Tubular pile composite foundation suitable for deep collapsible loess field and construction method thereof
Technical Field
The invention relates to the technical field of foundation treatment in collapsible loess areas, in particular to a tubular pile composite foundation suitable for a deep collapsible loess field and a construction method thereof.
Background
The problems of uneven deformation caused by consolidation settlement, humidification and wet settlement and the like after construction of the deep filled loess foundation are prominent, so that disasters such as foundation instability, building structure cracking, large deformation and the like are caused, and the service safety of an engineering structure is seriously influenced. The existing soft soil foundation treatment methods are numerous, and most of the existing soft soil foundations are not suitable for the foundation treatment of the special site. If the methods such as deep layer replacement and filling, pile foundation and the like are adopted, the treatment cost is too high, and if the methods such as dynamic compaction, replacement and the like are adopted, the bearing capacity of the treated foundation is insufficient, and the differential settlement after construction is still remarkable.
In view of the above problem, the relevant research has been started by those skilled in the art, as utility model patent application No. 201720526316.3 discloses a prefabricated porose awl type screw thread combination tubular pile, including pile body and circular aperture, the pile body includes awl type tubular pile section and cylinder threaded pipe pile section, and cylinder threaded pipe pile section sets up in the below that awl type tubular pile section is located, and the upper end external diameter of awl type tubular pile section is greater than the lower extreme external diameter of awl type tubular pile section, and the lower extreme external diameter of awl type tubular pile section is unanimous with the external diameter of cylinder threaded pipe pile section, and a plurality of circular apertures are seted up along pile body axial interval to the pile body. The invention patent with application publication number CN112392035A discloses a high-strength reinforced concrete pipe pile, which comprises a concrete pipe pile main body, a pile cap and a supporting seat, wherein the supporting seat is sleeved below the outer surface of the concrete pipe pile main body, a pipe pile hole penetrates through the supporting seat, the pile cap is sleeved above the outer surface of the concrete pipe pile main body, and a guide sleeve is fixed on the periphery of the top of the pile cap. However, the prior art only improves the pipe pile, and is still difficult to be completely suitable for the construction of deep collapsible loess fields.
Disclosure of Invention
The invention aims to provide a tubular pile composite foundation suitable for a deep collapsible loess field, which aims to solve the problems of insufficient bearing capacity and uneven settlement after construction of the existing foundation proposed in the background technology; the tubular pile composite foundation has the remarkable advantages of wide adaptability, high bearing capacity, strong deformation-resistant coordination capacity, good economy and the like.
In order to achieve the purpose, the invention provides a tubular pile composite foundation suitable for a deep collapsible loess field, which comprises a plurality of reinforcement mattress layers, a loess foundation layer and a subsidence tubular pile, wherein the subsidence tubular pile comprises a tubular pile arranged in the loess foundation layer, the top end of the tubular pile is connected with a pile cap through a connecting joint, the pile cap comprises a pile cap body and a pile cap framework arranged in the pile cap body, the pile cap framework comprises two groups of first reinforcing steel bars which are horizontally arranged from top to bottom, the two groups of first reinforcing steel bars are fixedly connected through vertical lapping reinforcing steel bars and inclined lapping reinforcing steel bars which are arranged at intervals, a plurality of second reinforcing steel bars are horizontally arranged on the lower first reinforcing steel bars, the plurality of second reinforcing steel bars are all vertically arranged with the first reinforcing steel bars, and the pile cap body is formed by pile cap concrete cast-in-place; the reinforced mattress layer is arranged on the loess foundation layer.
Furthermore, the tubular pile comprises a plurality of thread sections and a plurality of grouting sections, wherein the thread sections are arranged along the axial direction of the pile body at intervals, the grouting sections are adjacent to the thread sections, the thread sections are threads arranged on the outer surface of the pile body, and the grouting sections are a plurality of slurry leakage holes which are arranged on the pile body in a penetrating manner; closely knit packing has the thick liquid in the tubular pile, and the thick liquid passes through leak the excessive outer soil body in thick liquid hole and closely contact with around, be located the thick liquid in the tubular pile and spill over the outer thick liquid of tubular pile forms the slip casting body jointly.
Further, the depth of the thread is not less than 1.0 cm; a plurality of slurry leaking holes in each grouting section are arranged in a quincunx mode, the aperture of each slurry leaking hole is 1.0-2.0 cm, and the interval between every two adjacent slurry leaking holes is 10-20 cm.
Further, the cross section of pile cap is square or circular, the length of side or the diameter of pile cap are 3 ~ 5 times of tubular pile diameter.
Furthermore, a plurality of steel bar connecting holes are preset at the top end of the tubular pile, and one connecting joint is pre-buried in each steel bar connecting hole; the lower ends of the plurality of lap-jointed reinforcing steel bars are inserted into the corresponding reinforcing steel bar connecting holes one by one and are fixedly connected with the corresponding connecting joints.
Further, the tubular pile is prefabricated by reinforced concrete or shaped steel material and forms, the pipe diameter of tubular pile is 0.2 ~ 0.6cm, the pile length of tubular pile is 6 ~ 20 m.
Further, even interval is provided with many in the loess foundation layer reduce the heavy tubular pile, many reduce the heavy tubular pile and be in lay according to equilateral triangle or square in the loess foundation layer, adjacent two the interval of tubular pile is 0.8 ~ 2.0 m.
The invention also provides a tubular pile composite foundation construction method suitable for the deep collapsible loess field, which comprises the following steps:
s1, pressing the prefabricated pipe pile into the loess foundation layer by adopting a spiral extrusion pipe sinking method;
s2, filling grout into the tubular pile, enabling the grout to tightly fill the tubular pile, and enabling part of the grout to overflow through the grout leakage hole; slurry in the tubular pile and slurry overflowing out of the slurry leakage hole form a grouting body together;
s3, after the pipe pile construction is finished, firstly arranging a first steel bar, a vertical lapping steel bar, an inclined lapping steel bar and a second steel bar on the top of the pipe pile, and then pouring construction pile cap concrete on site to form a pile cap;
s4, repeating the steps to finish the construction of a plurality of subsidence reducing pipes in the loess foundation; coarse sand and geotechnical reinforcement materials are laid in the layered filling of the top parts of the multiple subsidence reducing pipe piles, and the construction of a reinforcement mattress layer is completed; thus obtaining the tubular pile composite foundation.
Further, in the step S2, M30 grouting mortar is filled into the pipe pile in a high-pressure grouting manner, and the mortar is diffused through the mortar leakage holes and then is in close contact with the surrounding soil body.
Further, the grouting pressure is 0.3-1.0 Mpa; in the grouting process, after the slurry overflows from the inside and the outside of the tubular pile, the orifice is sealed and pressurized for a period of time, and the grouting is stopped after the slurry overflows again.
Compared with the prior art, the invention has the following beneficial effects:
(1) the pipe pile composite foundation comprises a pipe pile, a pile cap and a connecting joint, wherein the pipe pile comprises a plurality of thread sections axially arranged along a pile body of the pipe pile at intervals and a plurality of grouting sections adjacent to the thread sections; the pile cap is beneficial to adjusting the load sharing ratio of pile soil, the thread section and the grouting section are beneficial to the close contact of the pile soil, and the synergistic effect of the pile and the soil between piles is fully exerted to bear the upper load; the tubular pile composite foundation has better anti-settling, anti-differential-settling and deformation coordination capabilities, has remarkable advantages particularly in deep filling collapsible loess areas, and can also be applied to foundation treatment in other soft soil areas.
(2) The pipe pile composite foundation of the invention is mainly formed by prefabricating and assembling reinforced concrete or section steel materials, adopts a spiral extrusion pipe sinking method to directly press the pipe pile composite foundation into a loess foundation, and has the advantages of simple and convenient manufacture, material saving, quick construction, economy, reliability and the like. The invention can adjust the size of the tubular pile structure according to the engineering requirements, is flexibly arranged, and improves the strength and rigidity properties of the tubular pile structure so as to meet the foundation bearing requirements under different conditions.
(3) The construction method of the invention fills slurry into the tubular pile in a high-pressure grouting mode, and the slurry is diffused through the slurry leakage hole and then forms a grouting body with the surrounding soil body; the screw thread section of the pile body of the sink pipe pile is embedded into the soil around the pile in the spiral extrusion sink pipe, and the friction effect around the pile is improved by embedding the reinforced pile soil contact effect; the pile cap is additionally arranged on the pile top, so that the pile-soil load sharing ratio can be adjusted; the invention fully exerts the synergistic effect of the tubular pile and the soil between the piles, so that the vertical bearing performance of the composite foundation is obviously improved, and the vertical bearing performance of the composite foundation is further improved; the bearing capacity and deformation resistance of the deep fill loess foundation can be improved and solved, and the safety of buildings in the deep fill loess field can be ensured.
In addition to the objects, features and advantages described above, other objects, features and advantages of the present invention are also provided. The present invention will be described in further detail below with reference to the drawings.
Drawings
The accompanying drawings, which are included to provide a further understanding of the embodiments of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the embodiments of the invention without limiting the embodiments of the invention. In the drawings:
FIG. 1 is a schematic structural view of a pipe pile composite foundation according to a preferred embodiment of the present invention;
FIG. 2 is a schematic view of a single-pile sinking reducing pipe pile composite foundation according to a preferred embodiment of the present invention;
FIG. 3 is a cross-sectional view of a sink reducing pipe pile according to a preferred embodiment of the present invention;
FIG. 4 is a schematic view of a structure of a pile cap of a sinking reduction pipe pile according to a preferred embodiment of the present invention;
FIG. 5 is a schematic view of a structure of a sink reducing pipe pile connection joint according to a preferred embodiment of the present invention;
fig. 6 is a schematic plan view of a subsidence pipe pile according to a preferred embodiment of the present invention;
wherein, 1-reducing and sinking tubular pile, 101-tubular pile, 102-pile cap, 10201-first reinforcing steel bar, 10202-vertical overlap reinforcing steel bar, 10203-inclined overlap reinforcing steel bar 10204-second reinforcing steel bar, 10205-pile cap concrete, 103-screw thread, 104-slurry leakage hole, 105-grouting body, 106-connecting joint, 2-reinforcing mattress layer and 3-loess foundation.
Detailed Description
Embodiments of the invention will be described in detail below with reference to the drawings, but the invention can be implemented in many different ways, which are defined and covered by the claims.
Referring to fig. 1 to 6, a tubular pile composite foundation suitable for a deep collapsible loess field includes a subsidence reducing tubular pile 1, a reinforcement mattress layer 2 and a loess foundation layer 3; the concrete structure is as follows:
constructing a plurality of subsidence reducing tubular piles 1 in the loess foundation layer 3 by adopting a spiral extrusion pipe sinking method, wherein each subsidence reducing tubular pile comprises a tubular pile 101, a pile cap 102, a grouting body 105 and a connecting joint 106; the tubular pile 101 is arranged in the loess foundation layer 3, the tubular pile is preferably prefabricated by reinforced concrete or section steel materials, and taking a precast concrete tubular pile as an example, the preferred pipe diameter is 0.2-0.6 cm, the wall thickness is 5-15 cm, the distance between the tubular piles is 0.8-2.0 m, and the pile length is 6-20 m, as shown in fig. 2 and 3. The pile cap 102 is made of cast-in-place reinforced concrete, the pile cap comprises a pile cap body and a pile cap framework arranged in the pile cap body, the pile cap framework comprises two groups of first reinforcing steel bars 10201 which are horizontally arranged up and down, and the two groups of first reinforcing steel bars are fixedly connected through vertical lapping reinforcing steel bars 10202 and inclined lapping reinforcing steel bars 10203 which are arranged at intervals; the level is equipped with many second reinforcing bars 10204 on the first reinforcing bar under, and many second reinforcing bars all set up with first reinforcing bar is perpendicular, and the pile cap body is pour in situ by pile cap concrete 10205 and forms. The cross section of the pile cap is square or circular, the side length or the diameter of the pile cap is 3-5 times of the diameter of the tubular pile, and the figure 4 shows. A plurality of steel bar connecting holes are preset at the top end of the tubular pile, a connecting joint 106 is pre-buried in each steel bar connecting hole, each connecting joint is a steel bar, and the length of each connecting joint 106 is not less than 15 cm. The lower ends of the multiple overlapping reinforcing steel bars are inserted into the corresponding reinforcing steel bar connecting holes one by one and fixedly connected with the pre-buried connecting joints, and then concrete is poured to complete the connection between the pile cap 102 and the tubular pile 101, as shown in fig. 5. Slurry is filled into the tubular pile in a high-pressure grouting mode, so that the subsidence reducing tubular pile 1 can be fully contacted with a loess foundation layer to better play a common role. And a reinforced mattress layer 2 with the thickness of 0.3-1.0 m is laid at the pile top of the sinking reduction tubular pile 1, so that the tubular pile composite foundation can be formed through the joint bearing effect of the piles and the soil between the piles.
In the preferred embodiment of the invention, the tubular pile comprises a plurality of threaded sections arranged at intervals along the axial direction of the pile body of the tubular pile and a plurality of grouting sections adjacent to the threaded sections, the threaded sections are deep groove threads 103 prefabricated on the surface of the pile body of the tubular pile, and the thread depth is not less than 1.0 cm. The slip casting section is for running through on the pile body and set up a plurality of hourglass thick liquid holes 104, prefers to leak thick liquid hole at the prefabricated aperture 1.0 ~ 2.0cm of tubular pile body interval 10 ~ 20cm, and a plurality of hourglass thick liquid holes are arranged in quincunx.
In the preferred embodiment of the present invention, the pipe pile is densely filled with slurry, and the slurry overflows through the slurry leaking holes and is in close contact with the surrounding soil, and the slurry in the pipe pile and the slurry overflowing out of the pipe pile together form the grouting body 105. Specifically, the interior of the subsidence reducing pipe pile 1 is filled with M30 cement mortar grouting body, the cement mortar can be closely contacted with the surrounding soil body after overflowing through the mortar leakage hole 104, and the grouting pressure can be 0.3-1.0 MPa; after the slurry overflows from the inside and the outside of the tubular pile 101, the orifice is closed and pressurized for a period of time, and the injection is stopped after the slurry overflows again.
In a preferred embodiment of the invention, a plurality of subsidence reducing pipe piles are arranged in the loess foundation layer, the plurality of subsidence reducing pipe piles are arranged in the loess foundation layer according to an equilateral triangle or a square, and the distance between two adjacent pipe piles is 0.8-2.0 m. The tubular pile 101 is directly pressed into the loess foundation layer 3 by adopting a screw extrusion sinking method, and then a pile cap 102 is constructed in a cast-in-place mode, as shown in fig. 6; in order to further enhance the rigidity of the pile body of the sinking-reducing pipe pile 1, a steel reinforcement cage can be additionally arranged in the pile body.
In the preferred embodiment of the present invention, the connection portions of the members can be welded or bolted firmly, and if the structural steel members are adopted, the surfaces of the structural steel members are all subjected to corrosion prevention treatment.
According to the tubular pile composite foundation applicable to the deep collapsible loess field, the threaded section of the pile body of the sinking tubular pile is embedded into the soil body around the pile in the spiral extrusion sinking pipe, and the friction effect around the pile is improved by embedding the reinforced pile soil contact effect; the pile cap is additionally arranged on the pile top, so that the pile-soil load sharing ratio can be adjusted. The invention can fully play the synergistic effect of the tubular pile and the soil between the piles, so that the vertical bearing performance of the composite foundation is obviously improved.
The invention relates to a vertical bearing mechanism of a tubular pile composite foundation suitable for a deep collapsible loess field, which comprises the following steps: the upper building load is transmitted to the reinforced mattress layer 2, the load is transmitted to the sinking reduction tubular pile 1 and the loess foundation 3 through the uniformly distributed load effect of the reinforced mattress layer 2, the contact effect of the sinking reduction tubular pile 1 and the surrounding soil body is enhanced through the pile cap 102, the threads 103 and the grouting body 105, and then the synergy of the tubular pile and the soil between the piles is fully played to bear the upper load.
The invention relates to a construction method of a tubular pile composite foundation suitable for a deep collapsible loess field, which comprises the following steps:
s1, pressing the prefabricated pipe pile 101 into the loess foundation layer by adopting a spiral extrusion pipe sinking method;
s2, filling grout into the tubular pile in a high-pressure grouting mode to enable the grout to tightly fill the tubular pile, enabling part of the grout to overflow through the grout leakage holes 104, and enabling the overflowing grout to be in close contact with the surrounding soil body; slurry in the pipe pile and slurry overflowing out of the slurry leakage hole form a grouting body 105; preferably, M30 cement mortar grouting body is adopted to fill the interior of the tubular pile, and the grouting pressure can be 0.3-1.0 Mpa; after the slurry overflows from the inside and the outside of the tubular pile, the orifice is closed and pressurized for a period of time, and the injection is stopped after the slurry overflows again.
S3, after the construction of the tubular pile is finished, firstly arranging a first reinforcing steel bar 10201, a lapping reinforcing steel bar 10202 and a second reinforcing steel bar 10203 at the top of the tubular pile, and then pouring construction pile cap concrete 10204 in situ to form a pile cap 102;
s4, repeating the steps S1-S3, and finishing constructing a plurality of reducing and sinking tubular piles 1 in the loess foundation; coarse sand and geotechnical reinforcement materials are laid in the layered filling of the top parts of the multiple subsidence reducing pipe piles, and the construction of the reinforcement mattress layer 2 is completed; thus, the pipe pile composite foundation is obtained.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.