Recyclable tie bar combined vacuum support system and construction method thereof

Abstract

The invention belongs to the technical field of geotechnical engineering foundation pit supporting, and provides a recoverable tie bar combined vacuum supporting system and a construction method thereof, due to the fact that tie bars have a great stabilizing effect on excavation of a foundation pit, the foundation pit can be excavated within a short time, and the construction efficiency is improved. Compared with a vacuum action gravity type foundation pit supporting system, the tie bar combined vacuum supporting system has obvious stability and construction period advantages. In addition, due to the fact that plastic drainage plate construction does not need to be carried out on a steep slope, the construction safety risk of drainage plate machinery is reduced. According to the method, a transverse drainage body composed of medium-coarse sand is not needed, the construction cost can be greatly reduced, recycling can be carried out after groove fertilization and complete backfilling, safety risks do not exist, and the construction cost can be reduced. Therefore, the method is superior to a vacuum gravity method in the prior art in the aspects of technology, construction period, safety, economy and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of foundation pit support in geotechnical engineering, and specifically relates to a recyclable tie rod combined vacuum support system and a construction method thereof. Background Art

[0002] When excavating foundation pits, sometimes soft soil foundations are encountered. Due to space limitations, foundation pits in soft soil foundations are generally not suitable for slope construction. Conventional pile row + internal support foundation pit support methods are expensive and time-consuming.

[0003] Chinese invention patent No. 200810236142.3 discloses a vacuum curtain water-stopping and atmospheric pressure support method for deep foundation pit excavation (hereinafter referred to as the "vacuum curtain method"). This method uses a vacuum curtain for water-stopping and uses the effect of atmospheric pressure to support the foundation pit. The construction is safer and does not require a supporting structure inside the foundation pit or drainage wells inside or outside the foundation pit. It has obvious advantages in terms of safety, reliability, time saving, and investment saving.

[0004] However, the above vacuum curtain method will reduce the stability of the pit wall due to vertical excavation, which limits the excavation depth of the foundation pit for this method; the vacuum curtain method requires the installation of side wall solidification walls, which increases the amount of work required to install the side wall solidification walls, which is not conducive to reducing the cost. The method of laying a sealing membrane on the top of the pit of the vacuum curtain method is similar to the traditional vacuum preloading foundation treatment method. The outer boundary of the sealing membrane is simply buried shallowly in the soil, which makes it easy for the vacuum pressure in the vacuum curtain to spread outward. The diffusion of vacuum pressure will reduce the vacuum degree within the curtain range, thereby reducing the stability safety factor of the pit wall; there is no vertical drainage body at the bottom of the pit, and the soil at the bottom of the pit will bulge or even be damaged.

[0005] Chinese invention patent No. 201210295813.9 discloses a vacuum-acting gravity-type foundation pit support system and construction method (hereinafter referred to as the "vacuum gravity method"). This method is a vacuum-acting gravity-type foundation pit support system that does not require the setting of side wall solidification walls and curtain bodies, can meet greater excavation depth requirements, has lower costs and shorter construction periods.

[0006] However, the above method still has the following problems:

[0007] 1. Although the construction of the vertical drainage body on the slope is gradually carried out in the foundation soil inside the vertical drainage body on the top of the pit every time the excavation depth is 1m, which can ensure a large vacuum on the slope and enhance the stability of the slope, the drainage board construction machinery is relatively large, and it is not easy to construct when the pit bottom is narrow, which is also easy to cause construction safety hazards.

[0008] 2. The lateral drainage body is a sand cushion layer composed of medium-coarse sand with a thickness of 0.4 to 0.6 meters. Sand has good air permeability, but because the sand cushion layer is a loose material, it will slide down on a slightly steep slope, making it difficult to construct. The vacuum pipeline can be directly connected to the permeable pipe that also serves as a reinforcement, which can also ensure the propagation of vacuum in the foundation without the need for medium-coarse sand.

[0009] 3. Stop vacuuming, then remove the vertical closed curtain at the bottom of the slope, the closed layer on the slope, the horizontal closed layer on the top of the pit and part of the vertical closed curtain on the periphery, and recycle the water-stop steel sheet piles and geomembranes. Recycling can save costs and protect the environment. Although the strength of the slope soil will be improved to a certain extent under the action of vacuum preloading, the stability of the slope mainly comes from the vacuum pressure on the slope. If the vacuuming is stopped, the slope is more likely to become unstable.

[0010] 4. The plastic drain board only plays a role in drainage and is only installed within the projection range of the pit top and slope, and cannot resist the uplift of the pit bottom. Summary of the invention

[0011] In order to make up for the shortcomings of the prior art and solve at least one of the technical problems raised in the background technology, the purpose of the present invention is to provide a recyclable tie rod combined vacuum support system that does not require a sand cushion layer, utilizes tie rods as drainage bodies, can meet the excavation requirements of steeper slopes, has recyclable tie rods, is safer to construct, has a more stable foundation pit, has a lower cost, a shorter construction period, and a large pressure difference between the inside and outside of the slope vacuum.

[0012] A recyclable tie rod combined with vacuum support system, comprising:

[0013] The pit top sealing anchor trench is a trench formed by digging downward at the end of the pit top horizontal sealing layer, the pit top horizontal sealing layer protective layer and the horizontal reinforcement layer of the anchor oblique reinforcement serving as the drainage body; the pit top horizontal sealing layer, the pit top horizontal sealing layer protective layer and the horizontal reinforcement layer of the anchor oblique reinforcement serving as the drainage body are all buried at the bottom of the trench;

[0014] The longitudinal horizontal vacuum pipe is set on the original ground at the top of the pit, the horizontal sealing layer at the top of the pit, and the vacuum pipe under the protective layer of the horizontal sealing layer at the top of the pit. It is parallel to the edge of the excavated foundation pit. The longitudinal horizontal vacuum pipe passes through the horizontal sealing layer at the top of the pit through the film outlet and is then connected to the vacuum pump.

[0015] The oblique tie bars also serve as drainage bodies, which are perforated steel pipes covered with geotextiles and arranged obliquely in the foundation soil within the perimeter of the foundation pit, and the bottom of a part of the oblique tie bars also serving as drainage bodies enters the pit bottom range, and the elevation is lower than the elevation of the ground at the bottom of the pit with the maximum excavation depth;

[0016] The horizontal reinforcement layer anchoring the oblique reinforcement and serving as the drainage body is set on the surface of the foundation soil at the top of the pit and connected to the oblique reinforcement and serving as the drainage body; the horizontal reinforcement layer anchoring the oblique reinforcement and serving as the drainage body is set under the longitudinal horizontal drainage pipe;

[0017] The sealing ditch at the bottom of the pit is excavated downward outside the projection range of the horizontal reinforcement layer 7, which is the lowest layer of anchored oblique reinforcement and also serves as a drainage body, to form a deep ditch outside the slope foot of the bottom of the pit.

[0018] As a further technical solution of the present invention: the horizontal sealing layer on the pit top is one or more layers of geomembrane.

[0019] As a further technical solution of the present invention: the protective layer of the horizontal sealing layer on the pit top is to lay one or more layers of geotextile under the horizontal sealing layer on the pit top.

[0020] As a further technical solution of the present invention: the slope sealing layer is a geomembrane independent of the horizontal sealing layer on the pit top; the slope sealing layer protective layer is one or more layers of geotextile laid under the slope sealing layer;.

[0021] As a further technical solution of the present invention: the oblique reinforcement also serves as a drainage body, which is a steel pipe wrapped with a geotextile. The bottom end of the steel pipe is blocked, and filter holes are evenly distributed on the pipe wall with a hole diameter of φ6-φ10mm. The vertical spacing of the steel pipes is 1-2m, and the horizontal spacing is 1-2m.

[0022] As a further technical solution of the present invention: the longitudinal horizontal vacuum tube adopts a PVC tube or a steel tube with a diameter of 50 mm.

[0023] As a further technical solution of the present invention: the horizontal reinforcement layer 7 for anchoring the oblique reinforcement and serving as the drainage body is a geogrid or a steel belt.

[0024] A construction method of a recyclable tie rod combined with a vacuum support system comprises the following steps:

[0025] S1. An oblique tie bar is set in the foundation soil within the range of the horizontal sealing layer at the top of the pit, which also serves as a drainage body. The bottom of a part of the oblique tie bar, which also serves as a drainage body, enters the pit bottom range, and the elevation is lower than the elevation of the ground at the bottom of the pit with the maximum excavation depth;

[0026] S2, on the surface of the foundation soil where the oblique reinforcement serving as the drainage body is installed, a horizontal reinforcement layer for anchoring the oblique reinforcement serving as the drainage body is arranged, and an anchoring device is arranged between the horizontal reinforcement layer 7 for anchoring the oblique reinforcement serving as the drainage body and the oblique reinforcement serving as the drainage body;

[0027] S3. Connect the oblique tie rod, which also serves as the top of the drainage body, to the longitudinal horizontal vacuum tube to ensure the sealing effect between the joints;

[0028] S4. Lay a horizontal sealing layer protective layer on the top of the pit on the horizontal reinforcement layer that anchors the oblique reinforcement and also serves as a drainage body;

[0029] S5. Laying the pit top horizontal sealing layer on the pit top horizontal sealing layer protective layer;

[0030] S6, passing the longitudinal horizontal vacuum tube through the pipeline film outlet device to pass through the pit top horizontal sealing layer and the pit top horizontal sealing layer protective layer, and then connecting to the vacuum pump through the vacuum pipeline;

[0031] S7, start the vacuum pump, and when the vacuum degree reaches 80kPa and the consolidation degree of the foundation soil reaches 20%, maintain the vacuum degree and excavate the foundation pit;

[0032] S8. Every time the excavation reaches 0.5m below the end of the next row of oblique reinforcement bars that also serve as drainage bodies, the newly excavated section is covered with a slope sealing layer protection layer, and then covered with a slope sealing layer. The slope sealing layer protection layer is firmly connected to the slope top or the previous slope sealing layer protection layer, so that it is sealed and connected to the slope top or the previous slope sealing layer, thereby forming a partial slope sealing layer and a slope sealing layer protection layer. The ends of the slope sealing layer and the slope sealing layer protection layer are buried in the slope surface for not less than 0.5m;

[0033] S9, repeat step S8 until the excavation reaches the designed depth of the foundation pit;

[0034] S10. At the bottom of the pit, a slope sealing layer and a slope sealing layer protective layer are formed on the slope surface and the pit bottom, a pit bottom sealing ditch is excavated outside the pit bottom projection surface at the end of the lowest row of oblique reinforcement bars which also serves as a drainage body, and the pit bottom slope sealing layer and the slope sealing layer protective layer are buried in the pit bottom sealing ditch.

[0035] As a further technical solution of the present invention, the following steps are also included:

[0036] S11, pouring the foundation pit bottom slab and carrying out the subsequent construction of the underground structure;

[0037] S12. Continue to vacuum and backfill the space between the foundation pit wall and the underground structure of the building until the original ground elevation is reached.

[0038] As a further technical solution of the present invention, the following steps are also included:

[0039] S13, stop vacuuming, then recover the oblique reinforcement that also serves as the drainage body 6, anchor the horizontal reinforcement layer 7 of the oblique reinforcement on the pit top and the longitudinal horizontal vacuum tube.

[0040] The beneficial effects of the present invention are as follows:

[0041] The present invention is a recyclable tie bar combined with a vacuum support system and a construction method thereof. The recyclable tie bar combined with a vacuum support system is mainly composed of two parts: an oblique tie bar and a vacuum pumping. The present invention is provided with an oblique tie bar that also serves as a drainage body. The slope soil is reinforced from the start of vacuum pumping, overcoming the delayed construction problem that the vertical drainage body of the slope in the vacuum gravity horizontal drainage method needs to be set up after the upper level slope is excavated, so that the strength of the slope soil is greatly improved and the slope is more stable. The oblique tie bar that also serves as a drainage body is directly connected to the longitudinal pipe. On the one hand, the vacuum is directly transmitted to the soil through the oblique tie bar that also serves as a drainage body, reducing unnecessary vacuum loss. On the other hand, the sand cushion layer is eliminated, saving the project cost, and also overcoming the problem that the sand cushion layer on the steep slope will slide, simplifying the construction process. The oblique tie bar that also serves as a drainage body is set in the foundation pit foundation. Under the action of vacuum support, the tie bar effect is increased, which better ensures the stability of the foundation pit than the vacuum gravity method. The end of the oblique reinforcement that also serves as the drainage body can enter the pit bottom, which is equivalent to a vacuum effect at the pit bottom, which can prevent the pit bottom from bulging and damaging. Backfilling the fertilizer tank during vacuuming can prevent the pit wall from collapsing due to stopping vacuuming and backfilling.

[0042] More simply:

[0043] The present invention utilizes the vacuum support and soil nail support principles, and obliquely arranges a drainage body in the foundation, thereby ensuring the vacuum effect while increasing the reinforcement effect of the soil body, which is more conducive to the stability of the foundation pit.

[0044] The invention eliminates the horizontal drainage body, which not only saves costs but also avoids the loss of vacuum degree in the shallow layer of the foundation.

[0045] The present invention obliquely arranges a drainage body in the foundation to ensure that the soil below the slope surface is reinforced from the beginning of vacuuming, which is beneficial to enhancing the strength of the foundation pit soil.

[0046] The present invention eliminates the need to recover materials such as oblique reinforcement bars that also serve as drainage bodies before backfilling the space between the foundation pit wall and the underground structure of the building, thereby ensuring the stability of the foundation pit during backfilling of the fertilizer trough (the space between the outer wall of the building and the edge of the foundation pit) and achieving the maximum degree of recovery in the true sense. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] The present invention will be further described below in conjunction with the accompanying drawings.

[0048] Figure 1 This is an axial view of a foundation pit used for supporting excavation according to the present invention;

[0049] Figure 2 It is the cross-section diagram of the recyclable tie rod combined with vacuum support system;

[0050] Figure 3 is a flowchart of the steps of monitoring the vacuum degree under the horizontal sealing layer on the top of the pit and its protective layer according to an embodiment of the present invention;

[0051] Figure 4 It is a flowchart of a system for monitoring the vacuum degree under the horizontal sealing layer on the top of a pit and its protective layer according to an embodiment of the present invention.

[0052] In the figure: 1. original ground at the top of the pit, 2. sealing anchoring ditch at the top of the pit, 3. horizontal sealing layer at the top of the pit, 4. protective layer of the horizontal sealing layer at the top of the pit, 5. longitudinal horizontal vacuum tube, 6. oblique reinforcement also serving as drainage body, 7. horizontal reinforcement layer of anchoring oblique reinforcement also serving as drainage body, 8. slope sealing layer, 9. protective layer of slope sealing layer, 10. ground at the bottom of the pit with maximum excavation depth, 11. sealing ditch at the bottom of the pit. DETAILED DESCRIPTION

[0053] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further explained below in conjunction with specific implementation methods.

[0054] Example 1

[0055] See also Figure 1 and Figure 2 As shown, the present invention is a recyclable tie rod combined vacuum support system, comprising: a pit top sealing anchoring ditch 2, a pit top horizontal sealing layer 3, a pit top horizontal sealing layer protective layer 4, a longitudinal horizontal vacuum tube 5, an oblique tie rod also serving as a drainage body 6, a horizontal rib layer 7 for anchoring oblique tie rods and also serving as a drainage body, a slope sealing layer 8, a slope sealing layer protective layer 9, and a pit bottom sealing ditch 11;

[0056] Among them, the pit top sealing anchor trench 2 is excavated downward at the end of the pit top horizontal sealing layer 3, the pit top horizontal sealing layer protective layer 4 and the horizontal reinforcement layer 7 of the anchored oblique reinforcement serving as the drainage body to form a trench of a certain depth. The pit top horizontal sealing layer 3, the pit top horizontal sealing layer protective layer 4 and the horizontal reinforcement layer 7 of the anchored oblique reinforcement serving as the drainage body are all buried at the bottom of the trench; the longitudinal horizontal vacuum tube 5 is a vacuum tube arranged below the original ground 1, the pit top horizontal sealing layer 3 and the pit top horizontal sealing layer protective layer 4 of the pit top, parallel to the excavated foundation pit edge, the longitudinal horizontal vacuum tube 5 passes through the horizontal sealing layer of the pit top through the film outlet, and then is connected to the vacuum pump; the oblique reinforcement serving as the drainage body 6 is a perforated steel pipe wrapped with geotextile and arranged obliquely in the foundation soil within a certain range around the foundation pit, and a part of the oblique reinforcement serving as the drainage body is arranged obliquely in the foundation soil within a certain range around the foundation pit. The bottom of the drainage body 6 enters the pit bottom range, and its elevation is lower than the elevation of the maximum excavation depth pit bottom ground 10; the horizontal reinforcement layer 7 anchored with oblique reinforcement and serving as the drainage body is arranged on the surface of the foundation soil at the top of the pit, and is connected to the oblique reinforcement and serving as the drainage body 6; the horizontal sealing layer 3 at the top of the pit is one or more layers of geomembrane; the horizontal sealing layer protective layer 4 at the top of the pit is one or more layers of geotextile laid under the horizontal sealing layer at the top of the pit; the horizontal reinforcement layer 7 anchored with oblique reinforcement and serving as the drainage body is arranged under the longitudinal horizontal drainage pipe; the slope sealing layer 8 is independent of the horizontal sealing layer geomembrane at the top of the pit; the slope sealing layer protective layer 9 is one or more layers of geotextile laid under the slope sealing layer 7; the pit bottom sealing ditch 11 is outside the pit bottom slope foot, and is excavated downward outside the projection range of the lowest layer of horizontal reinforcement layer 7 anchored with oblique reinforcement and serving as the drainage body to form a ditch of a certain depth.

[0057] The pit top sealing anchoring trench 2 can be excavated manually or mechanically, with a depth of about 2 meters and a width of about 1 meter at the pit bottom.

[0058] The oblique reinforcement also serves as the drainage body 6, which is a steel pipe wrapped with geotextile. The bottom of the steel pipe is blocked, and filter holes are evenly distributed on the pipe wall with a hole diameter of φ6-φ10mm. The vertical spacing of the steel pipes is 1-2m, and the horizontal spacing is 1-2m.

[0059] The longitudinal horizontal vacuum tube 5 is a PVC tube or a steel tube of φ50 mm.

[0060] The horizontal reinforcement layer 7 which anchors the oblique reinforcement and also serves as a drainage body is a geogrid or a steel belt.

[0061] For example, in a foundation pit project, the excavation depth is 6m and the plane size of the excavation is 20m×100m.

[0062] The excavation range is homogeneous foundation soil, and the soil parameters are:

[0063] Silty clay, gray to dark gray, fluid to soft plastic, saturated, natural bulk density γ = 16.5 kN / m 3, water content 51%, porosity 1.55, plasticity index I p = 18.9, Cu = 15.0 kPa, φu = 3.0°, basic bearing capacity σ0 = 40 kPa, permeability coefficient k ≤ 1 × 10 -7 m / s, which is soft soil with poor engineering properties.

[0064] The pit top sealing anchor trench 2 is 9m away from the pit top excavation, and is excavated downward to form a trench with a width of 1m and a depth of 2m; the pit top horizontal sealing layer 3 and its protective layer 4 and the horizontal reinforcement layer 7 for anchoring the oblique reinforcement are all buried at the bottom of the trench; the longitudinal horizontal vacuum pipe 5 adopts a φ50mm PVC pipe or steel pipe, which is arranged on the foundation soil surface 1, below the pit top horizontal sealing layer 3 and its protective layer 4, parallel to the excavated foundation pit edge, and the vacuum pipe passes through the pit top horizontal sealing layer through the film outlet, and is then connected to the vacuum pump; the oblique reinforcement also serves as a drainage body 6, which is a steel pipe wrapped with geotextile, the bottom end of the steel pipe is blocked, and filter holes are evenly distributed on the pipe wall, with an aperture of φ8, a vertical row spacing of 1.5m, and a horizontal spacing of 1.5m. The first row of steel pipes is arranged at a depth of 1m, the second row is arranged at a depth of 2.5m, the third row is arranged at a depth of 4m, the fourth row is arranged at a depth of 5.5m, and the fifth row is arranged at a depth of 7m. The bottom of the 5th row of oblique reinforcement bars, which also serves as a drainage body, enters the pit bottom range by 2m, and its elevation is lower than the elevation of the ground at the bottom of the pit with the maximum excavation depth; the horizontal reinforcement layer 7, which anchors the oblique reinforcement bars and also serves as a drainage body, is a geogrid, which is arranged on the surface of the foundation soil at the top of the pit and is connected to the steel pipe 6; the horizontal sealing layer 3 at the top of the pit is one or more layers of geomembrane; the horizontal sealing layer protective layer 4 at the top of the pit is one or more layers of geotextile laid under the horizontal sealing layer at the top of the pit; the geogrid is arranged under the PVC vacuum water pipe; the slope sealing layer 8 is one or more layers of geomembrane, which is independent of the horizontal sealing layer geomembrane at the top of the pit; the slope sealing layer protective layer 9 is one or more layers of geotextile laid under the slope sealing layer; the pit bottom sealing ditch 11 is 5m outside the pit bottom slope foot.

[0065] Example 2

[0066] The present invention is a construction method of a recyclable tie rod combined with a vacuum support system, comprising the following steps:

[0067] S1. An oblique tie bar serving as a drainage body 6 is arranged in the foundation soil within the setting range of the horizontal sealing layer 3 at the top of the pit, and the bottom of a part of the oblique tie bar serving as the drainage body 6 enters the pit bottom range, and the elevation is lower than the elevation of the ground at the bottom of the pit with the maximum excavation depth;

[0068] S2, on the surface of the foundation soil where the oblique reinforcement also serves as the drainage body 6 is installed, a horizontal reinforcement layer 7 for anchoring the oblique reinforcement also serves as the drainage body is arranged, and an anchoring device is arranged between the horizontal reinforcement layer 7 for anchoring the oblique reinforcement also serves as the drainage body and the oblique reinforcement also serves as the drainage body 6;

[0069] S3, connect the top of the oblique tie bar which also serves as the drainage body 6 with the longitudinal horizontal vacuum tube to ensure the sealing effect between the joints;

[0070] S4, laying a horizontal sealing layer protective layer 4 on the top of the pit on the horizontal reinforcement layer 7 that anchors the oblique reinforcement and also serves as a drainage body;

[0071] S5, laying the pit top horizontal sealing layer 3 on the pit top horizontal sealing layer protective layer 4;

[0072] S6, passing the longitudinal horizontal vacuum tube 5 through the pipeline film outlet to pass through the pit top horizontal sealing layer 3 and the pit top horizontal sealing layer protective layer 4, and then connecting to the vacuum pump through the vacuum pipeline;

[0073] S7, start the vacuum pump, and when the vacuum degree reaches 80kPa and the consolidation degree of the foundation soil reaches 20%, maintain the vacuum degree and excavate the foundation pit;

[0074] S8. Every time the excavation reaches 0.5m below the end of the next row of oblique reinforcement bars that also serve as drainage bodies 6, the newly excavated section is covered with a slope sealing layer protective layer 9, and then covered with a slope sealing layer 8. The slope sealing layer protective layer 9 is firmly connected to the top of the slope or the previous slope sealing layer protective layer 9 by a hand-held sewing machine, and is sealed and connected to the top of the slope or the previous slope sealing layer 8 by heat sealing overlap, thereby forming a partial slope sealing layer 8 and a slope sealing layer protective layer 9. The ends of the slope sealing layer 8 and the slope sealing layer protective layer 9 are buried in the slope surface for not less than 0.5m to ensure their sealing performance;

[0075] S9, repeat step S8 until the excavation reaches the designed depth of the foundation pit;

[0076] S10, at the bottom of the pit, a slope sealing layer 8 and a slope sealing layer protective layer 9 are formed on the slope and the bottom of the pit, a pit bottom sealing groove 11 is excavated outside the pit bottom projection surface at the end of the bottom row of oblique reinforcements that also serve as drainage bodies 6, and the pit bottom slope sealing layer 8 and the slope sealing layer protective layer 9 are buried in the pit bottom sealing groove 11;

[0077] S11, pouring the foundation pit bottom slab and carrying out the subsequent construction of the underground structure;

[0078] S12. Continue to vacuum and backfill the space between the foundation pit wall and the underground structure of the building until the original ground elevation is reached.

[0079] S13, stop vacuuming, then recover the oblique reinforcement that also serves as the drainage body 6, anchor the horizontal reinforcement layer 7 of the oblique reinforcement on the pit top and the longitudinal horizontal vacuum tube.

[0080] Exemplarily, S1, oblique reinforcement bars serving as drainage bodies 6 are set in the foundation soil within the setting range of the horizontal sealing layer 3 on the pit top, and the bottoms of a part of the oblique reinforcement bars serving as drainage bodies enter the pit bottom range, with an elevation lower than the elevation of the ground at the bottom of the pit with the maximum excavation depth; in this project, steel pipes with filter holes wrapped with geotextiles are used as oblique reinforcement bars serving as drainage bodies 6, with a total of 5 rows, with a vertical spacing of 1.5m in each row and a horizontal spacing of 1.5m between the steel pipes.

[0081] S2, on the foundation soil surface 1 where the oblique reinforcement also serves as the drainage body 6 is installed, a horizontal reinforcement layer 7 for anchoring the oblique reinforcement also serves as the drainage body is arranged, wherein a geogrid is used as the horizontal reinforcement layer; an anchoring device is arranged between the horizontal reinforcement layer 7 for anchoring the oblique reinforcement also serves as the drainage body and the oblique reinforcement also serves as the drainage body 6;

[0082] S3, connect the oblique tie rods 6, which also serve as the top of the drainage body, with the longitudinal horizontal vacuum pipe 5 to ensure the sealing effect between the joints. In this project, the longitudinal horizontal vacuum pipe 5 uses a PVC pipe of φ50mm;

[0083] S4, laying a pit top horizontal sealing layer protective layer 4 on the horizontal reinforcement layer 7 for anchoring oblique reinforcement, the pit top horizontal sealing layer protective layer is a layer of geotextile;

[0084] S5. Lay the pit top horizontal sealing layer 3 on the top of the pit top horizontal sealing layer protective layer 4. In this project, the pit top horizontal sealing layer 3 is a two-layer sealing film;

[0085] S6, passing the longitudinal horizontal vacuum tube 5 through the pipeline film outlet to pass through the horizontal sealing layer 3 and the protective layer 4 on the top of the pit, and then connecting it to the vacuum pump through the vacuum pipeline;

[0086] S7, start the vacuum pump, and when the vacuum degree reaches 80kPa and the consolidation degree of the foundation soil reaches 20%, maintain the vacuum degree and excavate the foundation pit;

[0087] S8, dig to 0.5m below the end of the next row of oblique reinforcements that also serve as drainage bodies 6, which are 1.5m, 3.0m, 4.5m, and 6.0m in this project; cover the newly excavated section with a slope sealing layer protective layer 9, where a layer of geotextile is used as a protective layer, and then cover the slope sealing layer 8; the slope sealing layer protective layer is firmly connected to the top of the slope or the previous slope sealing layer protective layer 9 by a hand-held sewing machine, and is sealed and connected to the top of the slope or the previous slope sealing layer 8 by heat sealing, thereby forming a partial slope sealing layer and its protective layer, and the end of the slope sealing layer and its protective layer is buried in the slope surface for not less than 0.5m to ensure its sealing performance;

[0088] S9, repeat step S8 until the excavation reaches the designed depth of the foundation pit;

[0089] S10. At the bottom of the pit, similar to the construction method of S8, a pit bottom sealing layer and its protective layer are formed on the slope surface and the pit bottom. A pit bottom sealing ditch 11 is excavated outside the pit bottom projection surface at the end of the lowest row of oblique reinforcement bars that also serve as the drainage body. This place is 4m away from the bottom of the foundation pit slope, and the pit bottom sealing layer and its protective layer are buried in the pit bottom sealing ditch;

[0090] S11, pouring the foundation pit bottom slab and carrying out the subsequent construction of the underground structure;

[0091] S12. Continue to vacuum and backfill the space between the foundation pit wall and the underground structure of the building until the original ground elevation is reached.

[0092] S13. Stop vacuuming, then recover the oblique reinforcement which also serves as a drainage body, and anchor the horizontal reinforcement layer of the oblique reinforcement and the longitudinal horizontal vacuum tube on the pit top.

[0093] Example 3

[0094] like Figure 3 As shown, before excavating the foundation pit, in order to ensure that the vacuum degree under the horizontal sealing layer on the top of the pit and its protective layer can continue to meet the preset requirements, it is necessary to determine the sealing effect of the horizontal sealing layer on the top of the pit and its protective layer:

[0095] Step 1: Acquire the sealing data of the horizontal sealing layer on the top of the pit and the sealing data under the protective layer during the detection period, wherein the sealing data includes the vacuum degree of the horizontal sealing layer on the top of the pit and the sealing data under the protective layer, and perform data analysis on the sealing data to obtain the sealing abnormality value;

[0096] Specifically, the vacuum degree under the horizontal sealing layer on the top of the pit and its protective layer is obtained and compared with the vacuum degree threshold value;

[0097] If the vacuum degree under the horizontal sealing layer on the top of the pit and its protective layer is less than the vacuum degree threshold, an abnormal signal is generated;

[0098] If the vacuum degree under the horizontal sealing layer on the top of the pit and its protective layer is greater than or equal to the vacuum degree threshold, no processing is performed;

[0099] Based on the generated abnormal signal, the time period in which the abnormal signal is generated within the detection period is obtained, marked as the abnormal period, the total duration of the abnormal period is obtained, and the ratio is processed with the total duration of the detection period to obtain the abnormal duration ratio, marked as TZ;

[0100] Obtain the vacuum degree obtained at each time node that generates an abnormal signal during the abnormal period, perform a difference process between it and the vacuum degree threshold and take the absolute value to obtain the vacuum absolute difference, sum and average all the vacuum absolute differences during the abnormal period to obtain the vacuum absolute mean, and perform a ratio process between it and the vacuum degree threshold to obtain the abnormal degree ratio, which is marked as XZ;

[0101] The obtained abnormal time ratio TZ and abnormal degree ratio XZ are processed, and the sealing abnormality value YZ is obtained by the formula YZ=s1*TZ+s2*XZ, where s1 and s2 are both preset proportional coefficients, s1 is 0.36, and s2 is 0.64;

[0102] It should be noted that the purpose of the sealing abnormal value YZ is to determine the sealing condition of the horizontal sealing layer and its protective layer on the top of the pit by analyzing the duration and degree of vacuum failure under the horizontal sealing layer and its protective layer on the top of the pit during the detection period, which is conducive to ensuring the stability of the foundation pit in the future;

[0103] Step 2: Obtain the sealing abnormality value of the horizontal sealing layer on the pit top and its protective layer within the detection period, and judge whether the sealing condition of the horizontal sealing layer on the pit top and its protective layer is normal based on the sealing abnormality value. If the sealing condition is normal, generate a normal sealing signal; if the sealing condition is abnormal, generate an alarm signal and inspect and repair the horizontal sealing layer on the pit top and its protective layer;

[0104] Specifically, the sealing anomaly values ​​of the horizontal sealing layer on the top of the pit and under the protective layer within the detection period are obtained, and compared with the sealing anomaly threshold value;

[0105] If the sealing abnormality value is less than or equal to the sealing abnormality threshold, it means that the sealing conditions of the horizontal sealing layer on the top of the pit and its protective layer are normal, and a sealing normal signal is generated;

[0106] If the sealing abnormality value is greater than the sealing abnormality threshold, it means that the sealing conditions of the horizontal sealing layer on the top of the pit and its protective layer are abnormal, and an alarm signal is generated;

[0107] If an alarm signal is received, construction personnel will be immediately arranged to inspect the horizontal sealing layer and its protective layer on the top of the pit, find out the sealing holes and repair them in time;

[0108] The technical solution of the embodiment of the present invention is: obtaining the sealing data of the horizontal sealing layer on the pit top and the protective layer thereof within the detection period, performing data analysis on the sealing data, and obtaining the sealing abnormality value; obtaining the sealing abnormality value, and judging whether the sealing condition of the horizontal sealing layer on the pit top and the protective layer thereof is normal based on the sealing abnormality value; if the sealing condition is normal, generating a normal sealing signal; if the sealing condition is abnormal, generating an alarm signal and inspecting and repairing the horizontal sealing layer on the pit top and the protective layer thereof, thereby ensuring the stability of the subsequent deep excavation of the foundation pit.

[0109] Example 4

[0110] like Figure 3 As shown, based on Example 2, it also includes that before excavating the foundation pit, in order to accelerate the rate of increase of the vacuum degree under the sealing layer and thus achieve efficient vacuum preloading, it is necessary to determine whether the suspected influencing data has an influence on the rate of change of the vacuum degree, and then regulate the influencing factors:

[0111] Step 3: Based on the generated normal sealing signal, obtain the vacuum data and the suspected vacuum impact data within the historical monitoring period, wherein the historical monitoring period is the period when the vacuum degree under the horizontal sealing layer at the top of the pit and the protective layer thereof increases, the vacuum data includes the vacuum degree value under the horizontal sealing layer at the top of the pit and the protective layer thereof, and the suspected vacuum impact data includes the ambient temperature under the horizontal sealing layer at the top of the pit and the protective layer thereof, and perform data processing and analysis on the vacuum data and the suspected vacuum impact data to obtain the suspected impact value;

[0112] Specifically, several time nodes with equal distances are selected in the historical monitoring cycle, and the vacuum value of the horizontal sealing layer on the pit top and under the protective layer at each time node is obtained. A vacuum change curve is drawn with time as the X-axis and the vacuum value as the Y-axis. The slope of the vacuum change curve at each time node is obtained, and the vacuum change rate at each time node is obtained.

[0113] Divide the detection cycle evenly into several time periods. Based on any time period:

[0114] Obtain the vacuum degree change rate at the end time node and the beginning time node of the time period, and perform difference processing on the two to obtain the rate change value within the time period;

[0115] Get the temperature value at the end time node and the beginning time node of the time period, and perform difference processing on the two to obtain the temperature change value within the time period;

[0116] Compare and analyze the rate change value with the temperature change value;

[0117] If the two are both positive and negative, the time period is marked as the same direction time period;

[0118] If one is positive and the other is negative or both are 0, the time period is marked as an out-of-direction time period;

[0119] Obtain the number of inverse time periods in the historical monitoring cycle, and compare it with the total number of time periods in the historical monitoring cycle to obtain the inverse number ratio, which is marked as KI.

[0120] Based on any anisotropic time period, the rate change value and the temperature change value are ratio processed and the absolute value is taken to obtain the change correlation ratio. The variance of the change correlation ratio of all anisotropic time periods in the historical monitoring period is taken to obtain the change correlation variance, which is marked as SL.

[0121] The data of the anisotropic number ratio KI and the change correlation variance SL are processed, and the suspected influence value DH is obtained by the formula DH=a1*KI+a2*SL, where a1 and a2 are both preset proportional coefficients, a1 is 0.57, and a2 is 0.43;

[0122] It should be noted that the purpose of the suspected impact value DH is to determine the influence of temperature on the rate of change of vacuum degree by analyzing the change trend of the vacuum degree change rate and temperature under the horizontal sealing layer on the pit top and its protective layer, so as to increase the speed of vacuuming by regulating the influencing factors and achieve more efficient vacuum preloading.

[0123] Step 4: Obtain suspected influence values, and determine whether the temperature has an influence on the rate of change of the vacuum degree based on the obtained suspected influence values. If so, generate an influence signal;

[0124] Specifically, the obtained suspected impact value is compared with the impact threshold;

[0125] If the suspected impact value is greater than or equal to the impact threshold, it means that the ambient temperature under the horizontal sealing layer on the top of the pit and its protective layer has an impact on the rate of change of the vacuum degree, and an impact signal is generated;

[0126] If the suspected impact value is less than the impact threshold, it means that the ambient temperature under the horizontal sealing layer on the top of the pit and its protective layer has no effect on the rate of change of vacuum degree;

[0127] Step 5: Based on the impact signal, a control instruction is sent to control and adjust the ambient temperature of the horizontal sealing layer on the top of the pit and under the protective layer, so as to accelerate the rate of vacuum degree increase and achieve efficient vacuum preloading;

[0128] The technical solution of the embodiment of the present invention is: based on the generated normal sealing signal, the vacuum data and the suspected vacuum influence data within the historical monitoring period are obtained, wherein the historical monitoring period is the period of time when the vacuum degree under the horizontal sealing layer on the pit top and the protective layer thereof rises, the vacuum data and the suspected vacuum influence data are processed and analyzed to obtain the suspected influence value; based on the obtained suspected influence value, it is judged whether the temperature has an influence on the rate of change of the vacuum degree; based on the influence signal, a control instruction is sent to control and adjust the ambient temperature of the horizontal sealing layer on the pit top and the protective layer thereof, thereby accelerating the rate of increase of the vacuum degree and achieving efficient vacuum preloading.

[0129] Example 5

[0130] like Figure 4 As shown, the system for monitoring the vacuum degree of the horizontal sealing layer on the top of the pit and the vacuum degree under the protective layer includes:

[0131] Sealing data analysis module: obtains the sealing data of the horizontal sealing layer on the top of the pit and the sealing data under the protective layer during the detection period, wherein the sealing data includes the vacuum degree of the horizontal sealing layer on the top of the pit and the sealing data under the protective layer, performs data analysis on the sealing data, and obtains the sealing abnormal value;

[0132] Sealing condition judgment module: obtains the sealing abnormality value of the horizontal sealing layer on the pit top and its protective layer within the detection period, and judges whether the sealing condition of the horizontal sealing layer on the pit top and its protective layer is normal based on the sealing abnormality value. If the sealing condition is normal, a normal sealing signal is generated; if the sealing condition is abnormal, an alarm signal is generated and the horizontal sealing layer on the pit top and its protective layer are inspected and repaired;

[0133] Suspected impact analysis module: based on the generated normal sealing signal, the vacuum data and the suspected vacuum impact data within the historical monitoring period are obtained, wherein the historical monitoring period is the period when the vacuum degree under the horizontal sealing layer at the top of the pit and its protective layer increases, the vacuum data includes the vacuum degree value under the horizontal sealing layer at the top of the pit and its protective layer, and the suspected vacuum impact data includes the ambient temperature under the horizontal sealing layer at the top of the pit and its protective layer. The vacuum data and the suspected vacuum impact data are processed and analyzed to obtain the suspected impact value;

[0134] Impact judgment module: obtains suspected impact values, and judges whether the temperature has an impact on the vacuum degree change rate based on the obtained suspected impact values. If so, generates an impact signal;

[0135] Influencing factor control module: Based on the influencing signal, the control command is sent to control and adjust the ambient temperature of the horizontal sealing layer on the pit top and the ambient temperature under the protective layer, accelerate the rate of vacuum increase, and thus achieve efficient vacuum preloading.

[0136] The above shows and describes the basic principles, main features and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A recyclable reinforcement combined with vacuum support system, characterized in that: include: The pit top sealing anchoring groove (2) is a deep groove excavated downwards at the end of the pit top horizontal sealing layer (3), the pit top horizontal sealing layer protective layer (4) and the horizontal rib layer (7) anchored with oblique reinforcement and serving as a drainage body; the pit top horizontal sealing layer (3), the pit top horizontal sealing layer protective layer (4) and the horizontal rib layer (7) anchored with oblique reinforcement and serving as a drainage body are all buried at the bottom of the groove; A longitudinal horizontal vacuum pipe (5) is arranged below the original ground (1) at the top of the pit, the horizontal sealing layer (3) at the top of the pit, and the protective layer (4) at the horizontal sealing layer at the top of the pit, and is parallel to the edge of the excavated foundation pit. The longitudinal horizontal vacuum pipe (5) passes through the horizontal sealing layer at the top of the pit through a film outlet and is then connected to a vacuum pump. The oblique tie bars also serve as drainage bodies (6), which are perforated steel pipes covered with geotextiles and arranged obliquely in the foundation soil within the perimeter of the foundation pit, and the bottoms of a portion of the oblique tie bars also serve as drainage bodies (6) enter the pit bottom range, and the elevation is lower than the elevation of the ground surface (10) at the bottom of the pit at the maximum excavation depth; The horizontal reinforcement layer (7) anchoring the oblique reinforcement and serving as the drainage body is arranged on the surface of the foundation soil at the top of the pit and connected to the oblique reinforcement and serving as the drainage body (6); the horizontal reinforcement layer (7) anchoring the oblique reinforcement and serving as the drainage body is arranged below the longitudinal horizontal drainage pipe; The pit bottom sealing trench (11) is excavated downward outside the projection range of the horizontal reinforcement layer (7) of the lowest layer anchoring oblique reinforcement and serving as a drainage body to form a deep trench outside the pit bottom slope foot.

2. A recyclable tie rod combined with vacuum support system according to claim 1, characterized in that: The horizontal sealing layer (3) on the top of the pit is one or more geomembranes.

3. The recyclable tie rod combined vacuum support system according to claim 1 is characterized in that: The pit top horizontal sealing layer protection layer (4) is a layer or multiple layers of geotextiles laid under the pit top horizontal sealing layer.

4. The recyclable tie rod combined with vacuum support system according to claim 1, characterized in that: The slope sealing layer (8) is a geomembrane independent of the horizontal sealing layer on the top of the pit; the slope sealing layer protection layer (9) is one or more layers of geotextiles laid under the slope sealing layer (7);.

5. The recyclable tie rod combined vacuum support system according to claim 1 is characterized in that: The oblique reinforcement also serves as the drainage body (6), which is a steel pipe wrapped with geotextile. The bottom of the steel pipe is blocked, and filter holes are evenly distributed on the pipe wall. The hole diameter is φ6-φ10mm. The vertical spacing of the steel pipe is 1-2m, and the horizontal spacing is 1-2m.

6. The recyclable tie rod combined with vacuum support system according to claim 1, characterized in that: The longitudinal horizontal vacuum tube (5) is a PVC tube or a steel tube of φ50mm.

7. The recyclable tie rod combined with vacuum support system according to claim 1, characterized in that: The horizontal reinforcement layer (7) used for anchoring the oblique reinforcement and also serving as a drainage body is a geogrid or a steel belt.

8. A construction method of a recyclable reinforcement combined with a vacuum support system, characterized in that: The following steps are involved: S1, in the foundation soil within the range of the horizontal sealing layer (3) at the top of the pit, oblique reinforcement bars also serving as drainage bodies (6) are arranged, and the bottoms of a part of the oblique reinforcement bars also serving as drainage bodies (6) enter the range of the bottom of the pit, and the elevation is lower than the elevation of the ground at the bottom of the pit with the maximum excavation depth; S2, on the surface of the foundation soil where the oblique reinforcement serving as the drainage body (6) has been installed, a horizontal reinforcement layer (7) for anchoring the oblique reinforcement serving as the drainage body is arranged, and an anchoring device is arranged between the horizontal reinforcement layer (7) for anchoring the oblique reinforcement serving as the drainage body and the oblique reinforcement serving as the drainage body (6); S3, connecting the top of the oblique tie rod (6) which also serves as the drainage body to the longitudinal horizontal vacuum tube to ensure the sealing effect between the joints; S4, laying a horizontal sealing layer protective layer (4) on the top of the pit on the horizontal reinforcement layer (7) that anchors the oblique reinforcement and also serves as a drainage body; S5, laying the pit top horizontal sealing layer (3) on the pit top horizontal sealing layer protective layer (4); S6, passing the longitudinal horizontal vacuum tube (5) through the pipeline film outlet device, passing through the pit top horizontal sealing layer (3) and the pit top horizontal sealing layer protective layer (4), and then connecting to the vacuum pump through the vacuum pipeline; S7, start the vacuum pump, and when the vacuum degree reaches 80kPa and the consolidation degree of the foundation soil reaches 20%, maintain the vacuum degree and excavate the foundation pit; S8, when the excavation depth reaches 0.5 m below the end of the next row of oblique reinforcement bars that also serve as drainage bodies (6), the newly excavated section is covered with a slope sealing layer protective layer (9), and then covered with a slope sealing layer (8), the slope sealing layer protective layer (9) is firmly connected to the top of the slope or the previous slope sealing layer protective layer (9), so that it is sealed and connected to the top of the slope or the previous slope sealing layer (8), thereby forming a partial slope sealing layer (8) and a slope sealing layer protective layer (9), and the ends of the slope sealing layer (8) and the slope sealing layer protective layer (9) are buried in the slope surface by no less than 0.5 m; S9, repeat step S8 until the excavation reaches the designed depth of the foundation pit; S10, at the pit bottom, a slope sealing layer (8) and a slope sealing layer protective layer (9) are formed on the slope surface and the pit bottom, a pit bottom sealing groove (11) is excavated outside the pit bottom projection surface at the end of the lowest row of oblique reinforcement bars that also serve as a drainage body (6), and the pit bottom slope sealing layer (8) and the slope sealing layer protective layer (9) are buried in the pit bottom sealing groove (11).

9. The construction method of the recyclable tie rod combined with vacuum support system according to claim 8, characterized in that: The following steps are also included: S11, pouring the foundation pit bottom slab and carrying out the subsequent construction of the underground structure; S12. Continue to vacuum and backfill the space between the foundation pit wall and the underground structure of the building until the original ground elevation is reached.

10. A construction method of a recyclable tie rod combined with a vacuum support system according to claim 9, characterized in that: The following steps are also included: S13, stop vacuuming, then recover the oblique reinforcement which also serves as the drainage body (6), anchor the horizontal reinforcement layer (7) of the oblique reinforcement and the longitudinal horizontal vacuum tube on the pit top.

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