CN102890034A - Site direct-shearing rheological testing method and device - Google Patents

Abstract

The invention discloses an on-site direct shear rheology test method and its device. The earth column is cut on site, rigid plates are buckled around and on the top of the earth column, and a horizontal lever is placed on the tripod of the rigid plate on the top of the earth column. Hang a reinforcement cage at one end to prepare for adding sand bags. Use a dial indicator to test the vertical displacement of the top surface of the earth column under the target vertical pressure. After the vertical displacement is stable, apply horizontal shear force. A vertical lever is erected next to the rigid plate, and the bottom end of the lever is placed on the tripod of the horizontal shear load side rigid plate, and a horizontal steel cable is tied to the upper end of the lever, and a steel cage is hung under the steel cable. Sand bags are added step by step to provide horizontal shear force, and the horizontal displacement under the action of each level of horizontal shear force is tested by a dial indicator until the horizontal displacement becomes stable, and sand bags are added until the earth column is destroyed. The on-site direct shear rheological test scheme provided by the invention is simple to operate, can utilize on-site resources, and has low test cost.

Description

A kind of on-site direct shear rheological test method and its device

technical field

The invention relates to an on-site direct shear rheological test method, which is especially suitable for strata such as hard soil (or soft rock) in tunnels, and also relates to a device for realizing the method.

Background technique

As the transition medium between soil and rock, hard soil and soft rock have complex geomechanical properties, and they often exhibit rheological properties. With the development of infrastructure, a large number of tunnels, bridge foundations and roadbeds built on hard soil or soft rock have emerged. In order to ensure the safe use of infrastructure, it is necessary to study the rheological properties of hard soil and soft rock to provide guidance for design and construction. The advantage of the field test is that the rock and soil are less disturbed, and it is easy to maintain its original microstructure. At present, domestic on-site rheological tests are mainly carried out on the basis of load plate tests, and the American ASTM specification advocates radially loaded rheological tests in caverns. However, as we all know, most rocks and soils are damaged by shearing, and the direct shear test can more intuitively reflect the failure mechanism of rocks and soils. The difficult problem of rheological tests is how to provide stable pressure.

Contents of the invention

The first technical problem to be solved by the present invention is to provide an on-site direct shear rheological test method that is simple to operate, adapts to local conditions, fully utilizes on-site resources, and saves test costs.

The second technical problem to be solved by the present invention is to provide a device for realizing the on-site direct shear rheological test method.

In order to solve the above-mentioned first technical problem, the on-site direct shear rheological test method provided by the present invention selects a position on the spot and cuts and makes an earth column whose size is greater than 50cm × 50cm and less than 150cm × 150cm. The height is half of the side length, at least install side rigid plates on the horizontal shear loading side of the earth column, and pre-embed pressure boxes on the horizontal shear loading side and top of the earth column respectively, and use thin Fill the top surface and fill the sides with sand, cover the top of the earth column with the top rigid plate welded with the top of the first tripod, put the horizontal lever on the tripod, and one end of the horizontal lever is used as a rotation point , put it under the first fixed bracket, hang the first reinforcement cage at the other end of the horizontal lever, add the first batch of sandbags step by step into the first reinforcement cage, and move all the sandbags through the horizontal lever The dead load of the first batch of sandbags is transmitted to the earth column, and the vertical displacement of the top surface of the earth column under the vertical pressure is recorded by the first dial indicator until the displacement is under the required pressure. The lower tends to be stable, and begins to apply horizontal shear force; set up a vertical lever next to the side rigid plate loaded by horizontal shear force, the rotation point of the vertical lever is at the second fixed bracket, and the lower end of the vertical lever Resist on the second tripod of the side rigid plate, tie a steel cable at the upper end of the vertical lever, the steel cable passes through a pulley, and hang a second reinforcement cage on the steel cable , adjust the steel cable so that the steel cable connected to the upper end of the vertical lever is in a horizontal direction, keep the vertical pressure, and add the second batch of sandbags step by step in the second steel cage Increase the horizontal shear force by applying horizontal shear force until the sample is sheared, and record the horizontal displacement under the horizontal shear force at all levels through the second dial indicator until it tends to be stable; add the horizontal shear force step by step until the earth column is sheared. The horizontal displacement under the action of horizontal shear force at each level is tested separately.

If the earth column is irregular due to the weak surface, buckle the side rigid plate around the earth column.

Pressure cells are pre-embedded on the side and top of the horizontal shear load of the earth column respectively.

In order to solve the above-mentioned second technical problem, the device for realizing the on-site direct shear rheological test method provided by the present invention includes a side rigid plate that can be installed around the earth column, including a first triangular plate that is covered on the top of the earth column and welded on the top. The top rigid plate of the frame, put the horizontal lever on the first tripod, one end of the horizontal lever is placed under the first fixed bracket as a rotation point, and the second horizontal lever is hung on the other end of the horizontal lever. A reinforcement cage, the first batch of sandbags are added in the first reinforcement cage, and the first dial indicator is used to record the vertical displacement of the top surface of the earth column under the action of vertical pressure; a vertical lever is set Next to the side rigid plate loaded by horizontal shear force, the rotation point of the vertical lever is at the second fixed bracket, and the lower end of the vertical lever is against the second tripod of the side rigid plate Above, a steel cable is fastened at the upper end of the vertical lever, the steel cable passes through a pulley, a second reinforcement cage is hung on the steel cable, and a second reinforcement cage is added in the second reinforcement cage. Two batches of sand bags are equipped with a second dial indicator to record the horizontal displacement under the horizontal shear force at all levels.

The side and top pre-embedded pressure cells are respectively loaded on the horizontal shear force of the earth column.

The on-site direct shear rheological test method and its device adopt the above technical scheme, avoiding the use of expensive stabilized pressure jacks, and use dead loads to provide stable vertical pressure and horizontal shear force for direct shear rheological tests according to the principle of levers and pulleys . The dead load of the sand bag is transmitted to the earth column through the horizontal lever to provide a stable vertical pressure. Due to the principle of leverage, the weight of the sand bag in the reinforcement cage (including the reinforcement cage) only needs to be 1/l ₁ ( Let the horizontal lever arm ratio be l ₁ ). Use a dial indicator to record the vertical displacement of the top surface of the column under the vertical pressure, until the displacement tends to be stable under the required pressure, and start to apply horizontal shear. The vertical lever maintains vertical pressure, and sand bags are added step by step in the steel cage to apply horizontal shear force to increase the horizontal shear force until the sample is sheared, and the horizontal displacement under the horizontal shear force at all levels is recorded by the dial indicator until it becomes stable. Similarly, the weight of the sandbag in the reinforcement cage (including the reinforcement cage) only needs to be 1/l ₂ of the horizontal shear force (assuming that the ratio of the vertical lever moment arm is l ₂ ). This test scheme is technically feasible, easy to operate, adapted to local conditions, fully utilizes on-site resources, and saves test costs.

In summary, the present invention is an on-site direct shear rheological test method that is simple to operate, adapts to local conditions, makes full use of on-site resources, and saves test costs. The device has simple structure and reliable performance.

Description of drawings

Figure 1 is a sectional view of the vertical pressure loading system.

Figure 2 is a sectional view of the horizontal shear loading system.

Figure 3 is a top view of the layout of the horizontal dial indicator.

In accompanying drawing 1-3: 1-earth column, 2-side rigid plate, 3-side pressure box, 4-top pressure box, 5-plastic film, 6-top rigid plate, 7-first tripod, 8- The first dial indicator, 9-horizontal lever, 10-the first fixed bracket, 11-the first steel cage, 12-the first batch of sand bags, 13-vertical lever, 14-the second fixed bracket, 15-the second Tripod, 16-steel cable, 17-pulley, 18-second dial indicator, 19-second steel cage, 20-second batch of sand bags, 21-vertical pressure (provided by vertical pressure loading system)

Detailed ways

The specific implementation of the on-site direct shear rheological test device in the present invention will be described in detail below in conjunction with the accompanying drawings.

Referring to Fig. 1, Fig. 2 and Fig. 3, the size of earth column 1 is greater than 50cm * 50cm, less than 150cm * 150cm, and the height of earth column 1 is half of the side length, and side rigid plate 2 is housed around earth column 1, Cover the top of the earth column 1 with the top rigid plate 6 welded with the first tripod 7, and pre-embed the side pressure box 3 on the side of the horizontal shear load for testing the horizontal compressive stress, and pre-embed the top of the earth column 1 A top pressure box 4 is in preparation for testing the vertical pressure, the horizontal lever 9 is placed on the first tripod 7, one end of the horizontal lever 9 is placed under the first fixed bracket 10 as a rotation point, and the other end of the horizontal lever 9 is hung There is a first reinforcement cage 11, and the first batch of sand bags 12 are added in the first reinforcement cage 11, and the first dial indicator 8 is used to record the vertical displacement of the top surface of the earth column 1 under the action of vertical pressure; a vertical lever 13 is located next to the side rigid plate 2 loaded by horizontal shear force, the rotation point of the vertical lever 13 is at the second fixed bracket 14, and the lower end of the vertical lever 13 is against the second tripod 15 of the side rigid plate 2. A steel cable 16 is bolted to the upper end of the lever 13, and the steel cable 16 passes through a pulley 17. On the steel cable 16, a second reinforcement cage 19 is hung, and a second batch of sand bags 20 are added in the second reinforcement cage 19. A second batch of sandbags 20 is provided. The 200 meter 18 records the horizontal displacement under the horizontal shear force at all levels.

Referring to Fig. 1, Fig. 2 and Fig. 3, the use process of the present invention is as follows:

(a) cutting an earth column 1 whose size is greater than 50cm×50cm and less than 150cm×150cm on the stratum, the height of the earth column 1 is half of the side length of the earth column 1. If the earth column 1 is prepared for a long time, cover the earth column 1 with plastic paper during the interval to prevent moisture from volatilizing in the earth column 1 and cause the earth column 1 to crack.

(b) Erect the side rigid plates 2 on the four sides around the earth column 1 (if the earth column 1 is intact and there is no damage, the three non-horizontal shear loading surfaces do not need to erect the side rigid plates 2). Utilize the side rigid plate 2 to hoop the earth column 1, and pre-embed the side pressure box 3 on the horizontal shear loading side to prepare for testing the horizontal compressive stress (converted to horizontal shear stress according to the bearing area), and fill the earth square with fine sand The void between each side wall of the column 1 and the side rigid plate 2.

(c) A top pressure cell 4 is pre-buried on the top of the earth column 1 to prepare for testing the vertical pressure, and the top surface of the earth column 1 is filled with fine sand. Due to the long duration of the rheological test, in order to prevent the earth column 1 from cracking due to moisture volatilization, the earth column 1 is sealed with a plastic film (5, which is not convenient to be marked in the attached drawing), and then the top rigid board 6 and the top rigid board are laid. The size of 6 is slightly smaller than the size of earth column 1, so as to ensure that the top rigid plate 6 can enter the shear box surrounded by the side rigid plates 2. A first tripod 7 is welded on the top rigid plate 6 to provide a vertical pressure loading point.

(d) Set up a first dial indicator 8 at two relative positions of the top rigid plate 6 of the earth column 1 to prepare for testing the vertical displacement.

(e) Horizontal lever 9 is placed on the first tripod 7, one end of horizontal lever 9 rests under the first fixed support 10, as the rotation point of horizontal lever 9, hangs a first reinforcement cage 11 at the other end in order to prepare Put the first batch of sandbags 12 to load (in the excavation tunnel by step method, you can use the step height difference to hang the first steel cage 11, otherwise you need to dig a pit room). Through the first dial indicator 8, test the vertical displacement of the top surface of the earth column 1 under the two-stage load increment of the horizontal lever 9 and the first reinforcement cage 11, until the displacement tends to be stable.

(f) set up the vertical lever 13, its rotation point is at the second fixed bracket 14, and the lower end of the vertical lever 13 is against the second tripod 15 of the horizontal shear force loaded rigid plate, that is, the side rigid plate 2, on the vertical Bolt a horizontal wire rope 16 to lever 13 upper ends, by pulley 17, wire rope 16 direction becomes vertical.

(g) Two second dial gauges 18 are respectively installed on both sides of the side rigid plate 2 in the horizontal loading direction, in order to measure the horizontal displacement.

(h) Add the first batch of sand bags 12 step by step in the first reinforcement cage 11 of the vertical pressure loading system. According to the principle of leverage, the weight of the first batch of sand bags 12 is 1/l of the vertical load required by the earth column 1 ₁ . Under the action of each level of vertical load, the vertical displacement is recorded through the first dial gauge 8 until it tends to be stable. A horizontal shear load is applied until the target vertical pressure is reached.

(i) Hang a second reinforcement cage 19 on the steel cables of the horizontal shear loading system, test the horizontal displacement of the earth column 1 under the self-weight action of the second reinforcement cage 19, and record until the horizontal displacement tends to be stable.

(j) Add the second batch of sand bags 20 step by step in the second reinforcement cage 19 of the horizontal shear loading system. According to the principle of leverage, the weight of the second batch of sand bags 20 is 1/l of the required horizontal shear force of the earth column 1 _2. Record the horizontal displacement under each level of load until the horizontal displacement tends to be stable. Add a second batch of sandbags 20 until the earth column 1 is sheared.

(k) Unloading, remove the loading system, and the test is completed.

In the present invention, the vertical displacement is the average value of the displacements measured by the two first dial indicators 8 on the top of the earth column 1, and the horizontal displacement is the average value of the displacements measured by the four second dial indicators 18 on the side of the earth column 1. Although the vertical pressure and horizontal shear force can be directly calculated using the principle of leverage, the side pressure box 3 and the top pressure box 4 are buried in the earth column 1, which can help to check whether there is a problem with the force transmission device of the lower loading system.

Claims (5)

1. on-the-spot staight scissors rheological test method, it is characterized in that: select at the scene a position, be cut into size greater than 50cm * 50cm, earthwork post (1) less than 150cm * 150cm, the height of described cubic metre of earth of post (1) is half of the length of side, at least load onto side rigid plate (2) in the horizontal shear loading side of described cubic metre of earth of post (1), and with fine sand fill and lead up end face and the filling side, be welded with the top rigid plate (6) of the first tripod (7) at the top cover upper top of described cubic metre of earth of post (1), horizontal lever (9) is rested on the tripod (7), one end of described horizontal lever (9) is as the point of rotation, be shelved under the first fixed support (10), hang the first steel reinforcement cage (11) at described horizontal lever (9) other end, in described the first steel reinforcement cage (11), add step by step first sand pocket (12), by described horizontal lever (9) dead the carrying of described first sand pocket (12) reached on the described cubic metre of earth of post (1), adopt the vertical displacement of the end face of the lower described cubic metre of earth of post (1) of the first dial gauge (8) record vertical pressure (21) effect, until displacement tends towards stability, begin to apply horizontal shear under required pressure-acting; A vertical vertical lever (13) is other in the described side rigid plate (2) that horizontal shear loads, the point of rotation of vertical lever (13) is located at the second fixed support (14), described vertical lever (13) lower end is against on second tripod (15) of described side rigid plate (2), at described vertical lever (13) upper end bolt one cable wire (16), described cable wire (16) passes a pulley (17), at described cable wire (16) the second steel reinforcement cage (19) of having hung oneself, adjust described cable wire (16), make the described cable wire (16) that links to each other with described vertical lever (13) upper end in horizontal direction, keep vertical pressure (21), in described the second steel reinforcement cage (19), add step by step second batch sand pocket (20) and increase horizontal shear until cut off sample to apply horizontal shear, by horizontal shift under the second dial gauge (18) record horizontal shears at different levels, until tend towards stability; Add step by step horizontal shear, until a cubic metre of earth post (1) cut off, by the horizontal shift under every grade of horizontal shear effect of dial gauge (18) test.

2. on-the-spot staight scissors rheological test method according to claim 1 is characterized in that: if described cubic metre of earth of post (1) then buckled described side rigid plate (2) because plane of weakness exists irregularly around described cubic metre of earth of post (1).

3. on-the-spot staight scissors rheological test method according to claim 1 and 2 is characterized in that: the horizontal shear at described cubic metre of earth of post (1) loads sidepiece and the pre-buried pressure cell in top (3,4) respectively.

4. realize the device of on-the-spot staight scissors rheological test method claimed in claim 1, it is characterized in that: comprise to be installed in a cubic metre of earth post (1) side rigid plate (2) all around, comprise and cover the top rigid plate (6) that is welded with the first tripod (7) at top and the top of earthwork post (1), horizontal lever (9) is rested on described the first tripod (7), one end of described horizontal lever (9) is shelved under the first fixed support (10) as the point of rotation, be hung with the first steel reinforcement cage (11) at described horizontal lever (9) other end, be added with first sand pocket (12) in described the first steel reinforcement cage (11), adopt the vertical displacement of the end face of described cubic metre of earth of post (1) under the effect of the first dial gauge (8) record vertical pressure; A vertical lever (13) is located at described side rigid plate (2) side that horizontal shear loads, the point of rotation of described vertical lever (13) is located at the second fixed support (14), described vertical lever (13) lower end is against on second tripod (15) of described side rigid plate (2), at described vertical lever (13) upper end bolt one cable wire (16), described cable wire (16) passes a pulley (17), at described cable wire (16) the second steel reinforcement cage (19) of having hung oneself, in described the second steel reinforcement cage (19), be added with second batch sand pocket (20), be provided with horizontal shift under the second dial gauge (18) record horizontal shears at different levels.

5. the device of the on-the-spot staight scissors rheological test of realization according to claim 4 method is characterized in that: the horizontal shear at described cubic metre of earth of post (1) is loaded with the pre-buried pressure cell of sidepiece and top (3,4) respectively.

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