Recyclable reinforcing bar combined vacuum support system and construction method thereof

Abstract

The present application belongs to the technical field of foundation pit supporting in geotechnical engineering, and provides a recyclable tensile reinforcement combined vacuum supporting system and a construction method thereof. Since the tensile reinforcement itself has a great stabilizing effect on the excavated foundation pit, the foundation pit can be excavated in a relatively short time. The tensile reinforcement combined vacuum supporting system has obvious advantages in stability and construction period compared with the vacuum gravity type foundation pit supporting system. In addition, the present application can eliminate the need for plastic drainage board construction on steep slopes, thereby reducing the construction safety risk of drainage board machinery. The present application does not require a transverse drainage body composed of medium-coarse sand, which can greatly reduce the engineering cost. The present application can be recycled after the fat groove is completely backfilled, which not only eliminates the safety risk but also helps to reduce the engineering cost. Therefore, the present application is superior to the prior art vacuum gravity method in terms of technology, construction period, safety and economy.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of geotechnical engineering foundation pit support, in particular to a recyclable reinforcing bar combined vacuum support system and a construction method thereof. BACKGROUND

[0002] When excavating a foundation pit, sometimes a soft soil foundation is encountered. Due to space limitations, the foundation pit in the soft soil foundation is generally not suitable for construction by using the slope method. The conventional pile row + internal support foundation pit support method is high in cost and long in period.

[0003] A vacuum curtain water stop and atmospheric pressure support deep foundation pit excavation method (hereinafter referred to as the "vacuum curtain method") is disclosed in Chinese patent No. 200810236142.3. The method uses a vacuum curtain for water stop and utilizes the action of atmospheric pressure to support the foundation pit, which is safer to construct and does not require internal support structures in the foundation pit or internal and external dewatering wells, and has obvious advantages in safety and reliability, saving of construction period and investment.

[0004] However, the above-mentioned vacuum curtain method is limited in the application of the depth of the foundation pit excavation because the straight excavation reduces the stability of the pit wall, and the vacuum curtain method needs to set a side wall solidification wall, which increases the engineering quantity of setting the side wall solidification wall and is not conducive to reducing the cost. The way of laying the sealing membrane on the pit top of the vacuum curtain method is similar to the traditional vacuum preloading foundation treatment method, and the outer boundary of the sealing membrane is simply shallowly buried in the soil, which easily causes the vacuum pressure in the vacuum curtain to diffuse outward, and the diffusion of the vacuum pressure reduces the vacuum degree in the curtain range, thereby reducing the stability and safety factor of the pit wall. The pit bottom soil will be uplifted or even damaged without a vertical drainage body.

[0005] A vacuum-acting gravity type foundation pit support system and construction method (hereinafter referred to as the "vacuum gravity method") are disclosed in Chinese patent No. 201210295813.9. The method is a vacuum-acting gravity type foundation pit support system that does not need to set a side wall solidification wall and a curtain body, can meet the requirement of greater excavation depth, is lower in cost and shorter in construction period.

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

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

[0008] 2. The transverse drainage body is a sand cushion layer composed of medium-coarse sand with a thickness of 0.4-0.6 meters. The sand has good air permeability, but the sand cushion layer is a bulk material and will slide downward on a slightly steep slope, and the sand cushion layer is difficult to construct. The vacuum pipeline can be directly connected with the water-permeable pipe serving as a reinforcing bar, and the propagation of vacuum in the foundation can be ensured without the medium-coarse sand.

[0009] 3. The vacuum extraction is stopped, and then the vertical sealing curtain at the bottom of the slope, the sealing layer on the slope surface, the horizontal sealing layer on the top of the pit, and part of the peripheral vertical sealing curtain are removed, and the water-stop steel sheet pile and the geomembrane therein are recycled and reused. Recycling can save cost 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 surface. If the vacuum extraction is stopped, the slope is likely to be unstable.

[0010] 4. The plastic drainage board only plays a drainage role and is only arranged in the projected range of the top of the pit and the slope surface, and cannot resist the pit bottom uplift. SUMMARY

[0011] In order to make up for the deficiencies of the prior art and solve at least one technical problem proposed in the background art, the purpose of the present application is to provide a recyclable reinforcing bar combined vacuum support system which does not need to set a sand cushion layer, uses reinforcing bars as drainage bodies, can meet the excavation requirements of a steeper slope surface, the reinforcing bars can be recycled, the construction is safer, the foundation pit is more stable, the cost is lower, the construction period is shorter, and the internal and external pressure difference of the vacuum degree on the slope surface is larger.

[0012] A recyclable reinforcing bar combined vacuum support system, comprising:

[0013] The top sealing anchoring trench is a trench formed by excavating downward to a certain depth at the end of the horizontal reinforcing bar layer in which the top horizontal sealing layer, the top horizontal sealing layer protection layer, and the anchoring inclined reinforcing bar serve as drainage bodies; the top horizontal sealing layer, the top horizontal sealing layer protection layer, and the anchoring inclined reinforcing bar serving as the horizontal reinforcing bar layer are all buried in the bottom of the trench;

[0014] The longitudinal horizontal vacuum pipe is arranged below the original ground surface at the top of the pit, the top horizontal sealing layer, and the top horizontal sealing layer protection layer, is parallel to the excavated foundation pit side, and passes out of the top horizontal sealing layer through a membrane outlet, and is then connected to a vacuum pump;

[0015] The inclined reinforcing bar serving as a drainage body is a steel pipe with perforated holes wrapped with geotextile arranged in the foundation soil in the range of the periphery of the pit, and the bottom of part of the number of the inclined reinforcing bar serving as a drainage body enters the range of the pit bottom, with an elevation lower than the elevation of the ground surface at the maximum excavation depth;

[0016] The horizontal rib layer of the anchoring diagonal tensile rib and drainage body is arranged on the original ground of the pit top and is connected with the diagonal tensile rib and drainage body; the horizontal rib layer of the anchoring diagonal tensile rib and drainage body is arranged below the longitudinal horizontal drainage pipe;

[0017] The pit bottom sealing groove is formed by excavating a groove with a certain depth downward outside the pit bottom slope foot, outside the projection range of the lowermost horizontal rib layer of the anchoring diagonal tensile rib and drainage body.

[0018] As a further technical scheme of the present application, the pit top horizontal sealing layer is one or more layers of geomembrane.

[0019] As a further technical scheme of the present application, the pit top horizontal sealing layer protection layer is one or more layers of geotextile arranged below the pit top horizontal sealing layer.

[0020] As a further technical scheme of the present application, the slope sealing layer is independent of the geomembrane of the pit top horizontal sealing layer; the slope sealing layer protection layer is one or more layers of geotextile arranged below the slope sealing layer.

[0021] As a further technical scheme of the present application, the diagonal tensile rib and drainage body is a steel pipe wrapped with geotextile, the bottom end of the steel pipe is blocked, the pipe wall is uniformly distributed with filter holes with a diameter of φ6-φ10 mm, the vertical spacing of the steel pipe is 1-2 m, and the horizontal spacing is 1-2 m.

[0022] As a further technical scheme of the present application, the longitudinal horizontal vacuum pipe adopts a PVC pipe or a steel pipe with a diameter of φ50 mm.

[0023] As a further technical scheme of the present application, the horizontal rib layer 7 of the anchoring diagonal tensile rib and drainage body is a geogrid or a steel strip.

[0024] A construction method of a recyclable tensile rib combined vacuum support system, comprising the following steps:

[0025] S1, arranging the diagonal tensile rib and drainage body in the foundation soil within the setting range of the pit top horizontal sealing layer, and arranging the bottom of a part of the diagonal tensile rib and drainage body into the pit bottom range, with the elevation being lower than the elevation of the maximum excavation pit bottom ground;

[0026] S2, arranging the horizontal rib layer of the anchoring diagonal tensile rib and drainage body on the original ground of the pit top where the diagonal tensile rib and drainage body is arranged, and arranging the anchoring device between the horizontal rib layer of the anchoring diagonal tensile rib and drainage body and the diagonal tensile rib and drainage body;

[0027] S3, connecting the top end of the diagonal tensile rib and drainage body with the longitudinal horizontal vacuum pipe, and ensuring the sealing effect between the joints;

[0028] S4, arranging the pit top horizontal sealing layer protection layer on the upper surface of the horizontal rib layer of the anchoring diagonal tensile rib and drainage body.

[0029] S5. Lay a horizontal sealing layer on top of the pit top protective layer;

[0030] S6. Pass the longitudinal horizontal vacuum tube through the pipeline membrane outlet through the horizontal sealing layer and its protective layer at the top of the pit, and then connect it to the vacuum pump through the vacuum pipeline.

[0031] S7. Turn on the vacuum pump and wait until the vacuum degree reaches 80 kPa and the consolidation degree of the foundation soil reaches 20%. Maintain the vacuum degree and excavate the foundation pit.

[0032] S8. When excavating to a depth of 0.5m below the end of the next row of diagonal tie bars which also serve as drainage bodies, cover the newly excavated profile with a slope sealing layer and a protective layer, and then cover it with another slope sealing layer. The slope sealing layer and the protective layer should be firmly connected to the top of the slope or the protective layer above it, so that they are sealed together. This forms a partial slope sealing layer and a protective layer. The ends of the slope sealing layer and the protective layer should be buried in the slope for no 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 protection layer are formed on the slope and the bottom of the pit. The bottom sealing trench is excavated on the outside of the projection surface of the bottom of the pit at the bottom of the lowest row of diagonal tie bars, which also serve as drainage bodies. The bottom slope sealing layer and the slope sealing layer protection layer are buried in the bottom sealing trench.

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

[0036] S11. Pouring of the foundation slab of the pit, followed by subsequent construction of the underground structure;

[0037] S12. Continue vacuuming 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, it also includes the following steps:

[0039] S13. Stop vacuuming, then recover the diagonal tie rod that also serves as the drainage body 6, the horizontal reinforcement layer 7 of the diagonal tie rod anchored at the top of the pit, and the longitudinal horizontal vacuum pipe.

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

[0041] The application is a recyclable reinforcing bar combined vacuum supporting system and a construction method thereof. The recyclable reinforcing bar combined vacuum supporting system mainly consists of two parts of oblique reinforcing bars and vacuum extraction. The oblique reinforcing bars are used as drainage bodies, the slope surface soil is reinforced from the beginning of vacuum extraction, the problem of delayed construction that the vertical drainage body of the vacuum gravity horizontal drainage method needs to be set after the excavation of the upper slope surface is overcome, the strength of the slope surface soil is greatly improved, and the slope surface is more stable. The oblique reinforcing bars are directly connected with the longitudinal pipes, on the one hand, the vacuum is directly transmitted to the soil through the oblique reinforcing bars, unnecessary vacuum loss is reduced. On the other hand, the sand cushion layer is cancelled, the engineering cost is saved, the problem that the sand cushion layer on the steep slope surface slides is overcome, and the construction process is simplified. The oblique reinforcing bars are arranged in the foundation pit and the foundation, under the action of the vacuum support, the reinforcing bar effect is increased, the stability of the foundation pit is more guaranteed than the vacuum gravity method. The end of the oblique reinforcing bar can enter the pit bottom, which is equivalent to the vacuum effect in the pit bottom, and the pit bottom uplift damage can be prevented. The backfilling of the fat groove is carried out during the vacuum extraction, and the pit wall collapse caused by the stop of the vacuum extraction and backfilling can be prevented.

[0042] More simply:

[0043] The application utilizes the principles of vacuum support and soil nailing support, arranges the drainage bodies obliquely in the foundation, guarantees the vacuum effect, and increases the reinforcing bar effect of the soil, which is more beneficial to the stability of the foundation pit.

[0044] The application cancels the horizontal drainage body, saves the cost, and avoids the loss of the vacuum degree in the shallow layer of the foundation.

[0045] The application arranges the drainage bodies obliquely in the foundation, guarantees that the soil below the slope surface is reinforced from the beginning of the vacuum extraction, and is beneficial to the strength enhancement of the soil of the foundation pit.

[0046] The application does not need to recycle the materials such as the oblique reinforcing bars used as the drainage bodies in the space between the backfilled foundation pit wall and the underground structure of the building, guarantees the stability of the foundation pit during the backfilling of the fat groove (the space between the outer wall of the building and the foundation pit edge), and realizes the recycling in the true sense. BRIEF DESCRIPTION OF DRAWINGS

[0047] The application will be further described below in combination with the drawings.

[0048] Figure 1 It is a perspective view of the foundation pit for supporting excavation of the application;

[0049] Figure 2 It is a transverse sectional view of the recyclable reinforcing bar combined vacuum supporting system;

[0050] Figure 3 It is a step flow chart of the vacuum degree monitoring of the pit top horizontal sealing layer and the protective layer thereof in the embodiment of the application.

[0051] Figure 4 is a program block diagram of the system for monitoring the vacuum degree under the horizontal sealing layer and the protective layer of the top of the pit according to the embodiment of the present application.

[0052] In the figure: 1, the original ground of the top of the pit, 2, the sealing anchoring trench of the top of the pit, 3, the horizontal sealing layer of the top of the pit, 4, the protective layer of the horizontal sealing layer of the top of the pit, 5, the longitudinal horizontal vacuum pipe, 6, the oblique reinforcing bar and the drainage body, 7, the horizontal reinforcing bar layer anchoring the oblique reinforcing bar and the drainage body, 8, the sealing layer of the slope surface, 9, the protective layer of the sealing layer of the slope surface, 10, the ground of the bottom of the pit with the maximum excavation depth, 11, the sealing trench of the bottom of the pit. DETAILED DESCRIPTION

[0053] In order to make the technical means, creative features, purposes and effects of the present application easy to understand, the present application is further described below in combination with specific embodiments.

[0054] Embodiment 1

[0055] Please refer to Figure 1 and Figure 2 , the present application is a recyclable reinforcing bar combined vacuum support system, which comprises: the sealing anchoring trench 2 of the top of the pit, the horizontal sealing layer 3 of the top of the pit, the protective layer 4 of the horizontal sealing layer of the top of the pit, the longitudinal horizontal vacuum pipe 5, the oblique reinforcing bar and the drainage body 6, the horizontal reinforcing bar layer 7 anchoring the oblique reinforcing bar and the drainage body, the sealing layer 8 of the slope surface, the protective layer 9 of the sealing layer of the slope surface, and the sealing trench 11 of the bottom of the pit.

[0056] Among them, the pit top sealing and anchoring trench 2 is a trench of a certain depth excavated downwards from 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 that serves as a drainage body for anchoring diagonal tie bars. The pit top horizontal sealing layer 3, the pit top horizontal sealing layer protective layer 4, and the horizontal reinforcement layer 7 that serves as a drainage body for anchoring diagonal tie bars are all buried at the bottom of the trench. The longitudinal horizontal vacuum pipe 5 is a vacuum pipe set below the original ground surface 1, the pit top horizontal sealing layer 3, and the pit top horizontal sealing layer protective layer 4, parallel to the edge of the excavated foundation pit. The longitudinal horizontal vacuum pipe 5 passes through the pit top horizontal sealing layer through a film outlet and is then connected to a vacuum pump. The diagonal tie bar that also serves as a drainage body 6 is a perforated steel pipe wrapped with geotextile fabric that is arranged diagonally in the foundation soil within a certain range around the foundation pit, and some of the diagonal tie bars also serve as drainage bodies. The bottom of the drainage body 6 enters the pit bottom area, with an elevation lower than the elevation of the ground surface 10 at the maximum excavation depth of the pit bottom; the horizontal reinforcement layer 7, which serves as both an anchoring diagonal tie and a drainage body, is set on the original ground surface at the top of the pit and connected to the diagonal tie and drainage body 6; the horizontal sealing layer 3 at the top of the pit is one or more layers of geomembrane; the protective layer 4 for the horizontal sealing layer 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, which serves as both an anchoring diagonal tie and a drainage body, is set below the longitudinal horizontal drainage pipe; the slope sealing layer 8 is a geomembrane independent of the horizontal sealing layer at the top of the pit; the protective layer 9 for the slope sealing layer is one or more layers of geotextile laid under the slope sealing layer 8; the sealing ditch 11 at the bottom of the pit is excavated downwards to a certain depth outside the projection range of the lowest anchoring diagonal tie and drainage body horizontal reinforcement layer 7 at the toe of the pit bottom.

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

[0058] The inclined tie bar that also serves as the drainage body 6 is a steel pipe wrapped with geotextile. The bottom end of the steel pipe is sealed, and filter holes with a diameter of φ6-φ10mm are evenly distributed on the pipe wall. 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 made of 50mm PVC pipe or steel pipe.

[0060] The horizontal reinforcement layer 7, which serves as both an anchoring diagonal tie bar and a drainage body, is a geogrid or steel strip.

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

[0062] The excavation area consists of homogeneous foundation soil with the following soil parameters:

[0063] Silty clay, gray to dark gray, fluid to soft plastic, saturated, natural bulk density γ = 16.5 kN / m³ 3, moisture content 51%, void ratio 1.55, plasticity index Ip=18.9, Cu=15.0 kPa, φu=3.0°, basic bearing capacity σ0=40 kPa, permeability coefficient k≤1×10 -7 m / s, belongs to soft soil, and engineering property is poor.

[0064] The pit top sealing anchoring trench 2 is 9 m away from the pit top excavation, and is formed by downward excavation to form a trench with a width of 1 m and a depth of 2 m; the pit top horizontal sealing layer 3, the pit top horizontal sealing layer protection layer 4 and the horizontal muscle layer 7 of the anchoring inclined reinforcing bar are all embedded in the trench bottom; the longitudinal horizontal vacuum pipe 5 is a PVC pipe or a steel pipe with a diameter of 50 mm, is arranged below the pit top original ground 1, the pit top horizontal sealing layer 3 and the pit top horizontal sealing layer protection layer 4, is parallel to the excavated foundation pit side, the vacuum pipe passes out of the pit top horizontal sealing layer through a film outlet device, and is connected to a vacuum pump; the inclined reinforcing bar serving as a drainage body 6 is a steel pipe wrapped with geotextile, a bottom end of the steel pipe is blocked, filter holes with a diameter of 8 are uniformly distributed on a pipe wall, vertical spacing of the steel pipe is 1.5 m, horizontal spacing is 1.5 m, the first row of steel pipes is arranged at a depth of 1 m, the second row is arranged at a depth of 2.5 m, the third row is arranged at a depth of 4 m, the fourth row is arranged at a depth of 5.5 m, and the fifth row is arranged at a depth of 7 m; a bottom of the fifth row of inclined reinforcing bars serving as drainage bodies enters the pit bottom range of 2 m, and has an elevation lower than that of the maximum excavation pit bottom ground; the horizontal muscle layer 7 of the anchoring inclined reinforcing bar serving as a drainage body is a geogrid, is arranged on the pit top original ground and is connected to the inclined reinforcing bar serving as a drainage body 6; the pit top horizontal sealing layer 3 is one or more layers of geomembrane; the pit top horizontal sealing layer protection layer 4 is one or more layers of geotextile laid below the pit top horizontal sealing layer; the geogrid is arranged below the PVC vacuum water pipe; the slope sealing layer 8 is one or more layers of geomembrane and is independent of the pit top horizontal sealing layer geomembrane; the slope sealing layer protection layer 9 is one or more layers of geotextile laid below the slope sealing layer; and the pit bottom sealing trench 11 is 5 m away from the pit bottom slope foot.

[0065] Example 2

[0066] The application is a construction method of a recyclable reinforcing bar combined vacuum support system, and comprises the following steps:

[0067] S1, arranging the inclined reinforcing bar serving as a drainage body 6 in the foundation soil in the arrangement range of the pit top horizontal sealing layer 3, and arranging the bottom of part of the inclined reinforcing bar serving as a drainage body 6 into the pit bottom range, with an elevation lower than that of the maximum excavation pit bottom ground;

[0068] S2, arranging the horizontal muscle layer 7 of the anchoring inclined reinforcing bar serving as a drainage body on the pit top original ground of the arranged inclined reinforcing bar serving as a drainage body 6, and arranging the anchoring device between the horizontal muscle layer 7 of the anchoring inclined reinforcing bar serving as a drainage body and the inclined reinforcing bar serving as a drainage body 6;

[0069] S3, connect the top end of the oblique tensile reinforcement and drainage body 6 with the longitudinal horizontal vacuum pipe, and ensure the sealing effect between the joints;

[0070] S4, lay the pit top horizontal sealing layer protection layer 4 on the horizontal muscle layer 7 of the anchoring oblique tensile reinforcement and drainage body;

[0071] S5, lay the pit top horizontal sealing layer 3 on the pit top horizontal sealing layer protection layer 4;

[0072] S6, pass the longitudinal horizontal vacuum pipe 5 through the membrane outlet device out of the pit top horizontal sealing layer 3 and its pit top horizontal sealing layer protection layer 4, and then connect it to the vacuum pump through the vacuum pipe;

[0073] S7, start the vacuum pump, and after 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 depth reaches the next row of oblique tensile reinforcement and drainage body 6 end 0.5m, cover the slope sealing layer protection layer 9 on the newly excavated section, and then cover the slope sealing layer 8. The slope sealing layer protection layer 9 is firmly connected with the slope top or the upper slope sealing layer protection layer 9 by using a handheld sewing machine, and is sealed and connected with the slope top or the upper slope sealing layer 8 by using heat sealing lap joint, thereby forming part of the slope sealing layer 8 and the slope sealing layer protection layer 9. The end of the slope sealing layer 8 and the slope sealing layer protection layer 9 is buried in the slope surface by not less than 0.5m, to ensure its sealing performance;

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

[0076] S10, at the pit bottom, similar to the construction method of S8, form the slope sealing layer 8 and the slope sealing layer protection layer 9 on the slope and the pit bottom, and excavate the pit bottom sealing trench 11 outside the pit bottom projection surface of the lowermost row of oblique tensile reinforcement and drainage body 6 end. The pit bottom slope sealing layer 8 and the slope sealing layer protection layer 9 are buried in the pit bottom sealing trench 11;

[0077] S11, pour the foundation pit bottom plate and carry out the subsequent construction of the underground part of the structure;

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

[0079] S13, stop vacuuming, and then recycle the oblique tensile reinforcement and drainage body 6, the horizontal muscle layer 7 of the pit top anchoring oblique tensile reinforcement, and the longitudinal horizontal vacuum pipe.

[0080] Exemplarily, S1, the oblique reinforcing bars and drainage bodies 6 are arranged in the foundation soil within the range of the top horizontal sealing layer 3 of the pit, and the bottom of part of the oblique reinforcing bars and drainage bodies enters the range of the pit bottom, and the elevation is lower than the elevation of the ground surface of the maximum excavation pit bottom; in this project, the steel pipes with filter holes wrapped with geotextile are used as the oblique reinforcing bars and drainage bodies 6, and a total of 5 rows are arranged, and the vertical spacing of each row is 1.5 m, and the horizontal spacing of the steel pipes is 1.5 m.

[0081] S2, the horizontal reinforcing layer 7 of the anchoring oblique reinforcing bars and drainage bodies is arranged on the original ground surface 1 of the pit top of the arranged oblique reinforcing bars and drainage bodies 6, and geogrid is used as the horizontal reinforcing layer here; the anchoring device is arranged between the horizontal reinforcing layer 7 of the anchoring oblique reinforcing bars and drainage bodies and the oblique reinforcing bars and drainage bodies 6;

[0082] S3, the top end of the oblique reinforcing bars and drainage bodies 6 is connected with the longitudinal horizontal vacuum pipe 5, and the sealing effect between the joints is ensured, and in this project, the longitudinal horizontal vacuum pipe 5 adopts a PVC pipe with a diameter of 50 mm;

[0083] S4, the pit top horizontal sealing layer protection layer 4 is laid on the horizontal reinforcing layer 7 of the anchoring oblique reinforcing bars, and the pit top horizontal sealing layer protection layer is 1 layer of geotextile;

[0084] S5, the pit top horizontal sealing layer 3 is laid on the pit top horizontal sealing layer protection layer 4, and in this project, the pit top horizontal sealing layer 3 is 2 layers of sealing film;

[0085] S6, the longitudinal horizontal vacuum pipe 5 is pulled out of the pit top horizontal sealing layer 3 and the pit top horizontal sealing layer protection layer 4 through the pipe line film outlet device, and then connected to the vacuum pump through the vacuum pipe line;

[0086] S7, the vacuum pump is started, and after the vacuum degree reaches 80 kPa and the consolidation degree of the foundation soil reaches 20%, the vacuum degree is maintained, and the foundation pit is excavated;

[0087] S8, every time the excavation depth reaches the position 0.5 m below the end of the next row of oblique reinforcing bars and drainage bodies 6, that is, the depths of 1.5 m, 3.0 m, 4.5 m and 6.0 m in this project; the slope sealing layer protection layer 9 is covered on the newly excavated section, and a layer of geotextile is used as the protection layer here, and then the slope sealing layer 8 is covered; the slope sealing layer protection layer is firmly connected with the slope top or the previous slope sealing layer protection layer 9 by using a handheld sewing machine, and is sealingly connected with the slope top or the previous slope sealing layer 8 by using heat sealing lap joint, so as to form part of the slope sealing layer and the protection layer thereof, and the end of the slope sealing layer and the protection layer thereof is buried in the slope surface by not less than 0.5 m, so as to ensure the sealing property;

[0088] S9, the step S8 is repeated until the designed depth of the foundation pit is excavated;

[0089] S10, at the bottom of the pit, similar to the construction method of S8, the slope and the bottom of the pit form a slope sealing layer and its protective layer, and the last row of inclined reinforcement is used as the end of the drainage body. The bottom sealing trench 11 is excavated outside the bottom projection of the pit, which is 4m away from the slope bottom of the pit. The bottom sealing layer and its protective layer are buried in the bottom sealing trench;

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

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

[0092] S13, stop vacuuming, and then recycle the inclined reinforcement and drainage body, the horizontal reinforcement layer of the inclined reinforcement, and the longitudinal horizontal vacuum pipe.

[0093] Example 3

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

[0095] Step one: obtain the sealing data under the horizontal sealing layer and its protective layer of the pit top in the detection period, wherein the sealing data includes the vacuum degree under the horizontal sealing layer and its protective layer of the pit top, and the sealing data is analyzed to obtain the abnormal value of the sealing data;

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

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

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

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

[0100] The vacuum degree obtained in each time node of generating the abnormal signal in the abnormal period is obtained, which is processed by difference with the vacuum degree threshold value and takes the absolute value to obtain the vacuum absolute difference value. The sum of all vacuum absolute difference values in the abnormal period is averaged to obtain the vacuum absolute mean value, and it is processed by ratio with the vacuum degree threshold value to obtain the abnormal degree ratio, which is marked as XZ;

[0101] Data processing is performed on the obtained abnormal duration ratio TZ and abnormal degree ratio XZ, and an abnormal sealing value YZ is obtained through a formula YZ=s1*TZ+s2*XZ, wherein s1 and s2 are both preset proportion coefficients, s1 is 0.36, and s2 is 0.64.

[0102] It should be noted that the purpose of the abnormal sealing value YZ is to analyze the duration and degree of the vacuum degree under the top horizontal sealing layer and its protective layer in the detection period, and then determine the sealing condition of the top horizontal sealing layer and its protective layer, which is beneficial to subsequent guarantee of the stability of the foundation pit.

[0103] Step two: obtaining the abnormal sealing value under the top horizontal sealing layer and its protective layer in the detection period, judging whether the sealing condition of the top horizontal sealing layer and its protective layer is normal based on the abnormal sealing value, if the sealing condition is normal, generating a sealing normal signal, if the sealing condition is abnormal, generating an alarm signal and checking and repairing the top horizontal sealing layer and its protective layer.

[0104] Specifically, the abnormal sealing value under the top horizontal sealing layer and its protective layer in the detection period is obtained, and compared with the abnormal sealing threshold value.

[0105] If the abnormal sealing value is less than or equal to the abnormal sealing threshold value, it indicates that the sealing condition of the top horizontal sealing layer and its protective layer is normal, and a sealing normal signal is generated.

[0106] If the abnormal sealing value is greater than the abnormal sealing threshold value, it indicates that the sealing condition of the top horizontal sealing layer and its protective layer is abnormal, and an alarm signal is generated.

[0107] If the alarm signal is received, construction personnel are immediately arranged to check the top horizontal sealing layer and its protective layer, find out the sealing leaks and repair them in time.

[0108] The technical scheme of the embodiment of the application is: obtaining the sealing data under the top horizontal sealing layer and its protective layer in the detection period, performing data analysis on the sealing data to obtain the abnormal sealing value; obtaining the abnormal sealing value, judging whether the sealing condition of the top horizontal sealing layer and its protective layer is normal based on the abnormal sealing value, if the sealing condition is normal, generating a sealing normal signal, if the sealing condition is abnormal, generating an alarm signal and checking and repairing the top horizontal sealing layer and its protective layer, thereby ensuring the stability of the subsequent deep excavation foundation pit.

[0109] Embodiment 4

[0110] As shown in Figure 3 Based on embodiment 2, before excavating the foundation pit, in order to accelerate the rising rate of the vacuum degree under the sealing layer and thereby realize efficient vacuum preloading, it is necessary to judge whether the suspected influencing data has an influence on the vacuum degree change rate, and then control the influencing factors:

[0111] Step three: based on the generated sealing normal signal, obtaining vacuum data and vacuum suspected influence data in the historical monitoring period, wherein the historical monitoring period is the period of vacuum degree rising of the pit top horizontal sealing layer and its protective layer, the vacuum data includes the vacuum degree value of the pit top horizontal sealing layer and its protective layer, and the vacuum suspected influence data includes the environmental temperature of the pit top horizontal sealing layer and its protective layer; the vacuum data and the vacuum suspected influence data are processed and analyzed to obtain the suspected influence value;

[0112] Specifically, a plurality of time nodes with equal distance are taken in the historical monitoring period, the vacuum degree value of the pit top horizontal sealing layer and its protective layer at each time node is obtained, a vacuum degree change curve is drawn with time as the X axis and the vacuum degree value as the Y axis, the slope of the vacuum degree change curve at each time node is obtained, and the vacuum degree change rate at each time node is obtained.

[0113] The detection period is evenly divided into a plurality of time periods, and based on any time period:

[0114] The vacuum degree change rates at the end time node and the head time node of the time period are obtained, and the difference between the two is processed to obtain the rate change value in the time period;

[0115] The temperature values at the end time node and the head time node of the time period are obtained, and the difference between the two is processed to obtain the temperature change value in the time period;

[0116] The rate change value and the temperature change value are compared and analyzed;

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

[0118] If one is positive and the other is negative, or both are 0, the time period is marked as a different direction time period;

[0119] The number of different direction time periods in the historical monitoring period is obtained, and a ratio processing is performed between the number and the total number of time periods in the historical monitoring period to obtain a different direction number ratio, and mark it as KI;

[0120] Based on any different direction time period, the rate change value and the temperature change value are processed by ratio and take the absolute value to obtain a change correlation ratio, and the change correlation ratio of all different direction time periods in the historical monitoring period is taken to obtain a change correlation variance, and mark it as SL;

[0121] The different direction number ratio KI and the change correlation variance SL are processed, and the suspected influence value DH is obtained through the formula DH=a1*KI+a2*SL, wherein a1 and a2 are both preset proportion coefficients, a1 is 0.57, and a2 is 0.43;

[0122] It should be noted that the purpose of the suspected influence value DH is to analyze the change trend of the vacuum degree change rate and the temperature under the pit top horizontal sealing layer and its protective layer, judge the influence relationship of the temperature on the vacuum degree change rate, facilitate subsequent adjustment of the influencing factors to increase the vacuumizing speed, and realize more efficient vacuum preloading;

[0123] Step four: obtaining a suspected influence value, judging whether the temperature has an influence on the vacuum degree change rate based on the obtained suspected influence value, and generating an influence signal if the temperature has an influence on the vacuum degree change rate;

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

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

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

[0127] Step five: based on the influence signal, a control instruction is sent to control and adjust the environmental temperature under the pit top horizontal sealing layer and its protective layer, accelerate the rate of vacuum degree rise, and thus realize efficient vacuum preloading;

[0128] The technical scheme of the embodiment of the present application is: based on the generated sealing normal signal, vacuum data and vacuum suspected influence data in a historical monitoring period are obtained, wherein the historical monitoring period is the period of vacuum degree rise under the pit top horizontal sealing layer and its protective layer, the vacuum data and the vacuum suspected influence data are processed and analyzed, and a suspected influence value is obtained; based on the obtained suspected influence value, it is judged whether the temperature has an influence on the vacuum degree change rate; based on the influence signal, a control instruction is sent to control and adjust the environmental temperature under the pit top horizontal sealing layer and its protective layer, accelerate the rate of vacuum degree rise, and thus realize efficient vacuum preloading.

[0129] Embodiment 5

[0130] As shown in Figure 4 , the system for monitoring the vacuum degree under the pit top horizontal sealing layer and its protective layer comprises:

[0131] The sealing data analysis module: obtains sealing data under the pit top horizontal sealing layer and its protective layer in a detection period, wherein the sealing data comprises the vacuum degree under the pit top horizontal sealing layer and its protective layer, and the sealing data is analyzed to obtain a sealing abnormal value;

[0132] The sealing condition judgment module: obtains the sealing abnormal value under the pit top horizontal sealing layer and its protection layer in the detection period, judges whether the sealing condition of the pit top horizontal sealing layer and its protection layer is normal based on the sealing abnormal value, if the sealing condition is normal, generates a sealing normal signal, if the sealing condition is abnormal, generates an alarm signal and checks and repairs the pit top horizontal sealing layer and its protection layer;

[0133] The suspected influence analysis module: based on the generated sealing normal signal, obtains the vacuum data and vacuum suspected influence data in the historical monitoring period, wherein the historical monitoring period is the period of the vacuum degree rising under the pit top horizontal sealing layer and its protection layer, the vacuum data includes the vacuum degree value under the pit top horizontal sealing layer and its protection layer, and the vacuum suspected influence data includes the environmental temperature under the pit top horizontal sealing layer and its protection layer, the vacuum data and the vacuum suspected influence data are processed and analyzed to obtain the suspected influence value;

[0134] The influence condition judgment module: obtains the suspected influence value, judges whether the temperature has influence on the vacuum degree change rate based on the obtained suspected influence value, if there is influence, generates an influence signal;

[0135] The influence factor regulation module: based on the influence signal, sends a regulation instruction, thereby controls and adjusts the environmental temperature under the pit top horizontal sealing layer and its protection layer, accelerates the rate of the vacuum degree rising, and further realizes efficient vacuum preloading.

[0136] The above shows and describes the basic principles, main features and advantages of the present application. It should be understood by those skilled in the art that the present application is not limited to the above embodiments, and the above embodiments and descriptions in the specification are only to illustrate the principles of the present application, and various changes and improvements can be made without departing from the spirit and scope of the present application, and these changes and improvements all fall within the scope of the present application. The scope of protection of the present application is defined by the appended claims and their equivalents.

Claims

1. A recyclable rebar combined vacuum support system, characterized by: Comprise: The pit roof sealing anchor groove (2) is the groove which is excavated downwards to form the depth in the end of the pit roof horizontal sealing layer (3), the pit roof horizontal sealing layer protection layer (4) and the horizontal muscle layer (7) of the anchor inclined tension bar drainage body; The pit roof horizontal sealing layer (3), the pit roof horizontal sealing layer protection layer (4) and the horizontal muscle layer (7) of the anchor inclined tension bar drainage body are all buried in the groove bottom; The longitudinal horizontal vacuum tube (5) is set in the vacuum tube under the pit roof original ground (1), the pit roof horizontal sealing layer (3), the pit roof horizontal sealing layer protection layer (4), and is parallel with the excavated foundation pit side, the longitudinal horizontal vacuum tube (5) is worn out through the membrane emitter from the pit roof horizontal sealing layer, and is connected to the vacuum pump again; The inclined tension bar drainage body (6) is the steel pipe of the hole of the outer package geotextile which is set in the foundation soil in the range of the foundation pit periphery and is inclined, and the bottom of the part quantity of the inclined tension bar drainage body (6) enters the pit bottom range, the elevation is lower than the elevation of the maximum excavation pit bottom ground (10), and the top end of the inclined tension bar drainage body (6) is connected with the longitudinal horizontal vacuum tube (5); The horizontal muscle layer (7) of the anchor inclined tension bar drainage body is set in the pit roof original ground and is connected with the inclined tension bar drainage body (6); The horizontal muscle layer (7) of the anchor inclined tension bar drainage body is set under the longitudinal horizontal drainage tube; The pit bottom sealing groove (11) is the groove which is excavated downwards to form the depth outside the pit bottom toe, the projection range of the lowermost anchor inclined tension bar drainage body horizontal muscle layer (7) outside.

2. A recyclable rebar combined vacuum support system according to claim 1, characterized in that: The pit roof horizontal sealing layer (3) is one or more layers of geomembrane.

3. A recyclable rebar combined vacuum support system according to claim 1, characterized in that: The pit roof horizontal sealing layer protection layer (4) is one or more layers of geotextile which is laid under the pit roof horizontal sealing layer.

4. The recyclable rebar combined vacuum support system of claim 1, wherein: The slope sealing layer (8) is independent of the pit roof horizontal sealing layer geomembrane; The slope sealing layer protection layer (9) is one or more layers of geotextile which is laid under the slope sealing layer (8).

5. The recyclable rebar combined vacuum support system of claim 1, wherein: The inclined tension bar drainage body (6) is the steel pipe of the outer package geotextile, the bottom end of the steel pipe is blocked, the pipe wall is uniformly distributed with filter hole, the aperture is φ6-φ10mm, the vertical spacing of the steel pipe is 1-2m, and the horizontal spacing is 1-2m.

6. A recyclable rebar combined vacuum support system according to claim 1, wherein: The longitudinal horizontal vacuum tube (5) adopts the PVC pipe or steel pipe of φ50mm.

7. A recyclable rebar combined vacuum support system according to claim 1, wherein: The horizontal muscle layer (7) of the anchor inclined tension bar drainage body is the geogrid or steel strip.

8. A method of construction of a recyclable rebar combined vacuum support system, characterized by: Comprise the following steps: S1, the inclined tension bar drainage body (6) is set in the foundation soil in the range of the pit roof horizontal sealing layer (3) setting, and the bottom of the part quantity of the inclined tension bar drainage body (6) enters the pit bottom range, and the elevation is lower than the elevation of the maximum excavation pit bottom ground; S2, the horizontal muscle layer (7) of the anchor inclined tension bar drainage body is set in the foundation soil surface of the inclined tension bar drainage body (6) of the completed setting, and the anchor device is set between the horizontal muscle layer (7) of the anchor inclined tension bar drainage body and the inclined tension bar drainage body (6); S3, the top end of the inclined tension bar drainage body (6) is connected with the longitudinal horizontal vacuum tube, and the sealing effect between the joints is guaranteed; S4, the pit roof horizontal sealing layer protection layer (4) is laid on the upper surface of the horizontal muscle layer (7) of the anchor inclined tension bar drainage body; S5, laying a pit roof horizontal sealing layer (3) on the (4) of the pit roof horizontal sealing layer protection layer; S6, the longitudinal horizontal vacuum pipe (5) is out of the pit roof horizontal sealing layer (3) and its pit roof horizontal sealing layer protection layer (4) through the pipe line membrane applicator, and then connected to the vacuum pump through the vacuum pipe line; S7, start the vacuum pump, and after the vacuum degree reaches 80kPa and the ground soil consolidation degree reaches 20%, maintain the vacuum degree and excavate the foundation pit; S8, every time the excavation depth reaches the end of the next row of inclined reinforcement and drainage body (6) by 0.5m, cover the slope sealing layer protection layer (9) on the newly excavated profile, and then cover the slope sealing layer (8), the slope sealing layer protection layer (9) is firmly connected with the slope top or the previous slope sealing layer protection layer (9), so that it is sealed with the slope top or the previous slope sealing layer (8), thereby forming part of the slope sealing layer (8) and the slope sealing layer protection layer (9), the end of the slope sealing layer (8) and the slope sealing layer protection layer (9) is buried in the slope surface not less than 0.5m; S9, repeat step S8 until the excavation reaches the design depth of the foundation pit; S10, at the bottom of the pit, form the slope sealing layer (8) and the slope sealing layer protection layer (9) on the slope and the bottom of the pit, excavate the bottom sealing trench (11) outside the bottom projection of the end of the lowest row of inclined reinforcement and drainage body (6), and bury the bottom slope sealing layer (8) and the slope sealing layer protection layer (9) in the bottom sealing trench (11).

9. The recyclable rebar combined vacuum support system construction method according to claim 8, characterized in that: Further comprising the following steps: S11, pouring the foundation pit bottom plate, and carrying out subsequent construction of the underground part structure; S12, continue to vacuum, and backfill the space between the foundation pit wall and the underground part structure of the building until the original ground elevation is reached.

10. The recyclable rebar combined vacuum support system construction method according to claim 9, characterized in that: Further comprising the following steps: S13, stop vacuuming, and then recycle the inclined reinforcement and drainage body (6), the horizontal reinforcement layer (7) of the pit roof anchoring inclined reinforcement, and the longitudinal horizontal vacuum pipe.

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