CN208183816U - A kind of default section support pile experimental rig for simulating different bending strengths - Google Patents

Abstract

The utility model discloses a preset cross-section support pile test device for simulating different bending strengths, which is used for simulating the continuous damage process of foundation pit support piles, including prefabricated broken piles, gaskets, nuts, nylon bolts with eyes, Hinge fasteners, hinges and steel wire ropes, the middle part of the prefabricated broken pile is divided into the upper half pile and the lower half pile through the preset pile section, and the upper half pile and the lower half pile located inside the foundation pit are fastened by the hinge The eyelet nylon bolts are respectively installed on the upper half pile and the lower half pile outside the foundation pit, and the steel wire rope passes through the bolt eye of the eye nylon bolt and passes through the washer and nut fixed. The invention of the utility model can work normally as a common support pile in the excavation stage of the foundation pit, and can simulate the process of continuous destruction of the foundation pit after the preset breakable support pile breaks.

Description

A test device for simulating different flexural strengths with preset cross-section support piles

technical field

The utility model relates to a test device in geotechnical engineering, in particular, it is a device for simulating the continuous collapse of the foundation pit caused by the damage of several supporting piles in the foundation pit, through which the transmission of the continuous damage of the foundation pit can be obtained mechanism.

Background technique

In recent years, a large number of major foundation pit collapse accidents have occurred at home and abroad, such as Singapore, Hangzhou, Cologne and other places, causing very serious losses. According to these accidents, the instability and failure of foundation pits is a very complicated process, especially in the case of deep and large foundation pits with irregular plane shapes or complex support structures, the damage may be caused by a certain local failure It may also be caused by the failure of local support structures or local soil instability, and then cause the surrounding support structures to collapse in a large scale, that is, the collapse process of deep foundation pits is A continuous destruction process.

According to the records of the destruction process of the Nicoll Highway subway foundation pit accident in Singapore, it can be found that the collapse of the foundation pit with a length of nearly 100 meters started from the weakest position in the local area (that is, the position where the 66kV cable passes through and there is a gap in the ground connection wall). On the day of the incident, the purlins and supports of the ninth brace (S335) at the gap in the ground connection wall were first disengaged, which caused the ground connection wall to collapse. Two minutes after the damage stopped, the collapse began to develop along the length of the foundation pit. Until it collapses to 100m away. After a large number of foundation pit accidents, the investigation and summary of many accidents still ignore the continuous failure mechanism of the accidents.

In the field of structural engineering, research on the progressive collapse of multi-tall buildings, long-span structures, and bridges under unexpected conditions such as explosions, earthquakes, fires, and impacts has been relatively mature, and the research methods are also very rich, including theoretical derivation, models, etc. At the same time, many countries and regions have formulated relevant specifications and guidance documents for the progressive collapse resistance design of superstructures. Compared with the remarkable progress in the study of progressive failure in structural engineering, the research on progressive failure in the field of geotechnical engineering is still rare and has not attracted due attention.

The current stable failure modes of foundation pits (overall stability failure, overturning failure, pit bottom heave failure and kicking failure, etc.) obviously cannot reflect the characteristics and mechanism of continuous failure of deep foundation pits, and at the same time cannot provide sufficient information for the study of its control methods. Therefore, it is extremely necessary to conduct an in-depth study on the generation and evolution mechanism of such a major underground engineering disaster as the continuous failure of deep foundation pits. And the mechanism of natural termination, and the establishment of quantitative evaluation index and evaluation method to evaluate the possibility of progressive collapse of foundation pit, can put forward the theory and design method of preventing progressive collapse of foundation pit support structure.

Since the continuous failure of deep foundation pit is a problem of large deformation, nonlinearity and multi-field coupling, most of the existing methods such as limit equilibrium method, limit analysis method, conventional elastoplastic finite element method and strength reduction method can only involve The critical state of pits that are about to be destroyed, as for the development and evolution after the destruction begins, these traditional methods are difficult to simulate and describe. Therefore, in order to study the continuous failure of deep foundation pits, reasonable large deformation calculation methods and model tests and other continuous failure research methods are urgently needed to be explored.

At present, the process of partial collapse of foundation pit has been simulated through large-scale physical model tests, numerical simulation research, and setting breakable support piles. It is found that local collapse of foundation pits will cause a certain multiple of adjacent support piles to increase the bending moment. However, the rectangular PVC piles used in previous tests were too strong to simulate the process of progressive collapse of the foundation pit. Further exploration of test methods is needed to simulate the process of continuous collapse of the foundation pit.

Utility model content

The purpose of the utility model is to overcome the deficiencies in the prior art, to solve the problem of continuous failure of the foundation pit support piles along the length direction caused by the partial damage of the foundation pit support piles in the model test, and to provide a method for simulating different bending resistance. The strength preset section support pile test device, the utility model can work normally as a common support pile in the excavation stage of the foundation pit, and can simulate the continuous damage process of the foundation pit after the preset breakable support pile breaks.

The purpose of this utility model is achieved by the following technical solutions:

A prefabricated cross-section support pile test device for simulating different bending strengths, used to simulate the process of continuous failure of foundation pit support piles, including prefabricated broken piles, gaskets, nuts, nylon bolts with eyes, hinge fasteners, Hinge and steel wire rope, the middle part of the prefabricated broken pile is divided into the upper half pile and the lower half pile through the preset pile section, and the upper half pile and the lower half pile located inside the foundation pit are connected by the hinge fastener and the hinge The nylon bolts with eyes are respectively installed on the upper half pile and the lower half pile outside the foundation pit, and the steel wire rope passes through the bolt eye of the nylon bolt with eyes and is fixed by the gasket and the nut.

Further, the prefabricated broken piles are divided into the compression side and the tension side according to the difference in stress on the inner side of the foundation pit and the outer side of the foundation pit.

Further, simultaneous failure tests of different numbers of support piles can be simulated by adjusting the number of test devices.

Further, the prefabricated broken pile is a rectangular structure made of any one of aluminum, iron, stainless steel or PVC.

Compared with the prior art, the beneficial effects brought by the technical solution of the utility model are:

1. By presetting the sectional surface and connecting the compression side of the two truncated piles with a hinge, while the tension side is connected with a thin steel wire rope, the damage of the adjacent support pile caused by the initial partial support pile failure of the row pile support structure is simulated. Destruction, realizing the simulation of continuous destruction.

2. By adjusting the tensile strength of the wire rope to simulate the ultimate tensile strength of the support pile, the strength of the support pile can be adjusted according to the actual working conditions and according to the experimental requirements, and the support pile can be caused by local failure under the horizontal soil arch effect continuous destruction.

3. Connect the pressure side of the prefabricated broken pile with a hinge. The hinge can not only bear the shear force at the preset section to prevent shear damage, but also can freely rotate when the section reaches the limit bending moment and damage occurs, simulating the pile breaking ;

4. The simulation of the failure of the support pile due to the loading and unloading under the control of the bending moment is realized.

5. The overall structure of the utility model device is simple, practical and reliable, easy to operate and easy to realize, and it is of great significance for the model test research of simulating foundation pit excavation and local failure of supporting piles causing continuous failure.

Description of drawings

Fig. 1 is a schematic diagram of the utility model and a schematic diagram of a partially enlarged cross-sectional structure thereof;

Figure 2-1 and Figure 2-2 are schematic diagrams of the front structure of the tension side and the pressure side of the device of the present invention respectively;

Fig. 3 is the schematic diagram of the foundation pit of the utility model during the test.

Each device in the figure is: 1, gasket, 2, nut, 3, nylon bolt with eye, 4, hinge fastener, 5, hinge, 6, steel wire rope, 7, upper half pile, 8, lower half pile

Detailed ways

Below in conjunction with accompanying drawing, the utility model is further described.

As shown in Figures 1 to 3, a test device for simulating different bending strengths of preset section support piles is used to simulate the process of continuous failure of foundation pit support piles, including prefabricated broken piles, gasket 1, and nut 2 , eyelet nylon bolt 3, hinge fastener 4, hinge 5 and steel wire rope 6, the middle part of the prefabricated broken pile is divided into the upper half pile 7 and the lower half pile 8 through the preset pile section, and the upper half pile 7 and the lower half pile located inside the foundation pit The lower half piles 8 are connected by hinge fasteners 4 and hinges 5, and eyelet nylon bolts 3 are respectively installed on the upper half pile 7 and the lower half pile 8 outside the foundation pit, and the steel wire rope 6 passes through the eyelet nylon bolts 3. bolt eye and fix it with washer 1 and nut 2.

The method of use of the utility model device in the test process is as follows:

1. Butt the upper and lower half piles together, connect the pressure side of the upper and lower half piles with hinges and hinge fasteners, use a steel wire rope of a certain strength to pass through the screw eyes of the nylon bolts with eyes, and tighten the nuts to form A complete concrete implementing device of the utility model.

2. Place a certain number of the utility model at a predetermined position to prepare a model test soil.

3. After debugging and erecting the test monitoring equipment, carry out the test and excavate normally. At this time, the device of the utility model and the rest of the support piles form a cantilever-type pile row support. After the normal excavation reaches the predetermined depth, the excavation is stopped, and each Item detection indicators are detected.

4. Control the failure of the preset initial failure piles, simulate the collapse of the partial support piles in the foundation pit, and cause some basic utility model devices to break until the continuous collapse stops.

In the specific implementation process, the utility model selects rectangular PVC piles according to a certain rigidity similarity ratio, presets the cross section of the supporting piles, and defines the prefabricated broken piles on the inner side and outer side of the foundation pit according to the force of the pile body, which are respectively the compression side and the tension side. side, in the normal excavation stage of the foundation pit test, the axial force between the upper and lower broken piles is transmitted by the wire rope on the tension side, and the axial force and shear force between the upper and lower broken piles are transmitted by the hinge on the compression side, and a certain amount of the utility model Placed near the preset local failure position, that is, together with the rest of the intact support piles, it constitutes a cantilever-type pile row support structure; The damage of the protection pile is simulated, which causes the increase of the force on the pile body of the utility model adjacent to the damage, the steel wire rope on the tension side is broken, the upper half of the pile of the utility model collapses into the foundation pit, and the foundation pit is caused by the destruction of the local support pile. The continuous collapse of the support piles until the collapse finally stops.

The above is the use method of the test device for simulating the local damage of the foundation pit. By pasting the strain gauge on the utility model, it can be used to measure the bending moment of the pile body; The joint use of supporting piles can successfully simulate the transmission and termination of the continuous failure of the foundation pit, and obtain the load transfer mechanism of the continuous failure of the foundation pit.

Compared with the existing test device, the utility model differs in that:

By presetting the section of the pile and connecting the tension sides of the two sections of pile, that is, the upper and lower sections of the pile, with a thin steel wire rope, the strength of the supporting pile can be adjusted according to the actual working conditions and according to the experimental requirements. The steel wire rope uses nuts on both sides of the pile section. Firmly anchored to the pile surface to avoid slipping when under tension. The compression side of the prefabricated broken pile is connected by a hinge. The hinge can not only bear the shear force at the preset pile section to prevent shear damage, but also can freely rotate when the section reaches the limit bending moment and damage occurs, simulating the pile breaking , which cannot be realized by existing model support piles. The support piles commonly used in existing foundation pit tests are often simulated by aluminum or rigid PVC rectangular pipes, but the complete PVC model piles have high strength and cannot withstand the load range in the continuous failure model test of pile row support foundation pits. Destruction occurs. However, the utility model can realize the destruction of adjacent support piles caused by initial local support pile failure, that is, realize continuous failure simulation, and can realize the continuous failure of support piles caused by local failure under the horizontal soil arch effect.

The device of the utility model is ingenious in design, simple but powerful in function, easy to operate, good in repeatability of the test process, and can meet the needs of various sandy soil foundation pit model tests.

Although the test process of the present utility model has been described above, the use function of the present utility model is not limited to the above-mentioned specific embodiments, and the above-mentioned specific embodiments are only illustrative and not restrictive. Under the enlightenment of the utility model, personnel can also use it for the model test of continuous failure of foundation pits of other supporting structures without departing from the purpose of the utility model and the scope protected by the claims, all of which belong to the utility model scope of protection.

Claims (4)

1. a kind of default section support pile experimental rig for simulating different bending strengths, is continuously destroyed for simulating foundation pit supporting pile Process, which is characterized in that including prefabricated broken pile, gasket, nut, band eye nylon bolt, hinge fastener, hinge and steel wire Rope, the prefabricated broken pile middle part are divided into the upper half stake and lower half stake by default stake section, the upper half on the inside of foundation pit It is connected by the hinge fastener with hinge between stake and lower half stake, the upper half stake and lower half on the outside of foundation pit The band eye nylon bolt is installed respectively, the bolt eye with eye nylon bolt described in the steel wire penetrating simultaneously passes through described in stake Gasket and nut are fixed.

2. a kind of default section support pile experimental rig for simulating different bending strengths, feature exist according to claim 1 In, it is different with the stress on the outside of foundation pit on the inside of foundation pit by prefabricated broken pile, it is respectively divided into compression-side and tension side.

3. a kind of default section support pile experimental rig for simulating different bending strengths, feature exist according to claim 1 In by adjusting failure test while the experimental rig quantity analog difference number support pile.

4. a kind of default section support pile experimental rig for simulating different bending strengths, feature exist according to claim 1 In the prefabricated broken pile is the rectangular configuration being made of aluminum, irony, stainless steel or PVC any material therein.