CN109035998B

CN109035998B - Demonstration device for effective stress variation effect

Info

Publication number: CN109035998B
Application number: CN201811228234.6A
Authority: CN
Inventors: 江建洪; 冯建光
Original assignee: Suzhou University
Current assignee: Suzhou University
Priority date: 2018-10-22
Filing date: 2018-10-22
Publication date: 2021-02-19
Anticipated expiration: 2038-10-22
Also published as: CN109035998A

Abstract

The invention discloses a demonstration device for an effective stress variation effect, which comprises an experiment box, a filter screen, sandy soil, an eccentric pile, a shallow foundation, a tunnel and a conduit, wherein the filter screen is positioned at a certain position in the experiment box and divides the experiment box into a first compartment at the upper part and a second compartment at the lower part, the sandy soil is filled in the first compartment, the eccentric pile and the tunnel are buried in the sandy soil at a proper depth, the shallow foundation is arranged on the shallow layer of the sandy soil, one end of the conduit extends into the second compartment, and the other end of the conduit extends out of the top of the sandy soil. The effective stress in the sandy soil is changed by changing the height of the water level so as to simulate the influence of the change of the effective stress on the eccentric pile, the shallow foundation and the tunnel. The invention can visually observe the influence of the effective stress change on each structural model, deepens the understanding of the effective stress principle and can become an effective teaching tool.

Description

Demonstration device for effective stress variation effect

Technical Field

The invention relates to a demonstration device for an effective stress change effect, and belongs to the technical field of soil mechanics tests and geotechnical engineering.

Background

The effective stress principle is an important principle that the soil mechanics is different from other mechanics, and is a core base stone of the soil mechanics. The effective stress is a link or a bridge connecting the measurable load effect of the soil body strength, deformation and the like and the external load. But the effective stress itself can not be measured directly, and is relatively abstract, so that the deep teaching of the effective stress principle is relatively difficult. The effective stress principle can be demonstrated by the observable effective stress variation effect, but the device which can intuitively demonstrate the effective stress variation effect is also very lacking.

Disclosure of Invention

In order to solve the technical problems, the invention provides the demonstration device for the effective stress variation effect, which has the advantages of simple structure, simple and convenient operation and convenient observation.

The technical scheme adopted by the invention is as follows:

the utility model provides a presentation device of effective stress variation effect, includes experimental box, filter screen, sand, eccentric stake, shallow foundation, tunnel, pipe, the filter screen is laid a certain high department in the experimental box separates into the first compartment on upper portion and the second compartment of lower part with it, pack sand in the first compartment, it needs to explain, the size of filter screen net is less than the average particle diameter of sand to prevent that sand from losing and getting into the second compartment, influence demonstration result, eccentric stake with the tunnel is buried suitable degree of depth in sand respectively underground, the shallow layer of sand is arranged in to the shallow foundation, still be provided with a trompil that supplies the pipe to pass through on the filter screen, the pipe extends into the second compartment through trompil one end, and the other end extends the sand top.

As an improvement of the technical scheme, in order to facilitate observation, the experiment box is transparent, and a transparent scale is vertically arranged on the inner wall of the experiment box from the bottom to the top of the experiment box at the position of the axle center of the tunnel embedded in the experiment box.

As a further improvement to the above technical solution, the position where the tunnel is buried is closely attached to the transparent scale, so that the position change of the tunnel can be observed more accurately in the experimental process.

As an improvement to the above solution, the second compartment is filled with gravel, in which case the screen may be placed directly above the gravel layer.

As an improvement to the technical scheme, a water outlet is arranged at a position, close to the bottom of the experiment box, of the second compartment, so that water in the experiment box can be conveniently discharged after the experiment is finished, and the water outlet is in a closed state in the experiment process.

As an improvement to the above technical solution, a tray for placing weights is provided at an end of the eccentric pile, and when the eccentric pile is vertically buried in sand, the eccentric moment of the eccentric pile can be adjusted by adding or reducing weights to the tray.

As an improvement to the technical scheme, the shallow foundation is internally provided with a space for accommodating the weight, and the weight of the weight can be changed according to actual needs so as to adjust the base pressure of the shallow foundation.

As an improvement to the technical scheme, the tunnel is of an annular structure with one closed end and the other openable end, and sand can be filled into the tunnel to adjust the quality of the tunnel according to the requirement, so that the average weight of the tunnel model is similar to the actual situation.

The technical scheme of the invention has the beneficial effects that: the invention visually and effectively shows the effective stress variation effect by showing the influence of the effective stress variation on the eccentric pile, the shallow foundation, the tunnel and the like, thereby enhancing the understanding of the effective stress principle and simultaneously deepening the understanding of the pile foundation, the shallow foundation and the underground tunnel engineering.

Drawings

FIG. 1 is a front view of an apparatus for demonstrating the effect of effective stress changes, according to one embodiment of the present invention;

FIG. 2 is a top view of the above embodiment;

fig. 3 is a cross-sectional view of the above embodiment taken along a-a in fig. 2.

Description of reference numerals: 1. the experiment box comprises 1-1 parts of a experiment box body, 1-2 parts of a transparent scale, 2 parts of a fixed lantern ring, 2 parts of a drain pipe, 2-1 parts of a glass pipe, 2-2 parts of a latex pipe, 2-3 parts of a water stop clamp, 3 parts of gravel, 4 parts of a filter screen, 5 parts of sandy soil, 6 parts of a tray, 6-1 parts of a weight, 7 parts of an eccentric pile, 8 parts of a shallow foundation, 9 parts of a tunnel, 10 parts of a guide pipe.

Detailed Description

The following detailed description of embodiments of the present invention is provided in connection with the accompanying drawings and examples. The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.

Referring to fig. 1, which is a front view of a demonstration apparatus for effective stress variation effect according to an embodiment of the present invention, in combination with a sectional view in a front view direction shown in fig. 3, in this embodiment, the dimensions of the experimental box 1 are selected to be 50cm long, 30cm wide and 40cm high, the experimental box 1 is made of transparent organic glass and is reinforced by a hoop, and those skilled in the art can select experimental boxes of other dimensions and materials according to actual needs; before the demonstration experiment is carried out, a transparent scale 1-1 is vertically stuck from the bottom to the right side of the front vertical surface of the experimental box 1, and the transparent scale arranged at the position is preferable so as to observe the change in the experimental process more accurately; the sieve 4 is laid in parallel at a position lower than the inside of the experimental box 1, in the preferred embodiment shown in fig. 2, the sieve 4 is located at a position 5 cm away from the bottom surface of the experimental box 1, the sieve 4 divides the experimental box 1 into an upper first compartment and a lower second compartment, the first compartment is filled with sand 5, the sieve 4 can be fixed in the experimental box 1 by any means known to those skilled in the art, for example, by pasting, in a more preferred embodiment, a layer of gravel 3 can be laid in the first compartment, the gravel is not too large in particle size, the height of the gravel 3 is preferably 5 cm, then the sieve 4 is placed on the gravel 3, and finally the upper second compartment of the sieve 4 is filled with sand 5 in layers; in the process of filling the sandy soil 5, one side of a tunnel 9 is tightly attached to a transparent scale 1-1 and is perpendicular to the front vertical surface of the experiment box 1, the sandy soil 5 is continuously filled, and the layering and simple compaction are carried out, wherein the tunnel 9 can adopt a transparent annular glass tube with one openable end, and the inside of the transparent annular glass tube can be filled with sandy soil according to the requirement to adjust the quality of the transparent annular glass tube, so that the average weight of the tunnel model is similar to the actual condition; vertically inserting an eccentric pile 7 into sandy soil 5, repairing the sandy soil 5 disturbed at the periphery of the eccentric pile 7, arranging a tray 6 at the end part of the eccentric pile 7, and changing the eccentric moment of the eccentric pile by adjusting the mass of a weight in the tray 6; burying a shallow foundation 8 at a shallow layer on the top of the sandy soil 5, wherein in a preferred embodiment, a space for accommodating weights is arranged inside the shallow foundation 8, and the base pressure of the shallow foundation 8 is adjusted by changing the mass of the weights in the internal space of the shallow foundation 8; arranging a conduit 10, correspondingly arranging an opening for the conduit 10 to pass through on the filter screen 4, extending the conduit 10 into the second compartment through one end of the opening, extending the other end of the opening out of the top of the sandy soil 5, injecting water into the experiment box 1 through an external water source, fixing the conduit 10 on the rear vertical surface of the experiment box 1 through a fixing lantern ring 1-2 in the preferred embodiment, arranging a funnel at one end of the conduit extending out of the top of the sandy soil 5 in the further preferred embodiment, injecting water into the experiment box 1 through the funnel, measuring the rise of the water level by a transparent scale 1-1, and optionally, directly replacing the combination of the conduit and the funnel by a long-neck funnel, wherein the combination can be selected by a person skilled in the art according to actual needs; in a preferred embodiment, a water outlet is arranged in the second compartment near the bottom of the experimental box 1, the water outlet is closed during the experiment, in one embodiment, a plug is used for closing the water outlet during the experiment, in another embodiment, the water outlet is glued or mechanically connected with one end of a glass tube 2-1, the other end of the glass tube 2-1 is sleeved with a latex tube 2-2, a water stopping clip 2-3 is attached to the latex tube, and the water outlet is closed by the water stopping clip 2-3 during the experiment.

When the demonstration experiment is carried out, water is slowly injected into the experiment box 1 through the guide pipe 10, the water starts to permeate into the sandy soil in the first compartment after the second compartment is filled with the water, and the displacement changes of the eccentric pile 7, the shallow foundation 8 and the tunnel 9 and the deformation or damage of the soil around the eccentric pile, the shallow foundation 8 and the tunnel 9 are observed. Learn by the effective stress principle, the water level rises and will arouse the reduction of soil framework effective stress under the water level, and then arouse the reduction of eccentric stake 7 and shallow foundation 8 bearing capacity, the phenomenon that probably observes includes that originally balanced eccentric stake 7 inclines to tray one side, and shallow foundation 8 at sandy soil 5 top sinks, and tunnel 9 upwards displacement, the displacement of tunnel 9 can refer to the reading of scale 1-1 and confirm. The obvious degree of the phenomenon can be respectively improved by adjusting the weight mass corresponding to the eccentric pile 7, the internal weight mass corresponding to the shallow foundation 8 and the sand mass inside the tunnel 9.

Although the present invention has been described in terms of the above embodiments, it is to be understood that each of the above embodiments is not necessarily independent, and can be implemented independently or combined as appropriate by one of ordinary skill in the art to form other embodiments that can be understood and implemented by one of ordinary skill in the art.

Claims

1. A device for demonstrating the effect of effective stress changes, comprising: the experimental box is transparent, a transparent scale is vertically arranged on the inner wall of the experimental box at the position of an axis center where the tunnel is embedded from the bottom to the top of the experimental box, and a water outlet is arranged at a position, close to the bottom of the experimental box, of the second compartment; the second compartment is filled with gravel;

and a tray for placing weights is arranged at the end part of the eccentric pile.

2. A device for demonstrating the effect of changes in effective stress according to claim 1, wherein: one side of the tunnel is tightly attached to the transparent scale.

3. A device for demonstrating the effect of changes in effective stress according to claim 1, wherein: the shallow foundation is internally provided with a space for accommodating weights.

4. A device for demonstrating the effect of changes in effective stress according to claim 1, wherein: the tunnel is of an annular structure with one closed end and the other openable end.

5. A method for demonstrating the effect of effective stress change by using the device for demonstrating the effect of effective stress change according to any one of claims 1 to 4, wherein: and slowly injecting water into the experiment box through the guide pipe, and observing the displacement change of the eccentric pile, the shallow foundation and the tunnel and the deformation or damage of the peripheral soil body when the water starts to permeate into the sand soil in the first compartment after the second compartment is filled with the water.