CN209858359U - Shear strength testing arrangement - Google Patents
Shear strength testing arrangement Download PDFInfo
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- CN209858359U CN209858359U CN201920603123.2U CN201920603123U CN209858359U CN 209858359 U CN209858359 U CN 209858359U CN 201920603123 U CN201920603123 U CN 201920603123U CN 209858359 U CN209858359 U CN 209858359U
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Abstract
The utility model discloses a shear strength testing device and a shear strength and static sounding testing method thereof, which comprises a base, an injection system, a rotating system and a measuring system, wherein the injection system is arranged on the base, the rotating system is connected with the injection system, and the measuring system is connected with the rotating system; the measuring system comprises a probe rod and a conical head, one end of the probe rod is connected with the rotating system, and the other end of the probe rod is connected with the conical head; the conical head comprises a first conical head and a second conical head, and the first conical head and the second conical head can be connected to the probe rod in a replaceable manner; an annular pressure gauge is arranged on the circumference of the middle part of the first conical head; the fan-shaped conical plate of the second conical head is uniformly and vertically arranged on the circumference of the conical head body; the utility model can rapidly and conveniently obtain the data of the cohesive force c of the soil body and the internal friction angle phi of the soil body on site; the problems that the traditional cross plate shear test can only be used for measuring a soft soil layer and can only measure cohesive force and the application range is narrow are effectively solved; the device has simple structure, small volume and convenient carrying and use.
Description
Technical Field
The utility model relates to a geotechnical engineering technical field, in particular to shear strength testing arrangement.
Background
At present, the investment of highway side slope disease treatment engineering is huge, and the completion acceptance is only carried out according to the current industry standard for evaluating the effect of side slope treatment measures of the finished engineering. After the operation, the treatment and protection measures are not 'symptomatic medicine administration', whether the expected effect is achieved or not is achieved, and the research on the aspects of good or bad treatment effect and the like is few. Ecological slope protection is a new technology, mature design, construction and quantitative evaluation standard of slope protection effect are not available at home and abroad, along with the expansion of the application scale of ecological engineering slope protection, the problems are more and more complicated, and the problems are often difficult to solve only depending on some construction experience; for example: the problem of the dosage of the reinforcing material is solved, and if the dosage is too small, the slope surface is unstable; too large would result in waste and not economical.
In geotechnical engineering, the shear strength of a soil body, such as cohesive force and an internal friction angle of the soil body, is generally utilized to evaluate the bearing capacity or landslide resistance of the soil body; whileAt present, the method is suitable for in-situ penetration tests (such as cone dynamic penetration tests) or load tests, only can obtain normal stress intensity data of soil, and cannot obtain the shear strength of a soil body; the rectangular cross plate shear test is a simple and reliable in-situ test method for rapidly measuring the shear strength of a soil layer, is only suitable for clay layers in coastal saturated soft soil areas, can only measure the cohesive force c of the soil body, and cannot measure the internal friction angle of the soil bodyThe value and the application range are limited.
At present, no suitable geotechnical engineering exploration equipment is available in China, and the cohesive force c and the internal friction angle of the soil body can be quickly and conveniently obtained on siteIso-shear strength data; therefore, finding a simple and reliable shear strength device for in-situ measurement of soil mass is a problem to be solved urgently.
SUMMERY OF THE UTILITY MODEL
To the technical problem who exists among the prior art, the utility model aims to provide a shear strength testing arrangement can conveniently gain cohesion c and the soil body internal friction angle of the soil body on-the-spot fastThe data of (1).
In order to achieve the above purpose, the utility model adopts the following technical scheme:
a shear strength testing device comprises a base, an injection system, a rotating system and a measuring system, wherein the injection system is arranged on the base, the rotating system is connected with the injection system, and the measuring system is connected with the rotating system; the measuring system comprises a probe rod and a conical head, one end of the probe rod is connected with the rotating system, and the other end of the probe rod is connected with the conical head; the conical head comprises a first conical head and a second conical head, and the first conical head and the second conical head can be connected to the probe rod in a replaceable manner; the first conical head is of a conical structure, and an annular pressure gauge is arranged on the circumference of the middle part of the first conical head; the second conical head comprises a conical head body and four same fan-shaped conical plates, the conical head body is the same as the first conical head in shape and size, and the four same fan-shaped conical plates are uniformly and vertically arranged on the circumference of the conical head body.
Furthermore, the probe rod comprises an outer cylinder, a strain cylinder, a force guide rod, a strain gauge, a screw plug and a ball body; the outer cylinder is a cylinder structure with openings at two ends, and one end of the outer cylinder is fixedly connected with the rotating system; the strain cylinder is coaxially arranged in the outer cylinder, the strain cylinder is of a cylinder structure with one closed end and one open end, and the closed end of the strain cylinder is arranged close to the rotating system; the open end of the strain cylinder is fixedly connected with the inner wall of the outer cylinder; the force guide rod is coaxially arranged in the strain cylinder, one end of the force guide rod is connected with the closed end of the strain cylinder through a ball, and the other end of the force guide rod extends out of the outer cylinder; the screw plug is sleeved on the force guide rod and fixedly connected with the inner wall of the outer barrel; the force guide rod is provided with an annular boss, the annular boss is connected with the end face of the screw plug in an abutting mode, and the annular boss is arranged close to the strain cylinder; the strain gauge is arranged on the surface of the strain cylinder, and the extending end of the force guide rod is fixedly connected with the conical head.
Furthermore, the device also comprises a strain compensation sheet which is arranged on the wall of the strain cylinder; the strain gauge comprises two strain gauges which are symmetrically arranged, the strain compensation gauge comprises two strain compensation gauges which are symmetrically arranged, and the strain gauges are connected with the strain compensation gauges through four bridges.
Furthermore, the penetration system comprises a first motor, a first gear, a second gear, a transmission screw, a nut, an outer pipe and an inner pipe, wherein the first motor is arranged on the base, an output shaft of the first motor is connected with the first gear, and the second gear is meshed with the first gear; one end of the transmission screw is fixedly connected with the second gear, and the other end of the transmission screw is a free end; the nut is sleeved on the transmission screw rod, one end of the inner pipe is fixedly connected with the nut, and the other end of the inner pipe is connected with the rotating system; the outer pipe is sleeved outside the inner pipe, one end of the outer pipe is fixedly connected with the base, and the other end of the outer pipe is a free end; be provided with spacing boss on the inner wall of outer tube, spacing boss is parallel with the axis of outer tube, is provided with spacing recess on the outside circumference of nut, and spacing recess is connected with spacing boss cooperation.
Furthermore, the rotating system comprises a second motor, a third gear, a fourth gear, a rotating shaft and a drill chuck, the second motor is fixedly connected with the injection system, an output shaft of the second motor is connected with the third gear, the fourth gear is meshed with the third gear, one end of the rotating shaft is connected with the fourth gear, and the other end of the rotating shaft is fixedly connected with the drill chuck.
Further, the outer shell is of a cylindrical structure with openings at two ends, and the outer shell is sleeved on the outer sides of the injection system, the rotating system and the measuring system; one end of the outer shell is fixedly connected with the base, and the other end of the outer shell is a free end; the annular end plate is parallel and level with the free end of the outer shell and is fixedly connected with the free end of the outer shell, and the annular end plate is perpendicular to the outer shell.
Furthermore, an internal thread is arranged in a cone of the conical head, and the conical head is fixedly connected with the rotating system through a thread.
Furthermore, BF350 type strain gauges are adopted as the strain gauges.
Compared with the prior art, the beneficial effects of the utility model are that:
the utility model relates to a shear strength's testing arrangement, device simple structure, the volume is less, portable uses.
Furthermore, through set up a strain cylinder in the probe rod, be provided with the foil gage on the foil gage, realize the physical characteristic analysis to the detection area soil property through the pressure data to the foil gage acquisition, realized the function of static sounding, realized the effect that a device performance multiple function, filled the blank that slope surface soil body parameter can't the normal position test.
Furthermore, the end part of the outer shell is provided with the annular end plate, so that the annular end plate is tightly attached to the slope surface when the soil-block-type water-blocking device is used, and the cone head is ensured to vertically penetrate into a soil body.
Drawings
Fig. 1 is a schematic view of the overall structure of the testing device of the present invention;
FIG. 2 is a schematic diagram of a penetration system of the testing apparatus according to the present invention;
fig. 3 is a schematic structural diagram of an outer tube in the testing apparatus of the present invention;
fig. 4 is a schematic structural view of a nut in the testing device according to the present invention;
fig. 5 is a schematic structural diagram of a measurement system in the testing apparatus according to the present invention;
fig. 6 is a schematic structural diagram of a first cone head in the testing apparatus of the present invention;
fig. 7 is a schematic structural diagram of a second cone in the testing apparatus according to the present invention;
fig. 8 is a schematic structural view of a plug screw in the testing device according to the present invention;
fig. 9 is a schematic structural view of an annular end plate in the testing apparatus according to the present invention;
fig. 10 is a schematic side view of a cone head in the testing apparatus according to the present invention;
FIG. 11 is a graph of soil shear stress versus normal stress.
The measuring device comprises a base 1, an outer shell 2, a penetration system 3, a rotation system 4, a measuring system 5, an annular end plate 6, a first motor 31, a first gear 32, a second gear 33, a transmission screw 34, a nut 35, an outer tube 36, an inner tube 37, a first grip 38, a limiting groove 351 and a limiting boss 361; 41 a second motor, 42 a third gear, 43 a fourth gear, 44 a rotating shaft, 45 a drill chuck and 46 a second handle; the device comprises a 51 probe rod, a 52 conical head, a 511 outer cylinder, a 512 strain cylinder, a 513 force guide rod, a 514 strain gauge, a 515 strain compensation gauge, a 516 screw plug, a 517 sphere and a 5131 annular boss; 521 first cone, 522 second cone, 5211 ring gauge, 5221 cone body, 5222 fan-cone plate.
Detailed Description
The technical solutions of the embodiments of the present invention are explained and explained below with reference to the drawings of the embodiments of the present invention, but the embodiments described below are only preferred embodiments of the present invention, and not all embodiments. Based on the embodiments in the embodiment, other embodiments obtained by those skilled in the art without any creative work belong to the protection scope of the present invention.
In the following description, the terms "inside", "outside", "upper", "lower", and the like, which indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, are presented only for convenience in describing embodiments and simplifying operations, and do not indicate or imply that the indicated device or element must have a specific orientation, be constructed and operated in a specific range, and thus should not be construed as limiting the present invention.
Referring to the attached drawing 1, the utility model relates to a static sounding and shear strength testing device, which comprises a base 1, an outer shell 2, a penetration system 3, a rotation system 4 and a measuring system 5, wherein the base 1 is arranged at the upper end of the outer shell 2, and the outer shell 2 is of a cylindrical structure; the penetration system 3, the rotating system 4 and the measuring system 5 are all arranged in the outer shell 2, the penetration system 3 is arranged on the base 1, the rotating system 4 is connected with the penetration system 3, and the measuring system 5 is connected with the rotating system; the penetration system 3 is used for pushing the rotating system 4 and the measuring system 5 to move forwards slowly, the rotating system 4 is used for driving the measuring system 5 to rotate, and the measuring system 5 is used for testing the soil body in-situ static sounding and the shear strength.
Referring to fig. 1-4, the penetration system 3 comprises a first motor 31, a first gear 32, a second gear 33, a driving screw 34, a nut 35, an outer tube 36, an inner tube 37 and a first handle 38, wherein the first motor 31 is fixedly installed on the base 1, the first gear 32 is fixedly connected to an output shaft of the first motor 31, and the second gear 33 is engaged with the first gear 32; the first gear 32 is a driving gear, and the second gear 33 is a reduction gear; the second gear 33 is fixedly sleeved at the upper end of the transmission screw 34, and the lower end of the transmission screw 34 is a free end; the nut 35 is sleeved on the transmission screw 34, when the first motor 31 rotates, the transmission screw 34 is driven to rotate, the nut 35 moves oppositely along the transmission screw 34, and the nut 35 reciprocates up and down along the transmission screw 34; the outer tube 36 is of a cylindrical tube structure, the upper end of the outer tube 36 is fixedly connected with the base 1, the outer tube 36 is sleeved on the outer side of the inner tube 37, a limiting boss 361 is arranged inside the outer tube 36, a limiting groove 351 is formed in the outer cylinder of the nut 35, and the limiting boss 361 is connected with the limiting groove 351 in a matched mode so as to prevent the nut 35 from rotating relative to the outer tube 36 in the moving process; the inner tube 37 is disposed inside the outer tube 36, with a gap provided between the inner tube 37 and the outer tube 36; the upper end of the inner tube 37 is fixedly connected with the lower end face of the nut 35, and the lower end of the inner tube 37 is fixedly connected with the rotating system 4; the first handle 38 is disposed on one side of the base 1, and a start switch of the first motor 31 is disposed on the first handle 38 for controlling on/off of the first motor 31.
Referring to fig. 1, the rotating system 4 includes a second motor 41, a third gear 42, a fourth gear 43, a rotating shaft 44, a drill chuck 45 and a second handle 46; the second motor 41 is fixedly connected with the inner tube 37, a third gear 42 is sleeved on an output shaft of the second motor 41, and a fourth gear 43 is meshed with the third gear 42; the third gear 42 and the fourth gear 43 both adopt helical gears, the third gear 42 is a driving gear, and the fourth gear 43 is a driven gear; the upper end of the rotating shaft 44 is fixedly connected with the fourth gear 43, the lower end of the rotating shaft 45 is connected with a drill chuck 45, and the drill chuck 45 is used for being connected with the measuring system 5; the second handle 46 is disposed at the middle position of the outer side of the outer casing 2, and the second handle 46 is provided with an on-off switch of the second motor 41 for controlling the on-off of the second motor 41.
Referring to fig. 5-8, the measuring system 5 comprises a probe rod 51 and a conical head 52, wherein the upper end of the probe rod 51 is connected with the drill chuck 46, and the lower end of the conical head 52 is connected; the probe rod 51 comprises an outer cylinder 511, a strain cylinder 512, a force guide rod 513, a strain gauge 514, a strain compensation gauge 515, a screw plug 516 and a sphere 517; the outer cylinder 511 is a cylindrical structure with openings at two ends, internal threads are arranged at the upper end and the lower end of the outer cylinder 511, and the upper end of the outer cylinder 511 is in threaded connection with the drill chuck 46; the strain cylinder 512 is coaxially arranged in the inner cavity of the outer cylinder 511, the strain cylinder 512 is a cylinder with the upper end closed and the lower end opened, and the closed end of the strain cylinder 512 is arranged close to the rotating system; the outer side of the opening end of the strain cylinder 512 is provided with threads, the opening end of the strain cylinder 512 is connected with the inner wall of the lower end of the outer cylinder 511 through the threads, and the closed end of the strain cylinder 512 is arranged close to the lower end of the outer cylinder 511; the force guide rod 513 is coaxially arranged in the strain cylinder 512, and the upper end of the force guide rod 513 is connected with the closed end of the strain cylinder 512 through a ball 517.
The lower end of the force guide rod 513 extends out of the lower end of the outer cylinder 511, the screw plug 515 is sleeved outside the force guide rod 513, and a gap is formed between the screw plug 515 and the force guide rod 513; the outer circumference of the screw plug 515 is provided with a thread, the screw plug 515 is fixedly connected with the inner wall of the lower end of the outer cylinder 511 through the thread, the force guide rod 513 is further provided with an annular boss 5131, the end surface of the annular boss 5131 is abutted to the upper end surface of the screw plug 515, the annular boss of the force guide rod 513 is clamped above the screw plug 515, and the screw plug 515 can prevent the force guide rod 513 from falling off from the strain cylinder 512.
The lower end circumference of the force guide rod 513 is provided with an external thread, the conical head 52 is internally provided with an internal stepped hole, the lower half section of the internal stepped hole is provided with an internal thread, and the force guide rod 513 is fixedly connected with the conical head 52 through the thread; the upper half section of interior shoulder hole is provided with positioning groove, and the lower terminal surface of plug screw 515 is provided with the location boss, and the location boss of plug screw 515 and the positioning groove cooperation installation of conical head 52.
The conical head 52 comprises a first conical head 521 and a second conical head 522, and the first conical head 521 and the second conical head 522 can be connected to the probe 51 in a replaceable manner; the first conical head 521 is in a conical structure, and an annular pressure gauge 5211 is arranged on the circumference of the middle part of the first conical head 521; the second cone 522 includes a cone body 5221 and four identical fan-shaped conical plates 5222, the shape and size of the cone body 5211 are identical to those of the first cone 521, and the four identical fan-shaped conical plates 5222 are uniformly and vertically arranged on the circumference of the cone body 5211.
Further, the lower extreme of shell body 2 still is provided with ring end plate 6, ring end plate 6 and 2 lower extreme parallel and level of shell body and fixed connection, and ring plate 6 sets up with shell body 2 is perpendicular, during the use, hugs closely the setting with the slope surface of side slope, guarantees that the probe penetrates perpendicularly in the soil.
The utility model also provides a shear strength test method, specifically include following step:
step 1, installing a first conical head on a probe rod, starting a penetration system, closing a rotating system, pressing the first conical head into a soil layer with a preset depth through the penetration system, and measuring the normal stress sigma of the soil body with the depth by using an annular pressure gaugen；
Step 2, closing the penetration system, starting the rotating system, applying torque to the measuring system by using the rotating system under the state that the measuring system is not loaded with vertical load,determination of the maximum Torque T0，T0Measuring the inherent friction force generated between the system and the soil layer;
step 3, detaching the first cone head, installing a second cone head on the probe rod, pressing the second cone head into a preset soil layer at the same position or a position deviated from 5-10cm in the step 1, wherein the pressing depth of the second cone head is the same as that of the first cone head; then closing the penetration system and starting the rotation system, applying torque to the measurement system by using the rotation system, rotating the second conical head to shear and destroy the soil body to form a conical destruction surface, wherein the soil body resists the maximum torque T of the torqueN；
Step 4, obtaining the shearing torque T ═ T of the soil body sheared by the second cone according to the steps 2 and 3N-T0；
Step 5, repeating the test for multiple times on the same soil layer or side slope to obtain multiple groups of sigman、TNValue using a formulaDetermining the value of the array tau; in the formula, H is the height of a soil layer shearing cone; theta is an angle corresponding to the axis of the conical inclined surface; τ is shear stress;
step 6, utilizing coulomb formulaOr an empirical method is adopted to obtain the cohesive force c and the internal friction angle of the soil body
The calculation principle is as follows:
referring to fig. 10 and 11, the height of the soil layer shearing conical cone of the present invention is H, and considering the fan-shaped small area from the conical tip of the conical head to the position H, the angle of the conical tip of the conical head is θ, that is, the angle corresponding to the axis of the conical inclined plane of the conical head is θ; the distance from the conical tip of the conical head to the fan-shaped tiny area at the position h is l;
the mathematical expression that the distance from the conical tip of the conical head to the fan-shaped tiny area at h is l is as follows:
the small area of the cone tip shear plane of the cone is therefore:
let us say that the shear stress acting on a minute area is denoted as τ, the torque acting on a minute area is denoted as t,
therefore, the mathematical relationship between τ and t acting on a tiny area is:
and (3) carrying out integral calculation on the torque T in the small area, and solving the shearing torque T of the second cone head for shearing the soil body:
changing soil layer position, repeating the measurement according to the operation method steps to obtain different groups of sigmanAnd TNAccording to TNThe value and the calculation formula can calculate the array shearing stress tau;
referring to FIG. 11, the normal stress σ is calculated from the obtained array normal stress σnAnd shear stress τ, at σnThe section on the oblique line can be determined by plotting the horizontal axis and the vertical axis as τThe distance and the slope, the intercept is the cohesive force c of the soil body, and the slope is
It is also possible to use the molar-coulomb intensity formula:calculating the cohesive force c and the internal friction angle
The present invention will be described in further detail below.
The utility model relates to a shear strength testing device, which comprises a base 1, an outer shell 2, a penetration system 3, a rotation system 4, a measuring system 5 and an annular end plate 6;
the injection system 3 is an electric push rod, the injection system 3 comprises a first motor 31, the first motor 31 is connected with a first gear 32, the first gear 32 is connected with a second gear 33, the second gear 33 is connected with a transmission screw 34, the transmission screw 34 is connected with a nut 35, the first motor 31 is installed on the base 1, the base 1 is fixedly connected with the upper end of the outer shell 2, the nut 35 is fixedly connected with an inner tube 37, when the first motor 31 drives the transmission screw 34 to rotate, the nut 35 and the transmission screw 34 move relatively, and particularly, the nut 35 and the transmission screw 34 move back and forth between the upper position and the lower position of the transmission screw 34; for the nut 35, it is reciprocated between an initial position and an extreme position; for the whole penetration system 3, the relative movement between the inner tube 37 and the outer tube 36 is realized, and the rotation system 4 and the measurement system 5 are further pushed to move forwards slowly.
The limiting boss 361 arranged along the axial direction of the outer tube 36 in the outer tube 36 is matched and connected with the limiting groove 351 of the nut 35, so that the nut 35 is prevented from rotating in the process of moving up and down on the transmission screw 34.
The rotating system 4 mainly comprises a second motor 41, a third gear 42, a fourth gear 43, a rotating shaft 44 and a drill chuck 45; the output shaft of the second motor is connected with a third gear 42, the third gear 42 is a driving helical gear, the third gear 42 is in meshed connection with a fourth gear 43, the fourth gear 43 is a driven helical gear, the fourth gear 43 is fixed on a rotating shaft 44, and the end part of the lower end of the rotating shaft 44 is connected with a drill chuck 45.
The annular end plate 6 is arranged at the lower end of the outer shell 2, and when the conical head is used, the annular end plate 6 can be tightly attached to a slope surface, so that the conical head 52 can vertically penetrate through soil.
The first handle 38 is provided with a first motor starting switch which controls the penetration system 3 to enable the inner pipe 37 in the penetration system to extend up and down, so as to drive the conical head 52 to extend up and down; the first handle 46 is provided with a second motor start switch, and the second motor start switch controls the rotation system 4, so that the rotation system 4 rotates to drive the conical head 52 to rotate.
The measuring system 5 comprises a probe rod 51 and a conical head 52; the probe 51 comprises an outer cylinder 511, a strain cylinder 512 and a force guide rod 513; the outer cylinder 511 is a cylinder with openings at two ends, the upper end and the lower end of the inner cylinder wall of the outer cylinder 511 are both provided with internal threads, and the strain cylinder 513 is arranged in the inner cavity of the outer cylinder 511; the strain cylinder 512 is a cylinder with one end closed and the other end open, and the outer peripheral surface of the open end of the strain cylinder 512 is provided with an external thread matched with the internal thread of the inner cylinder wall of the outer cylinder 511; the wall of the strain cylinder 512 is provided with a strain gauge 514; the force guide rod 513 is a cylinder, an external thread is arranged on the outer peripheral surface of the lower end of the force guide rod 513, and the thread section of the lower end of the force guide rod 513 extends out of the outer cylinder 511 and the strain cylinder 127; the conical head 52 is provided with an inner stepped hole, and the lower half part of the inner stepped hole is an inner threaded hole; the conical head 52 is arranged below the outer cylinder 511, and the conical head 511 is fixed at the lower end of the force guide rod 513 in a way that an internal threaded hole of the conical head 511 is matched with a threaded section at the lower end of the force guide rod 513; the lower end of the outer cylinder 511 is provided with a screw plug 516, and the lower surface of the annular boss 5131 of the force guide rod 513 is abutted against the upper end surface of the screw plug 126.
The wall of the strain cylinder 512 is also provided with a strain compensation sheet 515; two strain gauges and two strain compensation gauges are arranged on the wall of the strain cylinder 512. The strain gauge 514 is attached to the surface of the strain cylinder 513, the strain gauge 514 is used for measuring the small change of the strain cylinder 512, and the resistance and the side friction resistance of the conical head 52 are obtained through calculation, so that the function of static sounding is realized.
The strain cylinder 512 is arranged in the outer cylinder 511 and is matched and connected with the outer cylinder 511 through threads, external threads at the lower end of the strain cylinder 512 are matched with internal threads at the lower part of the outer cylinder 511, and the open end of the strain cylinder 512 faces downwards; the upper half part of the force guide rod 513 goes deep into the inner cavity of the strain cylinder 512, part of the lower half part is positioned in the inner cavity of the outer cylinder, and part of the lower half part extends out of the outer cylinder; the part of the force guide rod 513 extending out of the outer cylinder is a threaded section of the force guide rod 513, and the threaded section of the force guide rod 513 is matched with the internal thread of the conical head 52, so that the conical head 52 and the force guide rod 513 can be fixed.
The screw plug 516 is screwed into the lower end of the outer cylinder 511, and the screw plug 516 is matched with the internal thread at the lowest end of the outer cylinder 511. The force guide rod 513 also passes through the screw plug 516, and the annular boss 5131 of the force guide rod 513 is just clamped on the upper end surface of the screw plug 516, so that the screw plug 516 can prevent the force guide rod 513 from falling out of the strain cylinder 512. The lower half of the plug screw 516 is inserted into the larger diameter hole of the upper half of the stepped hole of the conical head 52.
During testing, firstly, the first conical head 521 is installed at the lower end of the force guide rod 513, the first motor starting switch is started, the first probe 521 is slowly pressed into the soil body through the penetration system 3, and the pressing-in is stopped after the specified depth is reached.
When the first conical head 521 enters a soil body and receives the thrust of foundation soil, the thrust is transmitted to the force guide rod 513 through the first conical head 521, the force guide rod 513 is transmitted to the strain cylinder 512 through the sphere 517, so that the thrust of the foundation soil received by the first conical head 521 is changed into the tensile stress of the strain cylinder 512, the cylinder wall of the strain cylinder 512 generates micro strain under the action of the tensile stress of the strain cylinder 512, the micro strain is in the elastic strain range of the strain cylinder 512, the strain is linear strain, and the strain gauge 514 converts the micro strain into resistance transformation and transmits data to a computer; the computer analyzes and processes the signal and then converts the signal into soil pressure and frictional resistance data, and a worker can analyze the physical characteristics of the soil texture of the area through the pressure data.
Meanwhile, an annular pressure gauge 5211 is arranged in the middle of the first conical head, so that the average soil pressure acted on the first conical head 521 by the soil body, namely the normal stress of the soil body, can be obtained; specified depth below gradeThe normal stress sigma of the deep soil is recorded by the ring pressure gauge 5211n。
Then, the first motor starting switch is turned off, the second motor starting switch is turned on, the measuring system 5 applies torque to the probe rod 51 slowly by using the rotating system 4 under the state that the vertical load is not loaded, the probe rod 51 drives the first conical head 521 to rotate, and the maximum torque T is measured through the rotating speed of the second motor 410，T0Is the inherent friction force generated between the first conical head 521 and the soil layer;
secondly, the first conical head 521 is detached, the second conical head 522 is installed at the lower end of the guide rod 513, the second conical head 522 is pressed into the soil layer at the same position or a position deviated from 5-10cm in the previous step, the pressing-in is stopped when the soil layer pressing-in depth of the second conical head 522 is the same as the pressing-in depth of the first conical head, torque is applied to the second conical head 522 through the rotating system 4, the second conical head is rotated to shear and damage the soil body to form a conical damage surface, and the maximum torque T of the soil body resisting the torque is measured through the rotating speed of the second motor 41N；
Then, the shearing torque T of the soil body sheared by the fan-shaped conical plate probe is calculated to be TN-T0；
Secondly, repeating the steps, and repeating the test for multiple times on the same soil layer or side slope to obtain multiple groups of sigman、TNValue, using a formulaDetermining the value of the array tau; in the formula, H is the height of a soil layer shearing cone; theta is an angle corresponding to the axis of the conical inclined surface; τ is shear stress;
then, using coulomb formulaOr an empirical method is adopted to obtain the cohesive force c and the internal friction angle of the soil body
The middle cone head 52 and the probe rod 51 of the utility model are made of low carbon alloy steel material; the strain gauge 514 is a BF350 type strain gauge, and the base 1 is made of modified phenolic aldehyde; the utility model provides a probe rod adopts totally closed structure can realize temperature self compensation and creep self compensation simultaneously.
The strain gauge 514 and the strain compensation gauge 515 are designed as a four-bridge, the strain gauge 514 is used for measuring the small change of the strain cylinder 512, and the soil resistance and the side friction force on the conical head 52 are obtained through calculation, so that the function of static sounding is realized. The strain gauge 515 is used for parameter compensation, the strain gauge 514 is a strain sensor, and the strain gauge 515 is a parameter compensation gauge.
The utility model discloses a clumsy of traditional probe has been abandoned to miniaturized conical head, so can greatly improve work efficiency. By the utility model provides a whole weight of penetration test equipment that conical head constitutes is steerable about 10kg, far than current 2T-3T lightweight static sounding machine and artifical little screw drill light in weight, portable, swift, index quantization.
The utility model provides a shear strength test method, this method can the normal position survey soil layer shear strength fast portably, has effectively solved traditional cross plate shear test and can only be used for the measurement of weak soil layer, can only survey single value of cohesion c, problem that application range is narrow.
Meanwhile, in the test process, parameters such as side friction resistance and the like of the soil body can be measured, and the function of static sounding is realized. The utility model also provides a static sounding test method, specifically include following step:
step 1, installing a first conical head on a probe rod, starting a penetration system, closing a rotating system, pressing the first conical head into a soil layer with a preset depth through the penetration system, and obtaining soil body resistance and side friction force of the first conical head by using strain data of a strain gauge on a strain cylinder;
and 2, analyzing the soil resistance and the side friction force of the first conical head to obtain the physical and mechanical properties of the soil.
The utility model discloses realize a device performance multiple functions, this device is small, light in weight, and convenient to carry does benefit to and tests on the slope surface. The utility model discloses the volume is less, and convenient operation can obtain the shear strength parameter of the soil body and realize the function of static sounding simultaneously, has filled the blank of the unable normal position test of slope surface soil body parameter of side slope.
The static cone penetration test is an important in-situ test for geotechnical engineering exploration, and utilizes the quasi-static force of the test to press a cone probe into the soil through a series of probe rods at a constant penetration rate, and indirectly judges the physical and mechanical properties of the soil according to the measured resistance and side friction resistance of the soil body on the cone head. The static sounding can divide soil layers, evaluate the engineering characteristics of foundation soil, search and determine a pile foundation bearing layer, and pre-estimate the pile sinking possibility of a driven pile and the compactness of single-pile bearing capacity for testing artificial filling, the foundation reinforcement effect and the like.
However, the existing static sounding instrument has large volume and weight, and can only be used for testing in a relatively flat area, and for slope surfaces, the static sounding test cannot be carried out under the existing equipment condition.
The failure of most soil bodies is shear failure which basically obeys the Mohr-Coulomb, M-C criterion for short, for example, the shear failure is caused by that the self sliding force of a slope sliding body is larger than the maximum sliding resistance which can be exerted by a slope sliding surface when the slope unstably slides, and the maximum sliding resistance which can be exerted by the sliding surface can be obtained by the M-C criterion according to the actual sliding condition.
The M-C criterion comprises two shear strength parameters, namely cohesive force and internal friction angle, wherein the two shear strength parameters represent the shear capacity of the soil body and reflect the reliability of the shear failure of the soil body structure, so that the acquisition of the shear strength parameters is a basic condition for analyzing the shear failure resistance of the soil body and provides a basis for accurately preventing the shear failure of the soil body and predicting the shear failure range of the soil body.
In order to obtain M-C shear strength parameters of a soil body, an original soil sample is usually collected from an actual engineering point on site, the collected original soil sample is remolded indoors, a plurality of groups of standard soil samples capable of being subjected to direct shearing or triaxial shearing tests are prepared, the shear strength of the soil body in shear failure under different normal stress states is obtained through tests by changing the compression conditions of the soil samples, and then M-C strength curves are adopted for fitting test results in a normal stress and shear strength Cartesian coordinate system, so that the M-C strength parameters are obtained.
However, in the process of preparing the remolded standard soil sample, disturbance is generated on the original state of the soil sample, so that the stress state, the water content and the self structure of the soil body of the original soil sample and the remolded standard soil sample have certain differences, and the M-C shear strength parameter of the remolded standard soil sample obtained by an indoor test is difficult to truly reflect the shear strength characteristic of the original soil sample. Meanwhile, because the existing indoor test method needs to prepare a standard soil sample, the test operation process is complicated, and the operation proficiency of a preparation worker also has certain influence on the performance of the prepared soil sample. In addition, for the soil stability controlled by shearing damage, such as the anti-slip stability of a slope, the main factor influencing the analysis result is often the accuracy of the selection of the shear strength parameter, and if the shear strength parameter does not accord with the actual condition of the engineering, the calculated result may be exaggerated or conservatively estimated, thereby bringing adverse hidden danger to the engineering or causing the uneconomic optimization design of the engineering.
Claims (8)
1. A shear strength testing device is characterized by comprising a base (1), an injection system (3), a rotating system (4) and a measuring system (5), wherein the injection system (3) is arranged on the base (1), the rotating system (4) is connected with the injection system (3), and the measuring system (5) is connected with the rotating system (4); the measuring system (5) comprises a probe rod (51) and a conical head (52), one end of the probe rod (51) is connected with the rotating system (4), and the other end of the probe rod (51) is connected with the conical head (52); the conical head (52) comprises a first conical head (521) and a second conical head (522), and the first conical head (521) and the second conical head (522) are connected to the probe rod (51) in a replaceable way; the first conical head (521) is of a conical structure, and an annular pressure gauge (5211) is arranged on the circumference of the middle part of the first conical head (521); the second cone (522) comprises a cone body (5221) and four identical fan-shaped conical plates (5222), the shape and the size of the cone body (5221) are identical to those of the first cone (521), and the four identical fan-shaped conical plates (5222) are uniformly and vertically arranged on the circumference of the cone body (5221).
2. A shear strength testing device according to claim 1, wherein the probe (51) comprises an outer cylinder (511), a strain cylinder (512), a force guide rod (513), a strain gauge (514), a screw plug (516) and a sphere (517); the outer cylinder (511) is a cylinder structure with openings at two ends, and one end of the outer cylinder (511) is fixedly connected with the rotating system (4); the strain cylinder (512) is coaxially arranged in the outer cylinder (511), the strain cylinder (512) is of a cylinder structure with one closed end and one open end, and the closed end of the strain cylinder (512) is arranged close to the rotating system (4); the open end of the strain cylinder (512) is fixedly connected with the inner wall of the outer cylinder (511); the force guide rod (513) is coaxially arranged in the strain cylinder (512), one end of the force guide rod (513) is connected with the closed end of the strain cylinder (512) through a sphere (517), and the other end of the force guide rod (513) extends out of the outer cylinder (511); the screw plug (516) is sleeved on the force guide rod (513), and the screw plug (516) is fixedly connected with the inner wall of the outer cylinder (511); an annular boss (5131) is arranged on the force guide rod (513), the annular boss (5131) is abutted against the end face of the screw plug (516), and the annular boss (5131) is arranged close to the strain cylinder (512); the strain gauge (514) is arranged on the surface of the strain cylinder (512), and the extending end of the force guide rod (513) is fixedly connected with the conical head (52).
3. A shear strength testing device according to claim 2, further comprising strain compensation discs (515), wherein the strain compensation discs (515) are arranged on the wall of the strain cylinder (512); the strain gauge (514) comprises two strain gauges which are symmetrically arranged, the strain compensation gauge (515) comprises two strain compensation gauges which are symmetrically arranged, and the strain gauge (514) is connected with the strain compensation gauge (515) through a four-bridge connection.
4. A shear strength test device according to claim 1, wherein the penetration system (3) comprises a first motor (31), a first gear (32), a second gear (33), a transmission screw (34), a nut (35), an outer tube (36) and an inner tube (37), the first motor (31) is arranged on the base (1), an output shaft of the first motor (31) is connected with the first gear (32), and the second gear (33) is engaged with the first gear; one end of the transmission screw rod (34) is fixedly connected with the second gear (33), and the other end of the transmission screw rod (34) is a free end; the nut (35) is sleeved on the transmission screw rod (34), one end of the inner pipe (37) is fixedly connected with the nut (35), and the other end of the inner pipe (37) is connected with the rotating system (4); the outer pipe (36) is sleeved on the outer side of the inner pipe (37), one end of the outer pipe (36) is fixedly connected with the base (1), and the other end of the outer pipe (36) is a free end; be provided with spacing boss (361) on the inner wall of outer tube (36), spacing boss (361) are parallel with the axis of outer tube (36), are provided with spacing recess (351) on the outside circumference of nut (35), and spacing recess (351) are connected with spacing boss (361) cooperation.
5. A shear strength testing device according to claim 1, wherein the rotation system (4) comprises a second motor (41), a third gear (42), a fourth gear (43), a rotating shaft (44) and a drill chuck (45), the second motor (41) is fixedly connected with the penetration system (3), an output shaft of the second motor (41) is connected with the third gear (42), the fourth gear (43) is meshed with the third gear (42), one end of the rotating shaft (44) is connected with the fourth gear (43), and the other end of the rotating shaft (44) is fixedly connected with the drill chuck (45).
6. The shear strength testing device according to claim 1, wherein the outer shell (2) is a cylindrical structure with two open ends, and the annular end plate (6) is arranged on the outer side of the penetration system (3), the rotation system (4) and the measurement system (5); one end of the outer shell (2) is fixedly connected with the base (1), and the other end of the outer shell (2) is a free end; the annular end plate (6) is flush with and fixedly connected with the free end of the outer shell (2), and the annular end plate (6) is perpendicular to the outer shell (2).
7. A shear strength testing device according to claim 1, wherein the conical head (52) is internally threaded, and the conical head (52) is fixedly connected with the rotating system (4) by threads.
8. A shear strength testing device according to claim 2, wherein the strain gauge (514) is of BF350 type.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109991103A (en) * | 2019-04-28 | 2019-07-09 | 长安大学 | A kind of shearing strength test device and its shearing strength and static sounding test method |
| CN111829870A (en) * | 2020-07-09 | 2020-10-27 | 广州海洋地质调查局 | Static sounding testing device in sampling pipe |
| CN113607573A (en) * | 2021-05-14 | 2021-11-05 | 长安大学 | In-situ shearing testing device and method for loess in hole |
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2019
- 2019-04-28 CN CN201920603123.2U patent/CN209858359U/en active Active
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109991103A (en) * | 2019-04-28 | 2019-07-09 | 长安大学 | A kind of shearing strength test device and its shearing strength and static sounding test method |
| CN109991103B (en) * | 2019-04-28 | 2024-04-12 | 长安大学 | Shear strength testing device and shear strength and static cone penetration test method thereof |
| CN111829870A (en) * | 2020-07-09 | 2020-10-27 | 广州海洋地质调查局 | Static sounding testing device in sampling pipe |
| CN113607573A (en) * | 2021-05-14 | 2021-11-05 | 长安大学 | In-situ shearing testing device and method for loess in hole |
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