial shear stress) Calculated as follows:

[0169]

[0170] In the formula: F s整体 c is the overall safety factor along the entire depth of interface 3; i γ is the interfacial cohesion; H is the height of reinforced zone 2; K0 is the coefficient of earth pressure at rest; γ is the soil weight; Φ i η is the internal friction angle of the interface; η is the load reduction factor of the reinforced zone; 1 is the active earth pressure coefficient; q is the equivalent uniformly distributed ground surcharge; 2.0 is the safety factor limit for the overall stability of interface 3.

[0171] Preferably, in the above-mentioned continuous trenching process for designing and constructing the trench wall stability, step 5, ensuring that the local stability of the most dangerous locations at the interface meets safety requirements, refers to the local safety factor of the interface. satisfy:

[0172] ,

[0173] In the formula: F s (z) represents the local safety factor of interface 3 at depth z; τ f (z) represents the interfacial shear strength of interface 3 at depth z; τ(z) represents the interfacial shear stress of interface 3 at depth z; c i γ is the interfacial cohesion; K0 is the coefficient of earth pressure at rest; γ is the soil weight; z is the depth of the reinforced trench wall; Φ i η is the internal friction angle of the interface; η is the load reduction factor of the reinforced zone; p a (z) represents the total lateral earth pressure at depth z of the trench wall; 1.8 represents the safety factor limit for the local stability of interface 3.

[0174] The most dangerous locations on the interface are at the top or bottom of the hardened area.

[0175] When the most dangerous location of the interface occurs at the top of the reinforced zone, z=0 (earth pressure is small, but interface strength is also small), and the local safety factor of the interface is... ,satisfy:

[0176] F ;

[0177] In the formula: F s (0) is the local safety factor at z=0 at the top of interface 3; c i η is the interfacial cohesion; η is the load reduction factor of the reinforced zone; q is the equivalent uniformly distributed ground surcharge. 1.8 represents the active earth pressure coefficient; 1.8 represents the local safety factor limit.

[0178] When the most dangerous location of the interface occurs at the bottom of the reinforced zone, z=H (the earth pressure is high, but the interface strength is also high, and the local safety factor of the interface is high). ,satisfy:

[0179] This ensures that the local stability of the most unfavorable location on the interface meets safety requirements. The overall safety factor of the interface is greater than 2, and the local safety factors are both greater than 1.8, ensuring that the interface does not slip and fail, further guaranteeing the stability of the trench wall. Compared to traditional empirical methods, the method of this invention determines the width of the reinforced zone. It can effectively save grouting materials and construction costs, while ensuring construction safety, and has significant economic and social benefits.

[0180] like Figure 5 As shown, preferably, in step 6, when the bending strength condition or shear strength condition is not met, the width of the reinforced zone 2 is increased. And return to step 5; when the overall security factor of interface 3 is... If the local safety factor Fs(z) of interface 3 is less than 2.0 or less than 1.8, increase the interfacial cohesion ci and / or the interfacial internal friction angle Φi, and return to step 5.

[0181] Preferably, after returning from step 6 to step 5, if the width of the reinforced area 2 is increased... If the interfacial cohesion ci and / or the interfacial internal friction angle Φi increase, causing the change in the remeasured load reduction factor η to exceed 5%, return to step 1 to redetermine the load reduction factor of the reinforced area. .

[0182] like Figure 5 As shown, in the closed loop consisting of steps 5 and 6, the flexural strength, shear strength, and overall safety factor of interface 3 of the reinforced zone 2 are simultaneously checked in each round. The local safety factor Fs(z) of interface 3; when the bending strength condition or shear strength condition is not met, the width of the reinforced zone 2 is increased. When the overall security factor of interface 3 When the local safety factor Fs(z) of interface 3 is less than 2.0 or less than 1.8, adjust the interfacial cohesion ci and / or the interfacial internal friction angle Φi; when the width of the reinforced zone 2 is increased... If the interface 3 processing technology is changed and the retest result of the load reduction factor η changes by more than 5%, return to step 1 to redetermine the load reduction factor of the reinforced area. Only when the flexural strength, shear strength, and overall safety factor of interface 3 of reinforced zone 2 are met... When all four verifications, including the local safety factor Fs(z) of interface 3, meet the requirements, proceed to step 7.

[0183] For layered soil, the interval of Fs(z) calculation along the depth is no greater than 0.1H, and the calculation is densified at the stratum boundary, groundwater level and reinforcement process changes; the minimum value in the whole depth range is taken as the local stability verification result of the most dangerous position of interface 3.

[0184] This embodiment provides a design and construction method for the stability of the trench wall under a continuous trenching process. A specific continuous trenching test section is selected for illustration to determine the width of the reinforced zone 2 in the trench wall reinforcement and curing steps. The bending strength, shear strength, and overall and local stability of interface 3 of reinforced zone 2 were simultaneously verified. The test section had a trench length L1 of 18m, a trench width B1 of 1.2m, and a distance H from the bottom to the top of reinforced zone 2 of 6.0m. Reinforced zones 2 were set on both sides of the trench. The equivalent uniformly distributed ground surcharge q above the trench was 20kPa, and pore water pressure was neglected in the calculation. The soil weight γ was 18.5kN / m³, and the internal friction angle Φs was 28°. The elastic modulus of the material in reinforced zone 2 was 600MPa, and the unconfined compressive strength q... u The strength is 2.50 MPa, the tensile strength is 0.25 MPa, and the shear strength is 0.18 MPa; the interfacial cohesion ci before treatment is 6 kPa, and the interfacial internal friction angle Φi is 20°.

[0185] The test trench section is first set according to the width of reinforced zone 2. The depth was 2.4m. A monitoring section was set at the midpoint of the long side of each trench wall, with six measuring points along the depth direction at depths of 1.2m, 2.0m, 2.8m, 3.6m, 4.4m, and 5.2m. After installation, the strain gauges underwent temperature compensation and zero-point calibration. Data was continuously collected for 30 minutes before excavation; the sampling interval during the unsupported exposure phase was 60 seconds; when the strain change rate of three adjacent sampling periods did not exceed 5%, the corresponding measured value was taken as stable data.

[0186] The lateral earth pressures pa(zi) at the above six measuring points are 15.24 kPa, 20.58 kPa, 25.92 kPa, 31.27 kPa, 36.61 kPa, and 41.95 kPa, respectively. Based on the strain and the elastic modulus of the material in reinforced zone 2, the loads Preinforced(i) at each measuring point are calculated to be 9.14 kPa, 12.55 kPa, 16.33 kPa, 19.38 kPa, 22.70 kPa, and 26.01 kPa, respectively. The load reduction factor η for the reinforced zone is calculated as follows:

[0187]

[0188] The calculated load reduction factor η is 0.619, and the measured representative value of 0.62 is taken. Considering the monitoring dispersion and computational disadvantages, η is taken as 0.64 in the bending strength and shear strength verification, and η is taken as 0.60 in the anti-slip stability verification of interface 3; both are the design values ​​of the load reduction factor η under the corresponding verification conditions.

[0189] The width of reinforced zone 2 in this working condition The specific calculation steps for interface 3 stability are as follows:

[0190] The active earth pressure coefficient Ka is:

[0191]

[0192] Where: K a The active earth pressure coefficient is Φ; 28° is the internal friction angle Φ of the soil in this embodiment. s The value of is 0.361, which is the calculated active earth pressure coefficient.

[0193] According to the original calculation formula, without multiplying by the load reduction factor η, the bending moment at the bottom of the trench is 370.42 kN·m / m, and the shear force at the bottom of the trench is 163.55 kN / m. In the bending strength and shear strength verification, η is taken as 0.64. The load borne by reinforced zone 2, Preinforced = ηPtotal, is used to calculate the maximum bending moment in reinforced zone 2. and maximum shear force as follows:

[0194]

[0195] In the formula: η is the maximum bending moment of reinforced zone 2; 0.64 is the load reduction factor η used for bending strength verification; 370.42 kN·m / m is the bottom bending moment of the trench without multiplying by the load reduction factor; 237.07 kN·m / m is the maximum bending moment borne by reinforced zone 2.

[0196]

[0197] In the formula: η is the maximum shear force in reinforced zone 2; 0.64 is the load reduction factor η used for shear strength verification; 163.55 kN / m is the shear force at the bottom of the trench without multiplying by the load reduction factor; 104.67 kN / m is the maximum shear force borne by reinforced zone 2.

[0198] The required width of the reinforcement zone 2 is calculated based on the bending strength requirement. :

[0199]

[0200] In the formula: B is the minimum width of the reinforced zone 2 calculated according to the bending strength condition; =237.07 kN·m / m, which is the maximum bending moment in reinforced zone 2; f t =250kPa, which is the tensile strength of reinforced zone 2; 2.385m is the calculated value of the bending control width.

[0201] The required width of the reinforced zone 2 is calculated based on the shear strength condition. And considering a stress non-uniformity coefficient of 1.5:

[0202]

[0203] In the formula: B is the minimum width of the reinforced zone 2 calculated according to the shear strength condition; =104.67kN / m, which is the maximum shear force in reinforced zone 2; f v =180kPa, which is the shear strength of reinforced zone 2; 1.5 is the shear stress non-uniformity coefficient; 0.872m is the calculated value of the shear control width.

[0204] The larger of the width values ​​obtained from the flexural strength and shear strength conditions is taken, and then rounded up using the 0.10m construction width modulus to obtain the width of reinforced zone 2. It is 2.4m. Actual width used. Review:

[0205]

[0206] Where: σ max The maximum bending stress was obtained by verifying the actual width B = 2.4m; =237.07 kN·m / m, which is the maximum bending moment; B=2.4m, which is the actual reinforcement width; f t =250kPa, which is the tensile strength of reinforced zone 2.

[0207]

[0208] In the formula: τ max The maximum shear stress was obtained by verifying the actual width B = 2.4m; =104.67kN / m, which is the maximum shear force; B=2.4m, which is the actual reinforced width; 1.5 is the shear stress non-uniformity coefficient; f v =180kPa, which is the shear strength of reinforced zone 2.

[0209] Upon review, the maximum bending stress σmax is 246.95 kPa, which is less than the tensile strength ft = 250 kPa of the reinforced zone 2; the maximum shear stress τmax is 65.42 kPa, which is less than the shear strength fv = 180 kPa of the reinforced zone 2. The bending strength and shear strength conditions of the reinforced zone 2 both meet the requirements.

[0210] In the anti-sliding stability calculation of interface 3, the load reduction factor η is taken as 0.60, the interface internal friction angle Φi is taken as 20°, and the at-rest earth pressure coefficient K0 is calculated as follows:

[0211]

[0212] In the formula: K0 is the coefficient of earth pressure at rest; 20° is the internal friction angle Φ at the interface in this embodiment.i The value of is 0.658, which is the calculated coefficient of earth pressure at rest.

[0213] Before treatment, the interfacial cohesion ci was 6 kPa. The initial verification results for interface 3 are as follows:

[0214]

[0215] In the formula: F s整体 =1.77 is the overall safety factor before interface 3 optimization; 2.0 is the safety factor limit for the overall stability of interface 3.

[0216]

[0217] In the formula: F s (0) = 2.08 is the local safety factor at the top of the interface before optimization 3; F s (H)=1.72 is the local safety factor at the bottom of Interface 3 before optimization; 1.8 is the safety factor limit for the local stability of Interface 3.

[0218] After comparison, the overall safety factor Fs_overall for interface 3 is 1.77 < 2.0, and the local safety factor Fs(H) at the bottom of reinforced zone 2 is 1.72 < 1.8, which does not meet the judgment conditions for the overall stability of interface 3 and the local stability of the most dangerous location. The treatment process for interface 3 was optimized according to step 6, with increased density of grouting holes and additional grouting in the interface 3 area. After retesting with an in-situ interface direct shear test, the interface cohesion ci increased to 9 kPa, and the internal friction angle Φi remained at 20°; the width of reinforced zone 2... The load reduction factor η remained unchanged, with the change in the retest results being less than 5%, and the value of η remained unchanged under the corresponding verification conditions.

[0219] The anti-slip stability of interface 3 was recalculated using the optimized interfacial cohesion ci, and the verification results are as follows:

[0220]

[0221]

[0222] Fs(z) was calculated at 0.6m intervals along the depth of reinforced zone 2, with a minimum value of 1.88, located near the bottom of reinforced zone 2. Comparison showed that the overall Fs = 2.04 > 2.0, and the minimum Fs(z) = 1.88 > 1.8, satisfying the criteria for overall stability of interface 3 and local stability at the most dangerous location. Therefore, the width of reinforced zone 2 was finally determined. The design value of the interfacial cohesion ci is 2.4m and not less than 9kPa.

[0223] Compared with the traditional design method for the same working condition, the traditional method does not consider the load sharing between the undisturbed soil 1 and the reinforced zone 2, assuming that all lateral earth pressure is borne by the reinforced zone 2, and taking η=1.0. Under the same conditions of other parameters, =370.42 kN·m / m, =163.55kN / m; the bending control width is 2.98m, the shear control width is 1.36m, and the construction module is 0.10m. =3.00m. The engineering calculations for this invention take... =2.40m, the width of the reinforced zone is reduced by 20.0%. Reinforcement volume using traditional methods: 2 × 18 × 6 × 3.0 = 648.0m² 3 The solidified volume of this invention is: 2 × 18 × 6 × 2.4 = 518.4 m³. 3 The solidification volume was reduced by 129.6 m³, a 20% reduction, effectively saving construction costs.

[0224] The width of reinforced zone 2 as verified above. Construction is carried out using the parameters processed in Interface 3, including the following procedures:

[0225] Tank wall reinforcement and maintenance procedures: according to a width of 2.4m Reinforcement zone 2 is formed, and grouting holes are densified and grouting is added in the interface 3 area; after reinforcement, curing is carried out, and the width, uniformity, and unconfined compressive strength q of reinforcement zone 2 are tested. u And the interfacial cohesion (CI), after the test results meet the design requirements, proceed to the next process;

[0226] Deep trench excavation process: Deep trenches are excavated using continuous trenching equipment, the unsupported exposure time is controlled, and the strain of the reinforced area, the horizontal displacement of the trench wall and the ground settlement are monitored simultaneously; when the monitored value reaches 80% of the control value, an early warning is issued and the sampling interval is shortened; when the control value is reached, excavation is stopped.

[0227] Step 4 of hoisting the pre-support structure: After the deep trench reaches the design depth, hoist the pre-support structure 4 in a timely manner and check the position and connection status of the pre-support structure 4.

[0228] Axial force loading procedure for pre-supported structure 4: Apply axial force to the pre-supported structure in stages according to the special construction plan so that the pre-supported structure 4 forms effective support;

[0229] Trench backfilling process: After completing the subsequent structural construction, the trench backfilling is carried out according to the construction plan.

[0230] In summary, this embodiment utilizes the on-site determination of the load reduction factor η and the width of the reinforced zone 2. The mechanical calculations, parameter adjustments and verification after the initial verification of interface 3 failed, the sequential implementation of construction procedures and on-site monitoring verification formed a complete design and construction closed loop. Furthermore, when the cross-section of reinforced zone 2 is not rectangular, the actual cross-sectional area and section modulus are used to replace the rectangular cross-section calculation parameters; when earth pressure cells, distributed optical fibers, or inclinometers can obtain measurements equivalent to those of P reinforcement, they can replace strain gauges, but the requirements for the number of measuring points, depth coverage, zero-point baseline, sampling frequency, and stability data criteria must still be met.

[0231] The formation parameters, monitoring equipment, or construction equipment in the above embodiments can be replaced with equivalent ones according to engineering conditions, but P 总 P 加固 P 界面 , , , The names of Fs(z) and their correspondence in load distribution, strength verification of reinforced zone 2, and stability verification of interface 3 remain unchanged.

[0232] In summary, the design and construction method for tank wall stability under continuous trenching process provided by this invention has the following beneficial effects:

[0233] (1) The theoretical rigor has been significantly improved. By establishing a load ratio distribution model, the mechanical mechanism of the cooperative work between the reinforced zone and the original soil has been clearly revealed, especially the load transfer effect at the interface between the reinforced zone and the original soil. This has overcome the blindness of traditional empirical methods and provided a solid theoretical basis for the design of trench wall stability.

[0234] (2) The calculation method is simple and practical. The reinforced area is simplified into a cantilever beam model. Through clear calculation formulas and verification processes, the width of the reinforced area and the stability of the interface can be determined quickly and accurately. Compared with complex finite element analysis or finite difference method, the calculation complexity is greatly reduced, while ensuring the accuracy of the calculation, which is convenient for engineering applications.

[0235] (3) The design accuracy is significantly improved, and the width of the reinforced zone is determined by quantitative calculation. This avoids the problems of being overly conservative or insufficiently reinforced;

[0236] (4) Safety is fully guaranteed. Through multiple verification mechanisms, including verification of the flexural strength of the reinforced area, verification of the shear strength, and verification of the anti-sliding stability of the interface, a complete safety guarantee system is formed to ensure that the trench section can be self-stabilized in the unsupported exposed stage after excavation and before the pre-support system is put into use, effectively preventing the occurrence of safety accidents such as trench wall collapse.

[0237] (5) Strong applicability: This invention has established an analysis method specifically for the stress characteristics of narrow and deep trenches along the long side, filling the technical gap in this field. It is applicable to the construction of deep foundation pits and underground continuous walls under various geological conditions and has broad application value.

[0238] The above description is merely a description of preferred embodiments of the present invention and is not intended to limit the scope of the present invention in any way. Any changes or modifications made by those skilled in the art based on the above disclosure shall fall within the protection scope of the claims.

Claims

1. A method for designing and constructing the stability of the tank wall under a continuous trenching process, characterized in that... Used to determine the width of the reinforced zone in the trench wall reinforcement and curing process. The method includes the following steps: Step 1: Establish a load distribution model, including the total lateral earth pressure load acting on the trench wall. Decomposed into the load borne by the reinforced area Loads transferred between the reinforced zone and the undisturbed soil interface And determine the load reduction factor for the reinforced zone. ,0< <1, load reduction factor for reinforced zone Distribution coefficient characterizing the proportion of load borne by the reinforced zone; Step 2: Simplify the reinforced area into a vertical load-bearing member that bears lateral loads, and calculate the total lateral earth pressure pa(z) at the depth z of the trench wall. The value of z ranges from 0 to H, where H is the distance from the bottom to the top of the reinforced area. Step 3: Distribute the total lateral earth pressure on the trench wall according to the load reduction factor η to obtain the net distributed load acting on the reinforced area at depth z, and calculate the maximum bending moment and maximum shear force of the reinforced area based on the net distributed load acting on the reinforced area at depth z. Step 4: Determine the minimum width of the reinforced zone based on both the bending strength condition and the shear strength condition, and take the larger of the two values ​​as the width of the reinforced zone. ; Step 5: Perform anti-sliding stability calculation at the interface between the reinforced zone and the undisturbed soil. This calculation includes calculating the interfacial shear stress at depth z of the reinforced zone of the trench wall. The overall stability of the interface meets the safety requirements, and the local stability of the most dangerous part of the interface also meets the safety requirements. If the verification passes, proceed to step 7; if the verification fails, proceed to step 6. Step 6: Adjust the interface strength parameters or increase the width of the reinforced area. Return to step 5, where the interface strength parameters include the interface cohesion ci and the interface internal friction angle Φi. Step 7: Based on the width of the reinforced area and the interface stability calculation results determined above, implement the following steps in sequence: trench wall reinforcement and maintenance, deep trench excavation, hoisting and placing the pre-support structure, axial force loading of the pre-support structure, and trench backfilling, so as to ensure that the trench wall can be self-stabilized in the unsupported exposed stage after the deep trench excavation is completed and before the axial force loading of the pre-support structure.

2. The method for designing and constructing the stability of the tank wall under continuous trenching process according to claim 1, characterized in that... In step 2, the total lateral earth pressure pa(z) at depth z of the trench wall is calculated as active earth pressure, and the calculation formula is as follows: ,in: Active earth pressure coefficient, γ is the soil weight; z is the depth of the trench wall reinforcement zone; q is the ground surcharge.

3. The method for designing and constructing the stability of the tank wall under continuous trenching process according to claim 1, characterized in that... In step 4, the minimum width of the reinforced zone is determined based on the bending strength condition, and used as a verification of the bending strength, including: Calculate the section modulus of the reinforced zone : = 2 / 6; Meeting the bending strength requirement: the maximum bending stress in the reinforced zone. Tensile strength of reinforced area : In the formula: This represents the maximum bending stress in the reinforced area. This represents the maximum bending moment in the reinforced area. B is the section modulus of the reinforced zone; B is the width of the reinforced zone. The tensile strength of the reinforced area; To obtain the minimum width of the reinforced zone : .

4. The method for designing and constructing the stability of the tank wall under continuous trenching process according to claim 3, characterized in that... In step 4, the minimum width of the reinforced zone is determined based on the shear strength condition, and used as a shear strength verification, including: Satisfying the shear strength condition: mean shear stress The shear strength of the reinforced zone must be less than or equal to that of the reinforced zone. : In the formula: The average shear stress of the reinforced section; B is the maximum shear force in the reinforced zone; B is the width of the reinforced zone. The shear strength of the reinforced zone; Considering a stress non-uniformity coefficient of 1.5: In the formula: The maximum shear stress in the reinforced zone after considering the uneven distribution of shear stress; 1.5 is the shear stress unevenness coefficient; The average shear stress of the reinforced section; The shear strength of the reinforced zone; have to: ; In the formula: B is the minimum width of the reinforced zone required to meet the shear strength condition; f is the maximum shear force in the reinforced zone. v 1.5 represents the shear strength of the reinforced zone; 1.5 represents the shear stress non-uniformity coefficient.

5. The method for designing and constructing the stability of the tank wall under continuous trenching process according to claim 4, characterized in that... In step 4, taking the larger of the two values ​​as the width of the reinforced zone means obtaining the width of the reinforced zone while simultaneously satisfying both the bending strength and shear strength requirements. : =MAX In the formula: B is the width of the final reinforced area; This represents the maximum bending moment in the reinforced area. This represents the maximum shear force in the reinforced area. The tensile strength of the reinforced area; This represents the shear strength of the reinforced zone.

6. The method for designing and constructing the stability of the tank wall under continuous trenching process according to claim 1, characterized in that... In step 5, Calculate the interfacial shear stress at depth z of the reinforced zone of the trench wall. : In the formula: Let Z be the interfacial shear stress at depth z. η is the load reduction factor for the reinforced zone; p a (z) represents the total lateral earth pressure at depth z of the trench wall; (1-η) represents the proportion of load transferred through the interface; Calculate the interfacial shear strength at depth z of the reinforced zone of the trench wall. In the formula: τ f (z) represents the interfacial shear strength at depth z, and c i For interfacial cohesion; Let Φ be the normal stress at depth z of the interface. i The angle of friction within the interface.

7. The method for designing and constructing the stability of the tank wall under continuous trenching process according to claim 6, characterized in that... Normal stress at depth z of the interface =K0γz, where K0 is the static earth pressure coefficient, γ is the soil weight, and z is the depth of the trench wall reinforcement zone, with pore water pressure negligible.

8. The method for designing and constructing the stability of the tank wall under continuous trenching process according to claim 1, characterized in that... In step 5, ensuring the overall stability of the interface meets safety requirements means that the overall safety coefficient of the interface... In the formula: F s整体 c is the overall safety factor along the entire depth of the interface; i γ is the interfacial cohesion; H is the height of the reinforced zone; K0 is the coefficient of earth pressure at rest; γ is the soil weight; Φ i η is the internal friction angle of the interface; η is the load reduction factor of the reinforced zone; q represents the active earth pressure coefficient; q represents the equivalent uniformly distributed ground surcharge. 2.0 is the safety factor limit for the overall stability of the interface.

9. The method for designing and constructing the stability of the tank wall under continuous trenching process according to claim 1, characterized in that... In step 6, if the bending strength condition or shear strength condition is not met, the width of the reinforced zone is increased. And return to step 5; when the overall security level of the interface... If the value is less than 2.0 or the local safety factor Fs(z) of the interface is less than 1.8, increase the interfacial cohesion ci and / or the interfacial internal friction angle Φi, and return to step 5.

10. The method for designing and constructing the stability of the tank wall under continuous trenching process according to claim 9, characterized in that... After returning from step 6 to step 5, if the width of the reinforced area is increased... If the interfacial cohesion ci and / or the interfacial internal friction angle Φi increase, causing the change in the remeasured load reduction factor η to exceed 5%, return to step 1 to redetermine the load reduction factor of the reinforced area. .

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