What does the number of ramming passes depend on for the high compaction method?

According to the "Technical Code for Building Foundation Treatment" JGJ79-2012:

3. The number of ramming times should be determined according to the nature of the foundation soil. Generally speaking, a permeable foundation composed of coarse-grained soil can be rammed less times. On the contrary, the foundation with weak permeability composed of fine-grained soil requires more tamping times.

According to China's engineering practice, for most projects, the tamping times are used 2 times 4 times, and finally the low energy full ramming is used 2 times, which can generally achieve a good tamping effect. For the fine-grained soil foundation with weak permeability, the number of ramming times can be appropriately increased.

Specifically, you can view the construction drawings, and there are design requirements on the drawings.

The number of ramming times refers to the completion of a tamping process for a batch of points of the whole site with a certain number of consecutive times, and the number of ramming times of a single point is the number of ramming times of the whole site. Zhongnan Xiangji strong compaction company in accordance with the construction plan.

Carry out ramming.

Advantages of the high compaction method:

1. The equipment is simple, the process is convenient, and the principle is intuitive.

2. It has a wide range of applications and remarkable reinforcement effect.

3. It requires less personnel and the construction speed is fast. years of hunger.

4. It does not consume cement and steel, and the cost is low, and it can usually save 30% or 70% of the investment compared with the decoration and saving sales.

Disadvantages of the high compaction method:

1. The vibration is large and noisy, which is difficult to implement in the dense construction area of the urban area.

2. The theory of strong compaction is immature, and it is necessary to use on-site test tamping to finally determine the parameters of strong compaction.

3. The influence of the vibration of strong compaction on the surrounding buildings is not enough research.

Scope of application of the strong compaction method:

1. After years of practice and the update of strong compaction equipment, the construction of strong compaction method has been widely used in highway and railway, airport, nuclear power plant, Hongyou industrial zone, port reclamation and other foundation reinforcement projects, and has successful construction cases for relatively complex geology such as high fill foundation, high water content foundation, port reclamation foundation, seawater blowing and filling foundation, etc.

2. The strong compaction method is suitable for dealing with gravel soil, sand, low saturation silt and cohesive soil, collapsible loess, plain fill soil and miscellaneous fill soil.

3. Before the construction of strong compaction, one or several test areas should be selected on a representative site at the construction site for test tamping or experimental construction. The number of test areas should be determined according to the complexity of the construction site, the scale of construction and the type of building. <>

1. The soil is not as hungry as the rock.

The strong compaction method can be applied to reinforcing coarse-grained soil, fine-grained soil, saturated soil, unsaturated soil, and even ports, river water, and lower soil layers, such as fill, miscellaneous fill, sandy soil, cohesive soil, loess, and silt soil.

The heavy compaction method is only suitable for reinforcing slightly wet clayey soil, sand soil, loess, miscellaneous fill soil and layered fill above the groundwater level, and is not suitable for cohesive soil with high water content.

2. The reinforcement process is different.

The strong compaction method has a certain reinforcement range on the side, and its diameter is about times the diameter of the rammer, in order to make the soil on the side less disturbed, less uplift to form a lateral extrusion force, so that the soil is compressed, and the saturated soil forms pore water pressure, and is discharged under this pressure, and then compacted many times.

The law of heavy hammer tamping is different, it uses a ramming or a tamping half tamping, and there is no interval between each pass. It only compacts the soil under the hammer, so the reinforcement is shallow, and the sides are easy to bulge.

Rough start construction conditions of heavy hammer tamping method:

1. Technical information such as engineering geological survey report, hammer tamping site plan and design requirements for the effect of hammer tamping should be prepared.

2. The site has been leveled, the surface loose soil has been pre-compacted, and drainage facilities have been made around the foundation pit.

3. All obstacles and underground pipelines in the tamping site have been removed.

4. The site has been tested to determine the technical parameters of the limb building, such as the weight of the rammer, the diameter of the bottom surface and the falling distance, the final sinking amount and the corresponding tamping times and the total sinking amount, as well as the tamping sequence, the layout of the tamping point, etc. The in-situ test was carried out before tamping the foundation.

5. The measurement control has been done, the axis pile and the level base point pile are set, and the position of each ramming point is released, and the ash line or nail the wooden pile is studied.

Reinforcement characteristics of the strong compaction method:

1. Use simple equipment commonly used on the construction site;

2. The construction technology and operation are simple;

3. Wide range of applicable soil quality;

4. The reinforcement effect is remarkable, and the bearing capacity can be obtained, and the general foundation strength can be increased by 2 5 times;

5. The deformation settlement is small, the compressibility can be reduced by 2 10 times, and the impact depth of reinforcement can reach 6 10 meters.

Heavy hammer tamping is generally a cone, falling distance to meters, weight in general, strong tamping 8 to 20 meters, weight is also much larger than heavy hammer, generally 8 to 12t, my master said that according to the filling height of the roadbed, every 6 to 8 meters to hit [呲tooth].

Heavy hammer tamping is a kind of strong tamping, which is basically the same, and the tamping energy is different; The ramming energy of heavy hammer tamping is lower than that of strong tamping; to demarcate the boundary.

The ramming energy is not an order of magnitude, so the reinforcement mechanism is different. Heavy hammer tamping is the reinforcement of shallow soil, which belongs to the compaction mechanism; The strong compaction method is the reinforcement of deep soil, mainly the dynamic consolidation and dynamic compaction mechanism.

The strong compaction method has been widely used in our country, but its disadvantage is that the construction noise is large, the pollution is significant, the tamping energy per unit area is small, and the tamping is only dynamic compaction, due to the difference between the effective zone and the influence zone, the deep layer is difficult to achieve the effect of compaction, and the reinforcement depth is limited. For the foundation with deep and weak substratum, only by increasing the crane lifting capacity and increasing the hammer weight can it be effective. Due to the above-mentioned reasons, the popularization and use of the strong compaction method is limited in engineering.

The DDC pile is a deep filling of the hole with a strong compaction hammer, and the deep operation of the hole is carried out by layered strong compaction or strong compaction while filling. Its noise is small, the pollution is small, and under the action of a special hammer with low weight and high pressure, it can produce thousands of kn?m m2 high pressure strong kinetic energy.

Due to the small diameter of the pile hammer, the ramming energy per unit area of the DDC pile is much larger than that of the high compaction method under the same tamping weight and drop distance. During construction, the filler is layered in the hole from deep and shallow, and the layered strong compaction or ramming while filling is carried out, so this method has the effect of high kinetic energy, high pressure and strong compaction. In the deep direct reinforcement of the weak substratum, from the bottom to the top of the uniform reinforcement of the foundation, the deepest treatment depth of the DDC pile has reached 60m, and the strong compaction method is generally effective reinforcement depth of less than 10m, which is one of the very important characteristics of the DDC pile technology.

The strong compaction method is suitable for treating gravel soil, sandy soil, low saturation silt and cohesive soil, collapsible loess, miscellaneous fill soil and plain fill soil. For foundations such as silt and cohesive soil with high saturation, when backfilling stones, gravel or other coarse-grained materials in the tamping pit for strong compaction replacement, its applicability should be determined through field tests.

Strong compaction shall not be used for foundation reinforcement that does not allow a certain vibration impact on the buildings and equipment around the project, and vibration prevention and isolation measures shall be taken when necessary.

Summary. The number of times of strong compaction and the number of times of each ramming need to be determined according to the specific situation, and the following are the recommendations in general: for the case of strong compaction of the foundation, it is generally necessary to carry out 2 times of strong compaction.

For the first pass of strong compaction, it is recommended to carry out 3-4 ramming, and the ramming energy level is generally. For the second pass of strong compaction, it is recommended to carry out 2-3 ramming, and the tamping energy level is generally. The specific tamping times and ramming energy level also need to be comprehensively considered according to the nature, thickness, strong compaction range, design requirements and other factors of the foundation soil, so as to achieve the purpose of strengthening the foundation.

In the actual construction process, it is recommended to carry out on-site tests and adjust according to the test results to ensure that the strong compaction effect meets the design requirements.

The number of times of strong compaction and the number of times of each ramming need to be determined according to the specific situation, and the following are the recommendations in general: for the case of strong compaction of the foundation, it is generally necessary to carry out 2 times of strong compaction. For the first pass of strong compaction, it is recommended to carry out 3-4 ramming, and the ramming energy level is generally.

For the second pass of strong compaction, it is recommended to carry out 2-3 ramming, and the tamping energy level is generally. The specific number of tamping old coarse liquid and the tamping energy level also need to be comprehensively considered according to the nature, thickness, strong compaction range, design requirements and other factors of the foundation soil, so as to achieve the purpose of adding a bench to solidify the foundation. In the actual construction process, it is recommended to carry out on-site tests and adjust them according to the test results to ensure that the strong compaction effect meets the design requirements.

The last two strokes average the amount of ramming.

The average tamping settlement of the last two strokes refers to the depth of the tamping hammer sinking after each tamping when the second tamping of the strong compaction construction is carried out, and the average value of the last two tamping is taken as the settlement of each tamping stroke. This index can be used to evaluate the effect of strong compaction and the reinforcement of foundation soil. Under normal circumstances, the average tamping sink of the last two blows should be less than 5 cm, so that it can be considered that the strong compaction reinforcement effect meets the design requirements.

If the average tamping amount of the last two hits is too large, it means that the reinforcement effect of the foundation soil is not ideal, and further treatment is required. In the actual construction process, it is recommended to measure and record after each time of Zhiqing disturbing the strong compaction, so as to find and solve the problem in time to ensure that the strong compaction reinforcement effect meets the design requirements.