The phenomenon of quicksand in construction and the method of preventing and controlling quicksand 5

The quicksand phenomenon is when the hydrodynamic pressure is greater than or equal to the water-immersed bulk density of the soil, the soil particles lose their own weight and are in a suspended state, the shear strength of the soil is equal to zero, and the soil particles will flow with the seepage water.

Prevention and control of quicksand:1Reduce the pressure of moving water and soil 2Adopt the well water precipitation method 3Balance the hydrodynamic pressure. Mud wall protection, underground diaphragm wall, underwater excavation.

When the foundation pit is dug below the groundwater level, and when the pit is pumped again, sometimes the soil below the bottom of the pit can form a flowing state, and gushes into the foundation pit together with the groundwater, and this phenomenon is called quicksand.

There are specific measures for the prevention and control of quicksand as follows: Construction method in dry period Throwing boulder method 3Steel plate method, underwater excavation method, artificial groundwater level lowering method, underground diaphragm wall method.

Phenomenon: Quicksand is a phenomenon of soil, usually fine particles, uniform particles, loose and saturated non-cohesive soils are prone to this phenomenon. The formation of quicksand is diverse, but it has a great impact on the safety and normal use of buildings.

The phenomenon of quicksand can be stopped through prevention and other means.

Prevention and control methods: add drainage system. Chemicals are used to hinder the formation of quicksand.

Architecture] Animation of building construction technology, real-life demonstration (zero-based learning) - 12 generation and prevention measures of quicksand.

It should be called quicksand.

When the foundation pit excavation reaches below the groundwater level, and the soil is fine sand or silt, and the sump is used for precipitation, under the action of a certain hydrodynamic pressure, the soil under the pit will form a flow state, and flow into the pit with the groundwater, and this phenomenon is called quicksand phenomenon.

In the actual construction process, the methods of dealing with the foundation usually include soil replacement cushion method, deep compaction method, drainage consolidation method, chemical reinforcement method, reinforcement method and thermal method.

First, the phenomenon of quicksand.

The quicksand phenomenon refers to when the foundation pit excavation reaches below the groundwater level, and the soil is fine sand or silt, and the sump is used for precipitation, under the action of a certain hydrodynamic pressure, the soil under the pit will form a flow state, and flow into the pit with the groundwater, and the phenomenon that occurs is called the quicksand phenomenon.

Second, the harm of quicksand to the project.

Foundation is a very important part of the building, it has a great impact on the safety and normal use of the building, in the actual construction process must be combined with engineering geological conditions, building materials and construction technology and other factors, and the superstructure and the foundation are comprehensively considered, so that the foundation engineering is safe and reliable, economical and reasonable, advanced technology, convenient for construction. In the foundation construction process, if this problem is not solved, the foundation will flow with the sand layer, and the displacement will occur, so that the bearing layer of the foundation will change, which is very harmful to the building, and this phenomenon is absolutely not allowed.

When the foundation pit is excavated by the collection well dewatering method, when the foundation pit is excavated below the groundwater level, sometimes the bottom soil of the pit will become a flowing state, and the groundwater will pour into the foundation pit, which is called the quicksand phenomenon. The hazards of quicksand to the project.

When the quicksand phenomenon occurs, the subsoil completely loses its bearing capacity, the soil rises while digging, the construction conditions deteriorate, and in serious cases, it will cause collapse. If there is a building nearby, it will sink, tilt or even collapse due to the hollowing out of the foundation.

The main ways to prevent and control quicksand are: reducing or balancing the hydrodynamic pressure, trying to make the hydrodynamic pressure direction downward, cutting off the groundwater flow, etc. The specific measures are as follows.

1 Dry period construction method. The groundwater level is low in the dry season, the water level difference between the inside and outside of the foundation pit is small, and the hydrodynamic pressure is small, so it is not easy to produce quicksand.

2. Digging and throwing large stones. Dig the earthwork in sections, so that the excavation speed exceeds the sand speed, immediately after digging to the elevation, lay bamboo, reed mats, and throw large stones, in order to balance the hydrodynamic pressure, the quicksand is pressed. This method is suitable for the treatment of local or slight quicksand.

3. Set up the water-stopping curtain method to drive the continuous water-stopping supporting structure (such as continuous sheet pile, deep mixing pile, dense drainage cast-in-place pile, etc.) to a certain depth below the bottom surface of the foundation pit to form a closed water-stopping curtain, so that the groundwater can only seep from the lower end of the supporting structure to the foundation pit, increase the seepage path of groundwater flowing from the pit outside the foundation pit, reduce the hydraulic slope, thereby reducing the hydrodynamic pressure, and prevent the generation of quicksand.

4. Artificial lowering of groundwater level. That is, the well point precipitation method (such as light well point, tube well point, jet well point, etc.) is used to reduce the groundwater level below the bottom surface of the foundation pit, and the seepage of groundwater is downward, and the direction of the hydrodynamic pressure is also downward, so that the water can not seep into the foundation pit, which can effectively prevent the occurrence of quicksand. Therefore, this method is widely used and reliable.

Hello: 1. Quicksand: It is a sand material that falls due to strong winds or sand sediment materials that jump and roll due to wind.

2. Cause: The cause of quicksand trap is that the local sand particles are very special, they are all very uniform spherical particles, with little friction between each other, and they are easy to slide. As long as the sand surface is subjected to a little pressure, the static balance will be disrupted, and the sand particles will quickly slide around, causing foreign objects to sink in an instant, and along the depth, the humidity of the sand will be different, and a relative flow between the two layers of different humidity will be generated, that is, quicksand will be formed.

In addition, when the soil body is saturated by soaking, the hydrophilic colloidal particles in the soil particles absorb water and expand so that the density of the soil particles decreases, and when the hydrodynamic pressure exceeds the gravity of the soil particles, the soil particles produce suspended flow, and quicksand can be formed.

3. The prevention and control of quicksand is mainly to eliminate, reduce or balance the hydrodynamic pressure, and the specific measures are:

1) Construct an underground diaphragm wall for load-bearing and wall protection, and intercept water to prevent the occurrence of quicksand.

2) the use of non-draining underwater excavation, so that the water pressure inside and outside the pit is balanced, so that there is no quicksand conditions, the general caisson excavation adopts this method.

3) Use the dry season to construct in order to reduce the water level difference between the inside and outside of the pit.

4) The earthwork construction is carried out by using the method of artificially lowering groundwater such as light well point, jet well point, tube well well point and deep well point, so that the direction of hydrodynamic pressure is downward and the pressure between soil particles is increased, so as to effectively stop the occurrence of quicksand.

The uproar cake follows the barren Gewei Palace.

5) Use steel sheet piles to drive into a certain depth at the bottom of the pit to increase the distance of groundwater flowing into the pit from outside the pit, thereby reducing the hydraulic slope. It can reduce the dynamic pressure water and prevent the occurrence of quicksand.

The principle of controlling pipe gushing and quicksand (soil) is to prevent it, and when a large-scale quicksand (soil) danger occurs, there is no effective measure except for returning to the top of the soil first. The methods and measures for the prevention and control of pipe gushing and quicksand (soil) should be related to the engineering structure.

Main measures. The grass grid sand barrier is a kind of sand control method to prevent wind and fix sand and conserve water, and the net-like grass grid is like an inanimate desert miniature shelter belt, which is interlocking and connected.

1. What is a grass square?

Grass grid sand fixation, as the name suggests, is to use a bunch of discarded wheat straw to spread on the sand in a square shape, and then roll into the sand with a shovel, leaving 1 3 or half of the wheat grass naturally standing on the four sides, and then the sand in the center of the grid is pushed to the roots of the wheat grass around it, so that the wheat grass is firmly established on the sand.

2. Steps to make a grass checkered sand barrier.

There are three major steps to make a grass checkered sand barrier.

Clean up the straw. Wearing gloves, grab a handful of dry straw and pat it downwind, slapping off the crumbled or rotten low-quality straw, leaving only the high-quality long straw.

Stack wheat straw. Place the cleaned straw neatly on the edge of the square drawn in advance on the sand. When stacking, attention should be paid to keeping the thickness of the wheat straw moderate. (When stacking, care should be taken to keep the thickness of the wheat straw not too thick or too thin.)

If it is too thick, due to its own gravity, the wheat straw will easily fall down and will not be easy to stand on. If it is too thin, it will lead to insufficient sand resistance of the grass lattice [1])).

Stepping on shaping. When the shovel is pressed hard along the edge of the square, the middle of the straw will be stressed, and the ends will naturally erect to form a natural barrier. After stepping on the pressure, the sand on both sides of the wheat straw is pushed to the roots of the wheat grass around it, so that the wheat straw is firmly established on the sandy ground.

3. Grass checkered sand barrier tips.

There have been many other attempts to fix sand with grass walls. Later, it was found that other forms of grass walls, rectangles, triangles, prismatic shapes, circles, etc., are not as good as squares, that is, grass checkered sand barriers (when people try to make grass squares, in addition to 1 1 meter square, they also tie 1 2 meters, 2 2 meters, 2 3 meters and other specifications, and the experimental results prove that 1 1 meters in size, 10-20 cm high wheat straw squares have the best sand control effect. The main reason is that the central part of the sand is only hollowed out by the vortex generated by the air flow about 10 cm, while the central part of the 2 2 m and 2 3 m squares is deeply eroded, and the effect of sand fixation and sand control is not good.

It has also been measured that, in general, the wind mainly carries sand particles within 10 centimeters of the surface, beyond which there is very little sediment. In addition, snow control in winter is up to 100% effective. What's even more surprising is that the plants grown in the checkered world can grow vigorously and tall).

However, the straw squares will rot after 4 to 5 years of planting and need to be re-tied.

The way to prevent and control quicksand

There are three paths: one is to reduce or balance the moving water.

Pressure; The second is to try to make the direction of the DAO hydrodynamic pressure downward.

3. Truncated version of groundwater flow.

Specific measures for the right (1) Rush excavation method. (2) Sheet pile driving method. (3) Underwater excavation method. (4) artificial groundwater level lowering method, (5) dry period construction, and (6) underground diaphragm wall method.

1.Quicksand.

The phenomenon that the soil with a small particle size and no plasticity loses its stability under the impetus of dynamic water pressure and pours into the pit along with the groundwater is called quicksand.

2.Measures for the prevention and control of quicksand.

Construction in the dry period - when the construction period is not tight, and the difference between the abundant water level and the dry water level is large, sheet pile driving can be considered - a common construction method.

Excavation in water - commonly used in construction in rivers and lakes.

Artificial lowering of the groundwater level – a common construction method, such as the diaphragm wall method for well point dewatering – is slightly more expensive.

Throwing large stones and grabbing speed construction - a rescue construction method when quicksand has occurred.

Methods of controlling quicksand.

1.During the dry period, the groundwater level should be low, and the water level difference between the inside and outside of the pit should be small, so as to prevent and reduce the quicksand phenomenon.

2.Sheet piles are driven into the impervious layer along the periphery of the foundation pit, which can play the role of intercepting the water flow; Or drive into a certain depth of the bottom surface of the pit, so that the groundwater can be led to the bottom of the pit and flow into the foundation pit, not only increase the seepage length, but also change the direction of the dynamic water pressure, so that the purpose of the moving water lifting pressure can be reduced.

3.Excavation in water, neither drainage construction, so that the water pressure inside and outside the pit is balanced, so as not to form hydrodynamic pressure, such as caisson construction, sinking without drainage, digging in water, pouring concrete underwater, these are effective measures.

4.Artificially lowering groundwater, which is to intercept the flow of water and prevent groundwater from flowing into the foundation pit, so that it can not only prevent and control quicksand and bald pen collapse, but also improve construction conditions.

5.Underground diaphragm wall method, which is the underground diaphragm wall that is first poured to the reinforced concrete along the periphery of the foundation pit, so as to play the role of load-bearing, water interception and quicksand prevention, and at the same time is a reliable supporting structure for deep foundation construction.

6.Throw big rocks and rush to speed construction. If there is a local or slight quicksand phenomenon in the construction process, you can organize manpower to dig in sections, dig to the elevation, immediately lay the reed mat and throw large stones, increase the pressure of the figure, in order to balance the dynamic water pressure, and strive to complete the construction of the foundation in sections before the quicksand phenomenon is generated.

7.In addition, when the construction contains a large amount of groundwater soil layer or swamp area, the soil freezing method can also be used, and for the foundation engineering in the quicksand area, pile foundation or caisson construction should be used as much as possible to save costs.

Summary. It is to prevent the continued spread of quicksand, such as afforestation, the establishment of protective walls, and the return of farmland to forest.

It is to prevent the continued spread of quicksand, such as afforestation, the establishment of protective walls, and the return of farmland to forest.

1. Quicksand: It is a sand material that falls due to strong winds or sand sediments that jump and roll due to wind. 2. Causes:

The cause of the quicksand trembling oak trap is that the local sand grains are very special, they are very uniform spherical particles, with little friction between each other, and they are very easy to slide. As long as the sand surface is subjected to a little pressure, the static balance will be disrupted, and the sand eggplant particles will quickly slide around, so that the foreign objects will sink in an instant, and along the depth, the humidity of the sand will be different, and a relative flow will be generated between the two layers of liquid rot with different humidity, that is, quicksand will be formed.

The prevention and control of quicksand refers to the measures taken to prevent and stop the erosion and treatment of quicksand. The prevention and control of quicksand mainly takes the following measures: 1. Vegetation restoration

Vegetation is an effective measure to prevent quicksand, through vegetation restoration, the erosion of quicksand can be reduced, soil loss can be reduced, soil structure can be improved, soil fertility can be improved, soil moisture status can be improved, soil climate conditions can be improved, soil erosion can be reduced, and the ecological environment can be improved. 2. Forest and grass slope protection: Forest and grass slope protection refers to planting trees and herbaceous plants on the hillside to reduce the erosion of quicksand.

Plants can improve soil structure, increase soil erosion resistance, reduce the erosion of quicksand, improve soil moisture status, improve soil climate conditions, reduce soil erosion, and improve the ecological environment. 3. Slope protection engineering: The pure foundation of the slope protection engineering tunnel refers to the construction of slope protection structure on the hillside to reduce the erosion of quicksand.

Slope protection engineering can reduce the erosion of quicksand, improve soil structure, improve soil fertility, improve soil moisture, improve soil climate conditions, reduce soil erosion, and improve the ecological environment.