CN114032942A

CN114032942A - Construction method of pole tower foundation micro pile in soft soil foundation

Info

Publication number: CN114032942A
Application number: CN202111211017.8A
Authority: CN
Inventors: 陈友慧; 吕忠华; 李冬雪; 刘然; 潘琪; 吴昊; 马强; 张吉; 贾及汉; 陈国龙; 贾博; 吕铭; 吴卓航; 金子开; 卢天琪; 王勇; 刘岩; 王淼; 赫鑫; 金宇飞
Original assignee: STATE GRID LIAONING ECONOMIC TECHNIQUE INSTITUTE; State Grid Corp of China SGCC
Current assignee: STATE GRID LIAONING ECONOMIC TECHNIQUE INSTITUTE; State Grid Corp of China SGCC
Priority date: 2021-10-18
Filing date: 2021-10-18
Publication date: 2022-02-11

Abstract

The invention belongs to the technical field of electric power infrastructure construction, and particularly relates to a construction method of a pole tower foundation micro pile in a soft soil foundation. The method comprises the following steps: step 1, binding a reinforcement cage and a secondary grouting pipe; step 2, pile position positioning, hole forming and hole cleaning; step 3, placing a reinforcement cage and a next grouting pipe in the hole, and putting broken stone aggregate into the first grouting pipe; step 4, grouting in the primary grouting pipe, and forming a pile preliminarily; step 5, after the slurry is initially solidified, secondary grouting is carried out in the primary grouting pipe; and 6, forming a pile after the slurry is solidified. The invention has the advantages of safe construction of the tower foundation and convenient construction, can greatly shorten the construction period, occupies smaller area, reduces the construction cost and saves the fund. As the MP pile is a variable-section pile body, the bearing capacity of a single pile is greatly improved through a secondary grouting process, the bearing capacity after grouting is improved by 20-30% compared with the bearing capacity before grouting, and the service life of electric power infrastructure are effectively prolonged.

Description

Construction method of pole tower foundation micro pile in soft soil foundation

Technical Field

The invention belongs to the technical field of electric power infrastructure construction, and particularly relates to a construction method of a pole tower foundation micro pile in a soft soil foundation.

Background

With the rapid development of national economy in China, the investment of the nation in electric power infrastructure is increasing day by day. The land is big and living in China, a plurality of local landform units are piled up in the lake and marsh plain, the land topography is low, the ground is uneven, the land just meets rainy seasons before pile testing construction, and the low-lying part is more and deeper in accumulated water. Such regions typically have engineered geological features in various layers from top to bottom including: pond sludge, muddy clay and silt. In such environments, it becomes a difficult experience to set up a pole and tower foundation.

At present, the main type of pole tower foundation in soft soil foundation is the expansion type foundation. The design and calculation method of the extended foundation is simple, but the problems of large foundation square amount and excavation engineering amount, large occupied area, heavy construction equipment and difficulty in carrying exist. At present, a small-sized pile is commonly used and is provided with a root pile, and the root pile is a small-diameter cast-in-situ bored pile, and the diameter of the root pile is usually 0.1-0.25 m. Its advantages are flexible arrangement and mature design method. The main characteristics are as follows: (1) the construction site is small, the plane is 0.6-1.8 m generally, and the height is 2.1-2.7 m; (2) the drill hole is small, and the drill is suitable for various types of soil; (3) the arrangement form is flexible, and the inclined piles can be arranged; (4) compared with the cast-in-place pile with the same volume, the bearing capacity is higher. However, although the tree root pile is small in size and flexible in construction, the effect is not ideal when the tree root pile is used in a tower foundation of a soft soil foundation, and the bearing capacity of the tree root pile cannot meet the requirements of the existing construction process, so that certain potential safety hazards exist.

Disclosure of Invention

Aiming at the defects in the prior art, the invention provides a construction method of a pole tower foundation micro pile in a soft soil foundation. The invention aims to achieve the purposes of safe and convenient construction of the tower foundation, short construction period, small occupied area, reasonable manufacturing cost and obviously improved bearing capacity.

The technical scheme adopted by the invention for realizing the purpose is as follows:

a construction method of a pole tower foundation micro pile in a soft soil foundation comprises the following steps:

step 1, binding a reinforcement cage and a secondary grouting pipe;

step 2, pile position positioning, hole forming and hole cleaning;

step 3, placing a reinforcement cage and a next grouting pipe in the hole, and putting broken stone aggregate into the first grouting pipe;

step 4, grouting in the primary grouting pipe, and forming a pile preliminarily;

step 5, after the slurry is initially solidified, secondary grouting is carried out in the primary grouting pipe;

and 6, forming a pile after the slurry is solidified.

Further, the step 1 of binding the reinforcement cage and the secondary grouting pipe is to firstly bind the 1-inch secondary grouting pipe at the top of the reinforcement cage during construction; a plurality of small holes are uniformly formed in the secondary grouting pipe, and the outside of each small hole is sealed and blocked by a sealing material, so that cement slurry is prevented from entering the grouting pipe; the number of the secondary grouting pipes is generally 1-2; the sealing material is a polypropylene-ethylene mixed material.

Further, the pile position positioning, hole forming and hole cleaning in the step 2 are realized by positioning through a small-sized drilling machine and arranging a pile casing when a pile is formed; and then drilling, and cleaning the hole after the designed elevation is reached, so that no silt exists in the cleaned water, and the specific gravity of the cleaned mud is not more than 1.1.

Further, in the step 3, placing a reinforcement cage and a next grouting pipe in the hole, and putting gravel aggregate in the primary grouting pipe, the reinforcement cage bound with the secondary grouting pipe is firstly hung in the hole, then the primary grouting pipe is placed to the bottom of the hole, and then the gravel aggregate is put into the drill hole to the position of the hole opening; the number of the primary grouting pipes is generally 1-2; a plurality of small holes are uniformly formed in the primary grouting pipe at intervals, and the small holes are sealed and blocked by sealing materials to prevent cement mortar from entering the grouting pipe.

Further, grouting into the primary grouting pipe in the step 4, and primarily forming a pile, namely injecting cement mortar into the primary grouting pipe by using a grouting pump until an orifice emits the mortar; the specific gravity of the cement mortar reaches a water cement ratio of 0.5: 1, the corresponding site perfusion specific gravity is 1.8 to 2.0 through the site test.

Further, after the grout is initially set in the step 5, secondarily grouting into the primary grouting pipe, firstly lifting the primary grouting pipe to a position 3-4 m away from the orifice, and then secondarily grouting; carrying out secondary grouting 4-6 hours after the initial setting of the slurry; during the second grouting, firstly, high-pressure cement mortar is injected into the secondary grouting pipe by using a grouting pump, and the sealing material outside the secondary grouting pipe 2 is broken by using high pressure, so that the small hole is opened after grouting.

Further, the construction method of the pole tower foundation micro pile in the soft soil foundation further comprises the following steps: step 7, carrying out low strain detection on part of piles to check the quality of the pile body; the method comprises the following steps: the method comprises a single-pile vertical compression static load test, a single-pile vertical pulling static load test, a single-pile horizontal static load test, a single-pile compression and horizontal load combined loading test and a single-pile horizontal load combined loading test.

Further, the vertical resistance to compression static load test of single pile includes:

a. test data;

the loading grade of the vertical compression-resistant static load test of the single pile is shown in a table 3;

the pile top settlement amounts of the test piles D-1, D-2, D-5 and D-6 under the load action of each level are summarized in a table 4-a table 7;

summarizing a Q-S curve, a logQ-S curve and an S-lgt curve of the D-1 test pile under the action of loads at all levels;

b. analyzing test results;

d-1: when the pile is loaded to the first-stage load of 66kN according to the specified load level, the accumulated settlement of the pile top is 1.22 mm; when the twelfth-level load is loaded to 429kN, the accumulated settlement of the pile top is 33.05 mm; after unloading, the resilience of the pile top is measured to be 13.10mm, the residual settlement of the pile top is 19.95mm, and the resilience of the pile top is 39.6 percent; determining that the compressive ultimate bearing capacity is 363kN and the corresponding pile top settlement is 18.04 mm;

② D-2: when the pile is loaded to the first-stage load of 99kN according to the specified load level, the accumulated settlement of the pile top is 1.09 mm; when the load is loaded to the tenth level load of 396kN, the accumulated settlement of the pile top is 31.99 mm; measuring the resilience of the pile top to be 9.21mm after unloading, wherein the residual settlement of the pile top is 22.78mm, and the resilience of the pile top is 28.8%; determining that the compressive ultimate bearing capacity is 363kN and the corresponding pile top settlement is 22.13 mm;

③ D-5: when the pile is loaded to the first-stage load of 44kN according to the specified load level, the accumulated settlement of the pile top is 0.85 mm; when the load is loaded to the ninth-level load of 220kN, the accumulated settlement of the pile top is 9.20 mm; after unloading, measuring the resilience of the pile top to be 5.28mm, the residual settlement of the pile top to be 3.92mm and the resilience of the pile top to be 57.4 percent; the single pile test stops loading when the estimated compressive limit bearing capacity of the single pile is reached, the pile top does not reach a larger settlement amount at the moment, and the compressive limit bearing capacity of the test pile is larger than 220 kN;

d-6: when the pile is loaded to the first-stage load of 44kN according to the specified load level, the accumulated settlement of the pile top is 0.99 mm; when the seventeenth-level load is 396kN, the accumulated settlement of the pile top is 31.83 mm; after unloading, measuring the resilience of the pile top to be 12.72mm, the residual settlement of the pile top to be 19.11mm and the resilience of the pile top to be 40.0 percent; determining that the compressive ultimate bearing capacity is 330kN and the corresponding pile top settlement is 20.24 mm;

summarizing the ultimate compression bearing capacity of each test pile, as shown in table 2; from the analysis of the compression-resistant static load test results of all the test piles, the ultimate bearing capacity of the straight piles D-2 and D-6 is 363kN and 330kN respectively; the compressive ultimate bearing capacity 363kN of the inclined pile D-1 is greater than 220kN of the ultimate bearing capacity of D-5; the difference of the single-pile compression resistance limit bearing capacity of the vertical pile and the inclined pile is not large; the resilience rate of the pile top of the D-5 test pile is high and reaches 57.4 percent; the resilience rate of the pile tops of the rest test piles is between 28 and 40 percent, and the residual settlement is large;

analyzing the axial force and the side frictional resistance of the pile body according to the result of the steel bar stress meter; when the load is small, the load transmitted from the pile top is mainly born by the pile side frictional resistance of the upper soil layer; along with the increase of the load, the relative displacement between the pile and the soil is increased, and the frictional resistance is correspondingly increased; the pile side frictional resistance of the upper soil layer in the D-1 pile test reaches 43kPa and is gradually transmitted downwards; in the D-5 test pile test, the final loading value is small, and the pile side frictional resistance is only 21 kPa; in the process of increasing the load, the axial force of the pile end is basically kept unchanged or is not changed greatly; when the load of the D-1 test pile is increased to the last stage of 429kN, the axial force of the pile end is about 45kN and only accounts for 10.5 percent of the total load; when the load of the D-5 test pile is increased to the last stage of 220kN, the axial force of the pile end is small.

Further, the vertical resistance to plucking static load test of single pile includes:

a. test data;

the loading grade of the vertical uplift static load test of the single pile is shown in a table 9;

summarizing the pile top pulling forces of the D-2, D-3, D-4, D-5, D-7 and D-8 test piles under the action of loads at all levels in a table 8;

b. analyzing test results;

d-2: when the first-stage load is loaded to 36kN according to the specified load level, the accumulated uplift amount of the pile top is 0.58 mm; when the load is loaded to the tenth level load of 185kN, the accumulated uplift amount of the pile top is 26.99 mm; measuring the resilience of the pile top to be 9.25mm after unloading, wherein the residual uplift amount of the pile top is 17.74mm, and the resilience of the pile top is 34.3%; determining the ultimate pulling resistance bearing capacity to be 185 kN;

② D-3: when the pile is loaded to the first-stage load of 32.4kN according to the specified load level, the accumulated uplift amount of the pile top is 0.79 mm; when the load is loaded to the ninth-level load of 162kN, the accumulated uplift amount of the pile top is 9.21 mm; measuring the resilience of the pile top to be 5.47mm after unloading, wherein the residual uplift amount of the pile top is 3.74mm, and the resilience of the pile top is 59.4%; the single pile test stops loading when the estimated single pile uplift resistance limit bearing capacity is reached, and the ultimate uplift resistance bearing capacity of the test pile is larger than 162 kN;

③ D-4: when the first-stage load is loaded to 36kN according to the specified load level, the accumulated uplift amount of the pile top is 0.75 mm; when the load is loaded to the tenth level load of 185kN, the accumulated uplift amount of the pile top is 28.85 mm; measuring the resilience of the pile top by 10.83mm after unloading, wherein the residual uplift amount of the pile top is 18.02mm, and the resilience of the pile top is 37.5%; determining the ultimate uplift bearing capacity of the test pile to be 185 kN;

d-5: when the pile is loaded to the first-stage load of 44kN according to the specified load level, the accumulated uplift amount of the pile top is 0.78 mm; when the load is loaded to the thirteenth level load of 308kN, the accumulated uplift amount of the pile top is 118.83 mm; measuring the resilience of the pile top by 15.45mm after unloading, wherein the residual uplift amount of the pile top is 103.38mm, and the resilience of the pile top is 13.0%; determining the ultimate uplift bearing capacity of the test pile to be 220kN according to a Q-S curve graph, and the accumulated uplift amount of the corresponding pile top to be 16.03 mm;

d-7: when the pile is loaded to the first-stage load of 32.4kN according to the specified load level, the accumulated uplift amount of the pile top is 0.19 mm; when the load is loaded to the ninth-level load of 162kN, the accumulated uplift amount of the pile top is 6.04 mm; measuring the resilience of the pile top to be 4.28mm after unloading, wherein the residual uplift amount of the pile top is 1.76mm, and the resilience of the pile top is 70.9%; the single pile test stops loading when the estimated single pile uplift resistance limit bearing capacity is reached, and the ultimate uplift resistance bearing capacity of the test pile is larger than 162 kN;

sixthly, D-8: when the first-stage load is loaded to 36kN according to the specified load level, the accumulated uplift amount of the pile top is 0.87 mm; when the load is loaded to the eleventh level load of 202kN, the accumulated uplift amount of the pile top is 33.56 mm; after unloading, measuring the resilience of the pile top to be 12.32mm, wherein the residual uplift amount of the pile top is 21.24mm, and the resilience of the pile top is 36.7%; the ultimate uplift bearing capacity of the test pile is 202 kN;

analysis of the anti-pulling static load test results of all the test piles shows that the anti-pulling bearing capacity of the three vertical piles is relatively close; the ultimate uplift bearing capacity of the inclined pile D-5 is 220kN, and the ultimate uplift bearing capacities of the D-3 and the D-7 are greater than 162 kN; the difference between the ultimate uplift bearing capacity of the inclined pile and the ultimate uplift bearing capacity of the straight pile is small; the resilience rates of the pile tops of D-3 and D-7 are higher; the resilience rate of the pile tops of the rest test piles is 13-38%, and the residual deformation is large;

analyzing the axial force of the pile body and the side frictional resistance of the pile according to the result of the steel bar stress meter; in the D-5 test pile test, the pile side frictional resistance of the upper soil layer firstly reaches an extreme value of 34kPa and is gradually transmitted downwards; the D-3 and D-7 pile tests have the pile side frictional resistance of 18.4kPa and 13.5kPa respectively due to the small final load value.

Further, the single pile horizontal static load test comprises:

a. test data;

(1) the loading grade of the single-pile horizontal static load test is detailed in table 10;

(2) summarizing the pile top horizontal displacement amounts of the D-2, D-7 and D-8 test piles under the action of loads at all levels, and referring to tables 11-13 in detail;

(3) H-Y curves and logH-logY curves of the D-2, D-7 and D-8 test piles under the action of loads at all levels are summarized;

b. analyzing test results;

(1) d-2: after the horizontal load reaches 100kN, the horizontal displacement reaches 42.62mm, and the loading is stopped; after the H-Y curve shows that H is 90kN, the horizontal displacement of the pile top is obviously turned, the end point of a second straight line is located at 90kN, the horizontal limit bearing capacity is 90kN, and the corresponding horizontal displacement of the pile top is 22.05 mm;

(2) d-7: after the horizontal load reaches 110kN, the horizontal displacement reaches 43.32mm, and the loading is stopped; after the H-Y curve shows that H is 90kN, the horizontal displacement of the pile top is obviously turned, the end point of a second straight line is located at 90kN, the horizontal limit bearing capacity is 90kN, and the corresponding horizontal displacement of the pile top is 15.47 mm;

(3) d-8: after the horizontal load reaches 100kN, the horizontal displacement reaches 48.60mm, and the loading is stopped; after the H-Y curve shows that H is 90kN, the horizontal displacement of the pile top is obviously turned, the end point of a second straight line is located at 90kN, the horizontal limit bearing capacity is 90kN, and the corresponding horizontal displacement of the pile top is 29.80 mm;

(4) the influence of the existence of the steel pipe on the pile top on the horizontal ultimate bearing capacity of the pile is small, and the horizontal displacement of the pile with the steel pipe is smaller than that of the pile without the steel pipe; the bearing capacity of the inclined pile is not different from that of the straight pile, and the horizontal displacement of the inclined pile is smaller than that of the straight pile; the arrangement of steel pipes on the pile top and the inclination of the pile body are favorable for reducing the horizontal displacement under the action of horizontal load;

(5) and (3) analyzing economic and social benefits: compared with a 66 KV single-loop line tangent tower two-type foundation and a stepped concrete pouring foundation, the concrete is 4.52 cubic meters per micropore pile and 2.86 cubic meters; 450kg of steel/430 kg of microporous pile; the construction period is 8 days/the microporous pile is 4 days; temporary land occupation of 49 square meters/16 square meters of the microporous pile; meanwhile, the micro-porous pile is not dug and has no soil return; original soil is effectively utilized, and the bearing capacity of the microporous pile foundation is higher than 26%; the micropore pile is convenient for mechanized construction, protects the environment: the comprehensive cost is saved by 20%, the microporous pile foundation is used for 8% of foundations of 66 kilovolt and 35 kilovolt lines every year, and the economic benefit is 1160 ten thousand yuan every year;

analyzing investment benefits: investment is saved by 1160 ten thousand yuan each year, and investment is saved by 11600 ten thousand yuan accumulated in 10 years;

and (3) analyzing environmental protection benefits: the annual environmental protection benefit reaches more than 1000 ten thousand yuan.

The invention has the following beneficial effects and advantages that: the invention has the advantages of safe construction of the tower foundation and convenient construction, can greatly shorten the construction period, and can remarkably reduce the construction cost and save the fund because the occupied area is smaller. In addition, the MP pile is a variable-section pile body, so that the bearing capacity of a single pile is greatly improved by the secondary grouting process, the bearing capacity after grouting can be improved by 20-30% compared with the bearing capacity before grouting, the service life of electric power infrastructure can be effectively prolonged, and the MP pile is safer and more reliable. The characteristics of the MP pile of the invention can be fully exerted on the pole tower foundation of the soft soil foundation, so that the micro pile process is obviously improved, and good technical support is provided for the construction of power infrastructure in China.

Drawings

The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

FIG. 1 is a schematic diagram of the construction of positioning and setting a casing of a drilling machine according to the present invention; FIG. 2 is a schematic diagram of a drill drilling of the present invention; FIG. 3 is a schematic illustration of hole cleaning according to the present invention; FIG. 4 is a schematic view of the present invention showing the nested steel pipes, the reinforcement cage and the grouting pipe; FIG. 5 is a schematic view of the position of the grouting pipe in the present invention; FIG. 6 is a schematic illustration of the present invention showing gravel packing and grouting; FIG. 7 is a schematic diagram of the present invention illustrating lifting the primary grout pipe for re-grouting; FIG. 8 is a schematic diagram of secondary grouting in the present invention; FIG. 9 is a schematic diagram of a pile of the present invention; FIG. 10 is a graph of D-1 vertical compression static load Q-S in the present disclosure; FIG. 11 is a graph of D-1 vertical compression static load in the present disclosure; FIG. 12 is a graph of D-1 vertical compression static load in the present invention. FIG. 13 is a graph of D-2 horizontal static load H-Y in accordance with the present invention; FIG. 14 is a graph of D-7 horizontal static load H-Y in the present invention; FIG. 15 is a graph of D-8 horizontal static load H-Y in accordance with the present invention; FIG. 16 is a graph of D-2 level static load logH-logY in the present invention; FIG. 17 is a graph of D-7 level static load logH-logY in the present invention; FIG. 18 is a graph showing the D-8 level static load logH-logY in the present invention.

In the figure: the concrete pouring device comprises a primary grouting pipe 1, a secondary grouting pipe 2, a reinforcement cage 3, a protective cylinder 4, a nested steel pipe 5 and gravel aggregate 6.

Detailed Description

In order that the above objects, features and advantages of the present invention can be more clearly understood, a more particular description of the invention will be rendered by reference to the appended drawings. It should be noted that the embodiments and features of the embodiments of the present application may be combined with each other without conflict. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, however, the present invention may be practiced in other ways than those specifically described herein, and therefore the scope of the present invention is not limited by the specific embodiments disclosed below. The solution of some embodiments of the invention is described below with reference to fig. 1-18.

Example 1

The invention provides an embodiment, and relates to a construction method of a pole tower foundation micro pile in a soft soil foundation. The MP pile is different from the traditional tree root pile in that a secondary grouting process is adopted. Therefore, the MP pile is a variable-section pile body, and the bearing capacity of the single pile in the tower foundation of the soft soil foundation can be greatly improved through the secondary grouting process.

The invention relates to a construction method of a pole tower foundation micro pile in a soft soil foundation, which specifically comprises the following steps:

step 1, binding a reinforcement cage 3 and a secondary grouting pipe 2.

During construction, firstly, a 1-inch secondary grouting pipe 2 is bound on the reinforcement cage 3. The binding position is positioned at the top of the reinforcement cage 3. The reinforcement cage 3 can be the conventional equipment that uses, also can tailor the volume according to on-the-spot foundation pile body excavation depth and the volume of pouring and compile the shaping, belongs to the customization product. A plurality of small holes which are uniformly arranged are formed in the secondary grouting pipe 2 at intervals, in order to adapt to pressure release during grouting solidification, the outside of each small hole is sealed and blocked by sealing materials, and cement paste is prevented from entering the grouting pipe. The sealing material is a polypropylene-ethylene mixed material. The number of the secondary grouting pipes is generally 1-2.

And 2, positioning the pile position, forming holes and cleaning the holes.

As shown in fig. 1-3, fig. 1 is a schematic diagram of the positioning and casing setting construction of the drilling machine of the present invention, fig. 2 is a schematic diagram of the drilling machine of the present invention, and fig. 3 is a schematic diagram of the completion and cleaning of the drilling of the present invention. When the pile is formed, firstly, a small-sized drilling machine is used for positioning and arranging the protective cylinder 4 of the drilling machine, then, drilling is carried out, the diameter of the drilled hole is measured by adopting an aperture gauge, the hole is cleaned after the designed elevation is reached, no mud and sand exist in the cleaned water, and the specific gravity of the cleaned mud is not more than 1.1.

And 3, placing a reinforcement cage 3 and the next grouting pipe 1 in the hole, and putting broken stone aggregate 6 into the first grouting pipe 1.

As shown in fig. 4, fig. 4 is a schematic view of the nested steel pipes, the reinforcement cage and the grouting pipe in the invention; and (4) hoisting the reinforcement cage 3 bound with the secondary grouting pipe 2, and then lowering the primary grouting pipe 1 to the bottom of the hole. And throwing the gravel aggregate into the drill hole to the position of the hole opening. The number of the primary grouting pipes 1 is generally 1-2. A plurality of small holes which are uniformly arranged are formed in the primary grouting pipe 1 at intervals, and the small holes are sealed and blocked by sealing materials to prevent cement mortar from entering the grouting pipe.

Step 4, grouting into the primary grouting pipe 1 to form a pile preliminarily; a plurality of closed small holes are arranged on the primary grouting pipe 1 to adapt to pressure release during grouting solidification.

As shown in fig. 5-6, fig. 5 is a schematic diagram of the position of a grouting pipe in the invention, and fig. 6 is a schematic diagram of filling gravel to the position of an orifice and grouting to the orifice to discharge grout in the invention. And (5) injecting cement mortar into the primary grouting pipe by using a grouting pump until the orifice emits the mortar. The specific gravity of the cement mortar reaches a water cement ratio of 0.5: 1, the corresponding site perfusion specific gravity is 1.8 to 2.0 through the site test.

Step 5, after the slurry is initially solidified, secondary grouting is carried out in the primary grouting pipe 1;

as shown in fig. 7-8, fig. 7 is a schematic view of lifting a primary grouting pipe for grouting again in the invention, and fig. 8 is a schematic view of secondary grouting in the invention. And lifting the primary grouting pipe 1 to the position 3-4 m away from the orifice and then performing secondary grouting. And after the slurry is initially set, performing secondary grouting for about 4-6 hours. And during the second grouting, firstly, injecting high-pressure slurry into the secondary grouting pipe 2 by using a grouting pump, wherein the slurry is cement mortar. The sealing material outside the secondary grouting pipe 2 is broken by high pressure, namely, the cement mortar is injected in the so-called plug opening process. And small holes on the primary grouting pipe and the secondary grouting pipe are opened after grouting is finished.

And 6, after the slurry is solidified, finally forming the pile.

As shown in fig. 9, fig. 9 is a pile forming schematic diagram in the invention. And after the secondary injected slurry is solidified, finally forming the pile.

And 7, after completion, carrying out low strain detection on part of piles to check the pile body quality.

The quality of the hole forming and pile body concrete of the MP pile directly influences the pile body bearing capacity of the MP pile, so that the hole forming diameter and the pile body quality of part of pile construction need to be detected.

A JJC-IA bored concrete pile detection system is adopted for pore-forming quality detection, and the system comprises a JJY-2 type caliper. During the aperture measurement, the JJY-2 type caliper probe is placed at the bottom of a hole, four legs are opened in an umbrella shape and are tightly attached to the hole wall, the cable winch slowly lifts the probe through an orifice pulley, corresponding electric signals are output along with the change of the aperture, and the electric signals are received by a ground recorder and an aperture curve graph is drawn. The detection result of the pile forming quality of the test pile indicates that the pore diameter of the test pile meets the requirement.

The MP pile belongs to a small-diameter cast-in-situ bored pile, so that the quality of the pile body can be detected according to the detection means of the cast-in-situ bored pile. The pile forming quality detection aims to detect whether the phenomena of pile bearing capacity influence, such as necking, neck expanding, pile breaking, separation and the like, occur in the MP pile.

The quality of the pile body is detected by adopting a TNO low-strain test system introduced from the Netherlands to carry out low-strain detection, and the detection result shows that the quality of the pile body of the test pile is good.

The low strain detection of the partial piles is performed on a single pile test.

The single pile test comprises 8 single piles which are respectively D-1, D-2, D-3, D-4, D-5, D-6, D-7 and D-8.

Wherein D-2, D-4, D-6 and D-8 are vertical piles; d-1, D-3, D-5 and D-7 are oblique piles, 10-degree inclination angles are formed between the axial direction and the vertical direction of the piles, steel bar stress meters are buried in the piles, the stress meters are buried in 3 sections of the pile body along the depth direction, and 2 steel bar stress meters are arranged on each section.

The pile group number is: q-1 and Q-2, wherein Q-1 is a group of 16 piles, Q-2 is a group of 9 piles, a steel bar stress meter is embedded in ten piles of the group of Q-1 piles, and 5 soil pressure meters are embedded under a bearing platform.

The single pile test content comprises the following steps: the method comprises the following steps of a single-pile vertical compression static load test, a single-pile horizontal load test, a single-pile vertical uplift test, a single-pile compression and horizontal load combined loading test and a single-pile uplift and horizontal load combined loading test, wherein the specific test content of each single pile is shown in the table 1. In order to know the distribution condition of the friction resistance of the soil around the pile, the steel bar stress meter is tested under each level of load when the single pile static load test with the steel bar stress meter embedded is carried out.

Table 1 summary of contents of single pile test

The test method is carried out according to the main point of the single pile static load test in the national technical Specification for building pile foundations (JGJ 94-94) and by combining other relevant specification regulations. In order to successfully perform other subsequent tests, the single pile which needs to be subjected to various tests is not damaged except for the last test. The dial indicator, the oil pressure gauge and the jack need to be calibrated in advance during the test. The test equipment was installed according to the regulations of the building pile technical Specification (JGJ 94-94). The test apparatus includes:

the single-pile compression test adopts a pile weight platform reaction method. And during static load test equipment configuration, designing according to the determined estimated single-pile compression-resistant limit bearing capacity 213kN, wherein the length of a main beam and an auxiliary beam of the test reaction frame is 7m, and the weight of the main beam and the auxiliary beam is 450 kg. One high-pressure oil pump is used for supplying pressure, and one 300-ton hydraulic jack is used for loading. And a dial indicator is adopted for measuring the settlement of the pile top of the single pile.

During configuration of the single-pile horizontal test equipment, according to the determined estimated single-pile horizontal limit bearing capacity 59kN design, counter force is provided by single piles or grouped piles finished by surrounding tests, and horizontal thrust is applied by a 300-ton hydraulic jack. Two punctuation blocks are arranged on the pile body on the upper side and the lower side of the action line, and a dial indicator is arranged on the corresponding punctuation blocks to test the horizontal displacement.

And designing the single-pile uplift resistance test equipment according to the determined estimated uplift limit bearing capacity 162kN of the single-pile during configuration. A high-pressure oil pump is used for supplying pressure, and a 50-ton hydraulic jack is loaded to provide tension. The counterforce is provided by the foundation, and two steel beams with the length of 7 meters and the length of 450 kilograms are placed on the foundation to be used as counterforce supports. And a dial indicator is adopted for measuring the pulling amount of the top of the single pile.

The test equipment for the single-pile compression resistance and horizontal combined loading test adopts a loading and measuring system for a single-pile compression resistance test and a single-pile horizontal test. The test equipment for the single-pile pulling resistance and horizontal combined loading test adopts a loading and measuring system for the single-pile pulling resistance test and the single-pile horizontal test.

The invention relates to low strain detection of partial piles, which specifically comprises the following steps:

(1) and (3) carrying out a vertical compression static load test on the single pile.

The method comprises the following steps: a. test data.

The loading grade of the vertical compression-resistant static load test of the single pile is shown in a table 3.

And the pile top settlement amounts of the test piles D-1, D-2, D-5 and D-6 under the load action of each level are summarized in tables 4 to 7.

And the Q-S curve, the logQ-S curve and the S-lgt curve of the D-1 test pile under the action of loads at all levels are summarized as shown in the figures 10 to 12. FIG. 10 is a graph of D-1 vertical compression static load Q-S in the present disclosure; FIG. 11 is a graph of D-1 vertical compression static load in the present disclosure; FIG. 12 is a graph of D-1 vertical compression static load in the present invention.

b. And (5) analyzing test results.

D-1: when the pile is loaded to the first-stage load of 66kN according to the specified load level, the accumulated settlement of the pile top is 1.22 mm; when the load is loaded to the twelfth-stage load of 429kN, the accumulated settlement of the pile top is 33.05 mm. After unloading, the resilience of the pile top is measured to be 13.10mm, the residual settlement of the pile top is measured to be 19.95mm, and the resilience of the pile top is 39.6 percent. And determining the compressive ultimate bearing capacity to be 363kN, and the corresponding pile top settlement amount to be 18.04 mm.

② D-2: when the pile is loaded to the first-stage load of 99kN according to the specified load level, the accumulated settlement of the pile top is 1.09 mm; when the load is loaded to the tenth stage load of 396kN, the accumulated settlement of the pile top is 31.99 mm. After unloading, the resilience of the pile top is measured to be 9.21mm, the residual settlement of the pile top is 22.78mm, and the resilience of the pile top is 28.8 percent. And determining the compressive ultimate bearing capacity to be 363kN, and the corresponding pile top settlement amount to be 22.13 mm.

③ D-5: when the pile is loaded to the first-stage load of 44kN according to the specified load level, the accumulated settlement of the pile top is 0.85 mm; when the load is loaded to the ninth-stage load of 220kN, the accumulated settlement of the pile top is 9.20 mm. After unloading, the resilience of the pile top is measured to be 5.28mm, the residual settlement of the pile top is 3.92mm, and the resilience of the pile top is 57.4 percent. The single pile test stops loading when the estimated single pile compression resistance limit bearing capacity is reached, at the moment, the pile top does not reach a larger settlement amount, and the compression resistance limit bearing capacity of the test pile is larger than 220 kN.

D-6: when the pile is loaded to the first-stage load of 44kN according to the specified load level, the accumulated settlement of the pile top is 0.99 mm; when the load is loaded to the seventeenth stage load of 396kN, the accumulated settlement of the pile top is 31.83 mm. After unloading, the resilience of the pile top is measured to be 12.72mm, the residual settlement of the pile top is measured to be 19.11mm, and the resilience of the pile top is measured to be 40.0%. And determining that the compressive ultimate bearing capacity is 330kN, and the corresponding pile top settlement is 20.24 mm.

Fifthly, summarizing the ultimate compression bearing capacity of each test pile, as shown in table 2. From the analysis of the compression-resistant static load test results of all the test piles, the ultimate bearing capacity of the straight piles D-2 and D-6 is 363kN and 330kN respectively; the compressive ultimate bearing capacity 363kN of the inclined pile D-1 and the ultimate bearing capacity of the D-5 are greater than 220 kN. The difference of the single-pile compression-resistant limit bearing capacity of the vertical pile and the inclined pile is not large. The resilience of the pile top of the D-5 test pile is 57.4 percent, which is because the accumulated settlement of the pile top of the pile is smaller, the frictional resistance of the soil around the pile is not fully exerted, and the main deformation is the elastic deformation of the pile body. The resilience rate of the pile top of the rest of test piles is between 28 and 40 percent, and the residual settlement is large.

Analyzing the axial force and the side frictional resistance of the pile body according to the result of the steel bar stress meter. It can be seen from the distribution diagram of axial force of D-1 and D-5 pile body and pile side frictional resistance, when the load is small, the load transferred from pile top is mainly borne by the pile side frictional resistance of upper soil layer. Along with the increase of the load, the relative displacement between the pile and the soil is increased, and the frictional resistance is correspondingly increased. The pile side frictional resistance of the upper soil layer in the D-1 pile test reaches 43kPa and is gradually transmitted downwards; the D-5 test pile test has the advantage that the pile side frictional resistance is only 21kPa due to the small final loading value. In the process of load increase, the pile end shaft force (equal to the end bearing force) is basically kept unchanged or does not change greatly. When the load of the D-1 test pile is increased to the last stage of 429kN, the axial force of the pile end is about 45kN and only accounts for 10.5 percent of the total load. When the load of the D-5 test pile is increased to the last stage of 220kN, the axial force of the pile end is small.

TABLE 2 ultimate bearing capacity of vertical compression static load test

TABLE 3 single-pile vertical compression-resistant static load test load grading table

TABLE 4D-1 vertical compression static load test load and settlement data

TABLE 5D-2 vertical compression static load test load and settlement data

TABLE 6D 5 vertical compression static load test load and settlement data

TABLE 7D-6 vertical compression static load test load and settlement data

(2) And (3) carrying out a vertical uplift static load test on the single pile.

After the horizontal test is finished, the horizontal test is carried out, wherein the pile tops of the D-7 pile and the D-8 pile are free of steel pipes.

a. Test data.

The loading grade of the vertical uplift static load test of the single pile is shown in a table 9.

And the pile top pulling forces of the D-2, D-3, D-4, D-5, D-7 and D-8 test piles under the load action of each level are summarized in a table 8.

b. And (5) analyzing test results.

D-2: when the first-stage load is loaded to 36kN according to the specified load level, the accumulated uplift amount of the pile top is 0.58 mm; when the load is loaded to the tenth level of load of 185kN, the accumulated uplift amount of the pile top is 26.99 mm. And after unloading, measuring the resilience of the pile top to be 9.25mm, wherein the residual uplift amount of the pile top is 17.74mm, and the resilience rate of the pile top is 34.3%. The ultimate pullout resistance bearing capacity is determined to be at least 185 kN.

② D-3: when the pile is loaded to the first-stage load of 32.4kN according to the specified load level, the accumulated uplift amount of the pile top is 0.79 mm; when the load is loaded to the ninth-stage load of 162kN, the accumulated uplift amount of the pile top is 9.21 mm. And after unloading, measuring the resilience of the pile top to be 5.47mm, wherein the residual uplift amount of the pile top is 3.74mm, and the resilience of the pile top is 59.4%. The single pile test is terminated when the estimated single pile uplift resistance limit bearing capacity is reached, and the ultimate uplift resistance bearing capacity of the test pile is larger than 162 kN.

③ D-4: when the first-stage load is loaded to 36kN according to the specified load level, the accumulated uplift amount of the pile top is 0.75 mm; when the load is loaded to the tenth level of load of 185kN, the accumulated uplift amount of the pile top is 28.85 mm. And after unloading, measuring the resilience of the pile top to be 10.83mm, wherein the residual uplift amount of the pile top is 18.02mm, and the resilience of the pile top is 37.5%. The ultimate uplift bearing capacity of the test pile is determined to be at least 185 kN.

D-5: when the pile is loaded to the first-stage load of 44kN according to the specified load level, the accumulated uplift amount of the pile top is 0.78 mm; when the load is loaded to the thirteenth level load of 308kN, the accumulated uplift amount of the pile top is 118.83 mm. And after unloading, measuring the resilience of the pile top to be 15.45mm, wherein the residual uplift amount of the pile top is 103.38mm, and the resilience of the pile top is 13.0%. And determining the ultimate uplift bearing capacity of the test pile to be 220kN according to a Q-S curve graph, wherein the accumulated uplift amount of the corresponding pile top is 16.03 mm.

D-7: when the pile is loaded to the first-stage load of 32.4kN according to the specified load level, the accumulated uplift amount of the pile top is 0.19 mm; when the load is loaded to the ninth-level load of 162kN, the accumulated uplift amount of the pile top is 6.04 mm. After unloading, the resilience of the pile top is measured to be 4.28mm, the residual uplift amount of the pile top is 1.76mm, and the resilience rate of the pile top is 70.9%. The single pile test is terminated when the estimated single pile uplift resistance limit bearing capacity is reached, and the ultimate uplift resistance bearing capacity of the test pile is larger than 162 kN.

Sixthly, D-8: when the first-stage load is loaded to 36kN according to the specified load level, the accumulated uplift amount of the pile top is 0.87 mm; when the load is loaded to the eleventh-stage load of 202kN, the accumulated uplift amount of the pile top is 33.56 mm. After unloading, the resilience of the pile top is measured to be 12.32mm, the residual uplift amount of the pile top is 21.24mm, and the resilience of the pile top is 36.7%. The ultimate uplift bearing capacity of the test pile is determined to be 202 kN.

Analysis of the anti-pulling static load test results of all the test piles shows that the anti-pulling bearing capacity of the three vertical piles is relatively close; the ultimate uplift bearing capacity of the inclined pile D-5 is 220kN, and the ultimate uplift bearing capacities of the D-3 and the D-7 are greater than 162 kN. The difference between the ultimate uplift bearing capacity of the inclined pile and the ultimate uplift bearing capacity of the straight pile is small. The resilience rates of the pile tops of the D-3 pile and the D-7 pile are high, the accumulated uplift amount of the pile top of the single pile is small, the frictional resistance of soil around the pile is not fully exerted, and the main deformation amount is the elastic deformation of the pile body. The resilience rate of the pile top of the rest test piles is only 13-38%, and the residual deformation is large.

And analyzing the axial force of the pile body and the side frictional resistance of the pile according to the result of the steel bar stress meter. The change rule of the axial force of the pile body and the side frictional resistance of the pile in the anti-pulling static load test along the depth is similar to that in the anti-pressing static load test. The uplift load transmitted from the pile top is mainly born by the pile side frictional resistance of the upper soil layer. Along with the increase of the load, the relative displacement between the pile and the soil is increased, and the frictional resistance is correspondingly increased. In the D-5 test pile test, the pile side frictional resistance of the upper soil layer firstly reaches an extreme value of 34kPa and is gradually transmitted downwards; the D-3 and D-7 pile test tests have the pile side frictional resistance of only 18.4kPa and 13.5kPa respectively due to the small final load value.

TABLE 8 ultimate bearing capacity of vertical pulling-resistant static load test

Table 9 vertical pulling-resistant static load test load grading table

(3) And (4) carrying out horizontal static load test on the single pile.

And after the compression test is finished, performing the compression test, wherein the pile tops of the D-7 and D-8 are free of steel pipes.

a. Test data.

(1) The loading grade of the single pile horizontal static load test is detailed in table 10.

(2) The pile top horizontal displacement amounts of the D-2, D-7 and D-8 test piles under the load action of each level are summarized, and the detailed table is shown in tables 11-13.

(3) H-Y curves and logH-logY curves of the D-2 test piles, the D-7 test piles and the D-8 test piles under the action of loads of all levels are summarized, and the H-Y curves and the logH-logY curves are shown in figures 13-18.

b. And (5) analyzing test results.

(1) D-2: after the horizontal load reached 100kN, the horizontal displacement reached 42.62mm, thus terminating the loading. After the H-Y curve shows that H is 90kN, the horizontal displacement of the pile top is obviously turned, and the logH-logY curve shows that the end point of the second straight line is positioned at 90kN, so that the horizontal limit bearing capacity is 90kN, and the corresponding horizontal displacement of the pile top is 22.05 mm.

(2) D-7: after the horizontal load reached 110kN, the horizontal displacement reached 43.32mm, thus terminating the loading. After the H-Y curve shows that H is 90kN, the horizontal displacement of the pile top is obviously turned, and the logH-logY curve shows that the end point of the second straight line is positioned at 90kN, so that the horizontal limit bearing capacity is 90kN, and the corresponding horizontal displacement of the pile top is 15.47 mm.

(3) D-8: after the horizontal load reached 100kN, the horizontal displacement reached 48.60mm, thus terminating the loading. After the H-Y curve shows that H is 90kN, the horizontal displacement of the pile top is obviously turned, and the logH-logY curve shows that the end point of the second straight line is positioned at 90kN, so that the horizontal limit bearing capacity is 90kN, and the corresponding horizontal displacement of the pile top is 29.80 mm.

(4) The influence of the existence of the steel pipe on the pile top on the horizontal ultimate bearing capacity of the pile is small, but the horizontal displacement of the pile with the steel pipe is smaller than that of the pile without the steel pipe; the bearing capacity of the inclined pile is not much different from that of the straight pile, but the horizontal displacement of the inclined pile is much smaller than that of the straight pile. The arrangement of the steel pipe on the pile top and the inclination of the pile body are beneficial to reducing the horizontal displacement under the action of the horizontal load.

(5) And (3) analyzing economic and social benefits: compared with a 66 KV single-loop line tangent tower two-type foundation and a stepped concrete pouring foundation, the concrete is 4.52 cubic meters per micropore pile and 2.86 cubic meters; 450kg of steel/430 kg of microporous pile; the construction period is 8 days/the microporous pile is 4 days; temporary land occupation of 49 square meters/16 square meters of the microporous pile; meanwhile, the micro-porous pile is not dug and has no soil return; original soil is effectively utilized, and the bearing capacity of the microporous pile foundation is higher than 26%; the micropore pile is convenient for mechanized construction, protects the environment (no excavation, occupies less 50 percent, consumes less concrete by 56 percent, and has convenient construction with short construction period by 60 percent): the comprehensive cost is saved by 20%, the microporous pile foundation (2.9 ten thousand by 20% by 2000 foundation: 1160 ten thousand yuan) is used for 8% of foundations of 66 kilovolt and 35 kilovolt lines every year, and the economic benefit is 1160 ten thousand yuan every year. Analyzing investment benefits: the investment is saved by 1160 ten thousand yuan each year, and the investment is saved by 11600 ten thousand yuan accumulated in 10 years. And (3) analyzing environmental protection benefits: the annual environmental protection benefit reaches more than 1000 ten thousand yuan.

Table 10 horizontal static load test load grading table

TABLE 11D-2 horizontal static load test load and horizontal displacement data

Horizontal load (kN)	Horizontal displacement (mm)
		0	0
10	1.21
		20	2.14
30	4.23
		40	6.31
50	9.59
		60	11.10
70	13.54
		80	17.89
90	22.05
		100	42.62

TABLE 12D-7 horizontal static load test load and horizontal displacement data

Horizontal load (kN)	Horizontal displacement (mm)
		0	0
10	0.49
		20	1.36
30	2.40
		40	3.66
50	5.01
		60	7.03
70	9.86
		80	12.32
90	15.47
		100	27.14
110	43.32

TABLE 13D-8 horizontal static load test load and horizontal displacement data

Horizontal load (kN)	Horizontal displacement (mm)
		0	0
10	1.14
		20	2.51
30	3.93
		40	6.99
50	11.56
		60	15.60
70	18.99
		80	23.80
90	29.80
		100	48.60

Finally, the following conclusions were drawn from the above tests:

(1) from the analysis of single pile static load test results, the compressive limit bearing capacity of the D-1 test pile, the D-2 test pile and the D-6 test pile is 330kN-363kN, and the compressive limit bearing capacity of the D-5 test pile is greater than 220 kN; the ultimate uplift bearing capacity of the D-5 test piles and the ultimate uplift bearing capacity of the D-8 test piles are respectively 220kN and 202kN, and the ultimate bearing capacity of the D-2 test piles and the ultimate bearing capacity of the D-4 test piles are greater than 185 kN; the horizontal ultimate bearing capacity of the D-2 test piles, the D-7 test piles and the D-8 test piles is 90 kN; axial ultimate bearing capacity in a combined loading test of the compression resistance and the horizontal load of the D-5 test pile is 363 kN; axial ultimate bearing capacity in a combined loading test of the uplift resistance and the horizontal load of the D-1 test pile and the D-3 test pile is 202kN and 209kN respectively.

(2) From the analysis of the group pile static load test results, the ultimate bearing capacity of Q-1 in the compression-resistant and horizontal load combined loading test is 4642kN, and the ultimate bearing capacity of Q-2 is 2923 kN; in a horizontal static load test, the horizontal ultimate bearing capacity of Q-1 is 1000kN, and the horizontal ultimate bearing capacity of Q-2 is 550 kN; in the combined load test of the pulling resistance and the horizontal load, the ultimate bearing capacity of Q-1 is 3020kN, and the ultimate bearing capacity of Q-2 is 1523 kN.

(3) Most of the piles in the single-pile test have the resilience rate of less than 40 percent and have larger residual deformation, which is shown as the property of a friction pile.

(4) The inclination angle of the pile is small, the influence on the ultimate bearing capacity of the single pile is not great, but the distribution of the counterforce of the bearing platform in the pile group and the distribution of the load in each pile are influenced, so that the ultimate bearing capacity of the pile group is influenced.

(5) The existence of a steel pipe on the top of a single pile does not influence the horizontal ultimate bearing capacity of the pile, but the horizontal displacement of the pile with the steel pipe is smaller than that of the pile without the steel pipe; the bearing capacity of the inclined pile is not much different from that of the straight pile, but the horizontal displacement is much smaller than that of the straight pile. Therefore, the arrangement of the steel pipe on the pile top and the inclination of the pile body are beneficial to reducing the horizontal displacement under the action of the horizontal load.

(6) Compared with the tree root pile, the tower foundation miniature pile adopts a secondary grouting process, improves the performance of the side soil of the pile, and obviously improves the compression resistance, the pulling resistance and the horizontal load resistance of the pile.

Example 2

The invention also provides an embodiment, which is a construction method of the micro-pile in the soft soil foundation, and the construction method is as in embodiment 1, when in construction, all the test piles are 15m long, and the pile diameter is 250 mm. Except for the D-7 and D-8 test piles, steel pipes with the diameter of phi 219 multiplied by 4mm are adopted to replace reinforcement cages within 3m of the pile tops of the rest test piles, the reinforcement of a part of the pile body with the diameter of 3-10 m is 8 phi 14, and the reinforcement of the part of the pile body with the diameter of 10-15 m is halved; the stirrups adopt spiral stirrups phi 6@200, one phi 12 welding stiffening stirrup is arranged every 2m, the pile top stirrups are reinforced, and the pile body reinforcement is shown in figure 4-2. No. 425 ordinary portland cement is adopted as the cement, and cleaned macadam with the particle size of 15-25 mm is adopted as the macadam aggregate 6. The water-cement ratio of the primary grouting is 0.5, and the water-cement ratio of the secondary grouting is 0.5. The size of the single-pile bearing platform is 0.6 multiplied by 0.5 (height) m, the concrete of the bearing platform adopts C20, and the reinforcing bars of the bearing platform are phi 16@150 in two directions. The size of the 4 × 4 pile cap is 3.5 × 3.5 × 0.75 (height) m, and the size of the 3 × 3 pile cap is 2.6 × 2.6 × 0.75 (height) m. The concrete of the bearing platform adopts C25, and the reinforcing bars are phi 16@200 bidirectional.

A geological drilling machine capable of selecting any main shaft angle is adopted for test pile hole forming, and the outer diameter of a blade of a spiral drill rod is 250 mm; the pressure grouting equipment adopts a grouting pump for grouting.

In the present invention, the terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance. The terms "connected" and "fixed" are to be construed broadly, e.g., "connected" may be a fixed connection, a removable connection, or an integral connection. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations. In the description of the present invention, it is to be understood that the indicated orientations or positional relationships are based on the orientations or positional relationships shown in the drawings and are only for convenience in describing the present invention and simplifying the description, but do not indicate or imply that the indicated devices or units must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention.

In the description of the present specification, the description of the terms "one embodiment," "some embodiments," or the like, means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

Finally, it should be noted that: the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting the same, and although the present invention is described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: modifications and equivalents may be made to the embodiments of the invention without departing from the spirit and scope of the invention, which is to be covered by the claims.

Claims

1. A construction method of a pole tower foundation micro pile in a soft soil foundation is characterized by comprising the following steps: the method comprises the following steps:

step 1, binding a reinforcement cage and a secondary grouting pipe;

step 2, pile position positioning, hole forming and hole cleaning;

and 6, forming a pile after the slurry is solidified.

2. The method for constructing the micro pile of the pole tower foundation in the soft soil foundation according to claim 1, which is characterized in that: step 1, binding a reinforcement cage and a secondary grouting pipe, namely binding a 1-inch secondary grouting pipe at the top of the reinforcement cage during construction; a plurality of small holes are uniformly formed in the secondary grouting pipe, and the outside of each small hole is sealed and blocked by a sealing material, so that cement slurry is prevented from entering the grouting pipe; the number of the secondary grouting pipes is generally 1-2; the sealing material is a polypropylene-ethylene mixed material.

3. The method for constructing the micro pile of the pole tower foundation in the soft soil foundation according to claim 1, which is characterized in that: step 2, pile position positioning, hole forming and hole cleaning are carried out, wherein when a pile is formed, positioning is carried out through a small-sized drilling machine, and a pile casing is arranged; and then drilling, and cleaning the hole after the designed elevation is reached, so that no silt exists in the cleaned water, and the specific gravity of the cleaned mud is not more than 1.1.

4. The method for constructing the micro pile of the pole tower foundation in the soft soil foundation according to claim 1, which is characterized in that: step 3, placing a reinforcement cage and a next grouting pipe in the hole, and putting gravel aggregate in the primary grouting pipe, namely, firstly hanging the reinforcement cage bound with the secondary grouting pipe in the hole, then placing the primary grouting pipe to the bottom of the hole, and then putting the gravel aggregate into the drill hole to the position of an orifice; the number of the primary grouting pipes is generally 1-2; a plurality of small holes are uniformly formed in the primary grouting pipe at intervals, and the small holes are sealed and blocked by sealing materials to prevent cement mortar from entering the grouting pipe.

5. The method for constructing the micro pile of the pole tower foundation in the soft soil foundation according to claim 1, which is characterized in that: 4, grouting the primary grouting pipe and forming a pile preliminarily, namely injecting cement mortar into the primary grouting pipe by using a grouting pump until an orifice emits the mortar; the specific gravity of the cement mortar reaches a water cement ratio of 0.5: 1, the corresponding site perfusion specific gravity is 1.8-2.0 through site tests.

6. The method for constructing the micro pile of the pole tower foundation in the soft soil foundation according to claim 1, which is characterized in that: after the slurry is initially set, secondarily grouting into the primary grouting pipe, firstly lifting the primary grouting pipe to a position 3-4 m away from an orifice, and then secondarily grouting; carrying out secondary grouting 4-6 hours after the initial setting of the slurry; during the second grouting, firstly, high-pressure cement mortar is injected into the secondary grouting pipe by using a grouting pump, and the sealing material outside the secondary grouting pipe 2 is broken by using high pressure, so that the small hole is opened after grouting.

7. The method for constructing the micro pile of the pole tower foundation in the soft soil foundation according to claim 1, which is characterized in that: further comprising: step 7, carrying out low strain detection on part of piles to check the quality of the pile body; the method comprises the following steps: the method comprises a single-pile vertical compression static load test, a single-pile vertical pulling static load test, a single-pile horizontal static load test, a single-pile compression and horizontal load combined loading test and a single-pile horizontal load combined loading test.

8. The method for constructing the micro pile of the pole tower foundation in the soft soil foundation according to claim 7, which is characterized in that: the vertical resistance to compression static load test of single pile includes:

a. test data;

b. analyzing test results;

TABLE 2 ultimate bearing capacity of vertical compression static load test

TABLE 4D-1 vertical compression static load test load and settlement data

TABLE 5D-2 vertical compression static load test load and settlement data

TABLE 6D 5 vertical compression static load test load and settlement data

TABLE 7D-6 vertical compression static load test load and settlement data

9. The method for constructing the micro pile of the pole tower foundation in the soft soil foundation according to claim 7, which is characterized in that: vertical resistance to plucking static load test of single pile includes:

a. test data;

b. analyzing test results;

analysis of the anti-pulling static load test results of all the test piles shows that the anti-pulling bearing capacity of the three vertical piles is close; the ultimate uplift bearing capacity of the inclined pile D-5 is 220kN, and the ultimate uplift bearing capacities of the D-3 and the D-7 are greater than 162 kN; the difference between the ultimate uplift bearing capacity of the inclined pile and the ultimate uplift bearing capacity of the straight pile is small; the resilience rates of the pile tops of D-3 and D-7 are higher; the resilience rate of the pile tops of the rest test piles is 13-38%, and the residual deformation is large;

Table 9 vertical pulling-resistant static load test load grading table

10. The method for constructing the micro pile of the pole tower foundation in the soft soil foundation according to claim 7, which is characterized in that: the single pile horizontal static load test comprises the following steps:

a. test data;

b. analyzing test results;

Table 10 horizontal static load test load grading table

TABLE 11D-2 horizontal static load test load and horizontal displacement data

TABLE 12D-7 horizontal static load test load and horizontal displacement data

TABLE 13D-8 horizontal static load test load and horizontal displacement data