CN108301393B

CN108301393B - Watering impact rolling construction method for shallow hydraulic fill coral sand foundation

Info

Publication number: CN108301393B
Application number: CN201810147023.3A
Authority: CN
Inventors: 王新志; 陈伟俊; 朱长歧
Original assignee: Wuhan Institute of Rock and Soil Mechanics of CAS
Current assignee: Wuhan Institute of Rock and Soil Mechanics of CAS
Priority date: 2018-02-12
Filing date: 2018-02-12
Publication date: 2021-09-14
Anticipated expiration: 2038-02-12
Also published as: CN108301393A

Abstract

The invention relates to the field of shallow hydraulic fill coral sand foundation treatment, in particular to a construction method for watering, impacting and rolling a shallow hydraulic fill coral sand foundation. Aiming at the characteristics that a hydraulic filling coral sand foundation which is transported and filled again on site is loose, low in compactness and slightly large in compressibility, the construction method requires that a site is leveled firstly, then water is sprayed on the site until the coral sand foundation is close to an optimal water content state (the water content is more than or equal to 20%), then a 25kJ trilateral impact road roller is used for impact rolling, and water is sprayed all the time in the impact rolling process until the foundation is compacted. The number of times of impact rolling is 20, and then the roller is rolled to have no obvious wheel track by a 25t vibratory smooth roller. The construction method can improve the compaction degree of the dredger foundation of the hydraulic fill coral sand island, improve the bearing capacity of the foundation and reduce the post-construction settlement of the foundation, and has the advantages of simple operation and good effect.

Description

Watering impact rolling construction method for shallow hydraulic fill coral sand foundation

Technical Field

The invention relates to the technical field of hydraulic fill coral sand foundation treatment, in particular to a construction method for watering, impacting and rolling a shallow hydraulic fill coral sand foundation.

Background

The method for filling and building the island is characterized in that reef and coral sand in a coral reef lagoon are excavated and pumped to the reef field through a mud pump of a cutter suction dredger, and the reef and the coral sand are piled into a land area after water flows away to form the artificial island. The hydraulic fill artificial island foundation is mainly a mixture of coral reef limestone fragments and coral sand, and is called coral reef sand or coral sand. Reclamation of land on coral reef by blow-filling relates to the treatment of coral sand foundation by blow-filling.

The impact rolling technology is generally applied to foundation construction, the aim is to compact the foundation, and in actual construction, an impact type road roller and a smooth surface road roller are needed to continuously roll the foundation so as to improve the compactness. Through the impact of impact rolling equipment, can extrude out the air between the coral sand granule, granular material can combine inseparabler under the effect of impact force to ensure that it can bear bigger pressure in the later stage use, realize effective extension of foundation life-span. The impact rolling is a continuous impact rolling operation of static pressure, kneading and impact on the soil material along the ground by combining potential energy drop generated by the large and small radiuses of the polygonal roller and the kinetic energy of running, so as to form a high-amplitude and low-frequency impact compaction principle. At present, a 25kJ trilateral double-wheel impact road roller is used most, the static weight of double wheels is 12t, the optimal running speed is 12km/h, and the concentrated impact force on the ground is 2000-2500 kN, which is equivalent to 1111-1543 kPa. The high-energy impact force periodically and continuously impacts the ground to generate strong impact waves, the strong impact waves have the transmission characteristic of seismic waves downwards, the generated impact rolling function achieves super-heavy type compaction work, the compactness of the underground deep layer can be continuously accumulated and increased, the compactness reaches 1.0-1.5 m according to different properties of soil and stone materials, the compaction efficiency is better than that of the existing vibration compaction machine, the punched soil and stone filler is closer to an elastic state, the technical advantage of overcoming the hidden danger of soil and stone foundations is shown, and the method is the latest development of the soil and stone engineering compaction technology.

The compaction effect of soil is related to the water content at compaction. For drier soils, compaction is not easily achieved due to the high frictional resistance between the soil particles. When the soil has proper water content, water plays a role in lubrication, so that the frictional resistance among soil particles is reduced, and the soil is easy to compact. The optimal water content refers to the corresponding water content when the maximum compact state is reached under a certain ramming energy for specific soil. When the soil is at the optimal water content, the most economic compaction effect can be obtained and the maximum compactness can be achieved through dynamic compaction. Generally, the optimal water content of the land source soil is a fixed value, and different types of sandy soil have different optimal water contents, so that when the land source soil foundation is subjected to impact rolling treatment, the land source soil only needs to be ensured to reach the optimal water content before the impact rolling treatment. The hydraulic fill coral sand is non-cohesive soil with irregular particle shape, wide grading and easily broken particles, has physical and mechanical properties different from that of common land source hydraulic fill, and is proved by compaction tests to have the following characteristics: the hydraulic filling coral sand does not have the optimal water content, but can reach the maximum dry density when being the driest and close to saturation, which means that if the ground of the ground source is impacted and rolled according to the optimal water content, the hydraulic filling coral sand ground can not reach the optimal compaction effect. The invention mainly aims at the compaction treatment of shallow (within 1.0 meter) blow-filled coral sand foundation.

Disclosure of Invention

The invention aims to overcome the defects and provides a shallow hydraulic fill coral sand watering impact rolling construction method which is simple to operate and good in treatment effect, and the specific scheme is as follows:

a watering impact rolling construction method for shallow hydraulic fill coral sand foundation sequentially comprises the following steps:

(1) leveling the field (pushing back and forth for 1-2 times by a bulldozer), and simultaneously watering to ensure that the water content of the coral sand is more than or equal to 20%;

(2) then, a 25kJ trilateral impact road roller is used for impact rolling, and water spraying is always matched while the impact rolling is carried out, so that the water content of the coral sand is guaranteed to be more than or equal to 20% until the foundation is compacted;

(3) and finally, rolling (5-10 times) by using a 25t vibratory smooth surface roller until no obvious wheel track exists.

Further, the foundation compaction requirement of the step (2) is as follows: using a heavy dynamic penetration test (N)_63.5) And detecting the compaction degree of the foundation, wherein the average impact number within the penetration depth of 1.0m is not less than 12 impacts, and the continuous three-time impact number is not less than 10 impacts.

Further, the number of times of impact rolling in the step (2) is 20-25.

Further, the speed of impact rolling in the step (2) is 10-12 km/h; and (4) in the step (3), the speed of the 25t vibratory smooth surface roller is 10-12 km/h.

Further, the maximum value of the water content of the coral sand in the steps (1) and (2) is as follows: the coral sand with the depth of 1.0m of the surface layer reaches the water content of a saturated state.

Further, a watering cart is adopted in the step (2) to be matched with watering, the speed of the watering cart is the same as that of the road roller, the watering cart sprays water in front of the road roller, and the distance between the watering cart and the road roller is 5-10 m.

The 25kJ trilateral double-wheel impact is ground in work, and when the tractor dragged trilateral arc-shaped wheels to roll forward, the gravity center of the compaction wheel is alternatively changed from top to bottom from the height of the ground, and the generated potential energy and kinetic energy are concentrated to roll forward and downward to form huge shock waves.

In the process of impact rolling, the gravity center of the three-side arc wheel is lifted and lowered three times every time the three-side arc wheel rotates for one circle, and tamping impact and vibration effects are generated three times on the ground.

The specific impact action process is as follows: under the action of the tractor, the compaction wheel rolls forwards along the outline curve by means of friction force with the ground, when the gravity center is at the lowest point of the curve, the compaction wheel rolls forwards again, the gravity center starts to move upwards, kinetic energy brought by traction force is converted into potential energy and kinetic energy of the compaction wheel, the buffer mechanism starts to act, the buffer hydraulic cylinder of the energy accumulator contracts, and the energy accumulator stores energy. When the gravity center of the compaction wheel rolls forwards at the highest point of the curve, the potential energy of the compaction wheel begins to be converted into kinetic energy, the buffer hydraulic cylinder of the energy accumulator stretches, and the pressure energy in the energy accumulator is released and converted into the kinetic energy of the compaction wheel. Due to the special structure of the compaction wheel, the gravity center of the compaction wheel has a forward linear speed and a downward linear speed, and the impact compaction effect on the ground is started until the other curve of the compaction wheel is contacted with the ground. The larger the working speed of the tractor is, the larger the contraction of the buffer hydraulic cylinder of the energy accumulator is, the more the energy is accumulated, the larger the kinetic energy of the released energy converted into the compaction wheel is, the more the kinetic energy for generating impact compaction on the ground is, and the better the vibration excitation effect is.

For unsaturated soil of a common land source foundation, the foundation is compact and has low compressibility, when a punching wheel lands on the ground, due to the release of kinetic energy, instantaneous impact dynamic load is generated in a local area below the punching wheel, deep soil particles are quickly compacted and downwards transmitted, and impact energy is spread in an elastic half space in a vibration wave mode to enable the soil particles to be close to each other, gas and water in gaps are discharged, and the soil particles are rearranged to be compacted.

The dredger fill coral sand foundation has physical and mechanical properties different from those of general land source dredger fill, and coral sand generally refers to a special rock-soil medium which is caused by marine organisms (coral, seaweed, shell and the like) and is rich in calcium carbonate or other insoluble carbonate substances. Because the deposition environment is special and the large number of the particles are not carried for a long distance in the deposition process, the fine pores in the original biological skeleton are reserved, and therefore, the particles have the characteristics of being porous, irregular in shape, easy to break, easy to generate cementation among the particles and the like. The porous characteristic of coral sand granule leads to the seepage flow velocity too fast, water quality runs off easily, hardly be full of by water in the interior hole, under the impact load, can't form the high pore pressure between the coral sand granule, if wash and grind the in-process watering, then enable interior hole and be full of water as much as possible, thereby under the impact load, it forms the high pore pressure to change between the coral sand granule, instantaneous high pore pressure makes the soil granule inseparabler, coral sand contactless state has been changed, the corresponding improvement of the closely knit degree of ground. And the calcareous sandy is brittle and easy to break, a large amount of soil particles on the surface layer are broken during impact rolling, so that fine particles are formed, the flowability of the fine particles can be improved through the watering effect, and the fine particles are filled into the pores of the large particles, so that the compactness of the foundation is improved.

The invention is tested by experiments, the maximum dry density of the coral sand shows a trend of firstly reducing and then increasing along with the change of the water content, and when the water content reaches more than 20 percent, the maximum compaction dry density can reach 1.45g/cm³In addition, the island is frequently rained, the rainfall is large, the coral sand is high in permeability and is easily influenced by seawater permeation, so that the water content is controlled to be more than or equal to 20% in actual operation, and the hydraulic filling requirement of the coral sand can be met.

The construction method for watering, impacting and rolling the shallow hydraulic reclamation island foundation has the following advantages and beneficial effects:

1. before flushing and rolling and in the process of impact rolling, water is sprayed in a matching manner, so that the water content of the coral sand is more than or equal to 20% as much as possible, and the coral sand is guaranteed to achieve the most economic compaction effect and the most compactness.

2. The method has the advantages of improving the compaction degree of the dredger fill island foundation, reducing the porosity ratio, reducing the settlement of the foundation after construction, along with simple operation and good treatment effect;

3. the construction speed of impact rolling is high, the efficiency is high, the speed of impact rolling is 10-12km/h, and the efficiency is higher particularly for longer and wider foundation paragraphs;

4. the action range is large, the compaction influence depth of the impact roller is 1m, the compaction effect is better than that of the traditional compaction machine, and the problem that the thickness of the layer of the common road roller needs to be strictly controlled is effectively solved;

5. the labor cost is low, and the cost per square meter is about 2.5 yuan calculated according to 20 times of impact rolling;

6. the manufacturing cost is controllable and adjustable, and the processing thickness is adjustable;

7. the construction speed is fast, and the quality is controllable.

Drawings

FIG. 1 is a graph showing the maximum compacted dry density of the coral gravel soil of example 1 as a function of water content.

FIG. 2 is a plot of maximum compacted dry density of coral gravel in example 1 as a function of moisture content.

FIG. 3 is a plot of maximum compacted dry density of sand in coral of example 1 as a function of moisture content.

FIG. 4 is a flow chart of the construction process of watering, impacting and rolling the shallow hydraulic reclamation coral sand foundation of the present invention.

Detailed Description

The invention is further explained below based on the technical solutions described in the summary of the invention with reference to the specific embodiments and the drawings of the specification.

Example 1: and (3) discussing the maximum compaction dry density of the hydraulic filling coral sand along with the change of water content.

Collecting coral sand (coral gravel soil, coral gravel sand and coral medium sand) blown and filled in an island, respectively adding a certain amount of water into the coral sand, uniformly stirring, drying, controlling the water content and the like according to geotechnical test procedures, detecting the maximum compaction dry density according to geotechnical test method standard (GB/T50123-1999), and researching the trend of the maximum compaction dry density along with the change of the water content, wherein the detection results are respectively shown in figures 1-3.

As can be seen from FIG. 1, the maximum compacted dry density of the coral gravel soil when dried is 1.85g/cm³The maximum compacted dry density tends to decrease first and then increase with the increase of the water content, and reaches the minimum value when the water content is 14%; as can be seen from FIG. 2, the maximum dry density of coral gravel is 1.76g/cm³The maximum compaction dry density tends to decrease first and then increase, and reaches the minimum value when the water content is about 10%; as can be seen from FIG. 3, the maximum packing dry density of the sand in coral was 1.56 g/cm³The maximum compacted dry density tends to decrease first and then increase, and reaches a minimum value when the moisture content is 12%. The coral sand is mainly coral gravel sand and coral medium sandIt can be determined that: the maximum compaction dry density of the coral sand shows a trend of firstly reducing and then increasing along with the change of the water content, and when the water content reaches more than 20 percent, the maximum compaction dry density can reach 1.45g/cm³In addition, the island is frequently rained, the rainfall is large, the coral sand is high in permeability and is easily influenced by seawater permeation, so that the water content is controlled to be more than or equal to 20% in actual operation, and the hydraulic filling requirement of the coral sand can be met.

Example 2: a watering impact rolling construction method for shallow hydraulic fill coral sand foundation is shown in figure 4, and comprises the following steps:

firstly, the dredger fill coral sand foundation which is transported and filled again on site is loose, water is sprayed on the surface of the soil body, and then the soil body on the surface is fully mixed with the loose soil body;

step two, clearing and leveling the mixed foundation, pushing back and forth for 2 times by using a bulldozer, and sprinkling water by a sprinkler in cooperation with pushing to ensure that the water content reaches the design requirement (the water content is more than or equal to 20%);

thirdly, impacting and rolling for 20 times by using a 25kJ trilateral impact roller at the speed of 10-12km/h until the foundation is compacted, in the impact rolling process, watering by a watering cart in cooperation with watering to ensure that the water content reaches the design requirement (the water content is more than or equal to 20%), wherein the watering cart has the same speed as the roller, the watering cart sprinkles water in front of the roller, and the distance between the watering cart and the roller is about 5 m;

step four, removing redundant earthwork and leveling the field;

leveling and compacting, and grinding for 7 times at 10-12km/h by using a 25t vibratory smooth surface road roller until no obvious wheel track exists;

after the foundation compaction in the third step, the foundation compaction degree is detected, and a heavy dynamic penetration test (N) is adopted_63.5) The design requirement of the foundation compactness is that the average impact number within the penetration depth of 1.0m is not less than 12 impacts, and the continuous three-time impact number is not less than 10 impacts.

Taking a certain place for blowing and filling coral sand as an example for testing, the coral sand is coral medium sand, the coral medium sand is impacted and rolled according to the method, the water content is controlled to be 25 percent, and a 25KJ trilateral impact road roller and a 25t vibration smooth surface are controlledThe speed of the road roller is 10-12 km/h. After the foundation compaction in the third step, the foundation compaction degree is detected, and a heavy dynamic penetration test (N) is adopted_63.5kg), the average hit number within the penetration depth of 1.0m is 14 hits, and the number of consecutive three hits is not less than 12 hits.

Claims

1. The utility model provides a shallow layer hydraulic reclamation coral sand ground watering strikes rolls construction method, its characterized in that includes the following step in proper order:

(1) leveling the field, and simultaneously spraying water to ensure that the water content of the coral sand is more than or equal to 20%;

(3) finally, rolling the obtained product by using a 25t vibratory smooth surface road roller until no obvious wheel track exists;

the number of times of impact rolling in the step (2) is 20-25; the requirements for the foundation compaction are: detecting the foundation compaction degree by adopting a heavy dynamic penetration test, wherein the average impact number within the penetration depth of 1.0m is not less than 12 impacts, and the continuous three-time impact number is not less than 10 impacts;

the maximum value of the water content of the coral sand in the steps (1) and (2) is as follows: water content of coral sand reaching saturation state.

2. The construction method for watering, impacting and rolling the shallow hydraulic fill coral sand foundation according to claim 1, wherein the impacting and rolling speed in the step (2) is 10-12 km/h.

3. The construction method for watering, impacting and rolling the shallow hydraulic-filled coral sand foundation according to claim 1, wherein the speed of the 25t vibratory plain pavement roller in the step (3) is 10-12 km/h.

4. The watering impact rolling construction method for the shallow hydraulic fill coral sand foundation according to claim 1, wherein in the step (2), watering is carried out by using a watering cart in combination with the road roller, wherein the watering cart is at the same speed as the road roller, the watering cart is used for watering before the road roller, and the distance between the watering cart and the road roller is 5-10 m.