CN111980016A

CN111980016A - Stiff cement soil support pile and construction method thereof

Info

Publication number: CN111980016A
Application number: CN202010845135.3A
Authority: CN
Inventors: 于小娟; 吴海龙; 殷勇
Original assignee: Yancheng Institute of Technology
Current assignee: Yancheng Institute of Technology
Priority date: 2020-08-20
Filing date: 2020-08-20
Publication date: 2020-11-24

Abstract

The invention relates to a stiff cement soil supporting pile and a construction method thereof, wherein the supporting pile comprises a plurality of supporting single piles arranged in a row, any two adjacent supporting single piles are overlapped together, a stiff framework made of cotton straws is arranged in each supporting single pile, the stiff framework is of an I-shaped or double I-shaped framework structure, and the supporting pile can improve the bending strength and the shearing strength on the basis of ensuring low cost, so that the dual effects of retaining water and retaining soil can be exerted; the method adopts a jump driving construction method for construction, adopts a rotary pile driving construction method when single pile forming construction is carried out, but when the construction of a single pile for supporting an even number of single piles is carried out for hole digging, an umbrella-shaped flexible steel wire brush is arranged on a hole digging drill bit which is driven into the soil in a rotating mode, the outer diameter of the hole digging drill bit is smaller than the diameter of the flexible steel wire brush, the outer diameter of the flexible steel wire brush is the diameter of a pile to be formed, and the method can solve the problem of drilling and tube inserting of cement soil at the overlapping position of two adjacent cement soil piles.

Description

Stiff cement soil support pile and construction method thereof

Technical Field

The invention relates to a stiff cement soil support pile and a construction method thereof, and belongs to the technical field of foundation pit and side slope support.

Background

The cement soil pile is a pile body between soil body and concrete row pile, and can play a certain role in retaining soil while being generally used as a water-stop curtain for retaining water. The basic principle of cement reinforced soil is based on the physical and chemical reaction process of cement reinforced soil, it is different from concrete hardening mechanism, because of less cement mixing amount, the cement is reacted under the surrounding of soil which is a certain active medium, the hardening speed is slow, the action is complex, after the cement is hydrolyzed and hydrated to generate various hydrate, some of them can produce ion exchange and aggregation action and coagulation reaction, so that the strength of cement soil body can be greatly raised.

The cement-soil pile method is widely applied to the fields of foundation treatment, foundation pit or side slope support engineering. In the foundation pit engineering, the cement soil pile can play a certain role in retaining soil and can also play the roles of retaining water and stopping water, and the cement soil pile is a supporting and retaining structure which is simple and convenient to construct and low in cost. From the material strength perspective, although the compressive strength of the in-situ soil body can be increased by the doping of cement in a certain proportion, as the retaining structure, the bending strength of the retaining system after pile formation cannot meet the engineering requirements of the retaining structure due to the fact that the tensile strength of the cement soil is weak, so that in the actual foundation pit retaining engineering, a pure cement soil pile is mainly used as a waterproof curtain due to weak links such as low shear strength, poor bending resistance and the like, and the retaining effect of the cement soil pile is generally not considered. In contrast, it has been proposed that the soil retaining ability of a cement-soil pile is proportional to the amount of cement mixed, and the bending strength of the cement-soil pile can be improved by increasing the amount of cement mixed or by increasing the cross-sectional area of the cement-soil mixing pile. However, the method has the disadvantages of being uneconomical, inconvenient to construct and the like, for example, the increase of the section of the cement-soil pile is limited by the capacity of construction machinery and the limitation of a site and the like.

In order to improve the bending rigidity of the cement soil supporting pile, experts and engineers propose that H-shaped steel, I-shaped steel, channel steel or Larsen steel plate and the like are inserted into the solidified pile core, or a reinforcement material such as bamboo is inserted into the center of the solidified pile core so as to obviously improve the bending strength and the shearing strength of the solidified pile core, so that the soil retaining effect of the solidified pile core can be fully exerted, and the effects are verified by some practical engineering. Although these measures of adding the reinforcing bars can enhance the engineering properties of the cement-soil mixing pile, still have some disadvantages: in the aspect of reinforcing and curing piles by using section steel, I-shaped steel and the like, the using process of the reinforcement relates to a plurality of links such as leasing, entering and leaving, driving, back-drawing and the like, and the using cost is high; in addition, because of cost reasons, the section steel needs to be pulled out (pulled back) in the later period, but the section steel is difficult to pull out, and the ground disturbance is easily caused. Secondly, in the aspect of reinforcing and curing the pile by using moso bamboo and the like, the defects of the pile comprise: 1) the bamboo is uneven material, different parts have different influences on the physical and mechanical properties of the curing pile, the length is limited, and the tip part is too thin, so the utilization section of the bamboo is limited; 2) the connection reliability and convenience between the bamboo woods are deficient, and the connection is limited by the length of the bamboo woods, so that the reinforcement length of the bamboo woods is limited.

The common construction method of reinforced cement soil support piles (stiff cement soil piles) is to mix cement and soft soil on site, insert section steel or other reinforcing materials, and pull out the section steel after the support engineering is finished. This construction method has some drawbacks: the on-site cement soil stirring machine is heavy and inconvenient to construct, and the machine is inconvenient to enter when the soft soil strength of the on-site is very low. In addition, the later-stage steel bar pulling-out construction wastes time and labor, and can also cause disturbance to soil bodies around the foundation pit. In contrast, another construction method for stiff cement-soil piles is proposed: according to the construction method of the rotary excavating pile, firstly, holes are dug, then, the steel pile casing retaining wall is driven, then, the holes are cleaned, then, the stiff material is inserted into soil, finally, the mixed materials of the stirred soft soil, the cement, the additives and the like are poured into the steel pile casing, and finally, the steel pile casing is pulled out. The construction method has a great problem to be solved: the cement-soil piles with soil retaining and water retaining functions require that two adjacent cement-soil piles are overlapped, the cement-soil drilling and tube entering construction at the overlapped part is difficult, the cement-soil drilling at the adjacent formed overlapped part is easy to damage by forced drilling, and the soil drilling construction quality is difficult to guarantee, so that the popularization and the application of the construction method are hindered. Therefore, how to solve the problem of drilling cement into the cylinder at the overlapping position of two adjacent cement piles becomes a difficult problem to be solved urgently.

Disclosure of Invention

The technical problem solved by the invention is as follows: on one hand, the stiff cement soil support pile can improve the bending strength and the shearing strength on the basis of ensuring low cost, thereby playing the double effects of water retaining and soil retaining; on the other hand, the invention also provides a construction method capable of solving the difficult problem of drilling and tube entering of the cement soil at the overlapping part of two adjacent cement soil piles.

In order to solve the technical problems, one of the technical solutions proposed by the present invention is: a stiff cement soil supporting pile comprises a plurality of supporting single piles arranged in a row, wherein any two adjacent supporting single piles are partially overlapped together; a stiff skeleton made of cotton straws is arranged in the supporting single pile, and the stiff skeleton extends from the top to the bottom of the supporting single pile; the stiff skeleton is a skeleton structure which is composed of two flanges and a web plate and has an I-shaped cross section, or a skeleton structure which is composed of two flanges and two web plates and has a double I-shaped cross section.

In order to solve the technical problems, the second technical scheme provided by the invention is as follows: one of the technical schemes is a construction method of the stiff cement soil support pile, which comprises the following steps:

adopting a jump driving construction mode, firstly completing single-pile forming construction of a first supporting single pile and a third supporting single pile in sequence, and then completing single-pile forming construction of a second supporting single pile; then completing single-pile forming construction of a fifth supporting single pile and a fourth supporting single pile in sequence; repeating the steps until the pile forming is finished;

when the single pile is formed into a pile, a rotary digging pile construction method is adopted, namely, firstly, holes are dug, then the walls of the steel pile casings are protected, after the holes in the steel pile casings are cleared, the stiff frameworks are inserted into the steel pile casings, then the stirred cement-soil mixture is poured into the steel pile casings, and finally the steel pile casings are pulled out; when the hole is dug in the construction of the even number of supporting single piles, an umbrella-shaped flexible steel wire brush is installed on a hole digging drill bit which is driven into the soil in a rotating mode, the flexible steel wire brush is fixed on a drill rod through a fastener, and the outer diameter of the flexible steel wire brush is the diameter of a pile to be formed.

The invention makes full use of the good reinforcement property of the agricultural waste cotton straw, and prepares the cotton straw into the stiff skeleton standard component as the stiff material of the cement soil pile, thereby overcoming the defect of weak bending resistance of the cement soil pile. Meanwhile, the traditional hole forming drill bit is improved, and the flexible steel wire brush is arranged on the traditional hole forming drill bit, so that the problem that the holes are difficult to enter the cylinder at the hole digging position where every two cement soil piles are overlapped during the drilling construction of the stiff cement soil pile is solved.

The invention makes up for the defects that the existing cement-soil pile is applied to foundation pit support: 1) compared with the traditional single pure cement soil pile, the invention fully utilizes the higher tensile strength of the cotton straws and the characteristic of reinforcing the cotton straw framework space to strengthen the soil, thereby achieving the purpose of enhancing the bending strength and the shearing strength of the cement soil pile.

2) Compared with the method for increasing the cross-sectional area of the cement-soil pile, the method does not change the cross-sectional area of the original cement-soil pile, is convenient for normal use of the traditional construction machinery, has low cost, and can meet the construction requirement by using smaller pile diameter when the construction site limits the pile diameter of the cement-soil pile.

3) Compared with the traditional method for inserting the section steel into the cement-soil pile, the cotton straw framework does not need to be pulled out, so that the problems that the surface of the ground is disturbed and the cement-soil pile is affected due to the fact that the section steel is difficult to pull out and the like are avoided; compared with the traditional method of inserting moso bamboo into cement soil piles, the cotton straw stiff skeleton can ensure that the size of the cross section of the skeleton is uniform from top to bottom, the lap joint is good and convenient, and the length system is not limited, which can not be achieved by moso bamboo. In addition, the cost of the cotton straw skeleton is lower than that of steel bars, moso bamboos and the like, so that the cost is saved.

4) The invention avoids the defects of heavy machinery, inconvenient approach and the like of a cement-soil mixing pile method, solves the difficult problem that the pipe sinking is difficult to drill the cement soil at the overlapping part of every two cement-soil piles, and has better promotion effect on promoting the popularization and the application of the drilling and pipe sinking construction method.

Drawings

The invention will be further explained with reference to the drawings.

Fig. 1 is a schematic structural view of a stiff cemented soil retaining pile.

Fig. 2 is a schematic view of one of the molds for making a stiff skeleton.

Fig. 3 is a schematic view of a second mold for making a stiff skeleton.

Fig. 4 is a schematic view of a third mold for making a stiff skeleton.

Fig. 5 is a schematic view of a mold assembly for making a stiff skeleton.

FIG. 6 is a schematic structural view of a stiff skeleton.

Fig. 7 is a schematic view of a construction process of a stiff cemented soil retaining pile.

Fig. 8 is a schematic structural view of a flexible wire brush and a drill bit.

Reference numerals: 1. supporting single piles; 1-1, a first supporting single pile; 1-3, a third supporting single pile; 2. a stiff skeleton; 2-1, vertical cotton straws; 2-2, paving cotton straws; 3. an overlapping portion; 4. recessing; 5. a protrusion; 6. a drill stem; 7. a fastener; 8. a hole digging drill bit; 9. a flexible wire brush; 10. a slurry circulation hole; 11. and (6) tying a rope.

Detailed Description

Example one

The present embodiment relates to a stiff soil cement retaining pile, which, for simplicity of illustration, as shown in fig. 1, includes three retaining mono-piles 1 arranged in a row, wherein a first retaining mono-pile part and a second retaining mono-pile part are overlapped together (an overlapping part 3 thereof can be seen in fig. 1, that is, a part enclosed by a dotted line and an adjacent thick solid line), and a second retaining mono-pile part and a third retaining mono-pile part are overlapped together. A stiff skeleton 2 made of cotton straws is arranged in the supporting single pile 1, and the stiff skeleton 2 extends from the top to the bottom of the supporting single pile 1; the stiff skeleton is a skeleton structure which is composed of two flanges and a web plate and has an I-shaped cross section, or as shown in fig. 6 and 7, a skeleton structure which is composed of two flanges and two web plates and has a double I-shaped cross section. The H-shaped framework structure or the double H-shaped framework structure is a common reinforcing structure and is not repeated. The stiff skeleton 2 can fully utilize the high tensile strength of cotton straws and the characteristic of reinforcing and soil-consolidating of cotton straw skeleton space, and enhance the bending strength and the shearing strength of the cement soil support pile, so that the defect of weak bending resistance of the cement soil support pile is overcome, and the stiffness of the soil pile can be applied to support engineering and has double functions of soil and water retaining.

When the method is implemented, the stiff framework 2 can be prefabricated in an I-shaped or double I-shaped mould on site or elsewhere. Taking the double I-shaped stiff skeleton 2 as an example, the dies for manufacturing the stiff skeleton 2 are shown in fig. 2-5, all the dies are divided into three types, and the cross sections of the dies are in double I shapes. Wherein, the first type of mould is shown in fig. 2, one end of the first type of mould is provided with a recess 4 extending along the length direction, and the length of the first type of mould is 1 meter; as shown in fig. 3, the second type of mold has a protrusion 5 extending in the length direction at one end and a recess 4 matching with the protrusion 5 at the other end, and the length of the second type of mold is 1 meter, and obviously, the recess 4 also extends in the length direction; the third type of mould is shown in figure 4, one end of the third type of mould is provided with a protrusion 5 extending along the length direction, and the length of the third type of mould can be adjusted within the range of 0-1 meter. As shown in FIG. 5, the three types of molds form a splicing mortise and tenon structure through the matching of the depressions 4 and the protrusions 5, and are bundled by a binding rope at the splicing position to be connected into a mold combination with a required length. The cotton straws are placed in the frame, the vertical cotton straws 2-1 are placed firstly, then the flat cotton straws 2-2 are placed, the vertical cotton straws 2-1 and the flat cotton straws 2-2 are arranged in a staggered manner, and the cotton straws can be bundled at the joints of the cotton straws and can be lapped into a cotton straw stiff framework 2 with a cross section in a double I shape and any length, as shown in figure 6.

The manufacturing method of the I-shaped stiff skeleton is basically similar to that of the I-shaped stiff skeleton, and the difference is that the cross section of the selected die is I-shaped instead of double I-shaped.

The embodiment also relates to a construction method of the stiff cement soil support pile, which comprises the following steps:

as shown in fig. 7, the single-pile construction of the first supporting single pile 1-1 and the third supporting single pile 1-3 is completed in sequence by adopting the jump driving construction mode, and then the single-pile construction of the second supporting single pile is completed. The construction mode of beating is prior art, and is not described again.

When the single pile is formed into a pile, a rotary digging pile construction method is adopted, namely, firstly, holes are dug, then the steel pile casing walls are used, after the holes in the steel pile casing are cleared, the stiff framework is inserted into the steel pile casing, then the stirred cement-soil mixture is poured into the steel pile casing, and finally the steel pile casing is pulled out.

When the second supporting single pile is dug, because the diameter of the second supporting single pile is larger than the distance between the first supporting single pile 1-1 and the third supporting single pile 1-3, if a traditional drill bit is directly used for drilling, the first supporting single pile 1-1 and the third supporting single pile 1-3 are softer (the hardening speed of cement soil is lower), and a large amount of cement soil on the first supporting single pile 1-1 and the third supporting single pile 1-3 can be scraped off by the traditional drill bit to influence the construction quality. In this embodiment, a conventional drill is improved, as shown in fig. 8, firstly, the outer diameter of the boring bit 8 is ensured to be smaller than the diameter of the pile to be formed, so that the boring bit 8 contacts the first supporting single pile 1-1 and the third supporting single pile 1-3 as little as possible during boring, preferably, the diameter of the boring bit 8 is equal to the distance between the outer edges of the first supporting single pile 1-1 and the third supporting single pile 1-3, an umbrella-shaped flexible steel wire brush 9 is mounted on the boring bit 8, the flexible steel wire brush 9 covers the boring bit 8, the flexible steel wire brush 9 is fixed on the drill rod 6 through a fastener 7, and the outer diameter of the flexible steel wire brush 9 is the diameter of the pile to be formed.

Then, if more supporting single piles need to be constructed, completing the single-pile forming construction of a fifth supporting single pile and a fourth supporting single pile in sequence; and repeating the steps until the pile forming is finished.

Compared with the prior art, the embodiment has the following beneficial effects:

firstly, the supporting effect of the cotton straw supporting structure of the embodiment is obviously superior to that of a supporting system of a common cement-soil pile: (1) the cross section of the cotton straw stiff skeleton adopts an I shape or a double I shape, and the shearing resistance and the bending strength of the cement soil pile can be obviously improved. (2) The construction method of the embodiment avoids the defects of heavy machinery, inconvenient field entry and the like of a cement-soil mixing pile method, and solves the difficult problem that the cement-soil drilling and the cylinder entering at the overlapping part of two adjacent cement-soil piles are difficult.

Secondly, this embodiment efficiency of construction is high, low in production cost: (1) the cotton straw material has low cost and wide source. (2) The cotton straw stiff skeleton is inserted without special construction machinery, and the cotton straw skeleton is a prefabricated standard part, so that the cotton straw stiff skeleton has an obvious construction efficiency advantage. (3) The cotton straw stiff skeleton is disposable, does not need to be pulled out, can avoid the disturbance to the peripheral soil body of foundation ditch and keep the wholeness of soil cement pile when saving man-hour, makes it still keep good stagnant water characteristic when playing better retaining effect.

And thirdly, the embodiment adopts green and environment-friendly natural reinforced materials, and adapts to the sustainable development concept. The cotton stalk skeleton belongs to natural plant tendon material, and can not pollute underground soil body and water body in the soil body.

The present invention is not limited to the specific technical solutions described in the above embodiments, and other embodiments may be made in the present invention in addition to the above embodiments. It will be understood by those skilled in the art that various changes, substitutions of equivalents, and alterations can be made without departing from the spirit and scope of the invention.

Claims

1. A strength nature cement soil fender pile which characterized in that: the method comprises a plurality of supporting single piles arranged in a row, wherein any two adjacent supporting single piles are partially overlapped together; a stiff skeleton made of cotton straws is arranged in the supporting single pile, and the stiff skeleton extends from the top to the bottom of the supporting single pile; the stiff skeleton is a skeleton structure which is composed of two flanges and a web plate and has an I-shaped cross section, or a skeleton structure which is composed of two flanges and two web plates and has a double I-shaped cross section.

2. A construction method of the stiff cement-soil support pile according to claim 1, comprising the steps of:

when the single pile is formed into a pile, a rotary digging pile construction method is adopted, namely, firstly, holes are dug, then the walls of the steel pile casings are protected, after the holes in the steel pile casings are cleared, the stiff frameworks are inserted into the steel pile casings, then the stirred cement-soil mixture is poured into the steel pile casings, and finally the steel pile casings are pulled out; when the hole is dug in the construction of the even number of supporting single piles, an umbrella-shaped flexible steel wire brush is installed on a hole digging drill bit which is driven into the soil in a rotating mode, the outer diameter of the hole digging drill bit is smaller than the diameter of the flexible steel wire brush, the flexible steel wire brush is fixed on a drill rod through a fastener, and the outer diameter of the flexible steel wire brush is the diameter of a pile to be formed.

3. The stiff cement soil support pile according to claim 1, wherein the manufacturing method of the stiff skeleton is as follows: splicing a plurality of moulds with I-shaped or double I-shaped cross sections together to form a mould combination with a preset length, placing cotton straws in the mould combination and bundling the cotton straws to obtain the stiff framework with the preset length.

4. The construction method of a stiff cement-soil support pile according to claim 2 or 3, characterized in that: the flexible steel wire brush covers the upper part of the hole digging drill bit.