CN212225255U - Large-scale filling type karst cave geological tunnel foundation reinforcing structure - Google Patents

Abstract

A multi-column grouting steel pipe pile is arranged at the bottom of an inverted arch of a tunnel along the length direction of the tunnel and penetrates into an underground bedrock or a soil body with a certain depth, a graded broken stone cushion layer is laid above the steel pipe pile at the bottom of the tunnel, and a concrete bearing platform is poured above the graded broken stone layer. The utility model can meet the requirements of construction quality and service life of the karst cave geological tunnel foundation, has high bearing capacity, effectively controls the sinking of the filling type karst cave geological tunnel foundation, has good mechanical property of the cast-in-place pile, is not easy to break the pile, and effectively controls the phenomenon of hole collapse and hole blocking in the hole forming process of the cast-in-place pile; the whole foundation reinforcing structure is beneficial to maintaining the stability of water and soil in the tunnel mountain body and does not influence the natural water system environment.

Description

Large-scale filling type karst cave geological tunnel foundation reinforcing structure

Technical Field

The utility model relates to a tunnel foundation construction technical field specifically is a large-scale filling type solution cavity geological tunnel foundation reinforced structure.

Background

The highway is constructed in the karst landform mountain area, bridges need to be bridged when meeting water, holes need to be opened when meeting mountains, the bridge-tunnel ratio is even as high as 80%, tunnel engineering often needs to pass through unfavorable geology such as karst caves and underground rivers due to the development of mountain karsts, and due to the development influence of underground river watershed, a large amount of soft soil such as sandy soil, clay layers, black soil layers and clay breccid gravels are filled in the large karst caves. Because the bearing capacity of the soft soil layer is insufficient, the foundation is soft, and the bearing requirement of the pavement cannot be met, the karst cave geology needs to be reinforced. In a strong karst development area, a tunnel passes through a mountain and belongs to karst peak cluster landform, the landform of the mountain is complex, the geology inside the mountain is complex and changeable, and the tunnel often meets compact small karst caves and karst tanks and has no filler karst caves or filler type karst caves for foundation reinforcement.

At present, the method for treating the soft karst foundation at the bottom of the tunnel generally comprises a bridge spanning method and a root pile foundation reinforcing method. The bridge crossing method is to cross a soft soil zone by adopting a structure of an elevated bridge, but the operation space in a tunnel is limited, a large filling type karst cave is not suitable for the situation that a tunnel primary support bears large surrounding rock load, the construction period is long, the requirement on the geological situation of a tunnel base is strict, and the construction cost is high. The root pile reinforcing method is a foundation reinforcing method of small-diameter cast-in-place pile formed by using grouting method, and the formed pile is named as 'root', its required operation space is small, disturbance to original foundation is small, application range is extensive, etc. it has extensive application for treating various soft foundations.

When the reinforcing method of the tree root piles is used for reinforcing the tunnel foundation of the karst filling type karst cave landform, certain difficulties can still be encountered: 1. the large filling type karst cave is huge in internal space, a large amount of soft soil is filled, when a cast-in-place pile penetrates through the soft soil in the inner cavity of the karst cave, the soft soil cannot well support the side wall of the cast-in-place pile, namely, the cast-in-place pile is in a suspended state for a long section of length, and the cast-in-place pile without reinforcing steel bars is easy to break under the state that the side wall is not sufficiently supported; compared with a cast-in-place pile without a reinforcement cage, the reinforcement cage is arranged in the cast-in-place pile, so that the strength of the cast-in-place pile can be greatly improved, the pile breakage can be prevented, particularly on the road surface of a highway tunnel and the road section of a large-sized load-carrying truck, and the strength of the cast-in-place pile determines the bearing capacity of the road surface; when the reinforcement cage is placed in the pouring hole with the diameter smaller than 300mm, the reinforcement cage is difficult to place due to overlarge depth, the size of the reinforcement cage is small, the length-to-diameter ratio is overlarge, the manufacturing process is time-consuming and labor-consuming, and the like; 2. in the karst landform underground water vein and the high karst cave region, hole collapse is easy to occur when the karst cave is densely drilled, so that cast-in-place piles are repeatedly blocked, hole cleaning is very difficult, and the construction period is greatly prolonged. Therefore, the reinforcing construction of the tunnel foundation with karst cave landform has been a troublesome problem to be placed in front of constructors.

Disclosure of Invention

The utility model provides a large-scale filling type solution cavity geological tunnel foundation reinforced structure can satisfy the requirement of the construction quality and the life-span of large-scale filling type solution cavity geological tunnel foundation, and bearing capacity is high, controls karst section tunnel basement sinking effectively, and bored concrete pile mechanical properties is good, is difficult for disconnected stake, and the phenomenon of hole blocking takes place of collapsing is effectively controlled in the bored concrete pile pore-forming process; the whole foundation reinforcing structure is beneficial to maintaining the stability of water and soil in the tunnel mountain body and does not influence the natural water system environment.

In order to achieve the above purpose, the technical scheme of the utility model is as follows:

large-scale filling type solution cavity geological tunnel foundation reinforced structure arranges multiseriate slip casting steel pipe pile and goes deep into underground bedrock or go deep into certain degree of depth soil body along tunnel length direction at tunnel invert bottom, lays the level and joins in marriage the metalling above the steel pipe pile of tunnel bottom, pours above the level and joins in marriage the metalling and lays the concrete cushion cap. And constructing tunnel inverted arch primary support, inverted arch backfill and drainage facilities above a bearing platform formed by the graded broken stone cushion layer above the steel pipe pile and concrete, and finally constructing a tunnel pavement structure. The dead weight of the tunnel structure and the automobile load on the road surface are transmitted to the steel pipe pile through the bearing platform, and therefore the tunnel supporting structure and the tunnel road surface collapse phenomenon are avoided.

The multiple columns of grouting steel pipe piles are vertically downward from the middle of the multiple columns of grouting steel pipe piles, and the multiple columns of grouting steel pipe piles on the left side and the right side of the center line of the tunnel incline downward from two sides. The upward supporting function is greatly strengthened, the bearing platform at the top of the steel pipe pile is kept not to sink or collapse, and the whole steel pipe pile group does not deviate and skew.

The angle of the inclined angle of the two adjacent lines of the grouting steel pipe piles at the left side and the right side of the central line of the tunnel is 3 degrees larger than that of the inclined angle of the two adjacent lines of the grouting steel pipe piles at the outer side. Different inclination angle settings make the grouting steel pipe pile structure of downward divergent radiation type more perfect, and the bearing capacity is higher. It should be noted that if the grouting steel pipe piles on the two sides do not reach the bedrock, the length of the grouting steel pipe piles is not less than 28 m; and if the middle steel pipe pile does not reach the bedrock, the length of the middle steel pipe pile is not less than 15 m. If the grouting steel pipe pile is embedded into the bedrock, a solid supporting force foundation is directly provided for the bearing platform above, if the grouting steel pipe pile does not reach the bedrock, the length of the grouting steel pipe pile needs to be ensured to enable the grouting steel pipe pile to penetrate into the soil body, and the supporting force is provided for the bearing platform above by utilizing the static friction force between the grouting steel pipe pile and the soil body.

And a double-layer reinforcing mesh is arranged in the concrete bearing platform. The double-layer reinforcing mesh ensures that the bearing platform can still provide stronger tensile stress when bearing slight settlement acting force, and prevents the concrete bearing platform from cracking.

The grouting steel pipe pile is a composite structure obtained by coating a patterned steel pipe with concrete after grouting and solidification. The structure has the mechanical property and the strength of conventional reinforced concrete, is not easy to break a pile, is quick and convenient to install, and simultaneously provides a sunk channel for the grouting pipe.

The construction method of the large filling type karst cave geological tunnel foundation reinforcing structure comprises the following steps: the method comprises the following steps:

A. and (3) field measurement lofting: determining the pile position of each grouting steel pipe pile, and determining a drilling point; in the field measurement lofting process, in order to ensure the accurate positioning of a drilling point, a log with the diameter of 4cm and the length of 50cm is driven into the lofting point to be accurately positioned; according to a hole distribution plan of the grouting steel pipe pile, the transverse distance between pile positions on two sides of the tunnel is 70cm, and the transverse distance between pile positions in the middle is 100 cm; the maximum longitudinal distance between pile positions is 85 cm; the field pile position measurement lofting needs to be carried out strictly according to design parameters, and the pile position and the distance between the steel pipe piles cannot be changed at will so as to avoid reducing the requirement on the bearing capacity of the foundation; numbering each steel pipe pile, after measurement and lofting, before a drilling machine is in place, retesting the lofting point, and performing the next process after a field technician reports and supervises an engineer to check and recheck so as to ensure the position accuracy of the lofting point.

B. Drilling: drilling holes at the determined drilling points in batches at intervals, wherein the drilling hole intervals are staggered by 2 hole sites; according to the field condition, the drilling can not be carried out in sequence, the drilling needs to be carried out in a staggered mode, the drilling intervals are staggered by 2 hole positions, and the mutual interference in the drilling process is avoided. The drilling angle of the general inclined pile needs to be adjusted according to the performance of a drilling machine and the angle of the pile, and the drilling machine can be adjusted by the crawler-type semi-automatic multifunctional drilling machine according to the sequence of centering, leveling and fixing, so that the drilling machine is flexible. The allowable deviation of the equipment in the positioning and centering process is 2cm, and the verticality deviation of the active drill rod in the drilling process is less than 1%. After the crawler-type semi-automatic multifunctional drilling machine is in place, the direction of the drilling machine and the angle of a drill arm shaft are adjusted according to a drilling inclination angle and a drilling direction designed by construction, and the deviation of a pile position is required to be not more than +/-20 mm; the allowable deviation of the verticality of the vertical pile and the inclination of the inclined pile is not more than 1%, and the inclination of the inclined pile is correspondingly adjusted according to the design requirement.

C. Cleaning and checking holes: after hole forming, concentrated hole cleaning is carried out by adopting high-pressure air until no dust or gravel is blown out from an orifice, and then pile foundation drilling depth and hole cleaning acceptance check are carried out;

D. installing a steel perforated pipe: steel perforated pipes are arranged in the pile holes section by section, and secondary grouting pipes are pre-buried outside the pipes when the steel perforated pipes are installed; the steel perforated pipe is 4m long, and phi 15mm grouting holes are alternately drilled on the periphery of the pipe wall at intervals of 15 cm; the two ends of the steel perforated pipe are provided with teeth, and the two ends of the steel pipe are connected by an outer sleeve; when the steel perforated pipes are installed, 1 through long perforated iron sheet pipe is pre-buried outside the pipes to serve as secondary grouting pipes, and the steel perforated pipes are installed in batches.

E. Primary grouting: preparing a grouting machine and a pulping device on site by adopting a mode of grouting from bottom to top, stirring the grouting material on site to prepare the slurry, inserting a grouting pipe from the middle of a steel perforated pipe to the bottom of the pile, then starting grouting under the pressure of 0.3-1.0Mpa, and making the slurry flow upwards from the bottom of the hole until the slurry flows out of the orifice to stop grouting; because the diameter of the grouting steel pipe pile is smaller, the strength of the pile body backfill material is required to reach more than 35MPa according to the design requirement, the concrete construction process is limited in the miniature steel pipe pile, and in order to ensure that the strength of the pile body backfill material meets the requirement, the precast beam tension method prestressed pipe (hole) grouting and grouting material is determined to be adopted as the backfill material of the grouting steel pipe pile. The grouting material has the characteristics of excellent fluidity, stable slurry, good filling degree, adjustable setting time, no shrinkage and micro-expansion, high strength, no harmful substances to the steel pipe and the like; in order to ensure the construction mixing proportion of the pile body grouting material and the mechanical property, the workability and the durability of the formed steel pipe pile, the solidification time of the grouting material is regulated and controlled within 3-5 hours. Preparing a grouting machine and a pulping device on site, preparing enough grouting materials, and mixing the grouting liquid on site. During grouting, a grouting pipe is inserted from the middle of a phi 108 steel pipe to reach the bottom of the pile, then grouting is started, a retreating grouting method can be used, the first grouting pressure is controlled to be 0.3-1.0MPa, and the grout is made to flow upwards from the bottom of the hole until the grout flows out of the orifice and stops grouting. When the backfill material is ejected to the position of the hole opening, and the grout on the periphery of the steel pipe is ejected uniformly, the grouting is considered to be compact, and then the grouting pipe is pulled out. Because the slurry has better fluidity, the slurry rises from the bottom of the pile, and the compactness of the pile body is ensured. And after grouting of one steel pipe pile is finished, grouting of the next steel pipe pile. After grouting is finished, construction needs to be suspended, and the grouting pipe is timely cleaned.

F. Secondary grouting: before the primary grouting slurry is initially set, secondary grouting is carried out, and the slurry is injected into the bottom of a pile hole from a secondary grouting pipe by a grouting machine under the pressure of 2-4 MPa; after grouting is finished, if grout is solidified and retracted or falls back, timely supplementing grouting; the secondary grouting uses higher pressure to fill gaps at all corners of a pile hole with grout, so that pile body materials are more compact and pile breakage is prevented; the steel pipe pile is tightly combined with the pile hole, the static friction force is larger, and the supporting capacity is greatly increased; on the other hand, the slurry permeates into the surrounding soil body to generate countless fine dendritic structures, so that the contact area is further increased, and the bearing and supporting capacity is increased.

G. After one batch of grouting is finished, after the grouting slurry is initially set, then carrying out next batch of drilling construction;

H. and (3) tunnel ground construction: and after the grouting of the steel pipe pile is completed, cutting the exposed steel pipe head, excavating the tunnel bottom, paving graded broken stones on the pile top, paving a reinforcing mesh above the graded broken stones, and then pouring a concrete bearing platform to complete the construction of the karst cave geological tunnel foundation reinforcing structure. And after the pile body is backfilled with grouting material and reaches a certain strength, chiseling 40-60cm of material of the pile top, exposing a steel pipe at the pile top, cutting off the head of the steel pipe, and clearing the bottom by using a small excavator. And then, paving graded broken stones meeting the specification and design requirements on the bottom layer, wherein the maximum nominal grain size of the broken stones is less than 3cm, and the thickness of the graded broken stones is 30 cm. After the graded broken stone cushion layer is paved, a double-layer phi 16 reinforcing mesh is paved, and then when the concrete bearing platform is poured, the space between the reinforcing meshes in the bearing platform and the thickness of the protective layer are ensured to meet the standard requirements.

And D, during drilling in the step B, a steel sleeve protection wall follow-up method is adopted in the drilling process, in the primary grouting in the step E, the steel sleeve is lifted while stirring and grouting in the grouting process, and the steel sleeve is cleaned in time after being lifted. As the karst cave filling at the bottom of the tunnel is the clay clamping stone, the water content of the clay is high, in order to prevent hole collapse or hole shrinkage in the drilling process, the diameter of the steel sleeve is slightly smaller than that of the drilled hole in the drilling process, and the steel sleeve is pulled out after grouting and is recycled; when drilling, the diameter of the drill hole of the selected drill bit is slightly larger than the outer diameter of the steel sleeve, and after the drilling depth reaches the design requirement or the rock entering depth is larger than 2.0m, the steel sleeve follows up in time to prevent hole collapse or hole shrinkage and influence on the diameter of the drill hole.

And D, in the step D, installing the steel perforated pipes, welding a plurality of stiffening hoops around each section of steel perforated pipe to ensure that the steel perforated pipes are centered in the pile holes.

And D, mounting the steel perforated pipe, and processing 3-5 grouting holes with the diameter of 3.5-4.5cm in a staggered mode within the range of 1m of the length of the bottom of the steel perforated pipe so as to facilitate flowing grouting of slurry.

And D, in the step D, installing the steel perforated pipe, welding a plurality of reinforcing steel bars with the length of 45-55cm at the bottom end of the steel perforated pipe so as to form a certain space between the bottom of the pipe and the bottom of the hole and facilitate the slurry to flow out of the bottom of the pipe and flow out of the bottom of the hole.

Before the secondary grouting in the step F, plugging the pipe orifice at the upper end of the steel perforated pipe and the space between the outer wall of the steel perforated pipe and the inner wall of the pile hole top by using rubber plugs; and the gap between the inner wall of the pile hole top and the rubber plug is sealed and consolidated by water glass so as to prevent secondary grouting and slurry seepage.

The utility model discloses the advantage that possesses:

1. after the cast-in-place pile is formed, a structure that the solidified grouting material wraps the steel flower tube is formed, the steel flower tube is used as a concrete framework and is combined with the cast-in-place pile into a whole, and the mechanical property and the fracture resistance of the cast-in-place pile are greatly improved; meanwhile, the steel perforated pipe is used as a filling channel, so that the steel perforated pipe can easily enter the deep part of a pile hole, a smooth passage is provided for a subsequent entering grouting pipe, and the condition that the grouting pipe cannot be lowered due to friction with a rough hole wall is avoided.

2. In the drilling process, the steel sleeve is drilled by adopting a steel sleeve follow-up method, the phenomenon of frequent collapse and hole burying in the drilling process is effectively prevented, and finally the steel sleeve can be taken out and cleaned for use after the first grouting, so that the material consumption and waste are avoided.

3. The utility model discloses the mudjacking material who uses has excellent mobility, and the slurry is stable, and is full of, and the setting time is adjustable, does not have shrink, little inflation, and intensity is high, does not contain characteristics such as harmful substance to the steel pipe, has better closely knit degree, rigidity and intensity for traditional cast-in-place concrete, and the mudjacking slurry spreading capacity is stronger, and the usage is extensive, practicality, strong adaptability.

The performance requirements of the press mortar are as follows:

3. the construction method is specially used for the construction of large filling type karst cave foundations of tunnels in mountainous areas, the divergent radiation type cast-in-place piles have stronger bearing capacity than common tree root piles, are combined with upper gravel layers and concrete bearing platforms into a whole, the construction safety and the construction quality of the tunnel foundations are guaranteed, the requirements of meeting the structure safety and the service life are met, the sinking of the tunnel foundations of karst sections is effectively controlled, and the tunnel structures are effectively prevented from sinking and cracking of two linings.

Description of the drawings:

FIG. 1 is a view of the overall structure of the present invention;

FIG. 2 is a side view of the whole structure of the present invention;

FIG. 3 is a top view position structure diagram of a grouting steel pipe pile;

FIG. 4 is a schematic structural diagram of a grouting system;

FIG. 5 is a schematic side sectional view of a grouting steel pipe pile (before primary grouting);

3 FIG. 3 6 3 is 3 a 3 schematic 3 view 3 of 3 the 3 cross 3- 3 sectional 3 structure 3 A 3- 3 A 3 of 3 FIG. 35 3; 3

FIG. 7 is a schematic side sectional view of a grouting steel pipe pile (after primary grouting);

FIG. 8 is a flow chart of the steps of the construction method of the present invention;

1. a slurry filter; 11. a slurry funnel; 12. a primary filter hopper; 13. a secondary filter hopper; 21. grouting machine; 22. a pressure gauge valve; 23. a grouting pipe; 24. grouting return pipes; 25. a secondary grouting pipe; 31. a concrete cap; 32. a reinforcing mesh; 33. grading broken stone; 41. obliquely grouting the steel pipe pile; 42. directly grouting the steel pipe pile; 5. steel casing; 6. a steel floral tube; 61. a stiffening hoop; 62. reinforcing steel bars; 63. a rubber plug A; 64. a rubber plug B; 65. water glass.

Detailed Description

Example 1

According to the large filling type karst cave geological tunnel foundation reinforcing structure, multiple rows of grouting steel pipe piles are arranged at the bottom of an inverted arch of a tunnel along the length direction of the tunnel and penetrate into underground bedrock or soil body with a certain depth, a graded gravel layer is laid above the steel pipe piles at the bottom of the tunnel, and a concrete bearing platform is poured and laid above the graded gravel layer;

the middle columns of the grouting steel pipe piles are vertically downward, and the left and right sides of the center line of the tunnel are inclined downward;

the angle of the inclined angle of the two adjacent lines of the grouting steel pipe piles at the left side and the right side of the central line of the tunnel is 3 degrees larger than that of the inclined angle of the two adjacent lines of the grouting steel pipe piles at the outer side;

a double-layer reinforcing mesh is arranged in the concrete bearing platform;

the grouting steel pipe pile is a composite structure obtained by coating a patterned steel pipe with concrete after grouting and solidification.

Claims (5)

1. Large-scale filling type solution cavity geological tunnel foundation reinforced structure, its characterized in that: arranging a plurality of rows of grouting steel pipe piles at the bottom of an inverted arch of the tunnel along the length direction of the tunnel to penetrate into an underground bedrock or a soil body with a certain depth, paving a graded broken stone cushion layer above the steel pipe piles at the bottom of the tunnel, and pouring and paving a concrete bearing platform above the graded broken stone layer.

2. The large-scale filling type karst cave geological tunnel foundation reinforcing structure according to claim 1, characterized in that: the multiple columns of grouting steel pipe piles are vertically downward from the middle of the multiple columns of grouting steel pipe piles, and the multiple columns of grouting steel pipe piles on the left side and the right side of the center line of the tunnel incline downward from two sides.

3. The large-scale filling type karst cave geological tunnel foundation reinforcing structure according to claim 2, characterized in that: the angle of the inclined angle of the two adjacent lines of the grouting steel pipe piles at the left side and the right side of the central line of the tunnel is 3 degrees larger than that of the inclined angle of the two adjacent lines of the grouting steel pipe piles at the outer side.

4. The large-scale filling type karst cave geological tunnel foundation reinforcing structure according to claim 1, characterized in that: and a double-layer reinforcing mesh is arranged in the concrete bearing platform.

5. The large-scale filling type karst cave geological tunnel foundation reinforcing structure according to claim 1, characterized in that: the grouting steel pipe pile is a composite structure obtained by coating a patterned steel pipe with concrete after grouting and solidification.

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