CN208056133U - A kind of experimental rig of unitary variant assessment tapered pile anti_freeze uplift performance - Google Patents

Abstract

The utility model discloses a test device for evaluating the anti-freezing and pullout performance of conical piles with a single variable in permafrost regions. Circulation pipe, one side of the inner wall of the sample cylinder is provided with a moisture sensor, and the other side is provided with a temperature sensor; the top of the pile sample is provided with a load sensor, and the upper part of the fixed bracket is provided with a beam, which includes a triangular bracket and a load sensor. A trapezoidal stress dispersing pad between the sensor and the tripod, and a displacement sensor fixed on the loading device for monitoring the deformation of the crossbeam is arranged above the tripod. When using this test device, only the single variable of the cone angle is considered, and the single variable of the cone angle is changed for measurement, which avoids the influence of the weight and the lateral area of the pile on the anti-freezing and pulling out performance of the pile, and can be accurately and reasonably obtained The effect of different cone angles on the anti-freezing and pulling out performance of piles has guiding significance for the construction of actual projects.

Description

A single-variable test device for evaluating the anti-freezing and pulling-out performance of conical piles

technical field

The utility model relates to a test device for evaluating the anti-freezing and pulling performance of conical piles with a single variable, more specifically, a test device for evaluating the anti-freezing and pulling performance of conical piles with a single variable cone angle in permafrost regions.

Background technique

Permafrost is widely distributed in my country, and the permafrost area accounts for about three-quarters of the country's land area. With the advancement of construction, more and more infrastructures are being planned and built in permafrost areas in my country, and more and more problems are emerging. Among them, the problem of freezing and pulling out of pile foundation is one of the very important and difficult problems to solve. As a new type of pile foundation, conical piles have shown good results in the timeliness of anti-freezing and pulling out, but there is no unified conclusion on the mechanism of anti-freezing and pulling out of conical pile foundations, so from the quantitative From the perspective of theoretical analysis, it is of great value for the development of frozen soil engineering in my country to study the mechanism of anti-freezing and pulling out of conical pile foundations.

At present, there are many studies on conical piles at home and abroad. Although the pullout effects of different cone angles have been analyzed from indoor tests, field tests and numerical simulations, none of the current research on conical piles has considered the cone angle As a single variable, the analysis does not take into account the influence of gravity and the lateral area of the pile on the freezing and pulling force, so the accuracy of the relationship between the cone angle and the freezing and pulling performance of the pile is difficult to be convincing. Therefore, it is necessary to design a new type of test device based on the existing test device to measure the influence of the single variable of cone angle on the anti-freezing and pulling out performance of conical piles.

Contents of the invention

The technical problem to be solved by the utility model is to provide an evaluation test for the anti-freezing and pulling performance of conical piles that only considers the cone angle as a single variable in view of the influence of the cone angle of the cone-shaped pile in the permafrost region on the anti-freezing and pulling performance of the pile body. The device can accurately and reasonably obtain the influence of different cone angles on the anti-freezing and pulling out performance of piles.

In order to solve the above-mentioned technical problems, the technical scheme adopted by the utility model is: a test device for evaluating the anti-freezing and pulling performance of conical piles in permafrost regions with a single variable. The fixed bracket of the cylinder and the base of the lower part of the pile sample located in the sample cylinder, a refrigerant circulation pipe is arranged under the sample cylinder, a moisture sensor is installed on one side of the inner wall of the sample cylinder, and a water sensor is installed on the other side. There is a temperature sensor; a load sensor is arranged above the pile body sample, and a crossbeam is arranged on the upper part of the fixed bracket, and the crossbeam includes a triangular bracket fixed on the fixed bracket and a trapezoidal stress dispersion pad arranged between the load sensor and the triangular bracket block, and a displacement sensor fixed on the loading device for monitoring the deformation of the crossbeam is arranged above the tripod bracket.

Preferably, the pile body sample has a height of 25-35 cm, a small circle diameter of 2-8 cm, and a cone angle of 0-11°; the pile body sample is provided with lightweight polyurethane foam.

Preferably, the soil sample around the pile body sample is made of frost-heaving sensitive soil silty clay, the compaction degree is controlled at 93% to 97%, and the hair is shaved and compacted in layers; A moisture sensor is installed, and a temperature sensor is embedded every 5-6cm.

Preferably, the pile body sample needs to be designed on the basis of the pile body volume on the basis of 0° pile;

When designing the pile body, first ensure that the lateral surface areas of the pile body are equal, that is,

d _θ =d ₀ -h tanθ

Secondly, calculate the volume of the pile body according to the calculated diameter, namely

Thirdly, since the mass of piles with different cone angles is required to be equal, the excavation volume is calculated according to the calculated pile volume, that is,

V _{θ dig} = V _θ -V ₀

Finally, the specification of the excavated part is determined according to the calculated excavated volume, that is,

Among them, d ₀ is the diameter of the 0° pile (in cm), d _θ is the small circle diameter (in cm) of the conical pile with an angle of θ, h is the height of the pile body (in cm), and θ is The angle of the conical pile (unit is °), V _θ is the volume of the conical pile with the cone angle θ (the unit is cm ³ ), V ₀ is the volume of the 0° pile (the unit is cm ³ ), V _{θ is dug} as The volume (in cm ³ ) of the cone-shaped pile with the cone angle θ needs to be excavated, h _θ is the height (in cm) that needs to be excavated for the cone-shaped pile with the cone angle of θ, and d _θ is the cone angle of The diameter of the small circle (in cm) that needs to be excavated for the tapered pile of θ.

The beneficial effects produced by adopting the above-mentioned technical scheme are:

(1) When using this test device, only the single variable of the cone angle is considered, and the single variable of the cone angle is changed for measurement, which avoids the influence of the weight and the lateral area of the pile on the anti-freezing and pulling performance of the pile, and can be accurate and reasonable. The effect of different cone angles on the anti-freezing and pulling out performance of piles is obtained, which has guiding significance for the construction of actual projects;

(2) The utility model is suitable for testing the influence of the cone angle of the small-sized pile foundation on the anti-freezing and pulling out performance of the pile body in indoor tests and field in-situ tests.

Description of drawings

Fig. 1 is a structural representation of the utility model;

Fig. 2 is a side view of the pile body sample in the utility model;

Fig. 3 is a side view of a 5 ° pile body sample in the utility model;

Fig. 4 is a side view of a 9 ° pile body sample in the utility model;

Wherein: 1-1, moisture sensor; 1-2, test device for anti-freezing and pulling performance of pile body (remove the upper cold bath plate); 1-3, crossbeam; 1-4, displacement sensor; 1-5, load sensor; 1-6, temperature sensor; 1-7, sample cylinder; 1-8, refrigerant circulation pipe; 2-1, pile body sample; 2-2, polyurethane foam;

Detailed ways

In order to make the above purpose, features and advantages of the utility model more obvious and easy to understand, the technical solution of the utility model is clearly and completely described below in combination with the drawings and embodiments of the utility model. Apparently, the described embodiments are only some of the embodiments of the present invention, but not all of them. Based on the embodiments of the present utility model, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the scope of protection of the present utility model.

The utility model provides a new idea of testing the impact of the cone angle on the anti-freezing and pulling performance of the pile body. The method only changes the single variable of the cone angle for measurement, and avoids the influence of the weight and the side area of the pile body on the anti-freeze and pulling performance of the pile body. performance impact. The test device in the utility model is based on the improvement of the existing test device for testing the anti-freezing and pulling performance of pile bodies. The experimental device for testing the anti-freezing and pulling out performance of piles in "and its experimental methods".

It includes a specific cone-shaped pile body sample and an improved test device for testing the anti-freezing and pulling out performance of the pile body. The improved test device for the anti-freezing and pulling out performance of the pile body includes the original test device for testing the anti-freezing and pulling out performance of the pile body (the upper part of the cold bath plate is removed), various sensors and a displacement restraint reinforcement device. The displacement restraint reinforcement device is welded with trapezoidal stress Stainless steel beams with disperse pads and triangular brackets. When measuring the freezing and pulling force, add a trapezoidal stress dispersion pad and a beam of the triangular bracket, and add a displacement sensor to monitor the deformation of the beam; when measuring the freezing and pulling displacement, a displacement sensor is directly arranged on the top of the pile to measure the freezing and pulling displacement of the pile body .

Specifically: referring to accompanying drawing 1, it comprises sample cylinder 1-7, is used for fixing the fixed bracket 1-2 of sample cylinder 1-7 and is positioned at the bottom of pile body sample 2-1 in sample cylinder 1-7 The base of the sample cylinder 1-7 is provided with a refrigerant circulation pipe 1-8, and the difference is that a water sensor 1-1 is provided on one side of the inner wall of the sample cylinder, and a temperature sensor 1 is provided on the other side. -6; A load sensor 1-5 is provided above the pile sample 2-1, and a crossbeam is provided on the upper part of the fixed bracket, and the crossbeam includes a triangular bracket fixed on the fixed bracket and is arranged on the load sensor 1-5 and the triangular bracket. A trapezoidal stress dispersing pad between the brackets, and a displacement sensor 1-4 fixed on the loading device for monitoring the deformation of the crossbeam is arranged above the triangular bracket.

In order to make the anti-freezing and pulling effect of the conical pile body in the test device remarkable, the soil samples around the pile are frost-heave-sensitive soil silty clay, the compaction degree is controlled at 93%-97%, shaved and compacted in layers, and filled During the soil sampling process, a moisture sensor 1-1 is embedded every 10 cm, and a temperature sensor 1-6 is embedded every 5-6 cm. In order to ensure the unidirectional freezing of the conical pile, it is necessary to eliminate the influence of the normal frost heave force on the pile body, and ensure that the bottom of the pile body is kept at 1°C through the refrigerant circulation pipe 1-8. The data of various sensors can be collected by DT85 data collector.

Referring to accompanying drawing 2, described pile body sample 2-1 is 25～35cm in height, and its small circle diameter is 2～8cm, and cone angle is 0～11°, and in order to guarantee the single variable of cone angle, need to ensure pile With the body side surface area unchanged, the volume of the pile body is modified.

When testing the anti-freezing and pulling performance of piles, in order to ensure that the cone angle is the single variable of the test, and to ensure that the quality, height, and force-bearing side area of the pile remain unchanged, it is necessary to design the volume of the pile on the basis of a 0° pile. .

When measuring the freezing and pulling force, the purpose of the added trapezoidal stress dispersion block is to avoid stress concentration on the reaction beam; the purpose of the added triangle bracket is to increase the stiffness of the reaction beam; the purpose of the added displacement sensors 1-4 is to monitor The crossbeam is deformed to ensure zero displacement of the crossbeam; when measuring the freezing and pulling displacement, the reaction frame needs to be removed, and the function of the displacement sensor is to measure the freezing and pulling displacement of the pile body.

The above-mentioned pile samples were used to conduct a single-variable test to evaluate the anti-freeze and pull-out performance of conical piles. The specific steps are as follows:

The first step: prepare the test pile; the height of pile sample 2-1 is 25-35cm, the diameter of its small circle is 2-8cm, and the cone angle is 0-11°. In order to ensure the single variable of cone angle, it is necessary to ensure Under the condition that the lateral surface area of the pile remains unchanged, the volume of the pile is modified. As shown in Figure 2, in order to ensure that the cone angle is the single variable of the test and ensure that the mass, height, and force-bearing side area of the pile body remain unchanged, it is necessary to cut out the pile body volume on the basis of the 0° pile. First, ensure that the lateral surface areas of the piles are equal, that is,

d _θ =d ₀ -h tanθ

Secondly, calculate the volume of the pile body according to the calculated diameter, namely

Thirdly, since the mass of piles with different cone angles is required to be equal, the excavation volume is calculated according to the calculated pile volume, that is,

V _{θ dig} = V _θ -V ₀

Finally, the specification of the excavated part is determined according to the calculated excavated volume, that is,

Among them, d ₀ is the diameter of the 0° pile (in cm), d _θ is the small circle diameter (in cm) of the conical pile with an angle of θ, h is the height of the pile body (in cm), and θ is The angle of the conical pile (unit is °), V _θ is the volume of the conical pile with the cone angle θ (the unit is cm ³ ), V ₀ is the volume of the 0° pile (the unit is cm ³ ), V _{θ is dug} as The volume (in cm ³ ) of the cone-shaped pile with the cone angle θ needs to be excavated, h _θ is the height (in cm) that needs to be excavated for the cone-shaped pile with the cone angle of θ, and d _θ is the cone angle of The diameter of the small circle (in cm) that needs to be excavated for the tapered pile of θ.

The shape of the excavated volume is a conical pile with the same angle. The size of the excavated conical pile needs to be calculated according to the excavated volume, and after excavation, the filling strength meets the requirements, and the lightweight polyurethane with thermal insulation and waterproof properties Foam.

Step 2: Embedding test piles; place the piles in the experimental device. In order to make the conical piles in the test device have a significant anti-freezing and pulling effect, the soil samples around the piles are made of frost-heave-sensitive silty clay, and compacted. Control the temperature at 93% to 97%, scrape and compact in layers, and embed a moisture sensor 1-1 every 10cm and a temperature sensor 1-6 every 5-6cm during the process of filling the soil sample;

Step 3: Test the freezing and pulling force of the pile body during the one-way freezing process; ensure the one-way freezing of the test device and use the reaction force steel frame and load sensor to measure the freezing and pulling force, as shown in Figure 1, in order to eliminate the normal frost heaving force Influence, to ensure that the temperature of the refrigerant circulation pipe at the bottom of the pile is constant at 1°C, wrap the surrounding of the sample barrel with thermal insulation cotton, and place the entire test device in a high and low temperature alternating freeze-thaw cycle box for cooling and freezing;

Step 4: Repeat the content of the second and third steps to obtain the magnitude of the freezing and pulling force of the pile under different cone angles.

After the above test process, only the single variable of the cone angle was changed, and then the influence of different cone angles on the freezing and pulling force of the pile was obtained, which avoided the influence of the lateral area of the pile and the weight of the pile on the test results, and made the test data more accurate. precise.

The above process is only to measure the relationship between the freezing force and the cone angle. If the reaction force steel frame and the load sensor are removed in the third step, the displacement sensor is directly placed on the top of the pile and the first step to the fourth step are repeated. The effect of the cone angle on the displacement of the pile body in freezing and pulling out was obtained.

This test device can not only measure the impact of the cone angle, a single variable, on the freezing and pulling force of the pile, but also measure the influence of the cone angle on the freezing and pulling displacement of the pile. The test process of the effect of the cone angle, a single variable, on the freezing and pulling force of piles is described.

Example 1:

The first step: prepare the test pile; the height of the pile sample is 30cm, the diameter of the small circle is (2-8) cm, and the cone angles are 0°, 5°, 9° and 11° respectively. For a single variable, it is necessary to modify the volume of the pile while ensuring that the lateral surface area of the pile remains unchanged. As shown in Figure 2, in order to ensure that the cone angle is the single variable of the test and ensure that the mass, height, and force-bearing side area of the pile remain unchanged, the volume of the pile needs to be cut out on the basis of the 0° pile. First of all, ensure that the lateral surface areas of the piles are equal, and take the diameter of the 0° pile as 8cm, and first ensure that the lateral surface areas of the piles are equal, that is

d _θ =d ₀ -h tanθ

Secondly, calculate the volume of the pile body according to the calculated diameter, namely

Thirdly, since the mass of piles with different cone angles is required to be equal, the excavation volume is calculated according to the calculated pile volume, that is,

V _{θ dig} = V _θ -V ₀

Finally, the specification of the excavated part is determined according to the calculated excavated volume, that is,

Among them, d ₀ is the diameter of the 0° pile (in cm), d _θ is the small circle diameter (in cm) of the conical pile with an angle of θ, h is the height of the pile body (in cm), and θ is The angle of the conical pile (unit is °), V _θ is the volume of the conical pile with the cone angle θ (the unit is cm ³ ), V ₀ is the volume of the 0° pile (the unit is cm ³ ), V _{θ is dug} as The volume (in cm ³ ) of the cone-shaped pile with the cone angle θ needs to be excavated, h _θ is the height (in cm) that needs to be excavated for the cone-shaped pile with the cone angle of θ, and d _θ is the cone angle of The diameter of the small circle (in cm) that needs to be excavated for the tapered pile of θ.

The shape of the excavated volume is a conical pile with the same angle. The size of the excavated conical pile needs to be calculated according to the excavated volume, and after excavation, the filling strength meets the requirements, and the lightweight polyurethane with thermal insulation and waterproof properties Foam 2-2. The calculated data are shown in Table 1-1, the designed 5° pile is shown in Figure 3, and the designed 9° pile is shown in Figure 4.

Table 1-1 Pile Specifications

Step 2: Embedding test piles; place the piles in the experimental device 1-2. In order to make the conical piles in the test device have a significant anti-freezing and pulling effect, the soil samples around the piles are made of frost-heave sensitive soil silty clay , the compaction degree is controlled at 93% to 97%, shaved and compacted in layers, and a moisture sensor 1-1 is embedded every 10cm in the process of filling the soil sample, and a moisture sensor is embedded every (5~6)cm Temperature sensor 1-6;

The third step: test the freezing and pulling force of the pile body in the one-way freezing process; ensure the one-way freezing of the experimental device and use the reaction force steel frame 1-3 and the load sensor 1-5 to measure the freezing and pulling force, as shown in Figure 1, to eliminate For the influence of normal frost heaving force, it is necessary to ensure that the temperature of the refrigerant circulation pipe 1-8 at the bottom of the pile is constant at 1°C, and the displacement sensors 1-4 are arranged on the reaction frame to monitor the displacement of the reaction frame. The periphery of the barrel is wrapped with thermal insulation cotton, and the whole set of test equipment is placed in a high and low temperature alternating freeze-thaw cycle box for cooling and freezing;

Step 4: Step 4: Repeat the content of the second and third steps to obtain the magnitude of the freezing and pulling force of the pile under different cone angles.

The utility model mainly solves the problem of the impact of other variables on the anti-freezing and pulling performance of the pile body except for the variable of the cone angle. The method adopted in this test to cut out the volumes of different sizes of conical piles can avoid the influence of pile side surface area and pile weight on the anti-freeze and pull-out performance of piles, and it can be more clearly observed that the cone angle, a single variable, has a great influence on the anti-freezing performance of piles. The effect of pulling performance.

The above description of the disclosed embodiments enables those skilled in the art to realize or use the invention of the utility model. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the invention . Therefore, the invention of the utility model shall not be limited to these embodiments shown herein, but shall conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims (3)

1. a kind of experimental rig of unitary variant assessment tapered pile anti_freeze uplift performance comprising test specimen tube (1-7) is tried for fixed The fixing bracket (1-2) of sample cylinder (1-7) and the pedestal of lower part pile body sample (2-1) in test specimen tube (1-7), the examination Freezing liquid circulation pipe (1-8) is equipped with below sample cylinder (1-7), it is characterised in that：Side is passed equipped with moisture on the test specimen tube inner wall Sensor (1-1), the other side are equipped with temperature sensor (1-6)；The top of pile body sample (2-1) is equipped with load transducer (1-5), institute State fixing bracket top be equipped with crossbeam, the crossbeam include the A-frame being fixed on fixing bracket and be set to load transducer The trapezoidal stress of (1-5) between A-frame disperses cushion block, is equipped with and is fixed on loading device above the A-frame Displacement sensor (1-4) for monitoring beam deformation.

2. the experimental rig of unitary variant assessment tapered pile anti_freeze uplift performance according to claim 1, it is characterised in that：Institute It is 25~35cm to state pile body sample (2-1) highly, and axis of small circle is 2~8cm, and cone angle is 0~11 °；It is equipped in pile body sample Light polyurethane foam (2-2).

3. the experimental rig of unitary variant assessment tapered pile anti_freeze uplift performance according to claim 1, it is characterised in that：Stake It is 93%~97% that the periphery body sample (2-1) soil sample, which uses heave susceptibility soil silty clay, compaction Control, and shaving is simultaneously layered Hit reality；Soil sample is filled in the process every the embedding moisture transducer (1-1) of 10cm, every the embedding temperature sensing of 5~6cm Device (1-6).