Method for calculating overbreak and overfill of circular tunnel

Abstract

The application discloses a kind of circular tunnel overbreak rate and overfill rate calculation method in hydropower engineering field when hydropower engineering rough estimate is prepared.The application provides a kind of simple, reasonable, effective circular tunnel overbreak rate and circular tunnel direct lining, shotcrete post-lining overfill rate calculation method based on tunnel overbreak volume, overfill volume and related specification research, gives corresponding calculation formula, when hydropower engineering rough estimate is prepared, the formula can be used to calculate circular tunnel overbreak rate and direct lining, shotcrete post-lining tunnel overfill rate, solves tunnel excavation unit price, tunnel concrete lining unit price preparation uncertainty problem, improves the accuracy of engineering investment preparation results.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of water and electricity engineering, in particular to a method for calculating over-excavation rate and over-filling rate of circular tunnel. BACKGROUND

[0002] Water and electricity engineering has more underground projects, especially the popular pumped storage power station, the water delivery system and the plant are generally arranged underground, and the underground cavern group accounts for a large proportion of the engineering construction investment. During the excavation of underground cavern, over-excavation phenomenon is inevitable due to the influence of construction technology level and geological conditions. Over-excavation has different degrees of influence on the safety, quality, cost and progress of the project, mainly including the stability of surrounding rock and the increase of investment. Underground cavern generally needs concrete lining, and over-excavation will also cause over-filling of lining concrete, increase the cost of concrete lining, and have greater impact on investment. It is of great significance to reasonably predict the investment of water and electricity engineering to accurately determine the over-excavation rate and over-filling rate.

[0003] The specification document "Provisions for Engineering Quantity Calculation of Water and Electricity Engineering Design" stipulates that engineering quantity should be calculated according to the net value of the design geometric contour size of the building or project, and over-excavation and over-filling cannot be included in the design engineering quantity. However, over-excavation and over-filling are inevitable, and in actual processing, they are generally distributed in the comprehensive unit price. However, there is no provision for the calculation method of over-excavation rate and over-filling rate of circular tunnel in the current regulations and specifications, causing uncertainty in the preparation of stone excavation unit price and tunnel concrete lining unit price.

[0004] Over-excavation in stone excavation and over-filling in tunnel lining have a great impact on the comprehensive unit price, and further directly affect the project investment. Therefore, it is necessary to solve the problem of reasonable calculation of over-excavation rate and over-filling rate in the preliminary estimation stage. SUMMARY

[0005] In order to overcome the lack of over-excavation rate and over-filling rate calculation method in existing water and electricity engineering, which leads to the inability to estimate the project, the technical problem to be solved by the present application is to provide a method for calculating the over-excavation rate and over-filling rate of circular tunnel.

[0006] The technical scheme adopted by the present application to solve the technical problem is:

[0007] The method for calculating the over-excavation rate and over-filling rate of circular tunnel comprises the following steps:

[0008] a. Calculate the unit length circular tunnel, the design excavation radius of the tunnel is R, and the design excavation amount S of the unit length circular tunnel is calculated by using the area formula of a circle 设计开挖 = πR 2 .

[0009] b, set the radial overbreak value b, add the design excavation radius, calculate the total excavation amount of unit length circular tunnel after overbreak using the circular area formula S 超挖 = π(R + b) 2 ;

[0010] c, subtract the total excavation amount after overbreak from the design excavation amount S 设计开挖 , the overbreak amount of unit length circular tunnel is π(2bR + b 2 ), according to the ratio of overbreak amount to design excavation engineering quantity, the overbreak rate is obtained:

[0011]

[0012] d, for the tunnel directly lined with concrete after excavation, the lining thickness is T, calculate the cross-sectional area S 衬砌 = π(R - T) 2 of the concrete lining, the design lining filling amount of unit length circular tunnel is S 设计开挖 - S 衬砌 , equal to π(2RT - T 2 ), and the overfill amount is equal to the overbreak amount, according to the ratio of overfill amount to design lining filling amount, the overfill rate is obtained:

[0013]

[0014] For the tunnel that first sprays concrete and then lines after excavation, the thickness of sprayed concrete is δ, calculate the cross-sectional area S 喷混凝土 = π(R + b - δ) 2 of the sprayed concrete, the sprayed concrete amount of unit length circular tunnel is S 超挖 - S 喷混凝土 , equal to π(2Rδ + 2bδ - δ 2 ), and the overfill amount is equal to the overbreak amount minus the sprayed concrete amount, that is, π(δ 2 + 2bR + b 2 - 2Rδ - 0.4δ), according to the ratio of overfill amount to design lining filling amount, the overfill rate after spraying concrete is obtained:

[0015]

[0016] Further, the radial overbreak value b is 0.2m.

[0017] Further, the thickness of sprayed concrete δ is 0.08m.

[0018] The beneficial effects of the present application are: the present application provides a calculation method of overbreakage rate of circular tunnel and overfill rate of direct lining and post-spraying lining tunnel in the preliminary estimation stage of hydropower engineering, and gives a calculation formula, which is simple and feasible, the calculation result is accurate, and the calculation method is efficient, which can be used for calculating the overbreakage rate of circular tunnel and the overfill rate of direct lining and post-spraying lining tunnel in the preliminary estimation stage of hydropower engineering, solving the uncertainty problem of tunnel excavation unit price and tunnel concrete lining unit price, and improving the accuracy of engineering investment preparation results. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 is the overbreakage schematic diagram of the circular tunnel of the present application.

[0020] Figure 2 is the overfill schematic diagram of the circular tunnel under the condition of direct lining of the present application.

[0021] Figure 3 is the overfill schematic diagram of the circular tunnel under the condition of post-spraying concrete lining of the present application. DETAILED DESCRIPTION

[0022] The present application is further illustrated below in combination with the drawings and examples.

[0023] The present application studies the overbreakage amount, overfill amount and specification of the circular tunnel: the overbreakage within the design allowable overbreakage range can be included in the unit price, and the cost exceeding the design allowable range is borne by the contractor. In the preliminary estimation stage, for the circular tunnel, the overbreakage rate and the corresponding overfill rate are calculated according to the radial overbreakage b, and the calculation method of the overbreakage rate and the overfill rate of the circular tunnel is given, mainly including the following steps:

[0024] a, as shown in Figure 1 , taking a unit length of circular tunnel for calculation, the tunnel design excavation radius is R, and the unit length of circular tunnel design excavation amount S 设计开挖 is calculated by using the area formula of a circle 2 ;

[0025] b, set the radial overbreakage value as b, add the design excavation radius, and calculate the total excavation amount S 超挖 of the unit length of circular tunnel after overbreakage by using the area formula of a circle 2 ;

[0026] c, subtract the design excavation amount S 设计开挖 from the total excavation amount after overbreakage, and the unit length of circular tunnel overbreakage amount is π(2bR+b 2 ), according to the ratio of overbreakage amount to design excavation engineering quantity, the overbreakage rate is obtained:

[0027]

[0028] d. For tunnels where concrete lining is directly installed after excavation, the lining thickness is T, such as... Figure 2 As shown, the cross-sectional area S after concrete lining is calculated using the formula for the area of ​​a circle. 衬砌 =π(RT) 2 The design lining fill volume per unit length of a circular tunnel is S. 设计开挖 -S 衬砌 , equal to π(2RT-T) 2 The overfill volume is equal to the over-excavation volume. The overfill rate can be obtained by calculating the ratio of the overfill volume to the designed lining fill volume.

[0029]

[0030] For tunnels where shotcrete is applied before lining after excavation, the shotcrete thickness is δ, such as... Figure 3 As shown, the cross-sectional area S after shotcreting is calculated using the formula for the area of ​​a circle. 喷混凝土 =π(R+b-δ) 2 The amount of shotcrete per unit length of a circular tunnel is S. 超挖 -S 喷混凝土 , equal to π(2Rδ+2bδ-δ 2 The overfill amount equals the over-excavation amount minus the amount of sprayed concrete, which is π(δ). 2 +2bR+b 2 -2Rδ-0.4δ), based on the ratio of the overfill to the designed lining filling volume, the overfill rate after shotcreting can be obtained:

[0031]

[0032] Furthermore, for horizontal tunnels, the design generally allows for over-excavation of approximately 0.2m radially, so the radial over-excavation value b is preferably 0.2m. Additionally, according to the "General Estimate Quota for Hydropower Construction Projects (2007 Edition)," when calculating the overfill rate of tunnels where shotcrete is applied before lining, the preferred shotcrete thickness δ is 0.08m.

[0033] The present invention will be further illustrated below through specific embodiments.

[0034] Example 1:

[0035] Several typical circular tunnels with cross-sectional areas per unit length were selected for verification calculations, and their values ​​were compared and analyzed with the reference values ​​in the "Estimated Cost Quotas for Hydropower Construction Projects (2007 Edition)".

[0036] For the over-excavation rate of circular tunnels, the calculation method and formula presented in this paper are used, and the design excavation cross-sectional area is selected as 10–150 m². 2 The calculations were performed on 7 typical cross-sections, and the results were compared with the reference values ​​in Table 1.

[0037] Table 1 Calculation results of overbreak rate of circular tunnel

[0038]

[0039]

[0040] The overbreak rate plus the reasonable construction allowance is converted into the unit engineering quantity of the quota, which is the stone and ballast transportation quantity. From the analysis of Table 1, for the selected 7 typical sections, the stone and ballast transportation quantity calculated according to the formula is completely consistent with the corresponding quota stone and ballast transportation quantity, which shows that the calculation of the tunnel overbreak rate according to the calculation method and formula proposed in this paper is appropriate.

[0041] For the overfill rate of the circular tunnel with direct lining after excavation, 5 typical sections with design excavation section areas of 10-150 m 2 and a total of 15 lining thicknesses are selected, and the comparison and analysis of the calculation results and the quota reference values are listed in Table 2.

[0042] Table 2 Calculation results of overbreak rate of circular tunnel with direct lining

[0043]

[0044] For the tunnel with direct lining, the overfill quantity is equal to the overbreak quantity. The overfill rate plus the reasonable construction allowance is converted into the unit engineering quantity of the quota, which is the concrete transportation quantity. From the analysis of Table 2, for the selected 5 typical sections with a total of 15 lining thicknesses, the concrete transportation quantity under 4 lining thicknesses has a very small deviation from the corresponding quota concrete transportation quantity, and the concrete transportation quantity under the remaining lining thicknesses is the same as the corresponding quota concrete transportation quantity, which shows that the calculation of the tunnel overfill rate according to the calculation method and formula proposed in this paper is appropriate.

[0045] For the overfill rate of the circular tunnel with shotcrete lining after excavation, 5 typical sections with design excavation section areas of 10-150 m 2 and a total of 15 lining thicknesses are selected, and the comparison and analysis of the calculation results and the quota reference values are listed in Table 3.

[0046] Table 3 Calculation results of overbreak rate of circular tunnel with shotcrete lining

[0047]

[0048] For the tunnel with shotcrete and bolt support and post-lining, the overfilling quantity is equal to the over-excavation quantity minus the shotcrete quantity. The overfilling rate plus the reasonable construction additional quantity, converted into the fixed unit engineering quantity, is the lining concrete transportation quantity. From Table 3, for the 5 selected typical sections with a total of 15 lining thicknesses, the concrete transportation quantity for 2 lining thicknesses has a very small deviation from the corresponding fixed concrete transportation quantity, and the concrete transportation quantity for the remaining lining thicknesses is the same as the corresponding fixed concrete transportation quantity, indicating that the calculation method and formula proposed in this paper for calculating the tunnel overfilling rate are appropriate.

Claims

1. A method for calculating overbreak and underbreak of a circular tunnel, characterized in that, Comprising the following steps: a、Take the unit length of the circular tunnel for calculation, the tunnel design excavation radius is R, and the unit length of the circular tunnel design excavation amount S is calculated by using the area formula of the circle 设计开挖 = πR 2 ; b, set the radial overbreak value b, add the design excavation radius, calculate the total excavation amount of unit length circular tunnel after overbreak S using the circular area formula 超挖 = π(R+b) 2 ; c、The total excavation amount after over-excavation is reduced by the design excavation amount S 设计开挖 The over-excavation amount of a circular tunnel per unit length is: π(2bR+b 2 According to the ratio of the over-excavation amount to the design excavation engineering quantity, the over-excavation rate is obtained: d. For tunnels where concrete lining is directly installed after excavation, with a lining thickness of T, calculate the cross-sectional area S after concrete lining using the formula for the area of ​​a circle. 衬砌 =π(RT) 2 The design lining fill volume per unit length of a circular tunnel is S. 设计开挖 -S 衬砌 , equal to π(2RT-T) 2 The overfill volume is equal to the over-excavation volume. The overfill rate can be obtained by calculating the ratio of the overfill volume to the designed lining fill volume. For the tunnel which is excavated first and then sprayed concrete and then lined, the thickness of sprayed concrete is δ, the cross-sectional area S after spraying concrete is calculated by the area formula of circle 喷混凝土 = π(R + b - δ) 2 , then the sprayed concrete quantity per unit length of the circular tunnel is S 超挖 = π(R + b - δ) δ 喷混凝土 , which is equal to π(2Rδ + 2bδ - δ 2 ), and the overfilling quantity is equal to the over-excavation quantity minus the sprayed concrete quantity, i.e. π(δ 2 + 2bR + b 2 - 2Rδ - 0.4δ0, according to the ratio of the overfilling quantity to the designed lining filling quantity, the overfilling rate after spraying concrete can be obtained:

2. The method of claim 1, wherein the method is characterized by: Radial overbreak value b is 0.2m.

3. The method of claim 1, wherein the method is characterized by: Shotcrete thickness δ is 0.08m.

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