CN202989897U - Cross nose for measuring isotropic shearing strength of soil - Google Patents

Abstract

The utility model relates to a cross nose for measuring the isotropic shearing strength of soil, and aims to improve the measuring precision. The technical scheme is that the cross nose comprises a probe rod shaft, as well as two shearing plates mounted on the probe rod shaft. The cross nose is characterized in that the shearing plate is rhombus-shaped, wherein one of diagonal lines is superposed with the axis of the probe rod shaft; and a hard sleeve is coaxially sleeved outside the probe rod shaft, and the two are in rolling friction with each other. The cross nose is suitable for being used in the fields of in-situ testing technology of civil engineering, water resources and hydropower engineering and harbor navigation engineering.

Description

Measure the cross wrench of soil body isotropism shear strength

Technical field

The utility model relates to a kind of cross wrench of measuring soil body isotropism shear strength, mainly is applicable to civil engineering, Hydraulic and Hydro-Power Engineering, port navigation engineering in-situ testing technique field.

Background technology

At present the shear strength test of the soil body is divided into two kinds of laboratory test and in situ tests, in situ test is due to the advantage that has not disturbance of the soil body, be applicable to the not drained strength of the saturated cohesive soil of on-site measurement, its Instrument structure and easy to operate succinct is widely used in engineering construction.For the soil body, owing to affected by degree of consolidation difference and anisotropy mechanical characteristic, generally different with vertical direction shear strength value in the horizontal direction, the cross wrench that uses at present is rectangle, the damage of soil body face is the face of cylinder that comprises side and upper bottom surface, shear strength calculation formula is the approximate formula that supposition horizontal direction and vertical direction shear strength value equate, therefore computational methods are not strict, can produce larger error for some overconsolidated soil.The pivoting friction of feeler lever bar axle has also been offset the torsional moment of part in the soil body, has also brought impact for measuring accuracy.simultaneously because present four-bladed vane is limited to cylindrical side and upper bottom surface to the surface of shear of the soil body, soil body different angles plane of fracture shear strength value is different, for example bury class side slope is along near the soil shear strength the most dangerous slip surface face, namely the soil body plane of fracture angle corresponding with the sliding surface place is closely related, shear strength corresponding to different angles this moment should equate in isotropic medium, will show otherness in structural and anisotropic medium, how to record the shear strength value of the soil body different angles plane of fracture and be analyzed, it is also a focus of in-situ test.

Summary of the invention

The technical problems to be solved in the utility model is: for the deficiency of above-mentioned wrench form and computational methods, provide a kind of cross wrench of measuring soil body isotropism shear strength, improve to reach the purpose of measuring precision.

The technical scheme that the utility model adopts is: the cross wrench of measuring soil body isotropism shear strength, comprise feeler lever bar axle, and be installed on two shear plates on this bar axle, it is characterized in that: described shear plate is rhombus, and wherein diagonal and the dead in line of bar axle; The outer coaxial sleeve of described bar axle has a hard sleeve, and is rolling friction between the two.

Two shear plates are measure-alike, and are 90 degree quadrature arrangement.

Two shear plates are square, and are installed on the bar axle with removably.

the beneficial effects of the utility model are: 1, adopt the rhombus shear plate, and wherein diagonal and the dead in line of bar axle, in the test, the shear failure soil sample is the coniform of two symmetries in up and down in position, shear strength is owing to equating at each edges of boards test value, therefore the intensity of surveying is isotropism shear strength value, evaded the impact of Soil Anisotropic mechanical characteristic, the actual conditions that truly reflected shear breakage, when having overcome existing four-bladed vane test achievement arrangement, the problem that during with shear failure, the supposition of the shear strength of soil body horizontal direction and vertical direction equates, thereby improved the mensuration precision.2, the outer coaxial sleeve of bar axle has a hard sleeve, hard sleeve is with feeler lever bar axle injection soil layer, guarantee not contact with the soil body in feeler lever bar axle embedded depth scope, can because offsetting the part torsional moment with soil body friction, not make test more accurate when feeler lever bar axle rotates like this.

Description of drawings

Fig. 1 is stereogram of the present utility model.

Fig. 2 is elevation of the present utility model.

Fig. 3 is soil body shear breakage schematic diagram of the present utility model.

The specific embodiment

As shown in Figure 1 and Figure 2, the present embodiment comprises feeler lever bar axle 1, is installed on two shear plates 2 on this bar axle in disassembled mode, and coaxial sleeve is located at the outer hard sleeve 3 of this bar axle; Two shear plates 2 are the identical square of size, and both are 90 degree quadrature arrangement, wherein diagonal and 1 dead in line of bar axle of each shear plate 2; Between described hard sleeve 3 and bar axle 1, for rolling friction, and sleeve pipe 3 bottoms maintain an equal level with shear plate 2 top height, completely cut off contacting and friction of bar axle 1 and the soil body, make to apply torsional moment in the mensuration process and born by bar axle 1 fully.

Adopt aforementioned cross wrench to carry out the soil in-situ determination of shear strength, can ignore the anisotropic impact of soil body horizontal direction and vertical direction, its soil body shear breakage is laterally zygomorphic two taper seats, conversion by torsional moment and shear plate 2 sizes, can obtain 45 ° of inclined-plane isotropy shear strengths of the soil body, also can expand to the cross wrench of different water caltrops, obtain break shear strength on angle of soil body difference, for bury undrained shear strength in-situ test provides a kind of new approach.Concrete testing procedure is as follows:

A, with described cross wrench be pressed into the test soil body in, then bar axle 1 is applied certain torsional moment, carry out the original position vane shear test.Due to hard sleeve 3 with feeler lever bar axle 1 injection soil layer, guarantee in feeler lever bar axle 1 embedded depth scope contactless with the soil body, can be because not offsetting the part torsional moment with the soil body friction when feeler lever bar axle 1 rotates like this, torsional moment is all born by feeler lever bar axle 1, makes test more accurate.

As shown in Figure 3, this routine soil body shear breakage is two symmetrical taper seats of up and down, the soil shear strength value all equates in all directions on the destruction face, be that institute's measured value is soil body isotropism shear strength, evaded the impact of Soil Anisotropic mechanical characteristic, guaranteed the uniqueness of the shear strength value of surveying, this value can be considered soil body isotropism shear strength parameter.

B, try to achieve soil body undrained shear strength value C by following formula _u:

$c_u=\frac{3\mathrm{<figure-callout\; id="2"\; label="M"\; filenames="HDA00002544171300011.png,HDA00002544171300021.png"\; state="\{\{state\}\}">M</figure-callout>}}{2\mathrm{\&pi;}{a}^3}$

In formula, the torsional moment that when M is damage of soil body, bar axle 1 is applied, a is the length of side of shear plate 2.

The derivation of above-mentioned formula is as follows:

The surface of shear area is two taper seat area: S=2 * π * r * a=2 π ra;

On the rhombic plate length of side, soil body isotropism shear strength τ on the inclined-plane _fDistribute with del, its application point apart from the effect distance of bar axle is

(be that the triangle section of making a concerted effort is 2/3 base, be positioned near 1/3 place, base); In formula, r be the outer angle point of shear plate apart from feeler lever bar wheelbase from;

Therefore torsional moment M can be expressed as:

Wherein

Therefore: $M=S\&times;{\mathrm{\&tau;}}_f\&times;\frac{2}{3}r=\frac{2\mathrm{\&pi;}{a}^3}{3}\&times;{\mathrm{\&tau;}}_f;$

According to following formula, on 45 ° of destruction faces, undrained shear strength is:

The above, only one of them embodiment of the present utility model, also can expand to adopt different water caltrop θ (on shear plate, with that diagonal institute of the bar axle dead in line number of degrees to angle) the cross wrench, the shear strength value on mensuration soil body different angles shear failure plane.No matter adopt which kind of water caltrop cross wrench, during due to each the survey, every shear strength value corresponding to shear plate all equates, therefore each institute measured value is the isotropism shear strength of the soil body under different shear failure planes.

After the utility model expansion, can by shear plate in front long a, shear plate outward angle point apart from feeler lever bar wheelbase from r, obtain shear strength general formula under different shear failure planes:

Torsional moment is: $M=S\&times;{\mathrm{\&tau;}}_f\&times;\frac{2}{3}r=2\mathrm{\&pi;ra}\&times;{\mathrm{\&tau;}}_f\&times;\frac{2}{3}r=\frac{4}{3}\mathrm{\&pi;}{r}^{2}a{\mathrm{\&tau;}}_f$

Shear strength is: $c_u={\mathrm{\&tau;}}_f=\frac{3M}{4\mathrm{\&pi;}{r}^{2}a}$

This moment water caltrop

Also available water caltrop θ represents that the shear strength general formula is:

$c_u={\mathrm{\&tau;}}_f=\frac{3M}{4\mathrm{\&pi;}{a}^3{\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="HDA00002544171300011.png,HDA00002544171300021.png"\; state="\{\{state\}\}">cos</figure-callout>}}^2\frac{\mathrm{\&theta;}}{2}}$

Be analyzed with the overall merit soil body different angles plane of fracture under the otherness of shear strength, can estimate the Soil Anisotropic strength characteristics, also can be the project planner useful reference be provided.

Claims (3)

1. cross wrench of measuring soil body isotropism shear strength, comprise feeler lever bar axle (1), and be installed on two shear plates (2) on this bar axle, it is characterized in that: described shear plate (2) is rhombus, and wherein diagonal and bar axle (1) dead in line; The outer coaxial sleeve of described bar axle (1) has a hard sleeve (3), and is rolling friction between the two.

2. the cross wrench of mensuration soil body isotropism shear strength according to claim 1, it is characterized in that: two shear plates (2) are measure-alike, and are 90 degree quadrature arrangement.

3. the cross wrench of mensuration soil body isotropism shear strength according to claim 1 and 2, it is characterized in that: two shear plates (2) are square, and are installed on bar axle (1) with removably.

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