How to calculate the penetration degree of hammered pile, and how to calculate the depth of hammered

If the total number of feet of the last ten strokes is hit, the penetration degree of the final design is the hit.

Definition: Hammering and sinking piles is to use the instantaneous impact mechanical energy when the pile hammer falls, overcome the resistance of the soil to the pile, and destroy the static equilibrium state, resulting in the sinking of the pile body and reaching a new static equilibrium state. Hammer pile sinking is the most commonly used pile sinking method for prefabricated piles.

The construction speed of this method is fast, the degree of mechanization is high, the scope of adaptation is wide, and the degree of civilization on site is high, but there are public hazards such as soil crowding, noise and vibration during construction, which has restrictions on urban centers and night construction.

Principle: pile sinking equipment and selection.

The machinery and equipment used in piling mainly include three parts: pile hammer, pile frame and power device.

Pile hammer selection: drop hammer, single action hammer, double action hammer, diesel pile hammer and hydraulic hammer, etc.

How to calculate the depth of hammer sinking pile into the soil, the bending moment of the general passive earth pressure is calculated according to half, that is, the safety factor takes 2. Then the obtained h is multiplied by the depth of the cantilever sheet pile. Stress on sheet piles:

In the place where the shear force is 0, the bending moment held by the sheet pile skin is the largest, let the combustion depth be t, and the equation with the shear force of 0 can be found t, and then the difference between the bending moment of the active earth pressure and the passive earth pressure at t is the maximum bending moment of the sock sheet pile. The maximum stress of sheet pile should not exceed half of the allowable stress of steel in general use.

Generally, the penetration degree of pile sinking is controlled at 5 10mm, but for different pile hammers, the actual pile sinking capacity is quite different. At present, there does not seem to be a quantitative tenant index for the bearing capacity of a single pile corresponding to the sinking penetration of different pile hammers.

The methods and tools used in the penetration test (such as the standard penetration instrument) are clearly specified in the "Code for Design of Building Foundations" and "Technical Specifications for Building Pile Foundations".

Final penetration: during piling construction, the determination and recording of the final penetration, for the drop weight, single-action steam hammer and diesel hammer take the depth of the last 10 hits into the soil; And for the double-action steam hammer take the last 1 minute of the pile into the soil.

The measurement of penetration should be carried out under the specified conditions: that is, there is no damage to the pile top, no eccentricity of the hammer, and the pile shape and pile pad work normally under the specified hammer drop distance. If the penetration has reached the requirements and the pile tip elevation has not been reached, the hammering should continue to hit 3 formations, and the average penetration degree of 10 strokes per formation should not be greater than the specified number of grinding Zheng value.

Light and medium dynamic cone penetration for general cohesive soils; In addition to general cohesive soil, the standard penetration test can also be applied to silt and sand, including silt, fine and medium sand. For coarse sand, gravel sand, as well as gravel, pebbles and other gravel soils, heavy (2) dynamic penetration should be used. Standard penetration tests are often used in embankment projects.

The volume of a single pile is calculated by multiplying the cross-sectional area of the outer diameter of the steel pipe (excluding the pile hoop) by the design pile length (excluding the prefabricated pile tip) and the length of the additional irrigation method.

Irrigation length: the design has provisions, calculated according to the requirements of the design regulations, the design is not specified by the meter calculation, if the elevation of the pile top has reached the natural level according to the design regulations, the length of the irrigation is not counted (all kinds of cast-in-place piles are the same).

Ramming (single pile volume) project = pile pipe outer diameter cross-sectional area * (ramming or expanding part height + design pile length + irrigation length), ramming or expanding part height is calculated according to the design regulations;

The volume of the expanded pile is calculated by multiplying the volume of a single pile by the number of re-beating, and the re-beating part is multiplied by the coefficient.

The amount of the empty part of the immersed pipe cast-in-place pile is calculated according to the length from the natural floor elevation before piling to the design pile top elevation minus the irrigation length and multiplied by the pile cross-sectional area.

The volume of hammered immersed pipe cast-in-place pile should be reviewed by two calculations, and the error is not large (generally not more than 10%, which is very normal, and do not listen to the requirements of the supervisor sometimes brute).

1. The product of the cross-section of the cast-in-place pile and the design depth of the pile;

2. The actual volume quantity of the filler (or filler).

The final settlement is based on the theoretical figures. In general, it is possible to settle the bill without the actual number.