A cable shaft

Abstract

The present invention relates to a cable shaft, which includes a bottom plate, side walls and a cover plate that enclose the inner space of the shaft. The side walls are used to connect the cable conduits. The bottom plate has an overhanging portion that extends out of the outer edge of the side walls along the extension direction of the cable conduits. The cable conduits further include a balancing portion that is disposed on the overhanging portion of the bottom plate and is used to balance stress and support the cable conduits. The present invention can preferably solve the problem of uneven settlement between the cable conduits and the cable shaft, and has the advantages of convenient construction, short construction period and less investment required.

Description

Technical Field

[0001] The present invention belongs to the technical fields of electric power engineering and municipal engineering, and particularly relates to a cable shaft. Background Art

[0002] According to the laying requirements of power cables, a cable shaft (including a cable inspection well or a branch well) needs to be set every certain distance (generally not exceeding 100 m) along the path length direction. The internal clear space of the well should meet the requirements of cable laying and maintenance. Due to the need for personnel to enter for maintenance, the internal clear space height of the well is not less than ********, and considering the soil covering and the thickness of the bottom plate structure, the depth of the bottom plate of the well often exceeds ********. Considering the requirements of cable laying and personnel maintenance in the well, the width and length of the well are generally not less than ******** and ********. At this time, the reinforced concrete structure formed by the bottom plate, the surrounding side walls and the top plate of the well will form a cavity underground, and the weight of the well structure and the equipment load such as cables inside is less than the weight of the replaced soil mass.

[0003] Meanwhile, the side wall of the cable shaft needs to be connected to the cable duct bank. The soil covering of the cable duct bank is generally between ******** and ********, and its bottom does not exceed ********, and the cable duct bank is surrounded by concrete or backfilled with dense sand, and the weight of the cables in the duct bank is also heavier than the replaced part of the load, which results in a height difference in space docking at the connection between the duct bank and the shaft, and the additional stresses generated by the two on the underlying foundation soil are also different. Different additional stresses directly lead to the settlement difference at the connection between the duct bank and the shaft. In soft foundation soil layers with a high groundwater level, the uneven settlement at the connection often becomes one of the difficult problems in engineering quality control.

[0004] In order to solve the problem of uneven settlement at the connection between the cable duct bank and the cable shaft, the existing methods mainly include the following two:

[0005] One is to set mixing piles / jet grouting piles 3 as shown in Attachment Figure 1 and Attachment Figure 2 along the entire cable line, including 2 sections of cable duct banks and 1 section of cable shaft, or adopt other foundation treatment measures to increase the compression modulus of the foundation soil under the duct bank and the shaft, thereby reducing the value of uneven settlement several times and controlling it within the allowable range of the structure; the other is to set anti - pull piles 5 with steel bars 4 inside as shown in Attachment Figure 3 and Attachment Figure 4 under the shaft to reduce the additional stress difference of the foundation soil between the shaft and the duct bank, so as to reduce the amount of uneven settlement and also achieve the purpose of deformation control.

[0006] The existing two methods for solving uneven settlement have defects such as long construction period, high investment and inconvenient construction. Summary of the Invention Note: Some specific numerical values in the original text are replaced with ******** as they are not clear in the provided content. You can fill in the correct values according to the actual situation.

[0007] The object of the present invention is to provide a cable manhole for solving the problem of uneven settlement, which is convenient for construction, has a short construction period, and requires less investment.

[0008] To achieve the above object, the technical solution adopted by the present invention is:

[0009] A cable manhole includes a bottom plate, side walls and a cover plate that enclose the inner space of the manhole. The side walls are used to connect cable conduits. The bottom plate has an overhanging portion that extends beyond the outer edge of the side walls along the extension direction of the cable conduits. The cable conduits further include a balancing portion disposed on the overhanging portion of the bottom plate and used for balancing stress and supporting the cable conduits.

[0010] Using the formula calculate the unilateral overhanging length b of the bottom plate w , where P0 is the additional stress at the base of the conduit, l is the outer width of the cable manhole, b is the outer length of the cable manhole, t is the thickness of the overhanging portion of the bottom plate, γ g is the concrete specific weight of the bottom plate, γ m is the specific weight of the counterweight material used for the balancing portion, γ i is the original soil specific weight above the bottom plate before excavation, h i is the original soil thickness above the bottom plate before excavation, G1 is the self-weight of the cable manhole, and G2 is the load weight of the equipment and supports inside the cable manhole.

[0011] Preferably, the balancing portion has a bottom surface that abuts against the overhanging portion of the bottom plate, a top surface that abuts against the cable conduits, and outer side surfaces that connect the top surface and the bottom surface and are perpendicular to the extension direction of the cable conduits. The outer side surfaces are inclined relative to the bottom surface.

[0012] Preferably, the included angle between the outer side surface and the bottom surface is 45°.

[0013] Preferably, a concrete structure is cast between the balancing portion and the ground.

[0014] Preferably, a water-swellable rubber strip is provided between the cable conduits and the concrete structure.

[0015] Preferably, the cable manhole includes four side walls, namely a pair of oppositely arranged connecting side walls and a pair of oppositely arranged supporting side walls. The connecting side walls are used to connect the cable conduits. The supporting side walls have an extending portion that extends beyond the outer edge of the connecting side walls along the extension direction of the cable conduits. The extending portion is connected to the overhanging portion of the bottom plate.

[0016] Preferably, the balancing portion is formed of rubble or plain concrete.

[0017] Preferably, the cable shaft further includes a cushion layer disposed below the bottom plate.

[0018] Preferably, the cable shaft further includes cable brackets disposed in the internal space of the shaft.

[0019] Preferably, an inner wall is cast on the inner side of the side wall for connecting the cable conduits.

[0020] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art: The present invention can better solve the problem of uneven settlement between the cable conduits and the cable shaft, and has the advantages of convenient construction, short construction period and less investment required. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] FIG Figure 1 is a front view schematic diagram of an existing cable shaft provided with mixing piles / jet grouting piles.

[0022] FIG Figure 2 is a side view schematic diagram of an existing cable shaft provided with mixing piles / jet grouting piles.

[0023] FIG Figure 3 is a front view schematic diagram of an existing cable shaft provided with uplift piles.

[0024] FIG Figure 4 is a side view schematic diagram of an existing cable shaft provided with uplift piles.

[0025] FIG Figure 5 is a front view schematic diagram of the cable shaft of the present invention.

[0026] FIG Figure 6 is a side view schematic diagram of the cable shaft of the invention.

[0027] FIG Figure 7 is a top view schematic diagram of the cable shaft of the invention.

[0028] In the above drawings: 1. Cable well; 2. Cable conduits and their encapsulated concrete; 3. Mixing piles / jet grouting piles; 4. Steel bars; 5. Uplift piles;

[0029] 6. Bottom plate; 7. Side wall; 8. Cover plate; 9. Cushion layer; 10. Cable brackets; 11. Extended part; 12. Balancing part; 13. Cable cushion layer; 14. Concrete structure on the conduits; 15. Extended part. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0030] The present invention will be further described below in conjunction with the embodiments shown in the drawings.

[0031] Embodiment 1: As shown in FIGS. Figure 5 to FIGS. Figure 7As shown in the figure, a cable shaft includes a bottom plate 6, side walls 7, and a cover plate 8 that enclose the inner space of the shaft, and also includes a cushion layer 9 and cable brackets 10. The cable shaft includes four side walls 7, namely a pair of relatively arranged connecting side walls 7 and a pair of relatively arranged supporting side walls 7. The connecting side walls 7 are used to connect cable conduits. The cushion layer 9 is arranged below the bottom plate 6.

[0032] The bottom plate 6 has an outer extension portion 11 that extends beyond the outer edge of the side wall 7 along the extension direction of the cable conduit, so that the bottom plate 6 forms an extended bottom plate 6. The cable conduit further includes a balancing portion 12 arranged on the outer extension portion 11 of the bottom plate 6 and used for balancing stress and supporting the cable conduit. The balancing portion 12 is formed by rubble or plain concrete. It has a bottom surface that docks with the outer extension portion 11 of the bottom plate 6, a top surface that docks with the cable conduit, and an outer side surface that connects the top surface and the bottom surface and is perpendicular to the extension direction of the cable conduit. The outer side surface is inclined relative to the bottom surface. Usually, the included angle between the outer side surface and the bottom surface is 45°.

[0033] A concrete structure is cast secondarily between the balancing portion 12 and the ground. The concrete structure includes two parts, namely a cable cushion layer 13 located at the bottom of the cable conduit and extending along the cable trench, and a concrete structure 14 on the conduit located above the cable cushion layer 13 and extending upward to the ground to balance additional stress. The cable conduit and its encapsulated concrete are arranged within the concrete structure 14 on the conduit. A water-swelling rubber strip is arranged between the cable conduit and the concrete structure. Usually, the concrete structure 14 on the conduit is only correspondingly arranged above the outer extension portion 11 of the bottom plate 6 at the cable well.

[0034] The supporting side wall 7 has an extension portion 15 that extends beyond the outer edge of the connecting side wall 7 along the extension direction of the cable conduit. The extension portion 15 is connected to the outer extension portion 11 of the bottom plate 6. The length of the extension portion 15 of the supporting side wall 7 is the same as the length of the outer extension portion 11 of the bottom plate 6.

[0035] The cable brackets 10 are arranged in the inner space of the shaft. An inner wall is cast on the inner side of the side wall 7 used to connect the cable conduit.

[0036] The above solution is a shaft structure for controlling uneven settlement at the docking position with the cable conduit. Its design includes an extended bottom plate 6 for compensating stress difference and a balancing portion 12 structure of crushed stone or plain concrete for supplementary backfilling of the overlying load. The width of the space for the worker access part required for the construction of the shaft structure, which is 800 - 1000 mm, is utilized between the outer expansion parts. The force transmission paths of the shaft, conduit, and the foundation soil are clear. Compared with the method of controlling uneven settlement by ground treatment, it has the advantages of small investment, short construction period, and convenient construction, and is especially suitable for cable shafts that are sensitive to uneven settlement deformation at the connection under soft foundation soil conditions.

[0037] The cable shaft mainly includes the following aspects:

[0038] (1) The well body includes a bottom plate 6, side walls 7, and a cover plate 8, all of which are made of reinforced concrete. When the groundwater level is above the bottom plate 6, self-waterproof concrete needs to be used, and the impermeability grade shall not be lower than P6.

[0039] (2) The structure for balancing the replaced soil mass consists of three main parts: ① The reinforced concrete well structure, including the periphery of the well wall, the top plate, and the bottom plate 6, which is denoted as G1 during calculation; ② The equipment inside the well, i.e., the support structure, which is denoted as G2 during calculation; ③ The self-weight of the structure of the extended part outside the well bottom plate 6 and the counterweight structure such as the overlying crushed stones or plain concrete, which is denoted as G3 during calculation.

[0040] (3) The determination route of the well and its counterweight structure is as follows:

[0041] Calculate the additional pressure P0 (kPa) at the base of the pipe row. The calculation of this part of the pressure uses the self-weight load of the cables, pipes, and their overburden above the pipe row cushion 9 minus the overburden load before excavation; [[ID=I2]]

[0042] Control the additional pressure (kPa) at the bottom of the pipe row well to be equal to the additional pressure at the bottom of the pipe row, i.e., P1 = P0.

[0043] Calculate the self-weight G1 of the well structure, the load weight G2 of the equipment and supports inside the well, and finally balance the additional stress at the bottom of the well by controlling the outer extension length of the foundation bottom and the specific gravity of the counterweight material, and control it around P0. The calculation formula is:

[0044]

[0045] In formula (1): P0 - additional stress at the base of the pipe row (kPa)

[0046] l - outer width of the well (m)

[0047] b - outer length of the well (m)

[0048] b w - unilateral outer extension length of the bottom plate 6 required for counterweight (m)

[0049] t - thickness of the extended bottom plate 6, generally equal to the thickness of the bottom plate 6 of the well (m)

[0050] γ g - specific gravity of the bottom plate 6 concrete (kN / m 3 )

[0051] γ m - specific gravity of the counterweight material (kN / m 3 )

[0052] γ i - specific gravity of the original soil above the bottom plate 6 before excavation (kN / m3 )

[0053] h i —— Thickness of the original soil above the bottom slab 6 before excavation (m)

[0054] For formula (1), as long as there is an unknown, calculate and determine b w After that, the structure of the shaft where the difference between the additional stress at the bottom of the shaft and the additional stress at the bottom of the pipe row is 0 can be determined.

[0055] The above embodiments are only for illustrating the technical concept and features of the present invention, and the purpose is to enable those who are familiar with this technology to understand the content of the present invention and implement it accordingly, and it cannot be used to limit the protection scope of the present invention. All equivalent changes or modifications made according to the spirit and essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. A cable shaft, comprising a bottom plate, side walls and a cover plate that enclose the space inside the shaft, and the side walls are used for connecting cable conduits, characterized in that: The bottom plate has an outer extension portion extending beyond the outer edge of the side wall along the extension direction of the cable conduit, and the cable conduit further includes a balancing portion disposed on the outer extension portion of the bottom plate and used for balancing stress and supporting the cable conduit; Using the formula to calculate the unilateral overhanging length b of the bottom plate w , where P0 is the additional stress at the pipe trench foundation, l is the outer width of the cable shaft, b is the outer length of the cable shaft, t is the thickness of the overhanging part of the bottom plate, γ g is the concrete specific weight of the bottom plate, γ m is the specific weight of the counterweight material used for the balance part, γ i is the specific weight of the original soil above the bottom plate before excavation, h i is the thickness of the original soil above the bottom plate before excavation, G1 is the self-weight of the cable shaft, and G2 is the load weight of the equipment and brackets inside the cable shaft.

2. The cable shaft according to claim 1, wherein: The balancing portion has a bottom surface docked with the outer extension portion of the bottom plate, a top surface docked with the cable conduit, and an outer side surface connecting the top surface and the bottom surface and perpendicular to the extension direction of the cable conduit, and the outer side surface is inclined relative to the bottom surface.

3. The cable shaft according to claim 2, characterized in that: The included angle between the outer side surface and the bottom surface is 45°.

4. A cable shaft according to claim 1, characterized in that: A concrete structure is cast between the balancing portion and the ground.

5. The cable shaft according to claim 4, wherein: A water-swellable rubber strip is provided between the cable conduit and the concrete structure.

6. The cable shaft according to claim 1, wherein: The cable shaft includes four side walls, namely a pair of oppositely arranged connecting side walls and a pair of oppositely arranged supporting side walls. The connecting side walls are used for connecting the cable conduit, and the supporting side walls have an extension portion extending beyond the outer edge of the connecting side walls along the extension direction of the cable conduit, and the extension portion is connected to the outer extension portion of the bottom plate.

7. A cable shaft according to claim 1, characterized in that: The balancing portion is formed of rubble or plain concrete.

8. A cable shaft according to claim 1, characterized in that: The cable shaft further includes a cushion layer disposed below the bottom plate.

9. A cable shaft according to claim 1, characterized in that: The cable shaft further includes a cable support disposed in the well space.

10. A cable shaft according to claim 1, characterized in that: An inner wall is cast on the inner side of the side wall for connecting the cable conduit.

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