CN114164871A - Pressure monitoring device and pressure monitoring method for deep foundation pit - Google Patents
Pressure monitoring device and pressure monitoring method for deep foundation pit Download PDFInfo
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- CN114164871A CN114164871A CN202111331398.3A CN202111331398A CN114164871A CN 114164871 A CN114164871 A CN 114164871A CN 202111331398 A CN202111331398 A CN 202111331398A CN 114164871 A CN114164871 A CN 114164871A
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D33/00—Testing foundations or foundation structures
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D17/00—Excavations; Bordering of excavations; Making embankments
- E02D17/02—Foundation pits
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Abstract
The invention provides a pressure monitoring device and a pressure monitoring method for a deep foundation pit, wherein the pressure monitoring device comprises: the probe rod is internally provided with a cable; one end of the box body is detachably connected with the probe rod, the other end of the box body opposite to the one end is conical, and a cavity is formed in the box body; the pressure monitoring assembly comprises induction films and filter pieces, the induction films are arranged on two opposite sides of the cavity and connected with the box body, the induction films are connected with the cables to monitor the mean stress value, and the filter pieces are connected with the cables to monitor the pore water pressure value; wherein the sensing film and the filter element enclose the cavity and an outer surface of the sensing film is circular.
Description
Technical Field
The invention belongs to the technical field of civil engineering and constructional engineering, and particularly relates to a pressure monitoring device and a pressure monitoring method for a deep foundation pit.
Background
The lateral soil pressure and the pore water pressure of the enclosure wall are important monitoring items in the deep foundation pit construction process, and the stress, deformation and safety conditions of the enclosure wall and the foundation pit can be analyzed and judged by monitoring the change conditions of the lateral soil pressure and the pore water pressure of the enclosure wall so as to guide the information construction of the deep foundation pit.
The lateral soil pressure and the pore water pressure of the deep foundation pit enclosure wall are monitored mainly by respectively burying a soil pressure box and a pore water pressure meter through drilling holes at present, the drilling holes easily cause soil body disturbance, the backfilling is difficult to be compact, the pore water is easily communicated from top to bottom, and the test data is inaccurate.
Disclosure of Invention
In view of this, the present invention provides a pressure monitoring device, a monitoring structure and a pressure monitoring method for a deep foundation pit, so as to solve the technical problem of how to improve the pressure monitoring accuracy of the deep foundation pit.
The technical scheme of the invention is realized as follows:
the embodiment of the invention provides a pressure monitoring device for a deep foundation pit, which comprises: the probe rod is internally provided with a cable; one end of the box body is detachably connected with the probe rod, the other end of the box body opposite to the one end is conical, and a cavity is formed in the box body; the pressure monitoring assembly comprises induction films and filter pieces, the induction films are arranged on two opposite sides of the cavity and connected with the box body, the induction films are connected with the cables to monitor the mean stress value, and the filter pieces are connected with the cables to monitor the pore water pressure value; wherein the sensing film and the filter element enclose the cavity and the outer surfaces of the sensing film and the filter element are both circular.
In some embodiments, the sensing membrane and the filter element have the same axis of symmetry, and the outer surface of the sensing membrane and the outer surface of the filter element are both perpendicular to the axis of symmetry.
In some embodiments, the outer surface of the filter element is circular, and the outer surface of the sensing membrane and the outer surface of the filter element are equal in area.
In some embodiments, the outer surface of the sensing membrane and the outer surface of the filter element have a diameter of 50mm to 70 mm.
In some embodiments, the cartridge comprises: the cylindrical part is internally provided with the cavity, and the axis of the cylindrical part is superposed with the symmetry axes of the induction film and the filter element; one end of the cylindrical part, which is vertical to the axis direction, is connected with the probe rod; the conical part is connected to the other end, far away from the probe rod, of the cylindrical part.
In some embodiments, the diameter of the cylindrical portion is 70 to 90 mm; and/or the thickness of the cylindrical part in the axis direction is 10-20 mm.
In some embodiments, the tapered portion is smoothly connected to the cylindrical portion.
The embodiment of the invention also provides a pressure monitoring method for the deep foundation pit, which comprises the following steps: before a deep foundation pit is excavated, monitoring a plurality of pressure test values at monitoring points by adopting a pressure monitoring device according to a set time interval; averaging the plurality of pressure test values to obtain an initial pressure value; monitoring the real-time pressure value of the monitoring point according to a set time interval during the construction of the deep foundation pit; drawing a pressure change curve according to the pressure initial value and the real-time pressure value; and sending out an early warning signal under the condition that the pressure change curve exceeds a pressure early warning line.
In some embodiments, before excavating the deep foundation pit, the method further comprises: determining the position of the enclosure wall, and determining that the area positioned in the enclosure wall is a passive area and the area positioned outside the enclosure wall is an active area; and a plurality of monitoring points are determined in the active area and/or the passive area, and the horizontal distance between each monitoring point and the enclosure wall is 0.2-0.5 mm.
In some embodiments, the monitoring points are spaced from 1 to 2m apart in the vertical direction.
The embodiment of the invention provides a pressure monitoring device for a deep foundation pit, which comprises a probe rod, a box body and a pressure monitoring assembly, wherein a cavity is arranged in the box body, the pressure monitoring assembly comprises an induction membrane and a filtering piece which are arranged on two opposite sides of the cavity, the stress mean value of the deep foundation pit is monitored through the induction membrane, the pore water pressure value of the deep foundation pit is monitored through the filtering piece, and the outer surface of the induction membrane is circular. According to the invention, the sensing film is arranged in a circular shape, so that the distances from all points around the sensing film to the center are equal, and when the sensing film and the box body are placed at a monitoring point for stress monitoring, the arched effect can be reduced due to the circular arrangement of the sensing film, so that the stress mean value monitored by the sensing film is closer to the actual stress value of the monitoring point, and the accuracy of stress monitoring of the deep foundation pit is improved.
Drawings
FIG. 1 is a schematic side view of a pressure monitoring device according to an embodiment of the present invention;
FIG. 2 is a front view of a pressure monitoring device according to an embodiment of the present invention;
FIG. 3 is a rear view of a pressure monitoring device according to an embodiment of the present invention;
fig. 4 is a schematic view of an application scenario of the pressure monitoring apparatus according to the embodiment of the present invention;
FIG. 5 is a cross-sectional view taken along section A-A of the first embodiment of FIG. 4;
FIG. 6 is a cross-sectional view taken along section B-B of the first embodiment of FIG. 4;
FIG. 7 is a cross-sectional view taken along section A-A of the second embodiment of FIG. 4;
FIG. 8 is a cross-sectional view taken along section B-B of the second embodiment of FIG. 4;
fig. 9 is a flowchart of a pressure monitoring method for a deep foundation pit according to an embodiment of the present invention.
Description of reference numerals:
a. a pressure monitoring device; 1. a probe rod; 2. a box body; 21. a cavity; 22. a cylindrical portion; 23. a tapered portion; 3. a pressure monitoring assembly; 31. an induction film; 32. a filter member; 4. a connector; 5. an active region; 6. a passive region; 7. an enclosure wall; 10. a cable wire; b. the bottom surface of the deep foundation pit; c. a ground surface; d. the bottom surface of the enclosure wall.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
The individual features described in the embodiments can be combined in any suitable manner without departing from the scope, for example different embodiments and aspects can be formed by combining different features. In order to avoid unnecessary repetition, various possible combinations of the specific features of the invention will not be described further.
In the following description, the term "first/second/so" is used merely to distinguish different objects and does not mean that there is a common or relationship between the objects. It should be understood that the description of the "upper", "lower", "outer" and "inner" directions as related to the orientation in the normal use state, and the "left" and "right" directions indicate the left and right directions indicated in the corresponding schematic drawings, and may or may not be the left and right directions in the normal use state.
It should be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element. "plurality" means greater than or equal to two.
It should be noted that the deep foundation pit indicates a foundation pit with an excavation depth exceeding 6m, the subway deep foundation pit is a deep foundation pit excavated by a subway station built in an urban area, the excavation depth of the deep foundation pit of the existing subway station can reach more than 50m, and as the deep foundation pit structure is easily affected by various unstable factors, engineering accidents and geological disasters such as deformation, collapse and the like occur. Therefore, a pressure monitoring device is needed to monitor the geological conditions in the deep foundation pit.
First, the principle of pressure monitoring at a monitoring point in a foundation pit will be explained. The pressure monitoring device adopted in the related technology comprises a probe rod and a box body, wherein the box body is fixed at the lower end of the probe rod, a stress monitoring part and a water pressure monitoring part are respectively arranged on the surfaces of two sides of the box body corresponding to the probe rod, and the stress monitoring part receives the pressure action of a soil body in a foundation pit so as to monitor the stress mean value; the water pressure monitoring member is provided with a hole so that water flow in the foundation pit flows in, thereby monitoring a water pressure value. The thickness of the box body is generally thin, and the stress monitoring part and the water pressure monitoring part can be considered to be at the same position and belong to the same monitoring point approximately. In the related art, the stress monitoring member is generally a square stress sensing diaphragm, which can be regarded as a two-dimensional rectangle and is installed on one side surface of the box body, and because the rigidity of the stress sensing diaphragm is different from that of the box body, the soil body can generate an arch effect when acting on the stress sensing diaphragm and the box body, the arch effect is used for describing a phenomenon of stress transfer, and the reason for generating the arch effect is that the rigidity of an object acting on the soil body is different, so that the phenomenon of soil body movement caused by local soil pressure increase is generated. Under the state that the stress sensing diaphragm is arranged on the surface of the box body, the rigidity of the box body is greater than that of the stress sensing diaphragm, so that soil body moves from the stress sensing diaphragm to the box body, and an arch effect occurs; correspondingly, the stress value detected by the stress sensing diaphragm is smaller than that of an actual soil body without the pressure monitoring device, so that the condition of inaccurate monitoring stress occurs.
As shown in fig. 1, an embodiment of the present invention provides a pressure monitoring device for a deep foundation pit, which includes a probe 1, a box 2 and a pressure monitoring assembly 3. The probe 1 is an elongated rod-shaped member, but does not mean that the cross-sectional shape of the probe is necessarily circular, wherein the cross-section of the probe means a cross-section of the probe perpendicular to the longitudinal direction, that is, the cross-section may be other shapes such as an ellipse and a square. The probe rod 1 is arranged in the pressure monitoring device, so that the external equipment can be stably connected with the probe rod 1, and the difficulty of mounting the pressure monitoring device in a deep foundation pit is reduced. The probe rod 1 is hollow inside, and the hollow part penetrates through two ends of the probe rod 1 in the length direction. According to the embodiment of the invention, the probe rod is arranged in a hollow manner, on one hand, the cable 10 for transmitting electric power or information can be arranged in the probe rod in a penetrating manner, and on the other hand, the weight of the pressure monitoring device can be reduced, so that the difficulty of installing the pressure monitoring device in a deep foundation pit is reduced.
One end of the box body 2 is detachably connected with the probe rod 1, and the other end of the opposite end is conical, and it should be noted that the other end of the opposite end represents the end which is relatively far away from the probe rod 1 in the outer contour of the box body 2 in the extending direction, so that the probe rod 1 is arranged opposite to the conical end of the box body 2. Install pressure monitoring device at the in-process of deep basal pit, through adopting the fixed probe rod 1 of external equipment centre gripping, drive probe rod 1 and enter into the deep basal pit in, thereby drive whole pressure monitoring device and move in the deep basal pit, because the direction of motion is the upper portion from the deep basal pit motion downstream, for the control of the motion of pressure monitoring device, in-process at the motion, probe rod 1 is located upper portion for box body 2 relatively, make conical structure be located the lower part in the box body 2, conical structure of lower part earlier with the geological contact in the deep basal pit. In the embodiment of the present invention, the taper described herein means that the farthest end of the box body 2 away from the probe 1 is sharper than the end close to the probe 1, and if the direction from the end of the box body 2 connected to the probe 1 to the taper is defined as the first direction (up and down direction in fig. 1), the taper can also be used to mean that the area of the cross section of the box body 2 perpendicular to the first direction is smaller, that is, the cross section of the end of the box body 2 away from the probe 1 (lower end in fig. 1) is smaller than the cross section of the end of the box body 2 close to the probe 1 (upper end in fig. 1).
The area of the cross section of the case 2 perpendicular to the first direction may vary in various ways, for example, the cross section of the case 2 may gradually increase at a certain rate from the end far from the probe 1 (the lower end shown in fig. 1) to the end near the probe (the upper end shown in fig. 1); of course, the sectional area of the box body 2 may gradually increase from the end far away from the probe to the end near the probe according to a certain change rate, and then change according to other change rates, that is, the change of the sectional area in the first direction does not necessarily change monotonically according to the same change rate, as long as at least a portion of the box body 2 far away from the probe can be tapered.
According to the embodiment of the invention, one end (the lower end shown in figure 1) of the box body 2 far away from the probe rod 1 is set to be a conical structure, so that the area of the end part of the box body 2 which is initially contacted with the geology is reduced, the strength of the box body 2 which is acted with the geology can be improved under the action of a certain driving force, and the resistance of the pressure monitoring device penetrating into the soil is reduced, so that the soil disturbance to the same depth and point under the action of plane stress in the movement process of the pressure monitoring device is reduced, the pressure monitoring device can reflect the in-situ stress state of the geology more truly, and the monitoring accuracy of the horizontal stress and the pore water pressure can be improved.
As shown in fig. 1, the pressure monitoring assembly 3 includes a sensing film 31 and a filter 32, the sensing film 31 is used for monitoring a stress average value at a monitoring point in a deep foundation pit, the sensing film 31 can be slightly deformed under the action of a horizontal stress (which represents a stress in the left-right direction of fig. 1), and the pressure monitoring assembly 3 can convert the deformation amount of the sensing film 31 into the stress average value of the monitoring point. Wherein, be equipped with cavity 21 in the box body 2, response membrane 31 sets up in one side (the left side in fig. 1) of cavity 21, and response membrane 31 is connected with box body 2 to one side of closed cavity 21. The sensing film 31 may be a sheet-like structure, the cross section of the sensing film 31 is perpendicular to the first direction (vertical direction in fig. 1), the sensing film 31 may be a stainless steel high-elasticity film, and the sensing principle of the sensing film 31 is described as follows:
referring to fig. 1 and 2, the sensing film 31 is disposed at one side of the cavity 21, and in a state where the pressure monitoring device is inserted into the soil body, the sensing film 31 is subjected to a horizontal stress applied by the soil body, because the sensing film 31 is of a highly elastic structure, the sensing film 31 will deform at least in the horizontal direction (the left and right directions shown in fig. 1) under the action of horizontal stress, the cavity 21 can be filled with a conductive medium, the conductive medium will relatively displace under the action of the deformation of the sensing film 31, the pressure conduit is used for communicating the conducting medium with the micro pressure sensor, the conducting medium moves to the sensor along the pressure conduit under the action of the pressure of the sensing film, the micro pressure sensor can convert the monitored displacement of the conducting medium into the stress mean value of the whole sensing film 31, the stress mean value can be used to represent the horizontal stress at the center of the sensing film 31, and the center of the sensing film 31 can correspond to the position of the monitoring point.
It should be noted that the conductive medium in the embodiment of the present invention may be a medium with good conductivity, such as silicone oil, water, and an emulsifier, where the silicone oil has characteristics of good chemical stability, corrosion resistance, large molecular weight, and high viscosity, and is beneficial to improving the accuracy of stress monitoring. In some embodiments, the conductive medium may be degassed, for example, silicon oil is degassed and then injected into the cavity, and degassing may be performed by pumping gas in the silicon oil away by a vacuum pumping method, so that the deformation amount of the silicon oil is favorably converted into a displacement amount of the silicon oil under the effect of deformation of the sensing film, a risk of volume compression of the silicon oil due to gas existing in the silicon oil is reduced, and sensitivity of stress monitoring is favorably improved. In the process of installing the induction film on the box body, the cavity also needs to be vacuumized, so that the silicon oil can be slowly filled in the whole cavity, and the risk of air bubbles in the cavity is reduced.
What inductive film 31 and cable conductor 10 are connected and are shown is the form that the inductive film can transmit its data of deformation to the sensor through cable conductor 10, not inject inductive film 31 and cable conductor 10's relation of connection, that is to say, inductive film 31 is not direct to be contacted with cable conductor 10, inductive film 31 accessible conduction medium is through transmitting deformation to miniature pressure sensor, miniature pressure sensor can turn into the stress mean value that the inductive film received with the displacement volume of conduction medium, cable conductor 10 passes through cable conductor 10 with the stress mean value that miniature pressure sensor monitored again and transmits to receiving instrument, this receiving instrument can set up the outside at pressure monitoring device, for example, receiving instrument can set up on the bottom surface of deep basal pit, so that the convenient data of observing of monitoring of engineering personnel.
As shown in fig. 1 and 3, the filter 32 is disposed on the other side of the cavity 21 opposite to the sensing film 31, that is, the sensing film 31 and the filter 32 are disposed on the opposite sides of the cavity 21, and the filter 32 is connected to the case 2, and the filter 32 is connected to the cable 10 to monitor the pore water pressure value. The monitoring principle of the filter element 32 is explained below:
the filter 32 may be sized to the specific soil type and sensitivity of the monitoring, and the filter 32 is used to block soil particles from the soil and to conduct pore water from the soil. Where pore water refers to groundwater present in the pores between the loose sediment particles. Be provided with miniature water pressure sensor in the cavity, filter and be connected with miniature water pressure sensor, pore water can enter into miniature water pressure sensor through filtering piece 32 in to increase the water pressure in the miniature water pressure sensor, turn into the pore water pressure value of monitoring point with water pressure variation through pressure sensor. Wherein, miniature water pressure sensor can be connected with filtering a piece contact for filter the pore water in the piece and can directly enter into miniature water pressure sensor. It installs before the box body to filter the piece, can soak in degasification silicon oil with filtering, make the downthehole silicon oil that fills of filtering piece, set up pressure monitoring device behind the deep basal pit, moisture in the soil can enter into filtering in the piece from the hole of filtering piece, make the silicon oil pressurized removal in the filtering piece, make and filter the water pressure conversion in can the monitoring point and become the pressure that silicon oil received, the pressure conversion that rethread miniature water pressure sensor received silicon oil becomes interstitial water pressure value, miniature water pressure sensor actual monitoring data is the signal of telecommunication, miniature water pressure sensor accessible cable conductor 10 transmits the signal of telecommunication to the outside receiving instrument of pressure monitoring device, receiving instrument turns into digital signal with the signal of telecommunication again, in order for the engineering personnel to read and use.
In the embodiment of the present invention, the outer surfaces of the sensing film 31 and the filtering member 32 may be both provided in a circular shape, the outer surface of the sensing film 31 represents a side of the sensing film 31 relatively far from the cavity 21, that is, a side of the sensing film 31 contacting the soil, and the outer surface of the filtering member 32 also represents a side of the filtering member 32 relatively far from the cavity 21, that is, a side of the filtering member 32 contacting the soil. The circle indicates that distances from each point at the edge of the sensing film 31 to the center of the outer surface are approximately equal, and in consideration of dimensional errors in manufacturing, distances from each point at the edge of the sensing film 31 to the center of the outer surface are not absolutely equal, but the difference between the distances is smaller than a set threshold value to satisfy the equal characteristics described in the embodiments of the present invention.
According to the embodiment of the invention, the sensing film is arranged to be circular, namely, the distances from the edge of the sensing film to the center of the sensing film are equal, so that soil body slides uniformly from the center of the sensing film to the surrounding box bodies, and the soil body moves uniformly from the center to four directions, so that the arch effect can be reduced. According to the embodiment of the invention, the stress value obtained by monitoring through the circular sensing film is closer to the actual stress value, so that the accuracy of stress monitoring is improved.
In some embodiments, as shown in fig. 1, the pressure monitoring device further includes a connector 4, the connector 4 can be used to connect the probe rod 1 and the box body 2, the connector 4 can be connected with the box body 2 by welding, and the connector 4 can be detachably connected with the probe rod 1 by screwing, clamping, and the like. Wherein, the miniature pressure sensor can be arranged in the connector and is communicated with the cavity in the box body through the pressure conduit.
In some embodiments, as shown in fig. 1, the sensing film 31 and the filtering member 32 have the same axis of symmetry (dashed line in fig. 1), and the outer surface of the sensing film 31 and the outer surface of the filtering member 32 are perpendicular to the axis of symmetry. The sensing film 31 can be regarded as a cylinder, the symmetry axis of the sensing film 31 is arranged along the length extension direction of the cylinder, the filtering piece 32 can also be regarded as a cylinder, and the symmetry axis of the filtering piece 32 is arranged along the length extension direction of the cylinder. The symmetry axis indicates that the symmetry axes of the sensing film 31 and the filtering member 32 coincide, and the centers of the sensing film 31 and the filtering member 32 are located on the same symmetry axis. The actual stress mean value that the response membrane 31 monitored can be used for showing the horizontal stress of response membrane 31 central point department, the actual pore water pressure value that the filter piece 32 monitored can be used for showing the pore water pressure value of filter piece 32 central point department, under the condition that response membrane 31 and filter piece 2 coaxial arrangement, the monitoring point that response membrane 31 and filter piece 32 were actual all is located same symmetry axis, and the thickness of box body is less relatively, thereby the monitoring point that the response membrane 31 corresponds and the monitoring point that the filter piece 32 corresponds can be regarded as the monitoring to the horizontal stress and the pore water pressure value of same monitoring point, help improving the accuracy of monitoring position.
In some embodiments, as shown in connection with fig. 1-3, the outer surface of sensing membrane 31 and the outer surface of filter element 32 are equal in area. The outer surface corresponds to the surface contacting with the soil, and the areas of the outer surfaces of the sensing film 31 and the filtering element 32 are set to be equal, so that the sensing film 31 and the filtering element 32 have the same degree of stress dispersion through the arch effect, wherein the arch effect represents that the stress in the soil body is resisted by the shear strength of the soil body due to the different rigidity of the box body 2 and the pressure monitoring assembly 3, so that the pressure of the soil body at the pressure monitoring assembly 3 is dispersed onto the box body 2, the pressure at the pressure monitoring assembly 3 is reduced, and the pressure on the box body 2 is increased. Because the areas of the outer surface of the sensing film 31 and the outer surface of the filtering member 32 are equal, the degrees of stress dispersion at the sensing film 31 and the filtering member 32 are the same, the stress states monitored by the sensing film 31 and the filtering member 32 are both matched with the stress states at the centers of the sensing film 31 and the filtering member 32, the stress state monitored by the sensing film 31 can truly reflect the horizontal stress value at the center of the sensing film 31, the stress state monitored by the filtering member 32 can truly reflect the pore water pressure value at the center of the filtering member 32, and under the condition that the center of the sensing film 31 and the center of the filtering member 32 are located on the same symmetry axis, the monitored horizontal stress and the pore water pressure can reflect the stress state of the same monitoring point, thereby being beneficial to improving the accuracy of the stress state of the monitoring point.
In some embodiments, as shown in fig. 2 and 3, the diameter R1 of the outer surface of the sensing membrane 31 and the outer surface of the filter member 32 is 50mm to 70 mm. The particle sizes of different substances in the soil are different, and the stress values corresponding to the same monitoring point have certain difference.
In some embodiments, as shown in connection with fig. 1-3, the cartridge body 2 includes a cylindrical portion 22 and a conical portion 23. The axis of the cylindrical portion 22 coincides with the symmetry axis (broken line shown in fig. 1) of the sensing film and the filter, a cavity 21 is provided inside the cylindrical portion 22, one end (upper end shown in fig. 1) of the cylindrical portion 22 in the direction perpendicular to the axis is connected to the probe rod 1, and the other end (lower end shown in fig. 1) of the cylindrical portion 22 in the direction perpendicular to the axis is connected to the tapered portion 23. The vertical axis is a first direction (vertical direction in fig. 1), and the tapered portion 23 has a cross-sectional area that gradually increases from one end distant from the cylindrical portion 22 to one end close to the cylindrical portion in the first direction, and the cross-section is perpendicular to the first direction. According to the embodiment of the invention, the combination form of the cylindrical part and the conical part is arranged, so that the disturbance effect of the pressure monitoring device on soil in the burying process of the pressure monitoring device is reduced, and the accuracy of monitoring the stress state is further improved through the cylindrical part.
In some embodiments, as shown in fig. 1-3, the diameter R2 of the cylindrical portion is 70-90 mm, it should be noted that the cylindrical portion 22 is hollow to form the cavity 21, so the diameter of the cylindrical portion 22 includes an inner diameter and an outer diameter, and the diameter R2 of the cylindrical portion in the embodiment of the present invention is an outer diameter of the cylindrical portion 22 in a cross section perpendicular to the axis (the dotted line shown in fig. 1), and the inner diameter of the cylindrical portion 22 may correspond to the diameters of the filter element 32 and the sensing film 31, so as to facilitate the sealing installation of the filter element 32 and the sensing film 31 at two ends of the cavity 21 in the direction of the axis (the dotted line shown in fig. 1). According to the embodiment of the invention, the diameter R2 of the cylindrical part is set within the range of 70-90 mm, so that the rigid mounting requirement of the cylindrical part on the induction film and the filter element can be met, and the cylindrical part is not too wide, so that the risk of stress dispersion around the induction film is reduced.
In some embodiments, as shown in FIG. 1, the thickness M of the cylindrical portion 22 in the axial direction (the direction of the dotted line shown in FIG. 1) is 10 to 20 mm. According to the embodiment of the invention, the thickness of the cylindrical part is set to be 10-20 mm, so that the cavity in the cylindrical part can contain enough conducting media and is not too thick, the disturbance to soil is reduced, and the accuracy of soil stress monitoring is improved.
In some embodiments, as shown in FIG. 1, the tapered portion 23 smoothly connects with the cylindrical portion 22. The smooth connection means that the curvature rule of the connection part of the cylindrical part 22 and the tapered part 23 changes and has no convex value, so that the resistance of the soil to the box body is reduced, and the disturbance degree of the box body to the soil is reduced.
In some embodiments, as shown in fig. 1, the sensing film 31 and the filtering member 32 are flush with the surface of the cylindrical portion 22, that is, the surface of the sensing film 31 close to the soil (left side shown in fig. 1) is flush with the end surface (left end shown in fig. 1) of the cylindrical portion 22, and the surface of the filtering member 32 close to the soil (right side shown in fig. 1) is flush with the end surface (right end shown in fig. 1) of the cylindrical portion 22, so that the disturbance degree of the pressure monitoring device to the soil can be reduced, and the tightness between the sensing film, the filtering member, and the cavity can be improved.
As shown in fig. 4, the monitoring device according to the embodiment of the present invention may be applied to an area including the enclosure wall 7, wherein the active area 5 and the passive area 6 are used to indicate an area around the enclosure wall 7 in the deep foundation pit, the active area 5 is located outside (on the left side in fig. 4) the enclosure wall 7 of the deep foundation pit, and the soil pressure of the soil body outside the deep foundation pit acting on the enclosure wall 7 is the active soil pressure; the passive area 6 is located on the inner side (right side shown in fig. 4) of the enclosure wall 7 of the deep foundation pit, and the soil pressure acting on the enclosure wall 7 after the enclosure wall 7 deforms in the deep foundation pit is passive soil pressure. Wherein, a plurality of pressure monitoring devices a set up each monitoring point in active area 5 and/or passive zone 6, and monitoring point sets up at the interval in vertical direction (the upper and lower direction that is shown in fig. 4), and the distance L1 between a plurality of monitoring points is 1 ~ 2 m. According to the embodiment of the invention, the pressure monitoring devices are arranged in the passive area and the active area to monitor the lateral soil pressure and the pore water pressure at different depths of the deep foundation pit, and the stress and deformation of the enclosure wall at different depths and the safety condition of the deep foundation pit can be analyzed and judged according to the lateral soil pressure and the pore water pressure, so that the informatization degree of foundation pit construction is improved.
In some embodiments, as shown in FIG. 4, the horizontal spacing L2 between the monitoring points (coinciding with the location of the pressure monitoring device a in FIG. 4) and the enclosure wall 7 is 0.2-0.5 mm. According to the embodiment of the invention, the monitoring points are arranged in the range of the interval set distance of the enclosure wall, so that the monitoring points can monitor the stress condition around the enclosure wall and reduce the influence on the soil body around the enclosure wall.
In the embodiment of the invention, the pressure monitoring device can be embedded in various ways, deep foundation pits with different soil qualities can adopt different embedding methods, and the embedding method of the pressure monitoring device is described as follows:
in some embodiments, as shown in fig. 1, 5 and 6, in the case of disposing the pressure monitoring device a in cohesive soil and sandy soil, the cohesive soil may be classified into hard, plastic, soft and fluid according to the liquid index of the soil, and the sandy soil may be classified into loose, slightly dense, medium dense and dense according to the degree of compaction. The method provided by the embodiment of the invention is suitable for cohesive soil for flow molding, soft molding, plastic molding and hard molding, loose, slightly dense and medium dense silt and sand soil. As shown in fig. 5, in the passive area 6, a plurality of pressure monitoring devices a are sequentially penetrated from the bottom surface d of the enclosure wall to the bottom surface b of the deep foundation pit in a static pressure manner; as shown in fig. 6, a plurality of pressure monitoring devices a are sequentially penetrated from the bottom surface d of the enclosure wall to the ground surface c in the active area 5 by a static sounding machine. After the pressure monitoring device a is inserted, the probe rod 1 and the box body 2 are separated from the connector 4, the probe rod 1 is pulled out, the cable 10 for testing leads to the ground c from a hollow area in the probe rod, then the cable 10 is connected with a receiving instrument of the ground c, the horizontal distance L3 is 0.5-1 m when the pressure monitoring device a is buried, and the cable 10 in each pressure monitoring device a is protected conveniently.
In some embodiments, as shown in fig. 7 and 8, the method provided by the embodiments of the present invention is applicable to hard plastic, hard cohesive soil, dense silt, sand soil, weathered rock and other hard soil layers, a geological drilling rig is used to drill a hole in a monitoring area, the hole diameter of the geological drilling rig is 110-130 m, and in some embodiments may be 120mm, the hole extends from the ground to the bottom end of the enclosure wall 7, the pressure monitoring device a is placed at the bottom of the drilled hole (i.e., the first monitoring point), then clay balls are used to backfill the hole to be dense to the next monitoring point, then the pressure monitoring device a is placed at the monitoring point, and then the clay balls are used to backfill the next monitoring point, and referring to fig. 7, the passive area is used to sequentially bury the pressure monitoring device a from the bottom d of the enclosure wall to the bottom b of the deep foundation pit according to the steps; referring to fig. 8, the active area sequentially buries the pressure monitoring device a from the bottom surface d of the enclosure wall to the ground surface c in this step. All pressure monitoring devices a are brought to the ground via cable lines 10, which are fitted with the connection requirements of the 485 bus.
The embodiment of the invention also provides a pressure monitoring method for the deep foundation pit, as shown in fig. 9, the method comprises the following steps:
s1, before a deep foundation pit is excavated, monitoring a plurality of pressure test values at monitoring points by adopting any one of the pressure monitoring devices according to a set time interval; the pressure monitoring device can be connected with a measuring and controlling instrument with a 4G/5G function on the ground through a 485 bus, and the measuring and controlling instrument can be automatically controlled to read the horizontal total stress and the pore water pressure through monitoring the interactive access of cloud platform software. The horizontal total stress and the pore water pressure of the pressure monitoring device can be tested once every other day or once every day by using a measurement and control instrument one week before the deep foundation pit is excavated.
S2, averaging the multiple pressure test values to obtain an initial pressure value; for example, the average of 3 tests is used as the initial value of the lateral earth pressure and the pore water pressure of the enclosure wall.
S3, monitoring the real-time pressure value of the monitoring point according to a set time interval during the construction of the deep foundation pit; during the construction of the deep foundation pit, according to the requirements of the design drawing on monitoring frequency under different construction conditions, the monitoring frequency is set on the monitoring cloud platform, the monitoring effective stress shovel horizontal total stress and the pore water pressure value at different times are read by the measuring and controlling instrument and are synchronously sent to the monitoring cloud platform as the monitoring values of the lateral soil pressure and the pore water pressure of the enclosure wall at different times.
And S4, drawing a pressure change curve according to the pressure initial value and the real-time pressure value. The embodiment of the invention is convenient for observation and monitoring by drawing a pressure change curve.
And S5, sending out an early warning signal when the pressure change curve exceeds the pressure early warning line. Through monitoring cloud platform software, change curves of lateral soil pressure and pore water pressure of the monitored enclosure wall along with time are compared and judged with early warning values provided by a design drawing, and when the monitored values exceed the early warning values, early warning is provided for construction units, design units, construction units, monitoring units and the like.
The embodiment of the invention directly and quickly tests the in-situ horizontal total stress and the pore water pressure of the foundation soil body by the pressure monitoring device injection test, and can be widely applied to geotechnical engineering investigation of projects such as railways, highways, municipal administration, rail transit, house buildings and the like. The effective stress shovel is buried at the side wall of the deep foundation pit and can accurately monitor the lateral soil pressure and the pore water pressure.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention.
Claims (10)
1. The utility model provides a pressure monitoring device of deep basal pit which characterized in that includes:
the probe rod is internally provided with a cable;
one end of the box body is detachably connected with the probe rod, the other end of the box body opposite to the one end is conical, and a cavity is formed in the box body;
the pressure monitoring assembly comprises induction films and filter pieces, the induction films are arranged on two opposite sides of the cavity and connected with the box body, the induction films are connected with the cables to monitor the mean stress value, and the filter pieces are connected with the cables to monitor the pore water pressure value; wherein the sensing film and the filter element enclose the cavity and an outer surface of the sensing film is circular.
2. The pressure monitoring device of claim 1, wherein the sensing diaphragm and the filter element have the same axis of symmetry, and wherein the outer surface of the sensing diaphragm and the outer surface of the filter element are both perpendicular to the axis of symmetry.
3. The pressure monitoring device of claim 2, wherein the outer surface of the filter element is circular and the outer surface of the sensing diaphragm and the outer surface of the filter element are equal in area.
4. A pressure monitoring device according to claim 3, wherein the outer surface of the sensing diaphragm and the outer surface of the filter element have a diameter of 50mm to 70 mm.
5. The pressure monitoring device of claim 3, wherein the cartridge comprises:
the cylindrical part is internally provided with the cavity, and the axis of the cylindrical part is superposed with the symmetry axes of the induction film and the filter element; one end of the cylindrical part, which is vertical to the axis direction, is connected with the probe rod;
the conical part is connected to the other end, far away from the probe rod, of the cylindrical part.
6. The pressure monitoring device according to claim 5, wherein the diameter of the cylindrical portion is 70 to 90 mm;
and/or the presence of a gas in the gas,
the thickness of the cylindrical portion in the axis direction is 10-20 mm.
7. The pressure monitoring device of claim 5, wherein the tapered portion is smoothly connected with the cylindrical portion.
8. A pressure monitoring method for a deep foundation pit is characterized by comprising the following steps:
monitoring a plurality of pressure test values at monitoring points at set time intervals by using the pressure monitoring device of any one of claims 1-7 before excavating a deep foundation pit;
averaging the plurality of pressure test values to obtain an initial pressure value;
monitoring the real-time pressure value of the monitoring point according to a set time interval during the construction of the deep foundation pit;
drawing a pressure change curve according to the pressure initial value and the real-time pressure value;
and sending out an early warning signal under the condition that the pressure change curve exceeds a pressure early warning line.
9. The pressure monitoring method according to claim 8, further comprising, before excavating the deep foundation pit:
determining the position of the enclosure wall, and determining that the area positioned in the enclosure wall is a passive area and the area positioned outside the enclosure wall is an active area;
and a plurality of monitoring points are determined in the active area and/or the passive area, and the horizontal distance between each monitoring point and the enclosure wall is 0.2-0.5 mm.
10. The pressure monitoring method according to claim 9, wherein the distance between the monitoring points in the vertical direction is 1-2 m.
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