The operation of the standard penetration test, why do the standard penetration test

Standard penetration tests are mostly used in conjunction with drilling, and the key points of operation are:

The drilling tool is drilled to about 15 cm above the elevation of the test soil layer to avoid disturbance of the underlying soil.

Before penetration, the joint of the contact rod should be checked and should not be loosened. When penetrating, the piercing hammer falls at a distance of 76 cm, so that it falls freely, and the penetrator is driven straight into the soil layer by 15 cm. After each 30 cm hammer hit into the soil layer, it is the measured hammer number n.

The penetrator was proposed, and the soil sample in the penetrator was taken out for identification and description.

If it is necessary to proceed with the penetration test at the next depth, repeat the above procedure for the test.

When the length of the drill pipe is greater than 3 meters, the number of hammers should be corrected according to the following formula: the number of hammers in the standard penetration test, the correction factor of the length of the contact probe rod, such as the length of the contact rod is 3, 6, 9, 12, 15, 18, 21 meters, then the corresponding are70。

It should be ensured that the cutting edge (standard cutting edge) of the penetrator boot should be kept intact, and when there is damage such as notched or curled edge, its single length is greater than 5mm, or the total length is greater than 12mm, it should be discontinued;

The seams of the split penetrator (two halves of the cylinder) should be straight and tight, and the use should be stopped when there is distortion, expansion, staggered seam and other deformations;

The weight of the standard hammer is 76cm, the height of the free hammer of the guide rod is 76cm, and the error of the falling weight of the hammer mass and the falling distance of the guide rod exceeds the allowable range, it should be stopped;

Pay attention to the perpendicularity of the drill pipe and the guide rod to prevent shaking in the hole;

The diameter of the drill pipe must be 42;

The hammering speed should not exceed 30 hammers per minute, and the automatic hammer drop device should maintain normal drop and lifting performance, and should not have a lifting effect on the guide rod.

Repeat the next standard test, generally at a greater interval than the test.

For the drilling hole with the casing wall, the test depth should be less than 75cm below the casing mouth for the standard penetration test.

Pay attention to the drilling process and hole cleaning quality, and record the number of hits of the penetrator starting to penetrate 15cm to judge whether there is residual soil or disturbance degree at the bottom of the hole;

For the test section (i.e., the part of penetration 15 45cm), it is required to measure the cumulative penetration amount after each hammer stroke, and when the penetration amount is less than 2cm, the number of hammer strokes per penetration of 10cm is recorded. The relationship curve between the number of hammer strokes and the cumulative penetration amount was drawn to analyze whether the soil layer was uniform, and finally the number of hammer strokes in the 30cm test section was selected as the n value to be recorded.

The standard test needs to be coordinated with drilling, <>

The purpose of the standard penetration test is to judge the compactness of the sand or the consistency of the cohesive soil by the measured standard penetration hammer number n, so as to determine the allowable bearing capacity of the foundation soil; Evaluate the vibratory liquefaction potential of the sand and estimate the bearing capacity of the monopile; And can determine the soil profile and take disturbed soil samples for general physical tests.

The in-situ test method should be selected according to the geotechnical conditions, the requirements of the design parameters, the regional experience and the applicability of the test method. The standard penetration test is suitable for sandy, silt and general cohesive soils. In order to ensure the quality of the standard penetration test hole, rotary drilling is required to reduce the disturbance to the subsoil of the hole as much as possible.

When drilling to 15cm above the test elevation, stop drilling.

This is an in-situ assay method. Determine some of the characteristics of the foundation under the condition that the actual situation of the site is basically not changed. It can be used to determine the bearing capacity of the foundation on site. It can also be used to determine the liquefaction resistance of sandy soils.

The scope of application and function of the standard penetration test are as follows:

1) Take disturbed soil samples, identify and describe soil types, and name them according to the results of particle analysis.

2) According to the standard number of penetrations, the compactness of sand, the state of silt and load-bearing soil, the strength parameters of soil, the deformation modulus, and the bearing capacity of the foundation are evaluated by using regional experience.

3) Estimate the ultimate bearing capacity of a single pile and determine the possibility of pile sinking.

4) Determine the liquefaction possibility of saturated silt and sandy silt and the liquefaction grade of the field.

Under the hammer blow of a certain hammer weight and a falling distance, the number of strokes required for the probe to penetrate into the core crack of 30 cm is specified to determine the compactness of the sand or the consistency state of the cohesive soil, determine the allowable bearing capacity of the foundation soil, infer the shear strength of various types of soil, estimate the deformation modulus of the cohesive soil and evaluate the vibration liquefaction of the sand. At the same time, according to the difficulty of penetrating the beam pants, the soil layers of different properties can be qualitatively divided and the uniformity of the soil body can be evaluated, the filling quality can be checked, the position of the sliding zone and the soil hole can be explored, and the burial depth of the bedrock surface or gravel soil layer can be determined.

The standard penetration test is a method for determining the bearing capacity of the foundation of sand or cohesive soils in the field. The specific application scope and function are as follows: Wax Balance

The Standard Penetration Test (SPT) is a type of dynamic penetration test, which has been included in the Chinese National Code for the Design of Industrial and Minhong Nuclear Building Foundations. It uses a certain hammering function (hammer weight, falling distance 76cm), and drives a certain specification of the split pipe penetrator (the outer diameter of the split pipe is 51mm, the inner diameter is 35mm, the length is greater than 457mm, the lower end length is 76mm, the cutting angle is 18 ° 20 °, the pipe shoe with a thick end of the cutting edge, and the upper end is connected to the drill pipe) into the soil at the bottom of the drilling hole wheel, and according to the penetration impedance in the soil, the change of the soil layer and the engineering properties of the soil are judged. The purpose of the standard penetration test is to determine the bearing capacity of the foundation of sand or cohesive soil in situ.

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What are the steps and precautions of the standard penetration test method?

Steps:1Use a drilling rig to drill to the soil layer that needs to be tested by standard penetration, and after cleaning the hole, replace it with a standard penetrator and measure the depth size.

2.The penetrator is vertically driven into the test soil layer, first driven into 15cm, regardless of the number of strokes, and continues to penetrate into the soil for 30cm, and the number of hammer strokes is recorded, which is the number of standard penetrating strokes. 3.

The penetrator is proposed, the soil sample in the penetrator is taken out, the identification description and record are carried out, and then the drilling tool is replaced to continue drilling to the next depth that needs to be tested, and then the above operation is repeated, and the test can generally be carried out every interval. 4.The same soil layer should be tested several times, and then the average of the number of hammer strokes should be taken.

Notes:1Pay attention to the drilling process and the quality of hole cleaning, and record the number of hits when the penetrator starts to penetrate 15cm to judge whether there is residual soil or soil disturbance at the bottom of the hole; 2.

The drill pipe and guide rod are perpendicular to prevent shaking in the hole. 3.The test section is required to determine the cumulative penetration after each hammer blow.

When the amount of penetration is less than 2 cm in one penetration, the number of hammer blows per 10 cm of penetration is recorded.

What should be paid attention to when applying the standard to the test results?

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Hello dear dear, I have found the following information for you: What are the steps and precautions of the standard penetration test method? Steps:

1.Use the drilling rig to drill to the soil layer that needs to be tested by standard penetration, and after the hole is cleaned, change to the standard grip penetrator, and measure the depth size. 2.

The penetrator is vertically driven into the slag of the test soil layer, first driven into 15cm, regardless of the number of hits, and continues to penetrate into the soil for 30cm, and the number of hammer strokes is recorded, which is the number of standard penetrating strokes. 3.The penetrator is proposed, the soil sample in the penetrator is taken out, the identification description and record are carried out, and then the drilling tool is replaced to continue drilling to the next depth that needs to be tested, and then the operation is repeated to slow down the whispering operation, and the test can generally be carried out every interval.

4.The same soil layer should be tested several times, and then the average of the number of hammer strokes should be taken. Notes:

1.Pay attention to the drilling process and the quality of hole cleaning, and record the number of hits when the penetrator starts to penetrate 15cm to judge whether there is residual soil or soil disturbance at the bottom of the hole; 2.The drill pipe and guide rod are perpendicular to prevent shaking in the hole.

3.The test section is required to determine the cumulative penetration after each hammer blow. When the amount of penetration is less than 2 cm in one penetration, the number of hammer blows per 10 cm of penetration is recorded.

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The scope of application and function of the standard penetration test are as follows:

1. The application scope of the standard penetration test

1. Soil classification: The standard penetration test can be used to determine the physical properties of the soil such as strength, density, permeability, etc., and help classify different types of soil.

2. Determination of soil support resistance: The standard penetration test can be used to determine the static support resistance of the soil, and provide basic data for the construction of buildings, bridges, tunnels and other projects.

3. Soil permeability determination: The standard penetration test can be used to determine the permeability history coefficient of the soil, and provide basic data for soil seepage analysis and groundwater hydrological investigation.

4. Determination of soil bearing capacity: The standard penetration test can be used to determine the bearing capacity of the soil and provide a basis for engineering design.

5. Determination of soil density: The standard penetration test can be used to determine the density of the soil and calculate the "basic data" for soil settlement.

In general, the standard penetration test is a commonly used soil testing method in geoengineering, which can be used to determine the physical properties of soil, and provide important reference data for engineering design, soil seepage analysis, groundwater hydrological investigation, soil settlement calculation, etc.

Second, the role of the standard penetration test

2. Determine the bearing capacity of the soil: The standard penetration test can determine the static support resistance of the soil, which provides a basis for engineering design to determine the bearing capacity of the soil.

The scope of application and function of penetration test are as follows:

The standard penetration test can be used for sand, silt and general carrier soil, and finally used for n=2-50 pounding soil layers. It is mainly used for rolling and rolling: taking disturbed soil samples, identifying and describing soil types, and naming according to the results of particle analysis.

According to the standard number of hits n, using regional experience, the compactness of sand, silt, the state of carrier soil.

The strength parameters, deformation modulus, and bearing capacity of the soil are evaluated. Estimate the ultimate bearing capacity of a single pile and determine the possibility of pile sinking. Determine the liquefaction possibility and liquefaction grade of saturated silt and sandy silt.

The Standard Penetration Test (SPT) is a type of dynamic penetration testing, which is a method for determining the bearing capacity of sand or cohesive soils in situ. This method has been included in China's national code for the design of foundations for industrial and civil buildings. It makes use of a certain hammering function ( hammer weight 63

5kg, drop distance 76cm).

The insertor of a certain specification of the split tube type (the outer diameter of the split pipe is 51mm, the inner diameter is 35mm, the length is greater than 457mm, the lower termination length is 76 mm, the cutting angle is 18° 20°, and the end thickness of the cutting edge is 16mm pipe shoe, the upper end is connected to the drill pipe) into the soil at the bottom of the borehole, according to the penetration impedance in the soil, the change of the soil layer and the engineering properties of the soil are judged.

The measured number of strokes in the standard penetration test is the number of hammer strokes required by the standard penetrator to drive into the soil at a certain depth (30). The scope of application and function are as follows:

The Standard Penetration Test (SPT) is a type of dynamic penetration testing, which is a method for determining the bearing capacity of sand or cohesive soils in situ. This method has been included in the "Code for the Design of Industrial World Tourism and Civil Building Foundations" of China's redistribution country.

The hammer used to fall freely from a height of 1900px (76cm) is used to hammer the standard penetrator with a length of 51 centimeters, outer diameter centimeters, and inner diameter centimeters into the soil 750px (30cm), which is called the standard penetration number n.

The influencing factors of trials are complex. Some of these factors can be unified through standardization to reduce the impact on the test results, such as equipment, hammer drop method, test method and other influencing factors belong to this category; However, other factors, such as pole length, groundwater level, overlying pressure, etc., cannot be artificially controlled.

According to the number of hammer strokes in the standard penetration test, the physical state of sand, silt and cohesive soil, the strength of the soil, the deformation parameters, the bearing capacity of the foundation, the bearing capacity of the single pile, the liquefaction of sand and silt, and the possibility of pile formation can be evaluated.