Foundation on Sand and Non-plastic Soil:
Physicists and agronomists classify soils based on their workings. But the engineering classification of soil is a little different. In this case, more emphasis is placed on the behavior and characteristics of the ball as it lands on the ground. So the classification of soil is done keeping a watchful eye on the engineering religion, characteristics and behavior etc. Soil can be divided into two parts based on the size of the soil particles, e.g.
(A) Coarse grained soil:
Coarse grained soil and coarse grained soil are the aggregates of mineral particles, which are initially identified based on the shape of the particles. More than half of the weight of this soil can be seen with the naked eye. The components of this soil are gravel and sand. According to the MIT classification, if the size of the collar is larger than 2 mm, it is called gravel. On the other hand, if the size exceeds 200 mm, it is called a bulldozer. If the soil particles are visible to the naked eye but the size is less than 2 mm, then it is called sand. The sand can be further divided into ground, medium and fine.
(B) Fine grained soil:
Fine grained soil. Fine-grained soil is soil that has more than half the weight of each particle of soil so fine that they cannot be seen with the naked eye. Fine-grained soils are usually prone to cohesive. Its components are called silt and clay. Particle size typically ranges from 0.06 mm to 0.002 mm, according to the MIT classification. On the other hand, the particle size of clay is less than Q.X) 2 mm. The clay is highly prone to adhesion and adhesive when wet.
So there are two kinds of fine-grained soil,
E.g.-
1. Silt '
2. Clay.
The alley is again divided into three parts, viz
(A) Inorganic sediment
(B) Rock totr ')
(C) Plastic sult '.
Inorganic terms are formed by the relatively large particles of the microscopic small part of the soil. This strange phenomenon: Mall may or may not have a small amount of plasticity and cohesive force. This kind of silt is brought. Is considered as poly (Not-plastichii).
Fine-grained quartz grains with a very small amount of soft quality with full rock. And when smaller in size
If the acceptable amount of particles is in the particles then bend the particles. Called poly. This chapter discusses the construction of foundations based on sand and non-plastic ofit or silt.
Significant characteristics of sand and silt deposite:
(a) Non-plastic cohesionless silt has the same properties as fine sand. Sandy or loamy soil. Important engineering qualities are given below:
1. Very useful for foundation to support the structure. With the exception of loose sand, its bearing capacity is very low
2. Convenient to use as dam construction material. Because its shear strength is high and can be easily strengthened.
3. Backfill material for retaining wall, basement wall etc. can be easily used in Hilab and the amount of clothing is less.
4. Cannot be used for construction of earthen dams.
5. Addiction to clothes is more due to tremors.
The following are some of the important features to consider when building a foundation on sand and silt.
The foundation of the structure can be provided by footing, raft, pier or pile in sandy soil. But what kind of foundation
Will be selected, depending on ---
1. Relative density of sand and
2. On the position of the water table. The relative density of sand determines the bearing capacity of footings, piers or piles.
(a) Loading capacity of footing, pier or pile
(b) Settlement of footings, piers or piles and
(c) Resistance of pile. On the other hand, knowing the location of the water plane is very important. Because
(A) Drainage system for excavation under water and
(B) To calculate the increased construction cost for the foundation.
Thus, water affects the bearing capacity and weave of the flat soil.
(c) To calculate the increased construction cost for the foundation. Thus water affects the bearing capacity and weaving of flat soil.
Footing on the sand:
A) Design principle: In case of homogeneous or homogeneous sand the load-bearing relationship is given below: ---
Footing on the sand photo
In case of wide footing, the maximum bearing capacity is higher in a single area. The soil pressure for a particular garment is higher in the case of medium width (B, footing) than in large footings (B,) in short widths (1). By
(b) Drawn. Soil pressure q in the single case in the figure; And forest) has been shown. Clothes s; The pressure of the soil is q; The widening of the footing has made sense. But Footing's broad intelligence rate is comparative
Less. After reaching the maximum position of medium wide footing, the load gradually decreases but the load increases. Thus from the relationship between soil pressure and the width of the footing, the above behavior is correct for placing the footing on the sand. It also affects a number of topics, including the following:
- Relative density of the sand
- Depth of foundation
- Position of water table
In addition, from the shape of the curve in the figure, it can be concluded that,
(A) In case of short wide footing,
change of clothing is more due to slight change in actual soil pressure. The resulting bearing capacity failure is considered.
(i) In case of wide footing- change of clothes also decreases with slight change of pressure.
Therefore, bearing capacity failure may occur in case of wide footing as s¹ is much less relative to q¹.
(B) Considerations of settlement:
Dense sand is more dense than loose sand. Therefore the soil pressure and the standard penetration test for precise clothing should be related to the N-value. In 1947, Terzaghi and Peck developed that relationship. Based on general experience, he experimented with the N-values of lead, cloth and various sands. The value of S¹ limits the maximum wear with 2.5 cm (Iinch).
(C) Consideration of bearing capacity:
In case of short moon footing, if the soil pressure increases, the wear increases. This movement of the soil (Movemicat) is considered a failure of the bearing capacity. Therefore, footing should be provided on the sand in such an acceptable manner as to ensure that the fabric does not exceed 2.5 cm, subject to the previous conditions. For this reason, it is very important to determine the bearing capacity for the design.
Pile in sand:
Use of Piles: Piles are used in sandy soil for the following reasons, e.g.
(A) To transfer the load of super structure to the layer of dense soil through soft or compressible material.
(B) Piles are laid to increase the bearing capacity by strengthening the loose sand.
(C) Piles are laid to lay the foundation on the sand layer at greater depths.
(B) Piles driven to beating in dense sand.
If the material below the base level is too compressible or unstable, it cannot support the foundation. In that case, arrangements are made to move the ladder of the superstructure down to the power level below. If the hard layer is composed of sand car, be.
The pile is placed on a hard layer through a soft material so that it can carry a sufficient load. The speed of the rapper is medium but piles are placed one after the other at some distance. And if it is completely dense sand and it is not possible to enter more, then. Some more penetration is done from the point of obstruction. The lower part is made to carry the load through Huckin friction.
1) The carrying capacity of the pile should be calculated through the lead test.
2) Draw the lair-settlement curve to know the shape of the sand layer (Deposit).
3) If structurally the pile does not fail, the led-settlement county reaches the diagonal touch.
4) If the pile is placed in the soil does not fail, but if the load is increased, it will come slowly and will continue to be sown.
5) The design should be done with the lead taken up to the moment before the dress.
The amount of pile inserted into the sand has to be calculated to obtain the required bearing capacity. In order to pour this information, piles of different lengths have to be placed continuously. Record penetration during pile laying, then move on.
That is, the depth has to be found out through the led test of piles of different lengths. Apart from that, the driving resistance has to be taken out. However, in the case of very fine sand and silt, the obstacle is determined by means of a wave equation.
Compaction pile: -
When this pile is placed in loose sand, the sand becomes partially firm, because the amount of void in the sand is reduced. Vibration during pile laying also causes sand to harden. Ala again. By making a hole in the sand, the density can be increased by filling that hole with solid sand, but the pile is not suitable for laying.
In general, heavy taper piles are very efficient and cost effective. If the structure has to be placed on top of the pile footing, then several piles have to be placed together. However, the inner pile is placed first.
The approximate method is used to calculate the design load. When placing the center pile in the pile group, a small amount should be recorded for each injury. Then the other piles of the group have to be placed and the amount of clothing should be the same as the center pile.
Then the center pile has to be re-placed and the amount of clothing has to be recorded. After doing this a few times, the actual bearing capacity has to be ascertained through a live test.
Places in very fine sand and silt: ---
Pore water pressure has been ignored while laying piles in the sand. But this tends to accumulate when the piles are placed between the fine sand and the silt. As a result, the effective pressure between the particles decreases and so does the shearing resistance.
In this way, as the water pressure in the faucet increases, the soil becomes liquid at one point and the lateral shift of the previous placement pile rises to the top. Timber or shell pile floats more.
Therefore, heavy piles are placed in this case if the thin sand or silt is strong (Dense), but the pile creates more obstacles. This is because placing many piles together causes the water pressure between the particles to be negative.
Piers on sand: -
Pigeons are usually placed above the level of dense sand. The piers are placed according to the bearing pile to support the lead of the superstructure and it is viewed according to the column of the structure. Is transferred to the lacher on the hard layer.
Pigeons are usually placed above the level of dense sand. The piers are placed according to the bearing pile to support the lead of the superstructure and it is viewed according to the column of the structure. Is transferred to the lacher on the hard layer.
Conditions for use of piers:
Piers are used in terms of the following conditions, e.g.
1. If the soil is too soft or compressible to support the superstructure,
2. If there is a possibility of scouring the soil,
3. In the case of soils with large bulldozers that prevent pile penetration,
4. Piles are made instead of piles depending on the cost and construction method.
