CN206070573U - It is a kind of be applied under wear the big of heavily loaded highway and reinforce foundation ditch combinative structure across open trench tunnel and steel pipe - Google Patents

Abstract

This utility model is related under a kind of being applied to wear the big of heavily loaded highway and reinforces foundation ditch combinative structure with steel pipe across open trench tunnel, belongs to highway engineering technical field.The mould of China's capital construction in recent years is increased, and highway network is also constantly being encrypted, and the situation of tunnel Xia Chuan highways often occurs.It is a kind of complicated operating mode that existing heavily loaded highway is wherein worn greatly under, shallow embedding, multiple-arch tunnel, and this utility model proposes a kind of new combinative structure for the operating mode, to solve the technical barrier in terms of tunneling and two contradiction of tunnel top highway.This structure is made up of three parts：The pre-reinforcement supporting of foundation ditch both sides, open cut tunnel lining cutting, open cut tunnel backfill.Pre-reinforcement supporting is divided into two parts again：Steel pipe grouting and reinforcing Rock And Soil is set by wall profiles from foundation ditch both sides, that steel pipe grouting and reinforcing is set from excavation slope is domatic.Open cut tunnel lining cutting is large volume concrete structural.Three lamination of open cut tunnel backfill point is real to be filled.This new structure reasonable stress, better economy, with very strong practicality and dissemination.

Description

A large-span open-cut tunnel and steel pipe reinforced foundation pit group suitable for underpassing heavy-duty highways combined structure

technical field

The utility model belongs to the technical field of engineering, and in particular relates to a combined structure of a large-span open-cut tunnel and a steel pipe reinforced foundation pit suitable for underpassing a heavy-duty road.

Background technique

In recent years, with the expansion of infrastructure construction in my country, the level of roads has been greatly improved, and the road network has been continuously densified. A large number of tunnels and roads have intersected. Loading (such as coal transport) highway is a more complicated working condition.

For long-span and shallow-buried tunnels passing through existing roads, when the conditions for relocating the roads are met, the open-cut method is used for construction. A foundation pit is dug from top to bottom on the original ground, and the open-hole structure of the tunnel is poured in the foundation pit. , and then backfill to restore the original ground.

The key processes of the open cut method include: slope support, earthwork excavation, structural construction and waterproofing works, etc. Among them, slope support is the key technology to ensure safe construction. Slope support, that is, the conventional methods of foundation pit wall support mainly include: sloping excavation, steel support, continuous wall support, concrete pouring pile support, soil nail wall support, anchor (cable) support support, concrete and steel structure support, and combinations of the aforementioned types, etc.

The tunnel passes through the existing heavy-duty road. In order to prevent the post-construction settlement of the ground after the tunnel construction is completed, especially the uneven settlement: on the one hand, during the excavation of the foundation pit, the original Disturbance of the rock and soil mass, or pre-reinforce the part of the rock and soil mass in advance; on the other hand, after the pouring of the open cave is completed, there must be higher requirements for the backfill material and compaction degree of the cave roof. Based on this background and premise, the utility model proposes a combination structure of a large-span open-cut tunnel and a steel pipe reinforced foundation pit suitable for underpassing a heavy-duty highway, so as to overcome the deficiencies of the existing technology and solve the problems that need to be solved urgently in the field of engineering technology .

Contents of the invention

The purpose of this utility model is to solve the deficiencies of the prior art, and provide a combination structure of a large-span open-cut tunnel and a steel pipe reinforced foundation pit suitable for passing through a heavy-duty road. Strong practicability and promotional significance.

In order to achieve the above object, the technical scheme adopted by the utility model is as follows:

A combination structure of large-span open-cut tunnels and steel pipe reinforced foundation pits suitable for underpassing heavy-duty roads. On the road surface of the original heavy-duty roads, a road surface slot is arranged on both sides of the top of the foundation pit along the driving direction of the car. bottom level;

Each road surface slot is drilled downwards with a first reinforcement wall and a second reinforcement wall, and the wall direction of the first reinforcement wall and the second reinforcement wall is parallel to the driving direction of the car;

The first reinforcement wall is composed of multiple steel pipes of the same size arranged in a row, two adjacent steel pipes are parallel to each other, and the distance between them is 2m; the first reinforcement wall is perpendicular to the bottom surface of the road groove;

The second reinforcement wall is composed of multiple steel pipes of the same size arranged in a row, two adjacent steel pipes are parallel to each other, and the distance between them is 1m; the angle between the second reinforcement wall and the bottom surface of the road groove is 75°;

Taking the bottom surface of the pavement groove as the section, the distance between the first reinforcement wall and the second reinforcement wall at the section is 1m;

The lower part of the pavement groove is provided with a concrete connecting beam layer;

Multiple sets of third reinforcement walls are built along the slope of the foundation pit. The third reinforcement wall is composed of multiple steel pipes of the same size arranged in a row. Two adjacent steel pipes are parallel to each other with a distance of 1.2m; the third reinforcement wall The wall is perpendicular to the slope of the foundation pit, and forms an angle of 27° with the horizontal plane; the direction of the wall surface of the third reinforcement wall is consistent with the direction of the slope of the foundation pit on the slope from the top to the bottom of the slope; the adjacent two groups of third The distance between reinforced walls is 2m;

There is also a sprayed concrete layer on the slope of the foundation pit;

On the bottom of the foundation pit, there is an open-hole lining base cushion, and on the base cushion of the open-hole lining, there is an open-hole lining for a large-span multi-arch tunnel;

Between the slope of the foundation pit and the lining of the open hole, the concrete layer of rubble and the first layer of rubble are filled from bottom to top; the second layer of rubble is set between the lining of the open hole at the intersection of the double holes; Both the first mortared rubble layer and the second mortared rubble layer are at the same level as the outer top of the open tunnel lining;

A graded crushed stone filler layer is laid on the first mortared rubble layer and the second mortared rubble layer; a new heavy-duty highway pavement is laid on the graded crushed stone filler layer and the concrete connecting beam layer; the said The new heavy-duty highway pavement is on the same level as the original heavy-duty highway pavement;

Wherein, the top of the first reinforced wall and the top of the second reinforced wall are both arranged in the concrete connecting beam layer; the bottom of the first reinforced wall and the bottom of the second reinforced wall are located below the bottom elevation of the open cavity lining inverted arch;

The steel pipes in the first reinforced wall, the steel pipes in the second reinforced wall and the steel pipes in the third reinforced wall do not intersect.

Further, preferably, the slope ratio of the slope of the foundation pit is 1:0.5.

Further, it is preferable that the groove width of the road surface groove is 2m, and the groove depth is 0.9m.

Further, it is preferred that the width of the concrete connecting beam layer is 2m and the thickness is 0.5m

Further, it is preferred that both the top of the first reinforced wall and the top of the second reinforced wall extend into the concrete coupling beam layer by 0.3m; the bottom of the first reinforced wall and the bottom of the second reinforced wall both extend into the open hole lining At least 1.5m below the level of the vault bottom.

Further, preferably, the steel pipes used in the first and second reinforced walls are both φ108 steel pipes; the steel pipes used in the third reinforced wall are φ42 steel pipes with a length of 5m.

Further, it is preferred that the thickness of the base cushion of the open hole lining is 0.5m.

Further, it is preferred that the thickness of the rubble concrete layer is 6.5m; the height of the first mortared rubble layer is 5.5m; the height of the second mortared rubble layer is 3m; the height of the graded crushed stone filler layer is 1.2m.

Further, it is preferable that the minimum thickness of the open-hole lining arch ring is 1.1m.

Further, preferably, steel cages are provided in the steel pipes of the first reinforced wall, the steel pipes of the second reinforced wall and the steel pipes of the third reinforced wall; the steel pipes are perforated steel pipes that can be grouted.

The advantages and significance that the utility model has are reflected in:

The utility model is a combination structure of a large-span open-cut tunnel and a steel pipe reinforced foundation pit suitable for passing under a heavy-duty road. Aiming at the situation that a newly-built long-span and shallow-buried tunnel passes under an existing heavy-duty road, a cut-and-surface construction is proposed. The combined structure of the tunnel and the reinforced foundation pit solves two problems: first, the safe and economical construction of the new tunnel, that is, the structure has sufficient strength, stability and durability, and can meet the needs of operation after completion; , the restoration of the original existing road, especially the restoration of its heavy-duty function.

Post-construction settlement after construction is the main reason affecting the use of the original existing roads. In order to reduce settlement, it is necessary to prevent disturbance to the original rock and soil: before excavation of the foundation pit, the first reinforcement wall and the second reinforcement wall are set, first The rock and soil can be pre-reinforced by grouting, and the layout of the top of the first reinforcement wall and the second reinforcement wall refers to the section shape of the gravity retaining wall, forming a retaining wall that acts as a support in the original rock and soil; the foundation pit After excavation, the disturbed rock and soil mass under the slope is reinforced by grouting steel pipes in the third reinforcement wall, and the disturbed slope is sealed with shotcrete.

The tunnel is shallowly buried and directly bears the heavy load of the road above it. The design of the utility model determines the thickness of the structure through calculation, and sets the inverted arch as a flat bottom to facilitate construction. The intersection of the two arches is filled and leveled to form the second slurry. Laying stone layers to prevent stress concentration.

In order to reduce the excavation volume of earthwork and properly control the pre-reinforcement scale of the foundation pit, the excavation of the foundation pit is carried out according to the pre-reinforcement and steeper slope rate between the two excavation methods of slow slope and straight wall.

In addition, compare the structure of the utility model with the alternative bridge and rectangular underpass tunnel in terms of cost: compared with the bridge structure, one span of 40m or two spans of 20m, the utility model structure can save 20% of the cost Above; compared with the underpass tunnel with double-hole 20m rectangular section, the structure of the utility model can save more than 30% of the cost. In addition, the structure of the utility model is also superior to the other two types of structures in terms of the quickness of construction and the control effect of post-construction settlement.

In summary, this utility model is a combination structure of large-span open-cut tunnels and steel pipe reinforced foundation pits suitable for passing heavy-duty highways. The arched tunnel with reasonable stress is selected as the basic structure, and the original rock and soil are protected to the greatest extent through reinforcement measures. Without disturbance, backfill measures are taken to control post-construction settlement; the structure of the utility model not only safely and economically builds a new underpass tunnel, but also quickly and well restores the traffic of the existing heavy-duty road on the tunnel top. This structure has strong practicability and popularization significance.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description These are only some embodiments of the utility model, and those skilled in the art can also obtain other drawings based on these drawings without creative work.

Fig. 1 is a cross-sectional view of the arrangement of φ108 steel pipes on both sides of the foundation pit groove of the combined structure of the large-span open-cut tunnel and the steel pipe reinforced foundation pit of the utility model applicable to the heavy-duty highway.

Fig. 2 is a cross-sectional view of the excavation slope support of the utility model for a large-span open-cut tunnel and a steel pipe reinforced foundation pit combined structure foundation pit excavation slope support layout of a heavy-duty highway underneath.

Fig. 3 is a large sample diagram of foundation pit excavation slope support for a large-span open-cut tunnel and a steel pipe reinforced foundation pit combined structure of the utility model (taking the slope of the right half of the foundation pit as an example) for the utility model.

Fig. 4 is a plan view of the layout relationship between φ108 steel pipes and φ42 steel pipes in the combined structure of large-span open-cut tunnels and steel pipe-reinforced foundation pits of the present invention (taking the side wall of the right half of the foundation pit as an example).

Fig. 5 is a cross-sectional view of the open tunnel lining of the combined structure of the large-span open-cut tunnel and the steel pipe reinforced foundation pit of the utility model suitable for passing through heavy-duty highways.

Fig. 6 is a cross-sectional view of the backfilling of the combined structure of the large-span open-cut tunnel and the steel pipe reinforced foundation pit of the utility model suitable for passing through heavy-duty highways.

Fig. 7 is a cross-sectional view of backfill layering/blocking of the combined structure of the large-span open-cut tunnel and the steel pipe reinforced foundation pit of the utility model suitable for underpassing the heavy-duty highway.

Fig. 8 is a cross-sectional view of the combined structure of a large-span open-cut tunnel and a steel pipe reinforced foundation pit suitable for underpassing a heavy-duty road under the utility model.

Among them: 1. The pavement of the original heavy-duty road; 2. The foundation pit; 3. The pre-reinforcement support system; 3a. Grooving on the road surface; 3b. The first reinforcement wall; 3c. The second reinforcement wall; 3d. The concrete coupling beam layer ;4, foundation pit slope; 4a, sprayed concrete layer; 4b, third reinforcement wall; 5, base cushion of open hole lining; 6, open hole lining; Side wall and arch ring above the inverted arch; 7. Open hole backfill structure; 7a. Rubble concrete; 7b. First mortared rubble; 7c. Second mortared rubble; 7d. Graded crushed stone filling layer; 8. New Heavy-duty highway pavement;

The direction of the arrow is from the top of the slope to the bottom of the slope.

detailed description

Below in conjunction with embodiment the utility model is described in further detail.

Those skilled in the art will understand that the following examples are only used to illustrate the utility model, and should not be considered as limiting the scope of the utility model. If no specific technology, connection relationship or condition is indicated in the embodiment, it shall be carried out according to the technology, connection relationship or condition described in the literature in this field or according to the product specification. The materials or equipment used are not indicated by the manufacturer, and they are all conventional products that can be obtained through purchase.

A combination structure of large-span open-cut tunnels and steel pipe reinforced foundation pits suitable for underpassing heavy-duty roads. On the road surface 1 of the original heavy-duty road, a road surface slot is arranged on both sides of the top of the foundation pit 2 in the direction of vehicle travel. 3a, tank bottom level;

Each road surface slot 3a is drilled downwards with a first reinforced wall 3b and a second reinforced wall 3c, and the wall direction of the first reinforced wall 3b and the second reinforced wall 3c is parallel to the driving direction of the car; the first reinforced wall 3b is composed of multiple steel pipes of the same size arranged in a row, two adjacent steel pipes are parallel to each other, and the distance is 2m; the first reinforcement wall 3b is perpendicular to the bottom surface of the road groove 3a;

The second reinforced wall 3c is composed of multiple steel pipes of the same size arranged in a row, two adjacent steel pipes are parallel to each other, and the distance is 1m; the angle between the second reinforced wall 3c and the bottom surface of the road groove 3a is 75°;

Taking the bottom surface of the road groove 3a as the section, the distance between the first reinforcement wall 3b and the second reinforcement wall 3c at the section is 1m;

The lower part of the pavement groove 3a is provided with a concrete connecting beam layer 3d;

The road surface groove 3a, the first reinforced wall 3b, the second reinforced wall 3c, and the concrete connecting beam layer 3d together form a pre-reinforced support system 3;

Multiple sets of third reinforcement walls 4b are drilled along the slope 4 of the foundation pit. The third reinforcement walls 4b are composed of multiple steel pipes of the same size arranged in a row. Two adjacent steel pipes are parallel to each other with a distance of 1.2m. The third reinforcement wall 4b is perpendicular to the foundation pit slope 4, and is at an angle of 27° with the horizontal plane; the wall direction of the third reinforcement wall 4b is consistent with the direction of the foundation pit slope 4 of the slope where it is located from the top of the slope to the slope ; The distance between two adjacent groups of third reinforcement walls 4b is 2m;

A shotcrete layer 4a is also provided on the foundation pit slope 4;

On the bottom of foundation pit 2, there is a base cushion layer 5 for open hole lining, and on the base cushion layer 5 for open hole lining, there is an open hole lining 6 for a large-span multi-arch tunnel; 6a and the side wall above the inverted arch of the open-hole lining and the arch ring 6b.

Between the foundation pit slope 4 and the open hole lining 6, a rubble concrete layer 7a and a first grouted rubble layer 7b are filled from bottom to top; a second grouting layer is arranged between the double hole intersecting vault position and the open hole lining The rubble layer 7c; the first grouted rubble layer 7b and the second grouted rubble layer 7c are at the same level as the outer top of the open tunnel lining 6;

A graded crushed stone filler layer 7d is laid on the first mortared rubble layer 7b and the second mortared rubble layer 7c; a new heavy-duty filler layer is laid on the graded crushed stone filler layer 7d and the concrete coupling beam layer 3d. Highway pavement 8; the new heavy-duty highway pavement 8 is on the same level as the original heavy-duty highway pavement 1;

Wherein, the top end of the first reinforcement wall 3b and the top end of the second reinforcement wall 3c are both arranged in the concrete connecting beam layer 3d; the bottom end of the first reinforcement wall 3b and the bottom end of the second reinforcement wall 3c are located in the open hole At least 1.5m below the bottom elevation of inverted arch 6a;

The steel pipes in the first reinforced wall 3b, the steel pipes in the second reinforced wall 3c and the steel pipes in the third reinforced wall 4b do not intersect.

Preferably, the slope ratio of the slope of the foundation pit 2 is 1:0.5. The depth of the foundation pit 2 is comprehensively determined according to the specific design location, geological conditions and other conditions. The foundation pit 2 has a bottom width of about 36m, a top width of about 50m, and a depth of about 15m.

The groove width of the road surface groove 3a is 2m, and the groove depth is 0.9m.

The concrete connecting beam layer 3d has a width of 2m and a thickness of 0.5m.

The top of the first reinforcement wall 3b and the top of the second reinforcement wall 3c both extend into the concrete connecting beam layer 3d 0.3m; At least 1.5m below the bottom elevation of the arch 6a.

The steel pipes adopted in the first reinforced wall 3b and the second reinforced wall 3c are all φ108 steel pipes;

The steel pipe used for the third reinforced wall 4b is a φ42 steel pipe with a length of 5m.

The base cushion layer 5 of the open hole lining has a thickness of 0.5m. The thickness of the rubble concrete layer 7a is 6.5m; the height of the first mortared rubble layer 7b is 5.5m; the height of the second mortared rubble layer 7c is 3m; the height of the graded crushed stone filler layer 7d is 1.2m. The minimum thickness of the 6 arch rings in the lining of the open cave is 1.1m. Reinforcement cages are all provided in the steel pipes of the first reinforced wall 3b, the steel pipes of the second reinforced wall 3c and the steel pipes of the third reinforced wall 4b.

The above are the components and implementation points of a large-span open-cut tunnel and steel pipe reinforced foundation pit composite structure suitable for passing heavy-duty highways under the utility model. The construction process is briefly described as follows:

The first step is to construct the foundation pit pre-support system: grooves are made on the road surface on both sides of the tunnel roof; φ108 steel pipes are drilled from the grooves to form the first and second reinforcement walls.

The second step is to excavate the foundation pit, and lay φ42 steel pipes on the excavated slope to form the third reinforcement wall.

The third step is the pouring of the lining of the tunnel open hole: before pouring, if the bearing capacity of the foundation does not meet the requirements, measures should be taken to deal with the foundation; then a leveling cushion is set on the base of the inverted arch; and then the lining of a hole is poured from bottom to top, and then poured Another hole is lined.

The fourth step is backfilling of the tunnel open hole: the overall sequence of backfilling is from bottom to top; backfilling must be done symmetrically, and the height difference between the backfilling soil and stone surfaces on both sides shall not be greater than 0.5m.

The fifth step, finally, restore the original pavement: re-pave the pavement layer of the heavy-duty road on the top of the hole with a gravel filler layer.

The above is the implementation steps and process of a combination structure of a large-span open-cut tunnel and a steel pipe reinforced foundation pit suitable for passing through a heavy-duty highway under the present invention.

The basic principles, main features and advantages of the present utility model have been shown and described above. Those skilled in the art should understand that the utility model is not limited by the above-mentioned embodiments. The above-mentioned embodiments and descriptions only illustrate the principle of the utility model. Without departing from the spirit and scope of the utility model, the utility model The new model also has various changes and improvements, and these changes and improvements all fall within the scope of the claimed utility model. The scope of protection required by the utility model is defined by the appended claims and their equivalents.

Claims (10)

1. A combination structure of a large-span open-cut tunnel and a steel pipe reinforced foundation pit suitable for underpassing a heavy-duty highway, characterized in that: On the road surface of the original heavy-duty road, there is a road surface groove on both sides of the driving direction of the car on the top of the foundation pit, and the bottom of the groove is horizontal; Each road surface slot is drilled downwards with a first reinforcement wall and a second reinforcement wall, and the wall direction of the first reinforcement wall and the second reinforcement wall is parallel to the driving direction of the car; The first reinforcement wall is composed of multiple steel pipes of the same size arranged in a row, two adjacent steel pipes are parallel to each other, and the distance between them is 2m; the first reinforcement wall is perpendicular to the bottom surface of the road groove; The second reinforcement wall is composed of multiple steel pipes of the same size arranged in a row, two adjacent steel pipes are parallel to each other, and the distance between them is 1m; the angle between the second reinforcement wall and the bottom surface of the road groove is 75°; Taking the bottom surface of the pavement groove as the section, the distance between the first reinforcement wall and the second reinforcement wall at the section is 1m; The lower part of the pavement groove is provided with a concrete connecting beam layer; Multiple sets of third reinforcement walls are built along the slope of the foundation pit. The third reinforcement wall is composed of multiple steel pipes of the same size arranged in a row. Two adjacent steel pipes are parallel to each other with a distance of 1.2m; the third reinforcement wall The wall is perpendicular to the slope of the foundation pit, and forms an angle of 27° with the horizontal plane; the direction of the wall surface of the third reinforcement wall is consistent with the direction of the slope of the foundation pit on the slope from the top to the bottom of the slope; the adjacent two groups of third The distance between reinforced walls is 2m; There is also a sprayed concrete layer on the slope of the foundation pit; On the bottom of the foundation pit, there is an open-hole lining base cushion, and on the base cushion of the open-hole lining, there is an open-hole lining for a large-span multi-arch tunnel; Between the slope of the foundation pit and the lining of the open hole, the concrete layer of rubble and the first layer of rubble are filled from bottom to top; the second layer of rubble is set between the lining of the open hole at the intersection of the double holes; Both the first mortared rubble layer and the second mortared rubble layer are at the same level as the outer top of the open tunnel lining; A graded crushed stone filler layer is laid on the first mortared rubble layer and the second mortared rubble layer; a new heavy-duty highway pavement is laid on the graded crushed stone filler layer and the concrete connecting beam layer; the said The new heavy-duty highway pavement is on the same level as the original heavy-duty highway pavement; Wherein, the top of the first reinforced wall and the top of the second reinforced wall are both arranged in the concrete connecting beam layer; the bottom of the first reinforced wall and the bottom of the second reinforced wall are located below the bottom elevation of the open cavity lining inverted arch; The steel pipes in the first reinforced wall, the steel pipes in the second reinforced wall and the steel pipes in the third reinforced wall do not intersect. 2. The combined structure of a large-span open cut tunnel and a steel pipe reinforced foundation pit suitable for underpassing a heavy-duty road according to claim 1, wherein the slope ratio of the slope of the foundation pit is 1:0.5. 3. The combined structure of large-span open-cut tunnels and steel pipe reinforced foundation pits suitable for underpassing heavy-duty roads according to claim 1, characterized in that: the groove width of the road surface is 2m, and the groove depth is 0.9m. 4. The combined structure of large-span open-cut tunnels and steel pipe reinforced foundation pits suitable for underpassing heavy-duty roads according to claim 3, characterized in that: the width of the concrete connecting beam layer is 2m, and the thickness is 0.5m. 5. The combined structure of a large-span open-cut tunnel and a steel pipe reinforced foundation pit suitable for underpassing a heavy-duty road according to claim 4, characterized in that: both the top of the first reinforced wall and the top of the second reinforced wall extend into the The concrete connecting beam layer is 0.3m; the bottom of the first reinforced wall and the bottom of the second reinforced wall extend into the open hole lining at least 1.5m below the bottom elevation of the inverted arch. 6. The combined structure of a large-span open-cut tunnel and a steel pipe-reinforced foundation pit suitable for underpassing a heavy-duty road according to claim 1, wherein the steel pipes used for the first reinforcement wall and the second reinforcement wall are both φ108 steel pipes ; The steel pipe used in the third reinforcement wall is φ42 steel pipe with a length of 5m. 7. The combined structure of a large-span open-cut tunnel and a steel pipe reinforced foundation pit suitable for underpassing a heavy-duty road according to claim 1, wherein the thickness of the base cushion of the open-hole lining is 0.5m. 8. The combined structure of large-span open-cut tunnels and steel pipe reinforced foundation pits suitable for underpassing heavy-duty roads according to claim 7, characterized in that: the thickness of the rubble concrete layer is 6.5m; the height of the first grouted rubble layer is 5.5m; the height of the second grouted rubble layer is 3m; the height of the graded crushed stone filling layer is 1.2m. 9. The combined structure of a large-span open-cut tunnel and a steel pipe reinforced foundation pit suitable for underpassing a heavy-duty road according to claim 7, characterized in that the minimum thickness of the open-hole lining arch ring is 1.1m. 10. The combined structure of a large-span open-cut tunnel and a steel pipe reinforced foundation pit suitable for underpassing a heavy-duty road according to claim 1, characterized in that: the inner steel pipe of the first reinforced wall, the inner steel pipe of the second reinforced wall and Steel cages are arranged in the steel pipes of the third reinforced wall; the steel pipes are perforated steel pipes that can be grouted.