阅读说明：本技术 狭小基坑坡道支撑结构及施工方法 (Narrow foundation pit ramp supporting structure and construction method ) 是由 王峰 李伟福 尹奇 温亮华 林海旭 段亚伟 方振革 邓志辉 于帛弘 王翠秀 陈世 于 2021-07-28 设计创作，主要内容包括：本发明涉及狭小基坑坡道支撑结构技术领域,公开了一种狭小基坑坡道支撑结构及施工方法,包括:基坑,设置于所述基坑边缘的矩形状咬合撑,围绕所述基坑设置的环撑及以环撑直径为长度的对撑,对撑位于第三道环撑之间,所述环撑分为三层,沿环撑的圆周等距设置有立柱,立柱的底部设置有立柱桩,基坑的一侧设置有运输出口,由运输出口开始形成坡道,坡道分为两段,第一坡道的一端连接至所述运输出口,另一端连接至与坡道呈十字交叉设置的对撑,与所述对撑交叉部位形成放坡平台,第二坡道的一端连接至所述放坡平台,另一端延伸至基坑底部；所述对撑上还设置有用于转运土方的转运站,提高了基坑的施工效率,保证了在施工过程中的安全性。(The invention relates to the technical field of a ramp supporting structure of a narrow foundation pit, and discloses a ramp supporting structure of the narrow foundation pit and a construction method, wherein the ramp supporting structure comprises a foundation pit, a rectangular occlusion support arranged at the edge of the foundation pit, a ring support arranged around the foundation pit and a counter support taking the diameter of the ring support as the length, the counter support is positioned between third ring supports, the ring supports are divided into three layers, stand columns are arranged at equal intervals along the circumference of the ring support, stand column piles are arranged at the bottom of the stand columns, a transportation outlet is arranged at one side of the foundation pit, a ramp is formed by the transportation outlet, the ramp is divided into two sections, one end of a first ramp is connected to the transportation outlet, the other end of the first ramp is connected to the counter support which is crossed with the ramp, a slope placing platform is formed at the crossed part of the counter support, one end of a second ramp is connected to the slope placing platform, and the other end of the second ramp extends to the bottom of the foundation pit; still be provided with the transfer station that is used for transporting the earthwork to propping, improved the efficiency of construction of foundation ditch, guaranteed the security in the work progress.)

1. A narrow foundation pit ramp supporting structure is characterized by comprising a foundation pit (100), rectangular occlusion braces (200) arranged at the edge of the foundation pit (100), ring braces (300) arranged around the foundation pit (100) and diagonal braces (400) taking the diameter of the ring braces (300) as the length, wherein the diagonal braces (400) are positioned between third ring braces (300), the ring braces (300) are divided into three layers, stand columns (310) are arranged at equal intervals along the circumference of the ring braces (300), stand column piles (320) are arranged at the bottoms of the stand columns (310), a transportation outlet (170) is arranged at one side of the foundation pit (100), a ramp (500) is formed from the transportation outlet (170), the ramp (500) is divided into two sections, one end of a first ramp (510) is connected to the transportation outlet (170), the other end of the first ramp is connected to the diagonal braces (400) which are arranged in a crossed manner with the ramp (500), a slope platform (530) is formed at the intersection part of the second slope and the diagonal brace (400), one end of the second slope (520) is connected to the slope platform (530), and the other end of the second slope extends to the bottom of the foundation pit (100); the butt support (400) is also provided with a transfer station (410) for transferring earthwork.

2. A foothole ramp support structure according to claim 1, wherein a radial brace (210) and a corner brace (220) are arranged between the ring brace (300) and the bite brace (200), the radial brace (210) extends from a plurality of angles along the bite brace (200) to the ring brace (300) and is connected to an edge of the ring brace (300), and the corner brace (220) is connected to the adjacent bite brace (200).

3. A narrow foundation pit ramp supporting structure according to claim 1, wherein a plurality of supporting columns (420) are arranged at the bottom of the opposite support (400), the supporting columns (420) are arranged at two sides of the opposite support (400) in the width direction, cross rods (430) are arranged between the supporting columns (420), and diagonal supporting rods (440) are arranged between adjacent cross rods (430).

4. The ramp supporting structure for the narrow foundation pit according to claim 1, wherein the transfer station (410) is rectangular and comprises a bottom plate (411) and a baffle arranged around the bottom plate (411), the transfer station (410) is fixed on the opposite support (400), and the baffle (412) and the upper surface of the opposite support (400) are connected with a plurality of supporting rods (413).

5. A excavation slope support structure according to claim 1, characterized in that the bottom of the excavation (100) is provided with a doorsill (180), and the tops of the columns (310) and the support pillars are provided with crown beams (190).

6. A method of constructing a support structure for a foundation pit ramp according to any one of claims 1 to 5, the unearthing method comprising the steps of: the method comprises the following steps: supporting the periphery of a foundation pit (100) by using support piles and upright posts, dividing the foundation pit (100) into six areas including a first area (110) to a fifth area (150) and a central area (160), excavating a first layer of earthwork in a central island type excavation mode, excavating a first working surface of a ring support (300) in advance to construct a first inner support structure, wherein the excavation depth is 1.9m, excavating a first layer of earthwork at a temporary ramp, constructing the first ring support (300), installing a corner support (220) and a radiation support (210) between the first ring support (300) and an occlusion pile (200), pouring concrete among the first ring support (300), the corner support (220) and the radiation support (210), and backfilling the temporary ramp after the construction of the first inner support structure is completed;

step two: excavating a second layer of earthwork after the construction strength of the first ring support (300) reaches 85% of the design requirement, wherein the second layer of earthwork adopts a basin-type layered excavation mode, the excavation depth is 5.4m, road treatment is carried out in the foundation pit (100), four areas (140) are reserved for supporting the earthwork to be reserved as temporary ramps, excavation is not carried out temporarily, after the plate bottom excavation of the ramps (500) is finished, slope excavation is carried out from the outside of the occlusion support (200) to form the ramps (500), construction of an inner support structure of the second layer is started, the second ring support (300) is fixed on the upright column (310), a corner support (220) and a radiation support (210) are installed between the second ring support (300) and the occlusion support (200), and concrete is poured between the adjacent corner support (220) and radiation support (210);

step three: after the construction strength of the second ring brace (300) reaches 85 percent of the design requirement, excavating the third layer of earthwork, the third layer of earth adopts a basin-type layered excavation mode, the excavation depth is 5.2m, the excavation sequence is that the central area (160) → the three areas (130), the four areas (140) → the two areas, the first area (110) → the five areas (150), when the central area (160) is excavated, the ramp (500) is lengthened, three areas (130) and four areas (140) are excavated to the bottom of a third supporting beam, then excavating the second area (120) and the first area (110), constructing a third inner support structure, fixing a third ring support (300) on the upright post (310), and constructing the counter support (400), arranging a support column (420) and a support pile (450) at the bottom of the diagonal brace, and enabling the diagonal brace (400) and the ramp (500) to intersect to form the slope landing (530);

step four: excavating earthwork of a fourth layer after the construction strength of the third ring brace (300) reaches 85% of the design requirement, wherein the excavation depth of the second area (120) and the third area (130) is 3.7m, excavating earthwork of the third area (130) preferentially, excavating earthwork of the second area (120), after the excavation is finished, constructing corner braces (220) and radiation braces (210) in the second area (120) and the third area (130), excavating fifth earthwork of the first area (110) and the fourth area (140) simultaneously, the excavation depth is 4.9m, excavating earthwork of the fourth area (140) preferentially, and excavating earthwork of the first area (110);

step five: after the excavation of the earthwork of the fourth layer and the fifth layer is finished, slope elimination is carried out on the ramp (500), the earthwork of the ramp (500) is placed in the transfer station (410), the earthwork is transferred to the outside of the foundation pit (100) by a long-arm excavator on the outer side of the foundation pit (100), and construction of a doorsill support (180) is carried out after a working surface is provided.

7. The method for constructing a support structure of a slope of a excavation site of a PC200 and a PC120 according to claim 6, wherein the excavation tools used in the first to fourth steps are 4 PC200 excavators and 2 PC120 excavators, and the earth is loaded on a transport vehicle which transports the earth to the earth accumulation site via the slope (500).

8. The construction method of a narrow foundation pit and ramp supporting structure according to claim 6, characterized in that the foundation pit (100) is divided into five subareas, each earthwork layer is an excavated layer according to the depth of 2m, until each ring support (300) structure is constructed, the overexcavation depth is not more than 0.2m below the supporting bottom elevation so as to support the supporting structure.

9. The construction method of the ramp support structure of the narrow foundation pit according to claim 6, wherein a thick soil layer of 200mm-300mm is reserved at the bottom of the foundation pit (100) and the pit wall and is trimmed by manual excavation.

10. The construction method of the slope support structure of the narrow foundation pit according to claim 6, wherein the slope gradient of the slope is set to 15% -17%, the width of the slope is 8m, and the two sides of the slope are arranged in a ratio of 1: 1.4-1: releasing slope according to the proportion of 0.65, spraying 100-thick C20 plain concrete protective surfaces on two sides of the slope, paving 0.5 m-thick brick slag on the slope surface, supplementing and compacting the thick brick slag in time along with loss, wherein the thick brick slag is used for preventing automobile tires from skidding; the slope is characterized in that water drainage holes are formed in two sides of the slope, PVC drainage pipes with the length of 0.5m and the diameter of 100mm are inserted into the water drainage holes according to a quincunx shape with the distance of 1.5m multiplied by 1.5m, the outer pipe orifices of the drainage pipes are slightly inclined downwards, the inclination angle is not smaller than 5%, water permeable holes are drilled in the upper half parts of the pipe walls of the drainage pipes, and coarse sand or round gravel is filled in the drainage pipes to serve as a water filtering material so as to prevent soil particles from losing.

Technical Field

The invention relates to the technical field of a ramp supporting structure of a narrow foundation pit, in particular to a ramp supporting structure of a narrow foundation pit and a construction method.

Background

At present, when beginning to build large-scale building, the foundation ditch generally needs to be excavated, the north side of this project is close to the subway, subway safety needs to be guaranteed, receive the surrounding environment restriction, the degree of depth of foundation ditch is big, construction space is narrow and small, the great foundation ditch of the degree of depth risk of collapsing is higher, when being close to the foundation ditch bottom at the in-process of construction, the degree of difficulty of earthwork outward transportation in the foundation ditch improves relatively, current grab bucket machine belongs to main equipment and works at foundation ditch edge, can cause the threat to the bearing structure of foundation ditch, and the slope that adopts once only to put the slope in narrow and small foundation ditch is big, all can cause huge difficulty to construction and earthwork outward transportation, consequently need a novel foundation ditch ramp bearing structure.

Disclosure of Invention

The application provides a narrow foundation pit ramp supporting structure and a construction method, and aims to solve the problems that the working efficiency is low, the construction risk is high, and excavated earthwork cannot be processed.

In order to solve the technical problem, the application provides a ramp supporting structure of a narrow foundation pit, which comprises a foundation pit, a rectangular occlusion support arranged at the edge of the foundation pit, a ring support arranged around the foundation pit and a counter support taking the diameter of the ring support as the length, wherein the counter support is positioned between a third ring support, the ring support is divided into three layers, stand columns are arranged at equal intervals along the circumference of the ring support, stand column piles are arranged at the bottoms of the stand columns, a transportation outlet is arranged at one side of the foundation pit, a ramp is formed by the transportation outlet, the ramp is divided into two sections, one end of a first ramp is connected to the transportation outlet, the other end of the first ramp is connected to the counter support which is crossed with the ramp, a slope placing platform is formed at the crossed part of the counter support, one end of a second ramp is connected to the slope placing platform, and the other end of the second ramp extends to the bottom of the foundation pit; the butt support is also provided with a transfer station for transferring earthwork.

In some embodiments of this application, the ring props with be provided with radiation between the interlock props and the corner brace, the radiation props along the interlock props by a plurality of angles to the ring props extends and is connected to the edge of ring props, the corner brace is connected to adjacent the interlock props.

In some embodiments of the present application, a plurality of support pillars are disposed at the bottom of the diagonal brace, the support pillars are disposed at two sides of the diagonal brace in the width direction, cross bars are disposed between the support pillars, and diagonal braces are disposed between adjacent cross bars.

In some embodiments of this application, the transfer station is the rectangle form, includes the bottom plate and locates bottom plate baffle all around, the transfer station is fixed in to propping, the baffle with there are a plurality of bracing pieces to the upper surface that props.

In some embodiments of the present application, a doorsill brace is provided at the bottom of the foundation pit, and a crown beam is provided at the top of the pillar and the occlusive pile.

In some embodiments of the present application, a construction method of a ramp support structure of a narrow foundation pit is provided, and the unearthing method includes the following steps: the method comprises the following steps: adopting secant piles and upright piles to support the periphery of a foundation pit, dividing the foundation pit into six areas including one area, five areas and a central area, excavating a first layer of earthwork at a temporary ramp by adopting a central island type excavation mode, excavating a first layer of earthwork on a working surface of a ring support in advance to construct a first inner supporting structure, wherein the excavation depth is 1.9m, excavating the first layer of earthwork at the temporary ramp, constructing the first ring support, installing an angle support and a radiation support between the first ring support and the secant piles, pouring concrete among the first ring support, the angle support and the radiation support, and backfilling the temporary ramp after the construction of the first inner supporting structure is finished;

step two: excavating a second layer of earthwork after the construction strength of the first ring support reaches 85% of the design requirement, wherein the second layer of earthwork adopts a basin-type layered excavation mode, the excavation depth is 5.4m, road treatment is carried out in the foundation pit, the earthwork under the support of four areas is reserved to be used as a temporary ramp, excavation is not carried out temporarily, after the plate bottom of the ramp is excavated, slope-releasing excavation is carried out from the outside of the occlusion support to form the ramp, construction of an inner support structure of the second path is started, the second ring support is fixed on an upright post, an angle support and a radiation support are installed between the second ring support and the occlusion support, and concrete is poured between the adjacent angle support and the radiation support;

step three: excavating a third layer of earthwork after the construction strength of the second ring support reaches 85% of the design requirement, wherein the third layer of earthwork adopts a basin-type layered excavation mode, the excavation depth is 5.2m, the excavation sequence is the central area → the three areas, the four areas → the two areas, the first area → the five areas, when the central area is excavated, the ramp is lengthened, the three areas and the four areas are excavated to the bottom of a third supporting beam, then the second area and the first area are excavated, a third inner supporting structure is constructed, the third ring support is fixed on the upright post, the counter support is constructed at the same time, supporting columns and supporting piles are arranged at the bottom of the counter support, and the counter support and the ramp are crossed to form the slope placing platform;

step four: excavating earthwork of a fourth layer after the construction strength of the third ring support reaches 85% of the design requirement, wherein the excavation depth of the second area and the third area is 3.7m, the earthwork of the third area is preferably excavated, then the earthwork of the second area is excavated, after the excavation is finished, corner supports and radiation supports in the second area and the third area are constructed, meanwhile, the fifth layer earthwork of the first area and the fourth area is excavated, the excavation depth is 4.9m, the earthwork of the fourth area is preferably excavated, and then the earthwork of the first area is excavated;

step five: after the excavation of the earthwork of the fourth layer and the fifth layer is finished, slope elimination is carried out on the ramp, the earthwork of the ramp is placed in the transfer station, the earthwork is transferred to the outside of the foundation pit by a long-arm excavator on the outer side of the foundation pit, and construction of the doorsill support is carried out after a working surface is provided.

In some embodiments of the present application, the excavation tools used in the first to fourth steps are 4 PC200 excavators and 2 PC120 excavators, and load the earth into a transfer car that transports the earth to the earth pile via the ramp.

In some embodiments of the application, the foundation pit is in five subareas, each layer of earthwork is an excavation layer according to the depth of 2m, until each ring support structure is constructed, the overexcavation depth is not more than 0.2m below the elevation of the support bottom, so that the support structure can be conveniently supported.

In some embodiments of the application, a 200mm-300mm thick soil layer is reserved at the bottom of the foundation pit and the pit wall, and is manually excavated and trimmed.

In some embodiments of the present application, the slope rate of the ramp is set to 15% to 17%, the width of the ramp is 8m, and the slope is set to have a slope ratio of 1: 1.4-1: releasing slope according to the proportion of 0.65, spraying 100-thick C20 plain concrete protective surfaces on two sides of the slope, paving 0.5 m-thick brick slag on the slope surface, supplementing and compacting the thick brick slag in time along with loss, wherein the thick brick slag is used for preventing automobile tires from skidding; the slope is characterized in that water drainage holes are formed in two sides of the slope, PVC drainage pipes with the length of 0.5m and the diameter of 100mm are inserted into the water drainage holes according to a quincunx shape with the distance of 1.5m multiplied by 1.5m, the outer pipe orifices of the drainage pipes are slightly inclined downwards, the inclination angle is not smaller than 5%, water permeable holes are drilled in the upper half parts of the pipe walls of the drainage pipes, and coarse sand or round gravel is filled in the drainage pipes to serve as a water filtering material so as to prevent soil particles from losing.

Compared with the prior art, the invention has the following characteristics and beneficial effects:

1. the design load of the invention is mainly water and soil pressure according to the standard requirement, the additional load of the ground of the foundation pit is 20kPa according to the field situation, and the design of the supporting structure of the foundation pit is considered according to the limit state of the bearing capacity. The support structure is 0.2m away from the outer edge line of the basement of the main structure, pile bracing schemes are adopted around the foundation pit, snap piles with pile diameters of 1.2m are adopted for the snap piles, the cross piles are arranged in a one-to-one mode, the concrete label of the cross pile is C30, the concrete label of the cross pile is C15, the pile spacing is 1.0m, and the support piles are arranged in the bottom of the foundation pit by 13m, so that the stability of the periphery of the foundation pit is guaranteed.

2. The inner support mainly adopts a support mode of combining three ring supports and a pit bottom doorsill support, the radiation support and the corner support are arranged between the ring supports and the occlusion support, the stability of the inner support structure is ensured, the counter support is arranged between the third ring support, and a slope placing platform is formed at the joint of the counter support and the ramp, so that the current situation of one-time slope placing to the bottom is changed, the counter support structure is more stable, and the whole inner support system is safer.

3. The earthwork excavation is combined with the inner and outer supporting systems, the next earthwork excavation is carried out after the construction strength of each layer of supporting structure reaches 85% of the design requirement, excavation machinery is strictly forbidden to collide with supporting members such as supporting piles and supports in the excavation process, meanwhile, the transport vehicle runs on a ramp all the time, the influence of the transport vehicle on the inner and outer supporting systems is reduced to the minimum, the construction safety is guaranteed during construction, and the construction efficiency can be improved.

Drawings

FIG. 1 is a top view of an embodiment of the present invention;

FIG. 2 is a schematic illustration of a region distribution according to an embodiment of the present invention;

FIG. 3 is a schematic diagram illustrating a first step of an embodiment of the present invention;

figure 4 is a side view of a supporting structure of an embodiment of the present invention;

FIG. 5 is a schematic diagram of step two of the present invention;

FIG. 6 is a schematic diagram of step three of the present invention;

FIG. 7 is a diagram illustrating step four of the present invention;

fig. 8 is a perspective view of a transfer station in accordance with an embodiment of the present invention.

In the figure, 100, a foundation pit; 110. a first region; 120. a second zone; 130. three zones; 140. fourthly, a fourth zone; 150. fifthly, dividing; 160. a central region; 170. a transport outlet; 180. a doorsill support; 190. a crown beam; 200. an occlusion support; 210. a spider web support; 220. corner brace; 230. carrying out plain piling; 240. piling meat; 300. ring bracing; 310. a column; 320. a vertical column pile; 400. oppositely supporting; 410. a transfer station; 411. a base plate; 412. a baffle plate; 413. a support bar; 420. a support pillar; 430. A cross bar; 440. a diagonal brace; 450. supporting piles; 500. a ramp; 510. a first ramp; 520. a second ramp; 530. and (5) a slope-releasing platform.

Detailed Description

The following detailed description of embodiments of the present invention is provided in connection with the accompanying drawings and examples. The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.

In the description of the present application, it is to be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience in describing the present application and simplifying the description, but do not indicate or imply that the referred device or element must have a particular orientation, be constructed in a particular orientation, and be operated, and thus should not be construed as limiting the present application.

The terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present application, "a plurality" means two or more unless otherwise specified.

In the description of the present application, it is to be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present application can be understood in a specific case by those of ordinary skill in the art.

As shown in fig. 1, according to some embodiments of the present disclosure, a narrow foundation pit ramp supporting structure includes a foundation pit 100, a rectangular engaging support 200 disposed at an edge of the foundation pit 100, a ring support 300 disposed around the foundation pit 100, and a counter support 400 having a diameter of the ring support 300 as a length, wherein the counter support 400 is disposed between third ring supports 300, the ring support 300 is divided into three layers, vertical columns 310 are disposed at equal intervals along a circumference of the ring support 300, vertical column 310 piles are disposed at a bottom of the vertical columns 310, a transportation outlet 170 is disposed at one side of the foundation pit 100, a ramp 500 is formed from the transportation outlet 170, the ramp 500 is divided into two sections, one end of a first ramp 510500 is connected to the transportation outlet 170, the other end of the first ramp is connected to the counter support 400 disposed crosswise to the ramp 500, a ramp platform 530 is formed at a crossing portion of the counter support 400, one end of a second ramp 520500 is connected to the ramp platform 530, and the other end of the second ramp extends to the bottom of the foundation pit 100; the opposite support 400 is also provided with a transfer station 410 for transferring earthwork.

It should be noted here that the depth of the foundation pit 100 is about 20m, and the supporting scheme of the foundation pit 100 adopts a pile supporting scheme. The pile is a secant pile with the pile diameter of 1.2m, the arrangement of one pile and one pile is adopted, the label of 240 concrete of the meat pile is C30, the label of 230 concrete of the vegetable pile is C15, the pile spacing is 1.0m, and the pile of the secant pile is inserted into the bottom of a foundation pit by 13 m. The inner supporting structure is made of reinforced concrete.

According to some embodiments of the present application, a radial strut and a corner strut 220 are disposed between the ring strut 300 and the bite strut 200, the radial strut extends from a plurality of angles along the bite strut 200 toward the ring strut 300 and is connected to an edge of the ring strut 300, and the corner strut 220 is connected to an adjacent bite strut 200.

According to some embodiments of the present application, a plurality of support columns 420 are disposed at the bottom of the diagonal brace 400, the support columns 420 are disposed at two sides of the diagonal brace 400 in the width direction, cross bars 430 are disposed between the support columns 420, and diagonal braces 440 are disposed between adjacent cross bars 430.

According to some embodiments of the present application, the transfer station 410 is rectangular, and includes a bottom plate 411 and a baffle 412 disposed around the bottom plate 411, the transfer station 410 is fixed on the opposite support 400, and the baffle 412 and the upper surface of the opposite support 400 are connected to a plurality of support rods 413.

According to some embodiments of the present application, the bottom of the foundation pit 100 is provided with a sill brace 180 and the tops of the columns 310 and the spuds are provided with a crown beam 190.

According to some embodiments of the present application, a method of constructing a support structure for a ramp of a excavation includes: the method comprises the following steps: supporting the periphery of the foundation pit 100 by using secant piles and upright columns 310, dividing the foundation pit 100 into six areas including a first area 110-a fifth area 150 and a central area 160, excavating a first layer of earthwork, excavating a working surface of a first ring support 300 in advance by using a center island type excavation mode for constructing a first inner supporting structure, wherein the excavation depth is 1.9m, excavating the first layer of earthwork at a temporary ramp 500, constructing the first ring support 300 at the position, installing a corner support 220 and a radiation support between the first ring support 300 and the secant piles, pouring concrete among the first ring support 300, the corner support 220 and the radiation support, and backfilling the temporary ramp 500 after the construction of the first inner supporting structure is finished;

step two: excavating a second layer of earthwork after the construction strength of the first ring support 300 reaches 85% of the design requirement, excavating the second layer of earthwork in a basin-type layered excavation mode, wherein the excavation depth is 5.4m, performing road treatment in the foundation pit 100, reserving four areas 140 to support the lower earthwork to be reserved as a temporary ramp 500, not excavating temporarily, after the plate bottom excavation of the ramp 500 is finished, performing slope-releasing excavation from the outside of the occlusion support 200 to form the ramp 500, starting the construction of the inner support structure of the second layer, fixing the second ring support 300 to the upright column 310, installing a corner support 220 and a radiation support between the second ring support 300 and the occlusion support 200, and pouring concrete between the adjacent corner support 220 and the radiation support;

step three: excavating a third layer of earthwork after the construction strength of the second ring support 300 reaches 85% of the design requirement, wherein the third layer of earthwork adopts a basin-type layered excavation mode, the excavation depth is 5.2m, the excavation sequence is central area 160 → three area 130, four area 140 → two, one area 110 → five area 150, when the central area 160 is excavated, the ramp 500 is lengthened, the excavation is completed from the three area 130 and the four area 140 to the bottom of a third supporting beam, then the excavation is performed on the second area 120 and the first area 110, constructing a third inner supporting structure, fixing the third ring support 300 to the upright column 310, constructing a pair support 400, arranging a supporting column 420 and a supporting pile 450 at the bottom of the pair support 400, and enabling the pair support 400 and the ramp 500 to form a slope placing platform 530 in a crossed manner;

step four: after the construction strength of the third ring brace 300 reaches 85% of the design requirement, excavating the earthwork of the fourth layer, wherein the excavation depth of the second area 120 and the third area 130 is 3.7m, preferably excavating the earthwork of the third area 130, excavating the earthwork of the second area 120, after the excavation is finished, constructing the corner brace 220 and the radiation brace in the second area 120 and the third area 130, excavating the fifth layer earthwork of the first area 110 and the fourth area 140, wherein the excavation depth is 4.9m, preferably excavating the earthwork of the fourth area 140, and excavating the earthwork of the first area 110;

step five: after the excavation of the earthwork of the fourth layer and the fifth layer is completed, the slope 500 is removed, the earthwork of the slope 500 is placed in the transfer station 410, the earthwork is transferred to the outside of the foundation pit 100 by the long-arm excavator outside the foundation pit 100, and the construction of the doorsill support 180 is performed after the working surface is provided.

According to some embodiments of the present application, the excavation tools used in steps one through four are 4 PC200 excavators and 2 PC120 excavators, and load the earth to a transfer car that transports the earth to the earth pile via ramp 500.

According to some embodiments of the present application, the foundation pit 100 is divided into five sub-areas, each layer of earthwork is an excavated layer with a depth of 2m, until each ring support 300 is structurally constructed, the overexcavation depth is not more than 0.2m below the support bottom elevation, so as to facilitate the support structure formwork.

According to some embodiments of the application, a 200mm-300mm thick soil layer is reserved at the bottom of the foundation pit 100 and the pit wall, and is manually excavated and trimmed.

According to some embodiments of the present application, the slope gradient of the ramp 500 is set at 15% -17%, the width of the ramp 500 is 8m, and the slope of the ramp 500 is set at 1: 1.4-1: the slope is set at the proportion of 0.65, both sides of the slope 500 are sprayed with 100-thick C20 plain concrete protective surfaces, brick slag with the thickness of 0.5m is paved on the slope surface, the thick brick slag is instantly replenished and compacted along with the loss, and the thick brick slag is used for preventing the automobile tires from skidding; the ramp 500 both sides are provided with the outlet, and the PVC drain pipe that the outlet is 0.5m long, the diameter is 100mm is inserted according to the plum blossom type of interval 1.5m, and the outer mouth of pipe of drain pipe slightly downward sloping and inclination are not less than 5%, and the upper half of the pipe wall of drain pipe is bored and is equipped with the hole of permeating water, fills up coarse sand or round gravel as drainage material in the drain pipe to prevent soil particle material loss.

To sum up, the invention relates to the technical field of a ramp supporting structure of a narrow foundation pit, and discloses a ramp supporting structure of a narrow foundation pit and a construction method, wherein the ramp supporting structure comprises the following steps: the foundation pit is characterized by comprising a rectangular occlusion support arranged at the edge of the foundation pit, a ring support arranged around the foundation pit and a counter support taking the diameter of the ring support as the length, wherein the counter support is positioned between third ring supports, the ring supports are divided into three layers, stand columns are arranged at equal intervals along the circumference of the ring supports, stand column piles are arranged at the bottom of each stand column, a transportation outlet is arranged at one side of the foundation pit, a ramp is formed from the transportation outlet and divided into two sections, one end of a first ramp is connected to the transportation outlet, the other end of the first ramp is connected to the counter support which is arranged in a cross mode with the ramp, a slope placing platform is formed at the cross position of the counter support, one end of a second ramp is connected to the slope placing platform, and the other end of the second ramp extends to the bottom of the foundation pit; still be provided with the transfer station that is used for transporting the earthwork to propping, provide the efficiency of construction of foundation ditch, guaranteed the security in the work progress.

The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and substitutions can be made without departing from the technical principle of the present invention, and these modifications and substitutions should also be regarded as the protection scope of the present invention.