Method for determining the height of a cushion layer for controlled blasting of an underwater foundation pit disaggregation energy

Abstract

The present application relates to a kind of determination methods of underwater foundation pit disaggregation energy control blasting cushion height, the present application sets up n+1 buffer pad to be preferred height in the preferred range of the optimum height δ of buffer pad, using ansys finite element software, establish blasthole, bedrock, explosive, block, the finite element model of n+1 buffer pad to be preferred height, get the damage depth of bedrock under the action of blasting, then the damage depth of bedrock after using different buffer pad height is compared, the to-be-optimized height δ that satisfies the following conditions i It is the best selected thickness of buffer pad: the damage depth h of bedrock under the action of blasting i Gradually tend to be stable and the height of buffer layer is minimum at this time.The present application can meet the actual engineering problem, protect the excavation of bedrock at the same time, meet the blasting construction specification, avoid secondary construction, speed up construction efficiency and realize efficiency maximization.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of underwater foundation pit blasting. Specifically, it relates to a method for determining the height of a cushion layer for energy dissipation and controlled blasting of an underwater foundation pit. BACKGROUND

[0002] As a widely used excavation method in underwater engineering, blasting has good excavation effect and economy. However, during the blasting process, a huge shock wave is generated, which damages the foundation surface of the underwater rock mass and causes rock mass damage, thereby affecting the stability of the bedrock. In the traditional blasting process, a 1-2m thick protective layer is reserved, and then small-diameter blasting is used to excavate the protective layer, and finally manual prying is used to achieve the excavation of the blasting protective layer. However, this method is low in efficiency and costly, seriously affecting the construction period, and the damage to the rock mass at the bottom of the hole is difficult to control. The use of horizontal smooth blasting and horizontal pre-splitting blasting technology has good forming effect and damage control effect, but horizontal hole drilling is difficult, resulting in low construction efficiency and small blasting area, which cannot be used for large-area excavation. The use of flexible cushion at the bottom of the hole for small-step differential blasting has certain defects in material and structure, and the cushion effect of the shock wave is not good, the damage to the bedrock at the bottom of the hole is still large, and the foundation surface after blasting is uneven, which requires secondary blasting or manual prying, resulting in low construction efficiency. In deep water environment, due to water pressure and other factors, it is more difficult to produce cracks and throw than in open blasting, so the amount of explosive needs to be increased, which will increase the damage to the bedrock at the bottom of the hole. The use of composite energy dissipation structure can better control the damage effect of the bedrock, but the height of the flexible cushion layer will greatly affect the blasting effect. At present, the height of the flexible cushion layer in engineering blasting is mostly determined by experience, resulting in uneven blasting effect. If the height of the cushion layer is too high, the center of gravity of the explosive will move upwards, which is not conducive to the destruction of the bottom rock. If the height of the cushion layer is too low, the damage to the bottom rock will be serious. How to determine the height of the cushion layer to reduce the damage to the bedrock and achieve the protection of the foundation surface during blasting and excavation of the rock is a difficult problem that needs to be solved. SUMMARY

[0003] The technical problem to be solved by the present application is to provide a method for determining the height of a cushion layer for energy dissipation and controlled blasting of an underwater foundation pit.

[0004] To solve the above technical problems, the present application adopts the following technical solutions:

[0005] A method for determining the height of a cushion layer for energy dissipation and controlled blasting of an underwater foundation pit, comprising the following steps:

[0006] Step 1, determining the optimal range of the height of the cushion layer δ as 1 / 10-1 / 3h, h representing the depth of the blast hole;

[0007] Step 2, set n+1 buffer pad height δ of the to-be-optimized height δ0, δ1, δ2,..., δ i ,..., δ n , i≤n, wherein δ i is the i to-be-optimized height, δ i =0.1h+i△, △=(δ i -δ i-1 ) / n+1=[(1 / 3~1 / 10) / n+1]h;

[0008] Step 3, according to the rock foundation excavation engineering construction technical specification of hydraulic structure, the minimum damage factor of the bedrock is determined;

[0009] Step 4, using finite element software, respectively let the buffer pad height is to-be-optimized height δ0, δ1, δ2,..., δ n , establish n+1 finite element models of blast hole, bedrock, explosive, plug section and buffer pad;

[0010] Step 5, according to the finite element model obtained in the above step, the simulation blasting is carried out, and the damage depth h0, h1,..., h n of the blast hole corresponding to each finite element model is obtained when the blasting reaches the minimum damage factor;

[0011] Step 6, arrange h0, h1,..., h n in ascending order of subscript, select the minimum buffer layer height when the damage depth h i tends to be stable as the final buffer pad height.

[0012] Further, the finite element software is ansys finite element software.

[0013] Further, the n is a natural number of 1-4.

[0014] Further, the blast hole is located on the bedrock, the explosive is arranged in the blast hole, the buffer pad is arranged below the explosive, and the plug section is arranged above the blast hole.

[0015] Compared with the prior art, the above technical scheme has the following advantages:

[0016] 1. The buffer pad height of the energy dissipation control blasting of the underwater foundation pit can be accurately determined, the on-site construction is accurately guided, and the stability and safety of the bedrock are ensured.

[0017] 2. The difficulty of bottom bedrock excavation caused by excessive buffer pad height and the poor energy dissipation effect caused by small buffer pad height are avoided, and the damage of the hole bottom bedrock cannot be well controlled.

[0018] Therefore, this invention can not only meet practical engineering problems, but also comply with blasting construction specifications while protecting the excavation of bedrock, avoid secondary construction, speed up construction efficiency and maximize efficiency.

[0019] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. Attached Figure Description

[0020] Figure 1 This is a flowchart of the method of the present invention;

[0021] Figure 2 This is a schematic diagram showing the distribution of the blast holes, energy dissipation balls, explosives, and buffer pads.

[0022] The components represented by each part in the diagram are listed below:

[0023] 1. Buffer pad; 2. Energy dissipation ball; 3. Detonator; 4. Explosive section; 5. Blocking section; 6. Water medium Detailed Implementation

[0024] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0025] like Figure 1 As shown, in use, the buffer pad is located at the bottom of the blast hole to act as a blasting buffer. The method of the present invention is a method for determining the height of the blasting buffer pad for controlling the energy dissipation of underwater foundation pits, including the following steps:

[0026] Step 1:

[0027] 1.1 The preferred range for the height δ of the buffer layer is determined to be 1 / 3 to 1 / 10h, where h represents the borehole depth in meters;

[0028] 1.2 The optimal thickness of the buffer layer height δ is determined to be n+1, where n is 4. This is the (i-1)th optimal thickness δ of the adjacent reserved protective layer. i-1 Thickness difference Δ=δ i-δ i-1 = (1 / 3 - 1 / 10) / 5h, and the optimal heights for the buffer pad layer are δ0, δ1, δ2, δ3, and δ4, respectively.

[0029] in:

[0030] δ0 is the initial optimal height of the buffer layer height δ, δ0 = 0.1h = 0.2m.

[0031] δ1 is the first optimal height for the buffer layer height δ, δ1 = 0.1h + Δ = 0.3m.

[0032] δ2 is a second to-be-preferred height of the cushion layer height δ, δ2 = 0.1h + 2Δ = 0.4m,

[0033] δ3 is a third to-be-preferred height of the cushion layer height δ, δ3 = 0.1h + 2Δ = 0.5m,

[0034] δ4 is a fourth to-be-preferred height of the cushion layer height δ, δ4 = 0.1h + 2Δ = 0.6m;

[0035] 1.3 According to the construction technology specification for rock foundation excavation engineering of hydraulic structures, the allowable damage factor of the bedrock is 0.19;

[0036] Step 2:

[0037] 2.1 The finite element software ansys is used to establish the finite element models of the blast hole, the bedrock, the explosive, the plug and the five to-be-preferred thicknesses of the cushion layer.

[0038] 2.2 According to the finite element models of the blast hole, the bedrock, the explosive, the plug and the five to-be-preferred thicknesses of the cushion layer, the following can be obtained:

[0039] When the optimal thickness δ of the cushion layer is the initial to-be-preferred height δ0, the damage depth of the bedrock after the blasting action reaches the minimum damage factor is 1.74m;

[0040] When the optimal thickness δ of the cushion layer is the first to-be-preferred height δ1, the damage depth of the bedrock after the blasting action reaches the minimum damage factor is 1.66m;

[0041] Similarly:

[0042] When the optimal height δ of the cushion layer is the second to-be-preferred height δ2, when the optimal height δ of the cushion layer is the third to-be-preferred height δ3, and when the optimal thickness δ of the cushion layer is the fourth to-be-preferred height δ4, the damage depth of the bedrock after the blasting action reaches the minimum damage factor is 1.33m, 1.25m and 1.23m respectively;

[0043] Step 3:

[0044] According to step 1.3 and step 2.2, the damage depth of the bedrock after the blasting action reaches the minimum damage factor when the optimal height δ of the cushion layer is the n+1 to-be-preferred heights δ0, δ1, δ2, δ3 and δ4 is compared one by one, and the to-be-preferred height δ that meets the following condition is the optimal height of the cushion layer: i The damage depth h of the bedrock under the blasting action tends to be stable and has the minimum height, so the optimal height of the cushion layer in this embodiment is 0.5m. i

[0045] ​The above describes the best mode of the present application, wherein the parts not described in detail are the common knowledge of the ordinary skilled in the art. The scope of protection of the present application is defined by the content of the claims, and any equivalent transformation based on the technical inspiration of the present application is also within the scope of protection of the present application.

Claims

1. A method for determining the height of a cushion layer for mitigating the energy of an underwater foundation pit blasting, characterized in that, Comprise the following steps: Step 1, determine the range of buffer pad height delta is 1 / 10~1 / 3h, h indicates the hole depth; Step 2, set n+1 buffer pad height δ of the selected height δ0, δ1, δ2... δ i ......δ n , i≤n, where δ i is the i-th selected height, δ i =0.1h+i△, △=(δ i -δ i-1 ) / n+1=[(1 / 3~1 / 10) / n+1]h; Step 3, according to the water conservancy building rock foundation excavation engineering construction technical specification, determine the minimum damage factor of bedrock; Step 4, using finite element software, respectively let the height of the buffer cushion layer be the selected height δ0, δ1, δ2... δn, and establish n+1 finite element models of the blast hole, bedrock, explosive, plug section and buffer cushion layer. n , establish n+1 finite element models of the blast hole, bedrock, explosive, plug section and buffer cushion layer. Step 5: Based on the finite element model obtained in the previous step, perform simulated blasting to obtain the damage depths h0, h1... h corresponding to the borehole when the blasting reaches the minimum damage factor in each finite element model. n ; Step 6, arrange h0, h1... h in ascending order of the subscript n , select the damage depth h i The minimum cushion height when it tends to be stable as the final cushion height.

2. The method for determining the cushion height of the underwater foundation pit disaggregation energy control blasting according to claim 1, characterized in that, The finite element software is ansys finite element software.

3. The method for determining the cushion height of the underwater foundation pit disaggregation energy control blasting according to claim 1, characterized in that, N is a natural number of 1-4.

4. The method for determining the cushion height of the underwater foundation pit disaggregation energy control blasting according to claim 1, characterized in that, The blast hole is located on the bedrock, the blast hole is provided with explosive, the explosive is provided with a buffer pad below, and the blast hole is provided with a plug section above.

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