Rectangular deep shaft surrounding rock pressure calculation method and system

Abstract

The application discloses a rectangular deep vertical shaft surrounding rock pressure calculation method and system, and the method comprises the following steps: based on the soil-rock calculation principle, the surrounding rock pressure of the rectangular deep vertical shaft is divided into the soil pressure of the soil section of the rectangular deep vertical shaft and the surrounding rock pressure of the bedrock section of the rectangular deep vertical shaft; based on the Coulomb active soil pressure theory with cohesion, the soil pressure of the soil section of the rectangular deep vertical shaft is calculated; based on the tunnel surrounding rock pressure theory, the shallow-buried position surrounding rock pressure and the deep-buried position surrounding rock pressure of the bedrock section of the rectangular deep vertical shaft are calculated. The system comprises a soil-rock calculation module, a soil section calculation module and a bedrock section calculation module. By using the application, the high-precision and actual deep vertical shaft surrounding rock pressure calculation can be realized for the rectangular deep vertical shaft with the soil above and the bedrock below. The application can be widely applied to the technical field of tunnel engineering design.

Description

Technical Field

[0001] This invention relates to the field of tunnel engineering design technology, and in particular to a method and system for calculating the surrounding rock pressure of a rectangular deep vertical shaft. Background Technology

[0002] Safety exits and ventilation ducts in subway stations, as important auxiliary structures of the main station, are both deep shafts and deep foundation pits, and their design and construction have attracted much attention. The "load-structure" method is used in the design, and the value of the surrounding rock pressure, which is the main design load, is crucial, as it directly affects the rationality of the shaft lining design and even the safety of the shaft structure.

[0003] During the engineering design, the Chimbalevich method in the "Design Specifications for Highway Tunnels (JTG / T D70-2010)" is mainly used to calculate the surrounding rock pressure of the shaft. Its basic assumption is that when each rock layer around the shaft is damaged, a sliding prism appears, and the overburden layer above it is regarded as a uniformly distributed load acting on the damaged prism.

[0004] Section 20.2.7 of the "Design Specifications for Highway Tunnels (JTG / T D70-2010)" stipulates that the surrounding rock pressure of a shaft increases linearly within the same rock stratum, with the maximum pressure at the bottom of the shaft. The horizontal lateral pressure coefficient varies considerably for the same type of rock; for example, in weak rock strata, the horizontal lateral pressure coefficient ranges from 0.031 to 0.3, with the upper limit almost ten times the lower limit. The selection of the horizontal lateral pressure coefficient is highly subjective, leading to a degree of uncertainty in lining design. Related research has demonstrated a clear inflection point in the variation of surrounding rock pressure along depth. Above this inflection point, the surrounding rock pressure conforms to the traditional linear increase pattern; however, below this point, the lateral pressure gradually decreases, exhibiting a clear nonlinear characteristic. Therefore, the Chimbalevich method in the "Design Specifications for Highway Tunnels (JTG / T D70-2010)" has an excessively large safety margin, resulting in significant engineering waste and contradicting current green and environmentally friendly design principles. Summary of the Invention

[0005] To address the aforementioned technical problems, the present invention aims to provide a method and system for calculating the surrounding rock pressure of rectangular deep shafts, which can achieve high-precision and realistic calculation of the surrounding rock pressure of rectangular deep shafts with overlying soil and bedrock strata below.

[0006] The first technical solution adopted in this invention is: a method for calculating the surrounding rock pressure of a rectangular deep vertical shaft, comprising the following steps:

[0007] Based on the principle of separate calculation of soil and rock, the surrounding rock pressure of rectangular deep shafts is divided into soil pressure in the overburden section and surrounding rock pressure in the bedrock section.

[0008] Earth pressure in rectangular deep shafts with overburden sections is calculated based on the cohesive Coulomb active earth pressure theory.

[0009] Based on the theory of tunnel surrounding rock pressure, the surrounding rock pressure at the shallow and deep burial locations of a rectangular deep shaft in the bedrock section is calculated. Furthermore, the earth pressure in the overburden section of the rectangular deep shaft is calculated using the following expression:

[0010] e0=γHK a

[0011]

[0012]

[0013]

[0014] Where e0 represents the earth pressure of the shaft in the overburden section; γ represents the unit weight of the overburden section fill; H represents the fill depth; K a The value represents the active earth pressure coefficient; α represents the angle between the back of the wall and the vertical line; β represents the angle between the backfill surface and the horizontal plane. δ represents the internal friction angle; K represents the friction angle between the wall back and the backfill; q η represents the passive earth pressure coefficient; q represents the uniformly distributed load on the ground surface; η represents the cohesion coefficient; and c represents the soil cohesion.

[0015] Furthermore, the calculation expression for the surrounding rock pressure at the shallow burial location is as follows:

[0016] e i =γ1h i λ

[0017]

[0018]

[0019] Among them, e i Indicates the surrounding rock pressure at shallow burial locations; γ1 represents the unit weight of the fill soil in the bedrock section; h i λ represents the height of the cross section above the ground; λ represents the shallow buried lateral pressure coefficient; β1 represents the fracture angle at which maximum thrust is generated. θ represents the calculated friction angle of the surrounding rock; θ1 represents the friction angle between the two sides of the top soil column.

[0020] Furthermore, the calculation expression for the surrounding rock pressure at the deep burial location is as follows:

[0021] e1=γ1h q λ1=γ1×λ1×0.45×2 s-1 ×ω

[0022] ω = 1 + i(B - 5)

[0023] Where e1 represents the surrounding rock pressure at the deep burial location; γ1 represents the unit weight of the fill soil in the bedrock section; λ1 represents the lateral pressure coefficient at the deep burial location; h q ω represents the equivalent load height; s represents the surrounding rock grade; ω represents the width influence coefficient; B represents the shaft span; i represents the rate of increase or decrease in surrounding rock pressure when the shaft span increases or decreases by 1m.

[0024] The second technical solution adopted in this invention is: a rectangular deep vertical shaft surrounding rock pressure calculation system, comprising:

[0025] The soil and rock separation module divides the surrounding rock pressure of a rectangular deep shaft into soil pressure in the overlying section and surrounding rock pressure in the bedrock section, based on the principle of soil and rock separation.

[0026] The overburden section calculation module calculates the earth pressure of a rectangular deep shaft overburden section based on the cohesive Coulomb active earth pressure theory.

[0027] The bedrock section calculation module calculates the surrounding rock pressure at shallow and deep locations of a rectangular deep shaft in the bedrock section based on the tunnel surrounding rock pressure theory.

[0028] The beneficial effects of the method and system of this invention are as follows: For rectangular deep shafts with soil covering and bedrock below, this invention adopts the principle of soil-rock separation to divide the surrounding rock pressure of the rectangular deep shaft into soil pressure in the soil-covered section and surrounding rock pressure in the bedrock section; it calculates the soil pressure in the soil-covered section of the rectangular deep shaft based on the cohesive Coulomb active earth pressure theory; and it calculates the surrounding rock pressure in the shallow and deep burial positions of the rectangular deep shaft in the bedrock section based on the tunnel surrounding rock pressure theory. This achieves high-precision and realistic calculation of the surrounding rock pressure of deep shafts, making up for the deficiencies in the theoretical calculation of surrounding rock pressure of rectangular deep shafts and improving the rationality of shaft lining design. Attached Figure Description

[0029] Figure 1 This is a flowchart of the steps in the method for calculating the surrounding rock pressure of a rectangular deep vertical shaft according to the present invention;

[0030] Figure 2 This is a structural block diagram of a rectangular deep vertical shaft surrounding rock pressure calculation system according to the present invention;

[0031] Figure 3 This is a schematic diagram of the earth pressure calculation for the overburden section of a rectangular deep vertical shaft, according to the present invention, a method for calculating the surrounding rock pressure of a rectangular deep vertical shaft.

[0032] Figure 4 This is a schematic diagram illustrating the calculation of surrounding rock pressure in the bedrock section of a rectangular deep vertical shaft, according to the present invention, a method for calculating surrounding rock pressure in a rectangular deep vertical shaft.

[0033] Figure 5 This is a diagram showing the surrounding rock pressure distribution of a rectangular deep vertical shaft according to a specific embodiment of the present invention. Detailed Implementation

[0034] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. The step numbers in the following embodiments are only for ease of explanation and do not limit the order of the steps. The execution order of each step in the embodiments can be adapted according to the understanding of those skilled in the art.

[0035] Reference Figure 1 This invention provides a method for calculating the surrounding rock pressure of a rectangular deep vertical shaft, the method comprising the following steps:

[0036] S1. Based on the principle of separate calculation of soil and rock, the surrounding rock pressure of rectangular deep shafts is divided into soil pressure of rectangular deep shafts in the overburden section and surrounding rock pressure of rectangular deep shafts in the bedrock section.

[0037] Specifically, for composite strata with soil on top and bedrock below, the rock pressure of the shaft surrounding rock changes with depth at a significant inflection point. Therefore, based on the principle of soil-rock separation, this invention divides the rock pressure of rectangular deep shafts into soil pressure in the soil section and rock pressure in the bedrock section.

[0038] S2. Calculate the earth pressure of a rectangular deep shaft with overburden section based on the cohesive Coulomb active earth pressure theory.

[0039] Specifically, refer to Figure 3 The backfill section is mostly composed of plain fill and silty clay, possessing cohesion. Furthermore, the shaft structure tends to deform inwards towards the open surface after construction. The shaft opening in the backfill section is typically reinforced with grouting measures such as large pipe roofs, resulting in a rough backing that creates friction with the backfill. Therefore, the cohesive Coulomb active earth pressure theory is used to calculate the earth pressure on the rectangular deep shaft in the backfill section. The calculation expression is as follows:

[0040] e0=γHK a

[0041]

[0042]

[0043]

[0044] Where e0 represents the earth pressure of the shaft in the overburden section; γ represents the unit weight of the overburden section fill; H represents the fill depth; K a The value represents the active earth pressure coefficient; α represents the angle between the back of the wall and the vertical line; β represents the angle between the backfill surface and the horizontal plane. δ represents the internal friction angle; K represents the friction angle between the wall back and the backfill; q η represents the passive earth pressure coefficient; q represents the uniformly distributed load on the ground surface; η represents the cohesion coefficient; and c represents the soil cohesion.

[0045] In the specific implementation of this invention, the rectangular deep vertical shaft only considers the general case, satisfying the condition α=β=q=0. This condition is then substituted into the passive earth pressure coefficient K. q and active earth pressure coefficient K a From the expression, we can derive:

[0046] K q =1

[0047]

[0048] S3. Calculate the surrounding rock pressure at the shallow and deep positions of the rectangular deep vertical shaft in the bedrock section based on the tunnel surrounding rock pressure theory.

[0049] Specifically, refer to Figure 4 The horizontal load calculation methods for shallow and deep buried tunnels in the "Railway Tunnel Design Code (TB10003-2016)" were used to calculate the surrounding rock pressure at the shallow and deep buried locations of rectangular deep vertical shafts in bedrock sections, respectively. Among these calculations:

[0050] The calculation expression for the surrounding rock pressure at the shallow burial location of the rectangular deep vertical shaft in the bedrock section is as follows:

[0051] e i =γ1h i λ

[0052]

[0053]

[0054] Among them, e i Indicates the surrounding rock pressure at shallow burial locations; γ1 represents the unit weight of the fill soil in the bedrock section; h i λ represents the height of the cross section above the ground; λ represents the shallow buried lateral pressure coefficient; β1 represents the fracture angle at which maximum thrust is generated. θ represents the calculated friction angle of the surrounding rock; θ1 represents the friction angle between the two sides of the top soil column.

[0055] The calculation expression for the surrounding rock pressure at the deep burial location of the rectangular deep vertical shaft in the bedrock section is as follows:

[0056] e1=γ1h q λ1=γ1×λ1×0.45×2 s-1 ×ω

[0057] ω = 1 + i(B - 5)

[0058] Where e1 represents the surrounding rock pressure at the deep burial location; γ1 represents the unit weight of the fill soil in the bedrock section; λ1 represents the lateral pressure coefficient at the deep burial location; h qω represents the equivalent load height; s represents the surrounding rock grade; ω represents the width influence coefficient; B represents the shaft span; i represents the rate of increase or decrease in surrounding rock pressure for every 1m increase or decrease in B; when B < 5m, i = 0.2; when B > 5m, i = 0.1.

[0059] The lateral pressure coefficient for deep burial has a corresponding range of values ​​according to the surrounding rock grade. Please refer to Table 1 for details.

[0060] Table 1. Lateral pressure coefficients of deep shafts

[0061] Surrounding rock level I~II III IV V VI Deep burial lateral pressure coefficient 0 <0.15 0.15～0.30 0.30～0.50 0.50～1.00

[0062] This invention utilizes data from a ventilation shaft in a Chongqing Metro station. The shaft has an excavation depth of 70m and an outer diameter of 17.0×6.0m. The secondary lining material is reinforced concrete. The lithology of the strata, from top to bottom, mainly consists of plain fill (15m thick) and moderately weathered sandy mudstone (55m thick), with a surrounding rock grade of IV and a calculated friction angle of 55°. The physical and mechanical parameters of the soil and rock are shown in Table 2 below.

[0063] Table 2 Geophysical and Mechanical Parameters

[0064] Material Name Elastic modulus (MPa) <![CDATA[Density (kg / m 3 )]]> Poisson's ratio Cohesion (kPa) Angle of internal friction (°) Plain fill soil 5 2000 0.35 5 25 Sandy mudstone 1281 2450 0.34 675 34

[0065] Substituting the data of the ventilation shaft of a certain Chongqing Metro station into the earth pressure calculation expression for the rectangular deep shaft with soil cover in S2, we get:

[0066]

[0067]

[0068]

[0069] e0=γHK a =20×15×0.22=66(kPa).

[0070] Substituting the data from the ventilation shaft of a Chongqing Metro station into the expression for calculating the surrounding rock pressure at the shallow buried location of a rectangular deep shaft in bedrock section S3, we obtain:

[0071] H p =2.5h q =2.5 × 0.45 × 2 s-1 ×ω=2.5×0.45×2 4-1 ×2.2=19.8(m)

[0072]

[0073]

[0074] e 15 =γ1h i λ=24.5×15×0.15=55.13(kPa)

[0075] e 34.8 =γ1h i λ=24.5×(15+19.8)×0.15=130.49(kPa)

[0076] Among them, H p This indicates the depth that marks the boundary between shallow and deep tunnels.

[0077] Substituting the data of the ventilation shaft of a certain Chongqing Metro station into the calculation expression for the surrounding rock pressure at the deep burial location of the rectangular deep shaft in bedrock section S3, we get:

[0078] e1=γ1h q λ1 = 0.3 × 24.5 × 0.45 × 2 4-1 ×2.2=58.22(kPa)

[0079] Finally, the earth pressure in the overburden section of the rectangular deep shaft, the surrounding rock pressure at the shallow burial location of the bedrock section of the rectangular deep shaft, and the surrounding rock pressure at the deep burial location of the rectangular deep shaft in the bedrock section, calculated by specific embodiments of the present invention, are summarized to obtain the distribution of the surrounding rock pressure of the shaft. See the specific reference below. Figure 5 The shaft lining can be designed in sections or uniformly designed according to the maximum surrounding rock load, depending on the distribution of the surrounding rock pressure.

[0080] Reference Figure 2 This invention provides a system for calculating the surrounding rock pressure of a rectangular deep vertical shaft, comprising:

[0081] The soil and rock separation module divides the surrounding rock pressure of a rectangular deep shaft into soil pressure in the overlying section and surrounding rock pressure in the bedrock section, based on the principle of soil and rock separation.

[0082] The overburden section calculation module calculates the earth pressure of a rectangular deep shaft overburden section based on the cohesive Coulomb active earth pressure theory.

[0083] The bedrock section calculation module calculates the surrounding rock pressure at shallow and deep locations of a rectangular deep shaft in the bedrock section based on the tunnel surrounding rock pressure theory.

[0084] The content of the above method embodiments is applicable to this system embodiment. The specific functions implemented in this system embodiment are the same as those in the above method embodiments, and the beneficial effects achieved are also the same as those achieved in the above method embodiments.

[0085] The above is a detailed description of the preferred embodiments of the present invention. However, the present invention is not limited to the embodiments described. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention. All such equivalent modifications or substitutions are included within the scope defined by the claims of this application.

Claims

1. A rectangular deep shaft surrounding rock pressure calculation method, characterized in that, The method comprises the following steps: The soil-rock pressure of the rectangular deep shaft is divided into the soil pressure of the soil covering section of the rectangular deep shaft and the surrounding rock pressure of the bedrock section of the rectangular deep shaft based on the soil-rock separation principle; The soil pressure of the soil covering section of the rectangular deep shaft is calculated based on the Coulomb active soil pressure theory with cohesion; The surrounding rock pressure of the shallowly-buried position and the deeply-buried position of the bedrock section of the rectangular deep shaft is calculated based on the tunnel surrounding rock pressure theory; The calculation expression of the surrounding rock pressure of the shallowly-buried position is as follows: wherein, represents the surrounding rock pressure at the shallow position; represents the fill density of the bedrock section; represents the height of the cross section from the ground; represents the lateral pressure coefficient at the shallow position; represents the rupture angle at which the maximum thrust is generated; represents the calculated friction angle of the surrounding rock; represents the friction angle on both sides of the roof soil column; The calculation expression of the surrounding rock pressure of the deeply-buried position is as follows: wherein, represents the surrounding rock pressure at the deep-buried position; represents the fill weight of the bedrock section; represents the lateral pressure coefficient at the deep-buried position; represents the equivalent load height; represents the surrounding rock grade; represents the width influence coefficient; represents the shaft span; represents the surrounding rock pressure increment or decrement rate when the shaft span is increased or decreased by 1 m. wherein represents the depth of the deep-shallow buried tunnel boundary.

2. The method according to claim 1, wherein, The calculation expression of the soil pressure of the soil covering section of the rectangular deep shaft is as follows: wherein, represents the earth pressure of the covered section of the shaft; represents the fill weight of the covered section; represents the fill depth; represents the active earth pressure coefficient; represents the angle between the wall back and the vertical line; represents the angle between the fill surface and the horizontal plane; represents the internal friction angle; represents the friction angle between the wall back and the fill; represents the passive earth pressure coefficient; represents the ground surface uniform load; represents the cohesion coefficient; represents the cohesion of the soil.

3. A rectangular deep shaft surrounding rock pressure calculation system characterized by, The method for calculating the soil-rock pressure of a rectangular deep shaft comprises the following steps: The soil-rock pressure of the rectangular deep shaft is divided into the soil pressure of the soil covering section of the rectangular deep shaft and the surrounding rock pressure of the bedrock section of the rectangular deep shaft based on the soil-rock separation principle; The soil pressure of the soil covering section of the rectangular deep shaft is calculated based on the Coulomb active soil pressure theory with cohesion; The surrounding rock pressure of the shallowly-buried position and the deeply-buried position of the bedrock section of the rectangular deep shaft is calculated based on the tunnel surrounding rock pressure theory.

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