CN114164871B - 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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- CN114164871B CN114164871B CN202111331398.3A CN202111331398A CN114164871B CN 114164871 B CN114164871 B CN 114164871B CN 202111331398 A CN202111331398 A CN 202111331398A CN 114164871 B CN114164871 B CN 114164871B
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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
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 following components: 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 an induction membrane and a filter element, wherein the induction membrane and the filter element are arranged on two opposite sides of the cavity and are connected with the box body, the induction membrane is connected with the cable to monitor the stress average value, and the filter element is connected with the cable to monitor the pore water pressure value; wherein the sensing membrane and the filter element enclose the cavity and the outer surface of the sensing membrane 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, the deformation and the safety condition of the foundation pit of the enclosure wall can be analyzed and judged by monitoring the change condition of the lateral soil pressure and the pore water pressure of the enclosure wall so as to guide the informatization construction of the deep foundation pit.
The lateral soil pressure and the pore water pressure of the deep foundation pit enclosure wall are monitored at present mainly by respectively burying a soil pressure box and a pore water pressure meter through drilling, soil disturbance is easily caused by drilling, backfilling is difficult to compact, and pore water is easily communicated up and down, so that test data are inaccurate.
Disclosure of Invention
In view of the above, the present invention provides a pressure monitoring device, a pressure 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 following components: 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 an induction membrane and a filter element, wherein the induction membrane and the filter element are arranged on two opposite sides of the cavity and are connected with the box body, the induction membrane is connected with the cable to monitor the stress average value, and the filter element is connected with the cable to monitor the pore water pressure value; wherein, the sensing film and the filter element close the cavity and the outer surfaces of the sensing film and the filter element are round.
In some embodiments, the sensing diaphragm and the filter have the same axis of symmetry, and the outer surface of the sensing diaphragm and the outer surface of the filter are 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 diameters of 50mm to 70mm.
In some embodiments, the cartridge comprises: the cylindrical part is internally provided with the cavity, and the axis of the cylindrical part coincides with the symmetry axes of the induction membrane and the filter element; one end of the cylindrical part perpendicular to the axis direction is connected with the probe rod; and the conical part is connected with the other end of the cylindrical part, which is far away from the probe rod.
In some embodiments, the diameter of the cylindrical portion is 70-90 mm; and/or the thickness of the cylindrical part in the axial direction is 10-20 mm.
In some embodiments, the taper is smoothly connected to the cylinder.
The embodiment of the invention also provides a pressure monitoring method of 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 according to set time intervals by adopting the pressure monitoring device according to any one of the above; averaging the pressure test values to obtain a pressure initial 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 the deep foundation pit is excavated, further comprising: determining the position of the enclosure wall, and determining the area positioned in the enclosure wall as a passive area and the area positioned outside the enclosure wall as 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 the monitoring points and the enclosure wall is 0.2-0.5 mm.
In some embodiments, the monitoring points are spaced apart by 1-2 m 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 induction membranes and filtering pieces which are arranged on two opposite sides of the cavity, the stress average value of the deep foundation pit is monitored through the induction membranes, the pore water pressure value of the deep foundation pit is monitored through the filtering pieces, and the outer surface of the induction membranes is round. According to the invention, the sensing film is arranged in a circular shape, so that the distances from each point around the sensing film to the center are equal, and when the sensing film and the box body are placed at the monitoring points for stress monitoring, the sensing film is arranged in the circular shape, so that the arch effect can be reduced, the stress average value monitored by the sensing film is relatively close to the actual stress value of the monitoring points, and the accuracy of monitoring the stress 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 diagram of an application scenario of a pressure monitoring device according to an embodiment of the present invention;
FIG. 5 is a section view of section A-A of the first embodiment of FIG. 4;
FIG. 6 is a section view of section B-B of the first embodiment of FIG. 4;
FIG. 7 is a section view of section A-A of the second embodiment of FIG. 4;
FIG. 8 is a section view of section B-B of the second embodiment of FIG. 4;
fig. 9 is a flowchart of a method for monitoring pressure of a deep foundation pit according to an embodiment of the present invention.
Reference numerals illustrate:
a. a pressure monitoring device; 1. a probe rod; 2. a case body; 21. a cavity; 22. a cylindrical portion; 23. a taper portion; 3. a pressure monitoring assembly; 31. an induction film; 32. a filter; 4. a connector; 5. an active region; 6. a passive region; 7. a retaining wall; 10. a cable; b. the bottom surface of the deep foundation pit; c. ground surface; d. the bottom surface of the enclosure wall.
Detailed Description
The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
The individual features described in the specific embodiments can be combined in any suitable manner, without contradiction, for example by combination of different specific features, to form different embodiments and solutions. Various combinations of the specific features of the invention are not described in detail in order to avoid unnecessary repetition.
In the following description, references to the term "first/second/are merely to distinguish between different objects and do not indicate that the objects have the same or a relationship therebetween. It should be understood that references to orientations of "above", "below", "outside" and "inside" are all orientations in normal use, and "left" and "right" directions refer to left and right directions illustrated in the specific corresponding schematic drawings, and may or may not be left and right directions in normal use.
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 one … …" 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.
The deep foundation pit is a foundation pit with the 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 the deep foundation pit structure is easily affected by various unstable factors, so that engineering accidents such as deformation collapse and geological disasters occur. Pressure monitoring devices are therefore required to monitor the geological conditions within deep foundation pits.
First, a principle of pressure monitoring at a monitoring point in a foundation pit will be described. The pressure monitoring device 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 piece and a water pressure monitoring piece are respectively arranged on the two corresponding side surfaces of the box body relative to the probe rod, and the stress monitoring piece is used for monitoring the stress average value by receiving the pressure action of soil in a foundation pit; the water pressure monitoring piece is provided with holes so that water flow in the foundation pit flows in, and therefore the water pressure value is monitored. The thickness of the box body is generally thinner, and the stress monitoring piece and the monitoring point corresponding to the water pressure monitoring piece can be considered to be the same position, and belong to the same monitoring point. In the related art, the stress monitoring piece is generally a square stress sensing diaphragm, which can be seen 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 arch effect is generated when the soil body acts on the stress sensing diaphragm and the box body, the arch effect is a phenomenon for describing stress transfer, and the reason for generating the arch effect is that the rigidity of the object acted on the soil body is different, so that the local soil pressure is increased to generate the phenomenon of soil body movement. In the state that the stress sensing diaphragm is arranged on the surface of the box body, the rigidity of the box body is larger than that of the stress sensing diaphragm, so that soil body moves onto the box body from the stress sensing diaphragm, and an arch effect appears; correspondingly, the stress value detected by the stress sensing diaphragm is smaller than the stress value of an actual soil body without the pressure monitoring device, so that the condition of inaccurate monitoring stress occurs.
As shown in fig. 1, the embodiment of the invention provides a pressure monitoring device for a deep foundation pit, which comprises a probe rod 1, a box body 2 and a pressure monitoring assembly 3. The probe 1 is shown as an elongated rod-like member, but it does not necessarily mean that the cross-section of the probe is circular, wherein the cross-section of the probe is a cross-section perpendicular to the length direction of the probe, that is, the cross-section may be elliptical, square, or other shapes. According to the embodiment of the invention, the probe rod 1 is arranged in the pressure monitoring device, so that the stable connection between external equipment and the probe rod 1 is facilitated, the difficulty in installing the pressure monitoring device in a deep foundation pit is reduced, and the probe rod 1 described in the embodiment of the invention is only used for limiting the function of being convenient to install, but is not limited in shape and structure. The probe rod 1 is hollow, and the hollow part penetrates through the two ends of the probe rod 1 in the length direction. According to the embodiment of the invention, the probe rod is arranged in the hollow mode, so that on one hand, the cable 10 used for transmitting power or information can be arranged in the probe rod in a penetrating mode, and on the other hand, the weight of the pressure monitoring device can be reduced, and the difficulty in 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 tapered, and it is to be noted that the other end of the opposite end represents an end relatively far 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 relatively arranged with the tapered end of the box body 2. The pressure monitoring device is installed in the process of the deep foundation pit, the probe rod 1 is clamped and fixed through external equipment, the probe rod 1 is driven to enter the deep foundation pit, the whole pressure monitoring device is driven to move in the deep foundation pit, the movement direction is from the upper part of the deep foundation pit to move downwards, in order to facilitate the control of the movement of the pressure monitoring device, in the movement process, the probe rod 1 is located at the upper part relative to the box body 2, the conical structure in the box body 2 is located at the lower part, and the conical structure at the lower part is firstly contacted with the geology in the deep foundation pit. The taper in the embodiment of the present invention indicates that the furthest end of the case 2 away from the probe 1 is more acute than the end near the probe 1, and if the direction from the end of the case 2 connected to the probe 1 to the taper is defined as the first direction (the up-down direction in fig. 1), the taper may also be used to indicate that the area of the cross section of the case 2 perpendicular to the first direction is smaller, that is, the cross section of the end of the case 2 away from the probe 1 (the lower end in fig. 1) is smaller than the cross section of the case 2 near the end of the probe 1 (the upper end in fig. 1).
The cross-sectional area of the case 2 perpendicular to the first direction may vary in various ways, for example, from one end far from the probe 1 (lower end shown in fig. 1) to one end near the probe (upper end shown in fig. 1), and the cross-sectional area of the case 2 may be gradually increased at a certain rate of change; of course, the cross-sectional area of the box body 2 may gradually increase according to a certain rate of change from the end far from the probe rod to the end near the probe rod, and then change according to other rates of change, that is, the change of the cross-sectional area in the first direction does not necessarily change monotonically according to the same rate of change, so long as at least a portion of the box body 2 far from the probe rod can be tapered.
According to the embodiment of the invention, the end (the lower end shown in fig. 1) of the box body 2, which is far away from the probe rod 1, is arranged to be of a conical structure, so that the initial contact area between the end of the box body 2 and the geology is reduced, the strength of the box body 2 and 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 disturbance to the soil body with the same depth and the same point under the action of the plane stress in the movement process of the pressure monitoring device is reduced, the pressure monitoring device can more truly reflect the in-situ stress state of the geology, and the accuracy of monitoring the horizontal stress and the pore water pressure can be improved.
As shown in fig. 1, the pressure monitoring assembly 3 includes a sensing membrane 31 and a filtering member 32, the sensing membrane 31 is used for monitoring a stress average value at a monitoring point in a deep foundation pit, the sensing membrane 31 can generate micro deformation under the action of horizontal stress (the stress in the left-right direction in fig. 1 is shown), and the pressure monitoring assembly 3 can convert the deformation of the sensing membrane 31 into the stress average value at the monitoring point. Wherein, the cavity 21 is disposed in the case 2, the sensing film 31 is disposed on one side (left side in fig. 1) of the cavity 21, and the sensing film 31 is connected with the case 2 to close one side of the cavity 21. The sensing film 31 may be regarded as a lamellar structure, the cross section of the sensing film 31 is perpendicular to the first direction (up-down 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 below:
referring to fig. 1 and 2, the sensing membrane 31 is disposed on one side of the cavity 21, in a state that the pressure monitoring device penetrates into a soil body, the sensing membrane 31 receives horizontal stress under the action of the soil body, because the sensing membrane 31 is disposed in a highly elastic structure, the sensing membrane 31 is deformed at least in a horizontal direction (left-right direction shown in fig. 1) under the action of the horizontal stress, the cavity 21 can be filled with a conductive medium, the conductive medium is relatively displaced under the action of the deformation of the sensing membrane 31, the conductive medium is communicated with the micro pressure sensor through the pressure conduit, the conductive medium moves to the sensor along the pressure conduit under the action of the pressure of the sensing membrane, the micro pressure sensor can convert the monitored displacement of the conductive medium into a stress average value of the whole sensing membrane 31, the stress average value can be used for representing the horizontal stress at the central position of the sensing membrane 31, and the central position of the sensing membrane 31 can correspond to the position set by the monitoring point.
It should be noted that the conductive medium in the embodiment of the invention may be a medium with good conductivity such as silicone oil, water, and emulsifying agent, where the silicone oil has good chemical stability, corrosion resistance, large molecular weight, and high viscosity, and is beneficial to improving accuracy of stress monitoring. In some embodiments, the conductive medium may be degassed, for example, the silicone oil may be degassed and then injected into the cavity, and the degassing may be performed by pumping the gas in the silicone oil by using a vacuum pumping method, so that the silicone oil is beneficial to converting the deformation into the displacement of the silicone oil under the action of deformation of the sensing film, reducing the risk of compression of the silicone oil due to the gas in the silicone oil, and improving the sensitivity of stress monitoring. In the process of installing the induction membrane on the box body, the cavity is also required to be vacuumized, so that the silicone oil fills the whole cavity slowly, and the risk of bubbles in the cavity is reduced.
The connection of the sensing film 31 and the cable 10 indicates that the sensing film can transmit deformation data to the sensor through the cable 10, and the connection relationship between the sensing film 31 and the cable 10 is not limited, that is, the sensing film 31 is not directly contacted with the cable 10, the sensing film 31 can transmit deformation to the micro pressure sensor through a conductive medium, the micro pressure sensor can convert displacement of the conductive medium into a stress mean value of the sensing film, the cable 10 transmits the stress mean value monitored by the micro pressure sensor to a receiving instrument through the cable 10, and the receiving instrument can be arranged outside the pressure monitoring device, for example, the receiving instrument can be arranged on the bottom surface of a deep foundation pit, so that engineering personnel can observe the monitored data conveniently.
As shown in fig. 1 and 3, the filter 32 is disposed on the other side of the cavity 21 opposite to the sensing membrane 31, that is, the sensing membrane 31 and the filter 32 are disposed on 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 principle of monitoring the filter element 32 is described below:
the filter 32 may be sized with the pores of the filter 32 according to the particular soil characteristics and sensitivity of the monitoring, the filter 32 serving to block soil particles from the soil and to conduct pore water from the soil. Wherein pore water means groundwater present in the pores between particles of loose sediment. The cavity is internally provided with a miniature water pressure sensor, the filtering piece is connected with the miniature water pressure sensor, pore water can enter the miniature water pressure sensor through the filtering piece 32 so as to increase the water pressure in the miniature water pressure sensor, and the water pressure variation is converted into a pore water pressure value of a monitoring point through the pressure sensor. The miniature water pressure sensor can be in contact connection with the filter element, so that pore water in the filter element can directly enter the miniature water pressure sensor. Before the filter element is installed at the box body, can soak the filter element in the silicone oil of degasification for the downthehole packing of filter element is filled with silicone oil, after setting up pressure monitoring devices in deep basal pit, the moisture in the soil can be followed the downthehole entering filter element of filter element, make the silicone oil pressurized movement in the filter element, make the filter element can change the pressure that the monitoring point in the water pressure received into the silicone oil, rethread miniature water pressure sensor converts the pressure that the silicone oil received into hole clearance water pressure value, miniature water pressure sensor actually monitors data and is the electrical signal, miniature water pressure sensor can pass through cable 10 with the electrical signal transmission to the outside receiving instrument of pressure monitoring devices, receiving instrument converts the electrical signal into digital signal again, for engineering personnel reads and uses.
In the embodiment of the present invention, the outer surfaces of the sensing film 31 and the filter element 32 may be circular, and the outer surface of the sensing film 31 represents the surface of the sensing film 31 relatively far from the cavity 21, that is, the surface of the sensing film 31 contacting with the soil, and the outer surface of the filter element 32 also represents the surface of the filter element 32 relatively far from the cavity 21, that is, the surface of the filter element 32 contacting with the soil. The circles indicate that distances from each point at the edge of the sensing film 31 to the center of the outer surface are approximately equal, and that the distances from each point at the edge of the sensing film 31 to the center are not absolutely equal in consideration of dimensional errors in manufacturing, but that differences in the distances are smaller than a set threshold value can satisfy the equal feature described in the embodiments of the present invention.
According to the embodiment of the invention, the sensing film is arranged in a round shape, namely, the distances from the edge of the sensing film to the center of the sensing film are equal, so that the soil body slides uniformly from the center of the sensing film to the box body around the sensing film, and the soil body movement from the center to four directions is basically uniform, so that the arch effect can be reduced. According to the embodiment of the invention, the stress value obtained through monitoring the circular induction 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, where the connector 4 may be used to connect the probe rod 1 and the box 2, the connector 4 may be connected to the box 2 by welding, etc., and the connector 4 may be detachably connected to the probe rod 1 by screwing, clamping, etc. 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 diaphragm 31 and the filter 32 have the same axis of symmetry (shown in phantom in fig. 1), and both the outer surface of the sensing diaphragm 31 and the outer surface of the filter 32 are perpendicular to the axis of symmetry. The sensing film 31 may be regarded as a cylinder, the symmetry axis of the sensing film 31 is disposed along the length extending direction of the cylinder, the filter 32 may also be regarded as a cylinder, and the symmetry axis of the filter 32 is disposed along the length extending direction of the cylinder. The same symmetry axis indicates that the sensing film 31 coincides with the symmetry axis of the filter element 32, and the centers of the sensing film 31 and the filter element 32 are located on the same symmetry axis. The actual stress average value monitored by the sensing film 31 can be used for representing the horizontal stress at the central position of the sensing film 31, the actual pore water pressure value monitored by the filtering piece 32 can be used for representing the pore water pressure value at the central position of the filtering piece 32, under the condition that the sensing film 31 and the filtering piece 2 are coaxially arranged, the actual monitoring points of the sensing film 31 and the filtering piece 32 are located on the same symmetrical axis, and the thickness of the box body is relatively smaller, so that the monitoring points corresponding to the sensing film 31 and the monitoring points corresponding to the filtering piece 32 can be regarded as the monitoring of the horizontal stress and the pore water pressure value of the same monitoring points, and the accuracy of the monitoring position can be improved.
In some embodiments, as shown in connection with fig. 1-3, the outer surface of sensing diaphragm 31 and the outer surface of filter element 32 are equal in area. The outer surface corresponds to the surface in contact with the soil, and the outer surface areas of the sensing film 31 and the filtering piece 32 are set to be equal in size, so that the stress is dispersed to the same extent by the sensing film 31 and the filtering piece 32 through the arch effect, wherein the arch effect means that the stress in the soil body is subjected to the impedance of the shear strength of the soil body due to the different rigidities of the box body 2 and the pressure monitoring assembly 3, the pressure of the soil body at the pressure monitoring assembly 3 is dispersed to 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 surface areas of the sensing film 31 and the outer surface area of the filter element 32 are equal, the stress dispersion degree of the sensing film 31 and the filter element 32 is the same, the stress states monitored by the sensing film 31 and the filter element 32 are matched with the stress states of the sensing film 31 and the filter element 32, the stress states monitored by the sensing film 31 can truly reflect the horizontal stress value of the central position of the sensing film 31, the stress states monitored by the filter element 32 can truly reflect the pore water pressure value of the central position of the filter element 32, and the monitored horizontal stress and the gap water pressure can reflect the stress state of the same monitoring point under the condition that the center of the sensing film 31 and the center of the filter element 32 are positioned on the same symmetry axis, so that the accuracy of the stress states of the monitoring point is improved.
In some embodiments, as shown in fig. 2 and 3, the diameter R1 of the outer surface of the sensing diaphragm 31 and the outer surface of the filter 32 is 50mm to 70mm. The particle sizes of different substances in the soil are different, and certain difference exists in stress values corresponding to the same monitoring point, and the diameter of the outer surface is set to be within a certain range, so that the soil in the range monitored by the sensing film 31 and the filtering piece 32 can cover a large number of particles, the monitored stress data can be close to the actual stress of the monitoring point, and meanwhile, the resistance generated by the sensing film and the filtering piece with the sizes in the installation process is small, so that the stress state of the stratum in situ is truly reflected, and the accuracy of the stress of the monitoring point is improved.
In some embodiments, as shown in connection with fig. 1-3, the cartridge 2 includes a cylindrical portion 22 and a tapered portion 23. The axis of the cylindrical portion 22 coincides with the symmetry axis (broken line in fig. 1) of the induction membrane and the filter, a cavity 21 is provided in the cylindrical portion 22, one end (upper end 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 in fig. 1) of the cylindrical portion 22 in the direction perpendicular to the axis is connected to the taper portion 23. The direction of the vertical axis is a first direction (up-down direction shown in fig. 1), and the tapered portion 23 gradually increases in cross-sectional area from one end away from the cylindrical portion 22 to one end close to the cylindrical portion in the first direction, the cross-section being perpendicular to the first direction. According to the embodiment of the invention, the combination form of the cylindrical part and the conical part is adopted, so that the disturbance effect 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, and it should be noted that the hollow cavity 21 is formed in the cylindrical portion 22, so that the diameter of the cylindrical portion 22 includes an inner diameter and an outer diameter, and in this embodiment, the diameter R2 of the cylindrical portion refers to the outer diameter of the cylindrical portion 22 in a section perpendicular to the axis (dashed 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 that the filter element 32 and the sensing film 31 are mounted at two ends of the cavity 21 in the direction of the axis (dashed line shown in fig. 1) in a sealing manner. 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 membrane and the filter element can be met, and the rigid mounting requirement is not too wide, so that the risk of stress dispersion around the induction membrane is reduced.
In some embodiments, as shown in FIG. 1, the thickness M of the cylindrical portion 22 in the axial direction (in the direction of the dashed line in FIG. 1) is 10-20 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 conductive medium 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 is smoothly connected with the cylindrical portion 22. The smooth connection means that the curvature of the portion where the cylindrical portion 22 is connected to the tapered portion 23 changes regularly without having a 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 element 32 are flush with the surface of the cylindrical portion 22, that is, the surface of the sensing film 31 near the soil side (the left side in fig. 1) is flush with the end surface of the cylindrical portion 22 (the left end in fig. 1), and the surface of the filtering element 32 near the soil side (the right side in fig. 1) is flush with the end surface of the cylindrical portion 22 (the right end in fig. 1), so that on one hand, the disturbance degree of the pressure monitoring device on the soil can be reduced, and on the other hand, the tightness among the sensing film, the filtering element and the cavity can be improved.
As shown in fig. 4, the monitoring device of the embodiment of the present invention may be applied to an area including a retaining wall 7, where an active area 5 and a passive area 6 are used to represent an area around the retaining wall 7 in a deep foundation pit, the active area 5 is located outside (left side in fig. 4) the retaining wall 7 of the deep foundation pit, and soil pressure of soil on the retaining wall 7 on the outer side of the deep foundation pit is active soil pressure; the passive area 6 is located inside the retaining wall 7 (right side shown in fig. 4) of the deep foundation pit, and the soil pressure in the deep foundation pit acting on the retaining wall 7 after the retaining wall 7 is deformed is the passive soil pressure. The pressure monitoring devices a are arranged at each monitoring point of the active area 5 and/or the passive area 6, the monitoring points are arranged at intervals in the vertical direction (up-down direction shown in fig. 4), and the distance L1 between the 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 of the deep foundation pit at different depths, and the stress, the deformation and the safety condition of the deep foundation pit at different depths of the enclosure wall can be judged according to the lateral soil pressure and the pore water pressure analysis, so that the informatization degree of foundation pit construction is improved.
In some embodiments, as shown in fig. 4, the horizontal distance L2 between the monitoring point (coinciding with the position 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 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 around the enclosure wall.
In the embodiment of the invention, the pressure monitoring device can be buried in various modes, and deep foundation pits with different soil properties can be buried in different ways, and the burying method of the pressure monitoring device is described as follows:
in some embodiments, as shown in connection with fig. 1, 5 and 6, in the case of disposing the pressure monitoring device a in the cohesive soil and the sand soil, the cohesive soil may be classified into hard, hard plastic, soft plastic and fluid plastic according to the liquidity index of the soil, and the sand 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 of flow plastic, soft plastic, plastic and hard plastic, loose, slightly dense and medium dense silt and sand soil. As shown in fig. 5, 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 in the passive area 6; as shown in fig. 6, a plurality of pressure monitoring devices a are sequentially penetrated into the ground c from the bottom surface d of the enclosure wall by static pressure in the active area 5 by using a static cone penetration machine. After penetrating into the pressure monitoring device a, the probe rod 1, the box body 2 and the connector 4 are separated, the probe rod 1 is pulled out, so that the cable 10 for testing is led to the ground c from a hollow area in the probe rod, the cable 10 is connected with a receiving instrument of the ground c, and the distance L3 in the horizontal direction is 0.5-1 m when the pressure monitoring device a is buried, so that the cable 10 in each pressure monitoring device a can be protected conveniently.
In some embodiments, as shown in fig. 7 and 8, the method provided by the embodiment of the invention is suitable for hard soil layers such as hard plastic, hard cohesive soil, compact silt soil, sand soil, weathered rock and the like, a geological drilling machine is used for drilling and burying a pressure monitoring device, the geological drilling machine is used for drilling holes in a monitoring area, the aperture of the geological drilling machine is 110-130 m, in some embodiments, the aperture can 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 drilling hole (i.e. a first monitoring point), then clay balls are used for backfilling and compacting to the next monitoring point, and the pressure monitoring device a is sequentially buried from the bottom surface d of the enclosure wall to the bottom surface b of a deep foundation pit in this step in a passive area as shown in fig. 7; referring to fig. 8, the active area sequentially embeds the pressure monitoring devices a from the bottom surface d of the enclosure wall to the ground c in this step. All pressure monitoring devices a are brought to the ground by means of the cable 10, which cable is fitted with the connection requirements of the 485 bus.
The embodiment of the invention also provides a pressure monitoring method of the deep foundation pit, as shown in fig. 9, comprising the following steps:
s1, before a deep foundation pit is excavated, monitoring a plurality of pressure test values at monitoring points according to set time intervals by adopting the pressure monitoring device according to any one of the above steps; the pressure monitoring device can be connected with a measurement and control instrument with a 4G/5G function on the ground through a 485 bus, and can read the horizontal total stress and the pore water pressure by automatically controlling the measurement and control instrument through monitoring cloud platform software interactive access. And 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 measuring and controlling instrument before the deep foundation pit is excavated.
S2, averaging a plurality of pressure test values to obtain a pressure initial value; for example, the average of 3 tests is taken as the initial value of the side soil pressure of the enclosure wall and the pore water pressure.
S3, monitoring real-time pressure values of monitoring points according to set time intervals during construction of the deep foundation pit; during deep foundation pit construction, according to the requirements of design drawings on monitoring frequencies under different construction working conditions, monitoring frequencies are set on a monitoring cloud platform, and the monitoring effective stress shovel horizontal total stress and pore water pressure values at different times are read by a measurement and control instrument and synchronously transmitted to the monitoring cloud platform to serve as monitoring values of lateral soil pressure and pore water pressure of a retaining 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 the pressure change curve.
And S5, sending out an early warning signal under the condition that the pressure change curve exceeds the pressure early warning line. And comparing and judging the monitored lateral soil pressure and pore water pressure change curves along with time with early warning values provided by the design drawing by monitoring cloud platform software, and providing early warning for construction units, design units, construction units, monitoring units and other reference units in time when the monitored values exceed the early warning values.
The embodiment of the invention directly and rapidly tests the in-situ horizontal total stress and the pore water pressure of the foundation soil body by penetrating the pressure monitoring device into the 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 side wall edge of the deep foundation pit can accurately monitor the lateral soil pressure and the pore water pressure by embedding the effective stress shovel, and the embodiment of the invention can solve the monitoring difficulty of the lateral soil pressure and the pore water pressure of the enclosure wall, save the monitoring cost and improve the construction efficiency.
The foregoing description is only of the preferred embodiments 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;
the box body, one end is detachably connected with the probe rod, the other end opposite to the one end is conical, a cavity is arranged in the box body, and a conducting medium is filled in the cavity;
the pressure monitoring assembly comprises an induction membrane and a filter element, wherein the induction membrane and the filter element are arranged on two opposite sides of the cavity and are connected with the box body, the induction membrane is connected with the cable to monitor the stress average value, and the filter element is connected with the cable to monitor the pore water pressure value; wherein the sensing membrane and the filter element close the cavity and the outer surface of the sensing membrane is circular;
a pressure conduit along which the conductive medium is movable under the sensing membrane pressure;
and the miniature pressure sensor is communicated with the pressure conduit to acquire the stress average value of the whole induction membrane.
2. The pressure monitoring device of claim 1, wherein the sensing diaphragm and the filter have the same axis of symmetry, and wherein the outer surface of the sensing diaphragm and the outer surface of the filter are 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 70mm.
5. A pressure monitoring device according to claim 3, wherein the cartridge comprises:
the cylindrical part is internally provided with the cavity, and the axis of the cylindrical part coincides with the symmetry axes of the induction membrane and the filter element; one end of the cylindrical part perpendicular to the axis direction is connected with the probe rod;
and the conical part is connected with the other end of the cylindrical part, which is far away from the probe rod.
6. The pressure monitoring device of claim 5, wherein the diameter of the cylindrical portion is 70-90 mm;
and/or the number of the groups of groups,
the thickness of the cylindrical portion in the axial direction is 10 to 20mm.
7. The pressure monitoring device of claim 5, wherein the taper is smoothly connected to the cylinder.
8. The pressure monitoring method for the deep foundation pit is characterized by comprising the following steps of:
monitoring a plurality of pressure test values at monitoring points at set time intervals by adopting the pressure monitoring device according to any one of claims 1-7 before a deep foundation pit is excavated;
averaging the pressure test values to obtain a pressure initial 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 method of pressure monitoring according to claim 8, further comprising, prior to the excavation of the deep foundation pit:
determining the position of the enclosure wall, and determining the area positioned in the enclosure wall as a passive area and the area positioned outside the enclosure wall as 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 the monitoring points 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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| CN111289159A (en) * | 2018-12-10 | 2020-06-16 | 香港理工大学 | Effective stress box for directly measuring effective stress in saturated soil |
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| US9546940B2 (en) * | 2015-06-03 | 2017-01-17 | Ramesh Chandra Gupta | Test device for determining three-dimensional consolidation properties of soils |
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| JP2000178956A (en) * | 1998-12-17 | 2000-06-27 | Ohbayashi Corp | Ground survey method |
| CN101575847A (en) * | 2009-06-02 | 2009-11-11 | 中铁第四勘察设计院集团有限公司 | Effective stress spade |
| CN103046525A (en) * | 2013-01-09 | 2013-04-17 | 中铁二十一局集团有限公司 | Facility and method for mechanical stability remote intelligent monitoring and three-dimensional early warning of deep foundation pit |
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