CN112227341B

CN112227341B - Applicable to the treatment method of piles first scattered and then rigid for filling works on under-consolidated soft soil foundations

Info

Publication number: CN112227341B
Application number: CN202011195496.4A
Authority: CN
Inventors: 章荣军; 黄悦; 郑俊杰; 董超强; 蒋达飞
Original assignee: Huazhong University of Science and Technology
Current assignee: Huazhong University of Science and Technology
Priority date: 2020-10-30
Filing date: 2020-10-30
Publication date: 2021-07-23
Anticipated expiration: 2040-10-30
Also published as: CN112227341A

Abstract

The invention belongs to the technical field of soft soil foundation treatment, and discloses a method for treating piles that are first scattered and then rigid, which are suitable for filling works on under-consolidated soft soil foundations. Before the construction of the landfill on the under-consolidated soft soil foundation, the gravel pile shall be constructed in the soft soil foundation, and the grouting pipe shall be inserted at the same time without grouting, and then the landfill construction shall be carried out. After the construction of the landfill, the soft soil generates excess pore water pressure under the action of the self-weight of the landfill and begins to drain and consolidate. At this time, the permeability coefficient of the gravel pile is large, which can be used as a drainage channel to accelerate the consolidation and settlement of the soft soil. When the consolidation and settlement of the soft soil of the foundation is substantially completed, the cement slurry is injected into the reserved grouting pipe, and the cement slurry penetrates into the gravel pile, so that the aggregate of the gravel pile is condensed into a rigid pile with greater rigidity; It can share more load to improve the bearing capacity of under-consolidated soft soil foundation and reduce the post-construction settlement of the foundation.

Description

First-dispersing and then-reinforcing pile treatment method suitable for filling engineering on under-consolidated soft soil foundation

Technical Field

The invention belongs to the technical field of soft soil foundation treatment, and particularly relates to a method for treating piles which are scattered first and then reinforced, and are suitable for filling projects on an under-consolidated soft soil foundation.

Background

At present, a soft soil foundation treatment method of under-consolidation generally adopts a surcharge or vacuum preloading drainage consolidation method or a surcharge and vacuum preloading drainage consolidation method, and then adopts cement mixing piles and the like to form a composite foundation. For filling projects on an under-consolidated soft soil foundation, the preloading is carried out by only utilizing the dead weight of filled soil, so that the method has great limitation, and is mainly characterized in that (1) the preloading treatment depth is limited; (2) the permeability coefficient of the soft soil is small, the drainage path is long, the dissipation of the ultra-static pore water pressure is very slow, and the construction period required by the stacking is long; (3) the ultra-static pore pressure in the unconsolidated soil is not completely dissipated, and consolidation settlement still occurs subsequently, so that the post-construction settlement is larger.

When a composite foundation is formed by constructing discrete material piles in soft soil and then performing filling construction and prepressing, the lifting range of the foundation bearing capacity of the soft soil foundation is limited; when a rigid pile is constructed in soft soil to form a composite foundation and then the soil filling construction is carried out for prepressing, the consolidation of the under-consolidated soft soil still needs a longer time, and the construction period of the preloading is longer. In view of the defects of the above treatment methods, a foundation treatment method for an under-consolidated soft soil foundation upper filling project, which has a short construction period and can greatly improve the bearing capacity of the foundation and control post-construction settlement, is to be developed.

Through the above analysis, the problems and defects of the prior art are as follows:

in the prior art, consolidation settlement of the under-consolidated soft soil foundation is slow, and the required construction period is long.

In the prior art, the consolidation settlement of the under-consolidated soft soil foundation is not thorough, so that the post-construction settlement is caused.

The composite foundation formed by the prior art can not meet the requirements of bearing capacity, construction period and post-construction settlement of the foundation at the same time.

The difficulty in solving the above problems and defects is: at present, a pile body in a composite foundation often cannot have drainage capacity and vertical rigidity, so that the requirements of foundation bearing capacity, construction period and post-construction settlement are met at the same time, certain difficulty is achieved, and improper treatment of construction cost can be improved more.

The significance of solving the problems and the defects is as follows: the drainage capacity and the vertical rigidity of the pile body in the composite foundation are exerted in different time periods, so that the construction period can be shortened, the construction progress is accelerated, the cost is saved, the post-construction settlement is reduced, and the bearing capacity requirement of the foundation is met.

Disclosure of Invention

Aiming at the problems in the prior art, the invention provides a method for treating piles which are firstly scattered and then reinforced and are suitable for filling projects on an under-consolidated soft soil foundation.

The invention is realized in this way, a method for treating the pile after the first scattering suitable for the filling engineering on the under-consolidated soft soil foundation comprises the following steps:

s1, flattening a soft soil foundation, measuring and lofting and fixing piles;

s2, forming holes by using a double-sleeve method, vibrating a steel grouting pipe together with the double sleeves to sink into soft soil, and checking whether the grouting pipe is smooth or not by injecting clear water after the grouting pipe is inserted;

s3, after hole forming, putting gravel into the pile to form a pile, and tamping the gravel pile after constructing the gravel pile at a certain height in the pile forming process;

s4, constructing a mattress layer after the gravel pile is formed, then performing pile filling construction to a preset height, and enabling a grouting pipe to penetrate through the pile filling soil to ensure that the grouting opening is above the surface of the pile filling soil, so that subsequent grouting is facilitated;

s5, after the soil filling construction is finished, preloading is carried out on the soft soil foundation under the action of soil filling gravity, hyperstatic pore water pressure is generated in the soft soil, and gravel piles in the soft soil can be used as drainage channels to accelerate consolidation settlement of the soft soil;

s6, after the pile is loaded for a period of time, checking a reserved grouting pipe, and injecting cement slurry into the pile by using a pressure pump after the grouting pipe is ensured to be smooth;

s7, the cement slurry permeates into the broken stones, and after a period of time, broken stone aggregate is condensed, so that the pile body becomes a rigid pile with higher rigidity.

Further, in step S2, the inner sleeve of the double sleeve is provided with a groove, and the inner wall of the outer sleeve is ribbed, so that the steel grouting pipe can be conveniently inserted and fixed between the gaps of the inner and outer sleeves, and can be simultaneously vibrated and sunk into the soft soil along with the double sleeve when the pipe is vibrated and sunk.

Further, in step S2, the steel grouting pipes are open-bottomed pipes, and two steel grouting pipes are provided for each pile, and are divided to be located on both sides of the pile body.

Further, in step S4, the grouting pipe may be lengthened by welding or the like to penetrate the fill, with the grouting opening being located above the fill.

Further, in steps S5 and S6, grouting is not performed immediately after completion of gravel pile construction, but in the first place, filling construction is performed, and grouting is performed when consolidation settlement of the soft soil foundation by preloading reaches 80% or more of the estimated total settlement.

Further, in step S6, cement grout is injected into the two steel grouting pipes simultaneously by the pressure pump, and sectional lifting grouting is adopted, and the grouting pipes are pulled out after grouting; grouting must be continuously carried out, and if interruption occurs due to reasons, grouting should be immediately processed, and grouting is resumed as soon as possible to ensure grouting quality. During grouting, the grouting amount and the grouting pressure are controlled well, and the relationship between the grouting amount and the grouting pressure is considered comprehensively to determine the basis for finishing grouting, and carefully do the grouting shielding work to avoid grouting return.

Further, in step S7, after a period of time after grouting, the pile bodies are coagulated into rigid piles, and the composite foundation is changed from a discrete material pile composite foundation to a rigid pile composite foundation. And (4) soft soil drainage consolidation at the discrete material pile composite foundation stage.

Another object of the present invention is to provide a pile-after-scattering processing apparatus suitable for a filling project on an under-consolidated soft soil foundation, comprising a soft soil foundation, the soft soil foundation comprising a plurality of piles; a steel grouting pipe is inserted in the pile; the steel grouting pipes are inserted into the double-sleeve interlayer; the bottom of the steel grouting pipe is provided with a grouting hole;

the pile is filled with a gravel pile; a mattress layer is laid on the upper part of the gravel pile; the upper part of the mattress layer is paved with stacking soil.

Further, the double-sleeve comprises an outer sleeve, an inner sleeve groove and an outer sleeve pipe rib;

the steel grouting pipe is positioned at the groove of the inner sleeve;

the outer sleeve ribs are positioned on two sides of the steel grouting pipe, and the outer sleeve ribs are positioned between the outer sleeve and the inner sleeve.

Further, the gravel pile is grouted to form a rigid pile.

By combining all the technical schemes, the invention has the advantages and positive effects that:

the pile is firstly scattered and then is rigid, namely a gravel pile is firstly constructed in a soft soil foundation, a grouting pipe is reserved but is not grouted immediately, the pile is grouted after the foundation is pre-pressed for a period of time by using the self weight of the filling soil or other methods, and the pile body forms a rigid pile after grouting. In the soil filling and pre-pressing stage, the gravel pile can play a role in draining water, so that the consolidation of the unconsolidated soil is accelerated, and the construction period is shortened; after the consolidation and settlement of the soft soil are approximately completed, cement slurry is injected, and the pile body becomes a rigid pile, so that more loads can be shared. The method has the advantages that the consolidation settlement of the under-consolidated soft soil foundation is quickly completed, the construction period is shortened, and the settlement after construction is reduced; and after consolidation and settlement are basically completed, a rigid pile composite foundation is formed, and the bearing capacity of the foundation is obviously improved.

Technical effect or experimental effect of comparison. The method comprises the following steps:

when only filling is adopted for carrying out preloading, the required construction period is long and is often as long as one year, and the settlement after construction is difficult to control; when a composite foundation is formed by constructing discrete material piles in soft soil and then performing filling construction and prepressing, the lifting range of the foundation bearing capacity of the soft soil foundation is limited; when a rigid pile is constructed in soft soil to form a composite foundation and then the filling construction is carried out for prepressing, the consolidation of the under-consolidated soft soil still needs a long time, and large negative friction resistance on the pile side, which is unfavorable for the foundation, can be generated.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiments of the present application will be briefly described below, and it is obvious that the drawings described below are only some embodiments of the present application, and it is obvious for those skilled in the art that other drawings can be obtained from the drawings without creative efforts.

Fig. 1 is a flowchart of a method for processing a pile after first scattering, which is suitable for a filling project on an under-consolidated soft soil foundation according to an embodiment of the present invention.

Fig. 2 is a top view of a double cannula provided by an embodiment of the present invention.

Fig. 3 is a schematic view of a gravel pile composite foundation before grouting according to an embodiment of the invention.

Fig. 4 is a schematic diagram of a post-grouting rigid pile composite foundation provided by an embodiment of the invention.

In fig. 2-4: 1. soft soil foundation; 2. double-casing; 2-1, outer sleeve; 2-2, inner sleeve; 2-3, inner sleeve groove; 2-4, outer sleeve pipe ribs; 3. steel grouting pipes; 4. gravel piles; 5. a mattress layer; 6. filling soil in a pile; 7. a rigid pile.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Aiming at the problems in the prior art, the invention provides a method for treating piles which are firstly scattered and then reinforced and are suitable for filling engineering on an under-consolidated soft soil foundation, and the invention is described in detail by combining the attached drawings.

As shown in fig. 1, the method for treating the first-scattered and second-rigid piles, which is suitable for the filling engineering on the under-consolidated soft soil foundation, provided by the invention comprises the following steps:

s101, flattening the soft soil foundation 1, measuring and lofting, and fixing piles, wherein the pile distance can be 4-6 times of the pile diameter, and the pile distance can be selected according to the actual situation of the foundation.

S102, selecting the length and the diameter of a pile according to engineering geological conditions, generally drilling through a soft soil layer to enable the end of the pile to enter a hard soil layer, forming a hole by using a double-casing method, sinking a steel grouting pipe 3 into soft soil along with a double-casing pipe 2 through vibration of mechanical equipment such as a vibration hammer, a crane and the like, inserting the steel grouting pipe 3 into the soft soil, and then injecting clear water through a grouting pump to check whether the grouting pipe is unblocked; as shown in fig. 2, the double sleeve 2 is provided with two grooves in the inner sleeve, and the inner wall of the outer sleeve is provided with ribs at the corresponding positions of the grooves of the inner sleeve, so that the steel grouting pipe 3 can be conveniently inserted into the gap between the inner sleeve and the outer sleeve and fixed at the grooves, and can be simultaneously vibrated along with the double sleeve to sink into soft soil during vibration pipe sinking; the steel grouting pipes 3 are steel pipes with holes at the bottom pipe bodies, and each pile is provided with two steel grouting pipes which are respectively positioned at two sides of the pile body.

S103, after hole forming, gravel is thrown in to form a pile, in the pile forming process, the gravel pile 4 is tamped after being constructed at a certain height, grouting is not performed immediately after the gravel pile is constructed, and only a grouting pipe is reserved for subsequent grouting.

S104, constructing a mattress layer 5 after the gravel pile is formed, and then performing pile filling 6 construction to a preset height; the grouting pipe 3 should reserve a sufficient length (capable of being lengthened by welding) on the surface of the foundation to penetrate through the filling soil, so as to ensure that the grouting opening is above the filling soil surface, and facilitate subsequent grouting work.

And S105, after the filling construction is finished, preloading is carried out for a period of time, hyperstatic pore water pressure is generated in the soft soil under the filling effect, the permeability coefficient of the gravel pile in the soft soil is large, the gravel pile can be used as a drainage channel, the drainage path is shortened, and the consolidation settlement of the soft soil can be accelerated remarkably.

S106, after a period of stacking, when the consolidation settlement of the soft soil reaches 80% or more of the estimated total settlement, grouting is started. And (3) checking the reserved grouting pipes, injecting cement slurry into the grouting pipes by using a grouting pump after the grouting pipes are ensured to be unblocked, grouting two grouting pipes 3 simultaneously during grouting, and adopting a grouting mode of sectional lifting. Because the grouting pipe is a bottom perforated pipe, cement slurry seeps out of the bottom of the grouting pipe, and the cement slurry gradually rises from the bottom of the gravel pile 4 in the sectional lifting process. During grouting, the recording work of grouting pressure, grouting amount, grouting time and other abnormal conditions is well done, the grouting amount and the grouting pressure are convenient to control, and the grouting amount of each pile is basically consistent. Grouting must be continuously carried out, and if interruption occurs due to reasons, grouting should be immediately processed, and grouting is resumed as soon as possible to ensure grouting quality. And after grouting, carefully performing slurry shielding work to avoid slurry return. And pulling out the grouting pipe after grouting.

S107, cement slurry permeates broken stones, and after a period of time, broken stone aggregate is solidified, the pile body becomes a rigid pile 7 with higher rigidity; at the moment, a rigid pile composite foundation is formed, and the bearing capacity of the foundation is obviously improved.

The invention provides a first-dispersing and second-reinforcing pile processing device suitable for filling engineering on an under-consolidated soft soil foundation, which comprises: the pile foundation comprises a soft soil foundation 1, a double-sleeve 2, an outer sleeve 2-1, an inner sleeve 2-2, an inner sleeve groove 2-3, an outer sleeve pipe rib 2-4, a steel grouting pipe 3, a gravel pile 4, a mattress layer 5, a pile filling 6 and a rigid pile 7.

Fig. 2 is a top view of a double cannula according to an embodiment of the present invention.

In the description of the present invention, "a plurality" means two or more unless otherwise specified; the terms "upper", "lower", "left", "right", "inner", "outer", "front", "rear", "head", "tail", and the like, indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, are only for convenience in describing and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed in a particular orientation, and be operated, and thus, should not be construed as limiting the invention. Furthermore, the terms "first," "second," "third," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

The above description is only for the purpose of illustrating the present invention and the appended claims are not to be construed as limiting the scope of the invention, which is intended to cover all modifications, equivalents and improvements that are within the spirit and scope of the invention as defined by the appended claims.

Claims

1. a method for the treatment of piles after first dispersing and then just piles that is applicable to filling works on under-consolidated soft soil foundations, it is characterized in that, the described method for treating firstly dispersing and then rigid piles that are applicable to filling works on under-consolidated soft soil foundations Methods include:

In the soft soil foundation, the gravel piles are constructed first, and the grouting pipe is inserted at the same time without grouting, and then the landfill construction is carried out;

After the construction of the landfill, the soft soil will generate excess pore water pressure under the action of the self-weight of the landfill and drain and consolidate;

When the consolidation and settlement of the soft soil of the foundation is completed, the cement slurry is injected into the reserved grouting pipe, and the cement slurry penetrates into the gravel pile, so that the aggregate of the gravel pile is condensed into a rigid pile with high rigidity;

The method for treating the piles first and then rigid, which is suitable for filling works on under-consolidated soft soil foundations, further includes:

S1, level the soft soil foundation, measure the stake out and fix the pile;

S2, use the double casing method to form a hole, vibrate the steel grouting pipe together with the double casing and sink it into the soft soil, insert the grouting pipe and inject clean water to check whether the grouting pipe is unobstructed;

S3, after the hole is formed, put in the gravel to form a pile, and in the process of forming the pile, the gravel pile is tamped after a certain height is constructed;

S4, after the gravel piles are formed into piles, the mattress layer is constructed, and then the landfill construction is carried out to the predetermined height, and the grouting pipe passes through the landfill;

S5. After the filling construction is completed, the soft soil foundation is preloaded under the action of the filling gravity, and excess pore water pressure is generated in the soft soil. The gravel piles in the soft soil are used as drainage channels to accelerate the consolidation and settlement of the soft soil. ;

S6, after stacking for a period of time, check the reserved grouting pipe, and inject cement slurry with a pressure pump after it is unblocked;

S7, the cement slurry penetrates into the crushed stone, and after a period of time, the aggregate of the crushed stone coagulates, and the pile body becomes a rigid pile with high rigidity;

In step S2, the inner casing of the double casing is provided with grooves, and the inner wall of the outer casing is ribbed, and the steel grouting pipe is inserted and fixed between the gaps of the inner and outer casings, and when the immersed pipe is vibrated, it is accompanied by the double casing. The pipe vibrates and sinks into the soft soil at the same time;

In step S2, the steel grouting pipe is an open bottom pipe, and each pile is provided with two steel grouting pipes, which are respectively located on both sides of the pile body;

In step S4, the grouting pipe is lengthened by welding technology, passes through the filling layer, and the grouting port is located on the upper part of the filling;

In step S5 and step S6, the gravel piles are not grouted immediately after the construction is completed, and the landfill construction is carried out first, and the consolidation settlement of the soft soil foundation is preloaded until the consolidation settlement reaches more than 80% of the estimated total settlement. grouting when

In step S6, the two steel grouting pipes are simultaneously injected with cement grout by a pressure pump, and a segmented lift grouting is used. After the grouting is completed, the grouting pipes are pulled out; the grouting is performed continuously;

In step S7, after grouting for a period of time, the pile body is solidified into a rigid pile, and the composite foundation is changed from a composite foundation of a bulk material pile to a composite foundation of a rigid pile.

2. A device used for the method of claim 1, which is applicable to the method for treating piles first and then rigid, which is suitable for filling works on under-consolidated soft soil foundations, comprising a soft soil foundation, wherein the soft soil foundation comprises a plurality of a pile; a steel grouting pipe is inserted into the pile; the steel grouting pipe is inserted into the double casing interlayer; the bottom of the steel grouting pipe is provided with a grouting hole;

The pile is filled with gravel piles; the upper part of the gravel pile is laid with a mattress; the upper part of the mattress is covered with landfill;

The double casing includes an outer casing, an inner casing, an inner casing groove, and an outer casing pipe rib;

The steel grouting pipe is located at the groove of the inner casing;

The outer casing pipe rib is located on both sides of the steel grouting pipe, and the outer casing pipe rib is located between the outer casing and the inner casing;

The crushed stone pile forms a rigid pile after grouting.