Knowledge fragments: construction of dynamic compaction, cost analysis of dynamic compaction works


Release Date:

2020-09-03

The strong compaction method is the super-force compaction method, also known as the driving force gravel soil method. It is the use of large and small chain-rail rammers to continuously lift 8-40 tons of heavy hammer type to high altitude (6-40 meters), so that it will fall down at will, to the foundation with destruction and vibration, and then improve the compressive strength of the foundation and reduce its expansion.

1. Definition

(1) The strong compaction method is the super-force compaction method, also known as the driving force gravel soil method. It is the use of large and small chain-rail rammers to continuously lift 8-40 tons of heavy hammer type to high altitude (6-40 meters), so that it will fall down at will, to the foundation with destruction and vibration, and then improve the compressive strength of the foundation and reduce its expansion.

(2) Tamping energy: the multiplication of hammer weight and falling distance is called tamping energy.

2. Scope of application

The dynamic compaction method can be used to solve the foundation of sandy soil, gravel soil, low contrast sand and cohesive soil, collapsibility, collapsibility and plain filling.

3. Efficacy of dynamic compaction method

(1) Improve the compressive strength of the foundation;(2) Reduce the expansion of the foundation soil;(3) Improve the anti-vaporization professional skills of the foundation soil;(4) Remove the collapsibility of the foundation soil.

4. Classification of dynamic compaction method

According to the tamping area, it is divided into two types: point tamping and full tamping.

(1) Point tamping: For foundation reinforcement, it is shallow in many aspects (within 3M) and is an independent foundation method. Only point tamping can be used.

(2) Full tamping: the foundation shall be reinforced deeper (above 3M) and shall be continuously basic. Point tamping shall be adopted first and then full tamping shall be adopted.

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Construction of dynamic compaction foundation foundation

1. Construction technology

(1) Do a good job of on-the-spot preparation before the construction of the construction project, including: finding out the hidden objects in the following categories, and selecting certain effective preventive measures to properly dispose of them; Adopt seismic grade shock absorber or other preventive measures; If the temperature in the place is high or there is water storage, preventive measures of lowering and drainage pipes shall be taken.

(2) Clear and level the site (as far as possible to maintain the level);

(3) The hard foundation cushion shall be paved, and the lifting machinery shall be used on it;

(4) Mark the location of the tamping point once, and * * * * measure the building elevation of the site;

(5) The lifting equipment shall immediately make the rammer heavier than the ramming point, and * * * * measure the elevation of the top of the hammer before ramming;

(6) Hoist the rammer to purchase the height-width ratio, open the hook-off mechanical equipment, learn to lower the hook after the rammer is randomly erected, and measure the building elevation of the top of the hammer again * * * *. If the bottom of the pit is found to be skewed, it should be leveled;

(7) Continuously process 6, according to the tamping frequency and operation specification required by the design scheme, carry out tamping at one tamping point;

(8) Change the tamping point, continue the process 5-7, and carry out the tamping of all tamping points;

(9) Use an excavator to level the ramming pit and measure the building elevation of the site;

(10) After the required interval, all ramming shall be carried out according to the above-mentioned process, and then full ramming shall be carried out with low mechanical kinetic energy, the surface soil of the site shall be compacted, and the building elevation after ramming shall be measured.

 

2. Ramming progress and number of blows

Ramming shall be carried out according to the characteristics of foundation soil, generally 2-5 times, the first 2-3 times are "point ramming" and the second time is "full ramming" (I. e. hammering marks overlap with each other). The loose topsoil layer in the middle of the ramming point with a short time shall be reinforced by the project structure. For inhalable granular soil with weak water absorption capacity, tamping can be promoted when indispensable.

3. Reasonable layout of ramming points

 

 

3, strong foundation foundation foundation construction machinery and equipment.

The key construction engineering construction machine is equipped with auxiliary mechanical equipment such as hoisting machinery, hook machinery and equipment, rammer and excavator, compaction machinery and equipment.

3.1. Lifting equipment

It is appropriate to adopt chain-rail hoisting equipment or other special-purpose hoisting machinery with professional skills of hoisting machinery above 15t, but the provisions on total hoisting weight of rammer and improvement of height-width ratio should be fully considered as far as possible, and safety devices should be set to prevent the boom from tilting backward during tamping.

3.2, hook

It is required to have sufficient compressive strength and do not cause sliding hook during hoisting. The hook is flexible and can maintain the stable landing of the rammer. In addition, the hook is time-saving, labor-saving and fast.

3.3. Rammer

Dynamic compaction foundation foundation foundation hammer weight can use 10~40t, the bottom way should choose ring or combination graphics. The raw material of the rammer is preferably aluminum alloy die-casting. If the standard is limited, the cold-rolled steel shell can be filled with concrete. The bottom end of the rammer should be symmetrically set up with several Φ 250~300mm and the wall surface to discharge the air outlet, so as to facilitate the rapid discharge of pit bottom gas when the rammer hits the ground and reduce the adsorption force of the pit bottom when the hammer is lifting. The area of hammer bottom should be established according to the characteristics of soil. For sandy soil and sandy gravel backfill, it is more suitable to choose a bottom area of 2~1 m2; For general cohesive soil, it is proposed to use 3~1 m2; For sludge gravel soil, it is proposed to choose 4~6 m2.

3.4. Auxiliary Mechanical Equipment

Excavators, small rollers, rammers, etc. are used for ramming money, leveling and tamping after tamping, and bulldozing and filling roadbed work of materials and stones.

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Brief Introduction of Dynamic Compaction Foundation Foundation

1. Advantages: The mechanical kinetic energy of one-time tamping is large, and all aspects of the foundation can be reinforced according to the manipulation of the tamping point, relative density and tamping method. After the structural reinforcement of the foundation foundation project by dynamic compaction, the foundation settlement of uneven foundation can be removed. The mechanical kinetic energy of one-time tamping on the construction site is very easy to manipulate, thus obtaining a foundation with uniform compaction.

 

2. Defects: there is no basic knowledge and sound calculation method of design scheme at this stage; The characteristics of industrial equipment and machinery and equipment are stipulated higher when the structure of various engineering projects is reinforced. Vibration and noise are large, the total number of urban population is heavy environmental pollution areas, and the areas with heavy environmental pollution of building structure are not suitable for application.

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