CN108507526B - Foundation pit deformation measuring device and measuring method thereof - Google Patents

Abstract

A foundation pit deformation measuring device and a measuring method thereof are disclosed, the measuring device comprises a steel wire, a spring, an inclination angle sensor, a displacement sensor, an upper fixing plate and a lower fixing plate, the upper fixing plate is fixed at the upper edge of the side wall of a foundation pit and is vertical to the side wall of the foundation pit, the bottom end of the steel wire is fixed at the bottom of the foundation pit close to the side wall of the foundation pit, the lower fixing plate is fixed at the top of the steel wire and is vertical to the steel wire, one ends of the spring and the displacement sensor are connected with the upper surface of the lower fixing plate, and; the elastic coefficient of the spring is 1-2N/mm; the inclination angle sensor is fixed at the top end of the steel wire, is arranged perpendicular to the steel wire and can be used for measuring the deflection angle of the steel wire; and (3) pre-tightening the spring and the steel wire before the measurement is started, and enabling the steel wire and the spring to be in a vertical stretching state. The device can replace the existing measuring methods such as a total station and the like, and the labor cost is saved.

Description

A kind of foundation pit deformation measuring device and its measuring method

technical field

The invention relates to a measuring device and a measuring method capable of monitoring the deformation of a foundation pit in real time, and belongs to the field of measuring the deformation of a foundation pit.

Background technique

With the continuous advancement of urbanization, the utilization rate of space in modern cities is getting higher and higher, and the phenomenon of urban congestion is becoming more and more serious. The development and utilization of urban underground space has become an inevitable trend of urban development. The use of a large number of underground spaces such as underground parking lots, underground shopping malls and underground tunnels has resulted in the excavation of deep underground foundation pits.

After the excavation of the foundation pit, the horizontal support force of the soil body is reduced, and the precipitation caused by the excavation of the foundation pit causes the groundwater level to decrease and the water level outside the pit to be unbalanced, resulting in a large water pressure difference, which increases the self-weight stress in the soil and many other factors. It may lead to the subsidence, lateral deformation, tilt, displacement, and even cracking of the surrounding important buildings and ground, affecting important buildings, personnel, and construction safety; in addition, considering the existing foundation pit support design method and geological conditions, support The protection scheme cannot completely guarantee the absolute safety of the foundation pit project. Therefore, it is very necessary to monitor the safety of the foundation pit construction for the surrounding important buildings and personnel as well as the foundation pit project itself.

At present, most of the methods used in foundation pit monitoring are the coordinate change method of the total station. The total station coordinate change method is to set several differential reference points in any stable and firm place outside the influence of foundation pit construction, and install permanent reflecting prisms on the differential reference points and deformation monitoring points. According to the shape of the foundation pit, a measuring station is arbitrarily set up to observe the three-dimensional coordinates of each point with the direction. The data of multiple observations are used as the benchmark for future deformation monitoring data processing after difference and adjustment. The three-dimensional direction observation of horizontal displacement and vertical displacement is carried out in one or several cycles per day; starting from the second observation, each station does not need to coincide with the previous one, but the three-dimensional measurement of the station must be measured by using the differential reference point. coordinate. Then, measure and calculate the coordinate value of each monitoring point this time. The differential adjustment calculates the deformation value of each monitoring point in the two directions of horizontal displacement and the deformation value of the settlement direction, that is, the deformation value in the three-dimensional direction. Then, according to the shape of the edge of the foundation pit, the displacement value in the 3-dimensional direction is converted into the horizontal displacement value and the vertical settlement value in the normal direction of the foundation pit edge.

Foundation pit monitoring has high requirements on data accuracy and monitoring frequency. Although the total station coordinate change method is simple to operate, because of manual operation, it requires staff to observe in one or several cycles per day, which is very labor-intensive and cannot be realized. Real-time measurement, and prone to measurement errors. Moreover, the total station coordinate change method can only measure the horizontal displacement of the foundation pit, but cannot measure the vertical settlement of the foundation pit, and the vertical settlement of the foundation pit is also a very important safety indicator. In modern urban construction, these shortcomings have brought hidden safety hazards in the construction of deep foundation pits, and many engineering accidents have been caused due to the imperfection of these detection systems. Therefore, researching and designing an efficient, accurate, stable, and real-time foundation pit deformation monitoring technology has become a technical problem that those skilled in the art need to solve urgently.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a measuring device and method for measuring the deformation of a foundation pit. The foundation pit measurement device and the measurement method can monitor the deformation of the foundation pit efficiently, accurately and stably.

The present invention achieves its purpose of firstly providing a foundation pit deformation measurement device, including steel wire, spring, inclination sensor, displacement sensor, an upper fixing plate and a lower fixing plate, and the upper fixing plate is fixed at the upper edge of the side wall of the foundation pit And perpendicular to the side wall of the foundation pit, the bottom end of the steel wire is fixed at the bottom of the foundation pit close to the side wall of the foundation pit, the lower fixing plate is fixed on the top of the steel wire and perpendicular to the steel wire, and one end of the spring and the displacement sensor is connected to the upper surface of the lower fixing plate. , the other end of the spring and the displacement sensor are connected to the lower surface of the upper fixing plate; the elastic coefficient of the spring is 1-2N/mm; the inclination sensor is fixed on the top of the steel wire, placed perpendicular to the steel wire, and can be used to measure the deflection of the steel wire angle; before starting the measurement, preload the spring and wire and keep the wire and spring in vertical tension.

Further, the displacement sensor of the present invention includes a magnetostrictive displacement sensor, a pull rod type linear displacement sensor and a capacitive displacement sensor.

The magnetostrictive sensor has high precision and can withstand high temperature, high pressure and strong vibration; it operates without wear and has good stability. The pull rod type linear displacement sensor is small in size, easy to install, diversified in output signal, high in precision and fast in response. Capacitive linear displacement sensor has simple structure, high temperature resistance, radiation resistance, high resolution, good dynamic response characteristics and low cost. Experiments show that the above three displacement sensors are used in the measuring device to measure the vertical displacement with accurate measurement results, convenient installation and strong adaptability.

The invention achieves its purpose and also provides two methods for measuring the deformation of the foundation pit using the above-mentioned foundation pit deformation measuring device. One of the methods is: real-time monitoring of the angle value θ measured by the inclination sensor and the displacement measured by the displacement sensor. value d, and determine the horizontal displacement X and vertical displacement Y of the foundation pit according to the measured angle value θ and displacement value d. The specific determination method is:

If the angle value θ≠0 and the displacement value d≥0, it is determined that the foundation pit only has a horizontal displacement X, X=2πh*θ/360°, where h is the initial foundation pit depth;

If the angle value θ=0 and the displacement value d≠0, it is determined that only the vertical displacement Y occurs in the foundation pit, and Y=d;

If the angle value θ≠0 and the displacement value d<0, it is determined that the foundation pit has both a horizontal displacement X and a vertical displacement Y, the horizontal displacement X=2π(h-d)*θ/360°, and the vertical displacement Y =d, where h is the initial foundation pit depth.

Another method is to monitor the angle value θ measured by the inclination sensor and the displacement value d measured by the displacement sensor in real time, and determine the horizontal displacement X and vertical direction of the foundation pit according to the measured angle value θ and displacement value d. The displacement Y, its specific determination method is:

If the angle value θ≠0 and the displacement value d≥0, it is determined that the foundation pit only has a horizontal displacement X, X=h*tanθ, where h is the initial depth of the foundation pit;

If the angle value θ=0 and the displacement value d≠0, it is determined that only the vertical displacement Y occurs in the foundation pit, and Y=d;

If the angle value θ≠0 and the displacement value d<0, it is determined that both the horizontal displacement X and the vertical displacement Y have occurred in the foundation pit, the horizontal displacement X=(h-d)*tanθ, and the vertical displacement Y=d, where , h is the initial depth of foundation pit.

The principle of the present invention is:

If the angle value θ≠0 and the displacement value d≥0, it is determined that the foundation pit only has a horizontal displacement X, because when the foundation pit only has a horizontal displacement, the upper edge of the sidewall of the foundation pit will drive the spring and the steel wire through the upper fixing plate to form a whole. The bottom end of the wire is fixed, so the wire will deflect relative to the vertical direction, and the angle displayed by the inclination sensor is the rotation angle θ. The deflection process of the wire may produce a very small stretch, which is negligible (d≥0). Since the horizontal displacement is very small compared with the depth h of the foundation pit, the horizontal displacement X can be obtained approximately by the arc length formula X=2πh*θ/360°, and the horizontal displacement X can also be approximately obtained by the sine formula, X=h *tanθ.

When the foundation pit has vertical displacement (foundation pit settlement), the vertical deformation of the steel wire and the spring as a whole will be concentrated in the spring part, so the vertical displacement of the foundation pit can be obtained by measuring the expansion and contraction of the spring by the displacement sensor. If the angle value θ=0 and the displacement value d≠0, it is determined that the foundation pit only has vertical displacement, and the vertical displacement Y of the foundation pit can be obtained by measuring the expansion and contraction of the spring by the displacement sensor, Y=d; d is the displacement sensor measured value.

If the angle value θ≠0 and the displacement value d<0, it is determined that both the horizontal displacement X and the vertical displacement Y have occurred in the foundation pit. The horizontal displacement X of the foundation pit is obtained by the arc length formula, X=2π(h-d)*θ/360°, which can also be obtained approximately by the sine formula, X=h*tanθ The vertical displacement Y=d, where h is Initial foundation pit depth.

After calculation, using an inclination sensor with an accuracy of 0.01°, when the depth of the foundation pit is 15 meters, the measurement accuracy of the above two measurement methods in the horizontal displacement is about 2.5mm. In the project, the early warning value of the 15-meter foundation pit required to be detected is 3mm. Therefore, this measuring device fully meets the requirements of foundation pit measurement. The measurement accuracy of vertical displacement depends on the displacement sensor, which can be selected according to needs.

Compared with the prior art, the beneficial effects of the above-mentioned foundation pit deformation measuring device are:

1. The device can replace the existing measurement methods such as total station, which greatly reduces the work intensity of the staff, saves the labor cost, and has high detection accuracy and low cost; through the inclination sensor measurement, the data can be visually displayed to the testing personnel, and the There are no professional requirements for testing personnel; and remote automatic monitoring can be developed without the need for staff to monitor on-site.

2. By using the inclination sensor and displacement sensor together, the horizontal displacement and vertical displacement can be measured in real time, and the displacement type and displacement data can be determined according to the measurement data, and the deformation of the foundation pit in all directions can be comprehensively determined.

4. The selection of springs with an elastic coefficient of 1-2N/mm can ensure that the springs and steel wires can be fully pre-tightened in the initial state, and the steel wires and springs are inclined as a whole when horizontal displacement occurs at the upper edge of the sidewall of the foundation pit. Obtain the angle and calculate the horizontal displacement at the upper edge of the sidewall of the foundation pit; it can also ensure that when the foundation pit undergoes vertical displacement (foundation pit settlement), the vertical deformation of the steel wire and the spring as a whole will be concentrated in the spring part, which can be adjusted by displacement The sensor measures the expansion and contraction of the spring to obtain the vertical displacement of the foundation pit.

Description of drawings

FIG. 1 is a schematic diagram of the overall arrangement of an embodiment of the present invention.

FIG. 2 is an enlarged schematic view of part A in FIG. 1 .

FIG. 3 is a schematic diagram of the principle of measuring the horizontal displacement X of the foundation pit by the arc length formula according to an embodiment of the present invention.

FIG. 4 is a schematic diagram of the principle of measuring the horizontal displacement X of a foundation pit by a sinusoidal formula according to an embodiment of the present invention.

FIG. 5 is a schematic diagram of the principle of measuring the vertical displacement Y of a foundation pit according to an embodiment of the present invention.

6 is a schematic diagram of the principle of measuring the horizontal displacement X and the vertical displacement Y of the foundation pit by the arc length formula according to an embodiment of the present invention.

FIG. 7 is a schematic diagram of the principle of measuring the horizontal displacement X and the vertical displacement Y of the foundation pit by the sinusoidal formula according to an embodiment of the present invention.

In the figure, M represents the side wall of the foundation pit.

Detailed ways

Example

Figures 1 and 2 show a foundation pit deformation measurement device, comprising a steel wire 1, a spring 2, an inclination sensor 3, a displacement sensor 4, an upper fixing plate 5 and a lower fixing plate 6, and the upper fixing plate 5 is fixed on the foundation The upper edge of the pit side wall is perpendicular to the side wall of the foundation pit; the bottom end of the steel wire 1 is fixed at the bottom of the foundation pit near the side wall of the foundation pit, and the lower fixing plate 6 is fixed on the top of the steel wire 1 and is perpendicular to the steel wire 1, the spring 2 and the displacement sensor One end of 4 is connected to the upper surface of the lower fixing plate 6, and the other end of the spring 2 and the displacement sensor 4 is connected to the lower surface of the upper fixing plate 5; the elastic coefficient of the spring 2 is 1-2N/mm; the inclination sensor 3 Fixed on the top of wire 1 and placed perpendicular to wire 1, it can be used to measure the deflection angle of wire 1; before starting the measurement, pre-tighten spring 2 and wire 1, and make wire 1 and spring 2 in a vertical tension state.

In this example, the displacement sensor 4 includes a magnetostrictive displacement sensor, a rod-type linear displacement sensor and a capacitive displacement sensor.

In this example, the size of the spring 2 is as follows: the outer diameter is 8 mm, the length is 30 mm, and the thickness of the spring wire is 1 mm.

A kind of measuring method of above-mentioned foundation pit deformation measuring device is: real-time monitoring angle value θ measured by inclination sensor 3 and displacement value d measured by displacement sensor 4, and according to the measured angle value θ and displacement The value d determines the horizontal displacement X and vertical displacement Y of the foundation pit. The specific determination method is:

If the angle value θ≠0 and the displacement value d≥0, it is determined that the foundation pit only has a horizontal displacement X, X=2πh*θ/360°, where h is the initial foundation pit depth;

If the angle value θ=0 and the displacement value d≠0, it is determined that only the vertical displacement Y occurs in the foundation pit, and Y=d;

If the angle value θ≠0 and the displacement value d<0, it is determined that the foundation pit has both a horizontal displacement X and a vertical displacement Y, the horizontal displacement X=2π(h-d)*θ/360°, and the vertical displacement Y =d, where h is the initial foundation pit depth.

Another kind of measurement method of the above-mentioned foundation pit deformation measuring device is: real-time monitoring angle value θ measured by inclination sensor 3 and displacement value d measured by displacement sensor 4, and according to the measured angle value θ and The displacement value d determines the horizontal displacement X and vertical displacement Y of the foundation pit. The specific determination method is:

If the angle value θ≠0 and the displacement value d≥0, it is determined that the foundation pit only has a horizontal displacement X, X=h*tanθ, where h is the initial depth of the foundation pit;

If the angle value θ=0 and the displacement value d≠0, it is determined that only the vertical displacement Y occurs in the foundation pit, and Y=d;

If the angle value θ≠0 and the displacement value d<0, it is determined that both the horizontal displacement X and the vertical displacement Y have occurred in the foundation pit, the horizontal displacement X=(h-d)*tanθ, and the vertical displacement Y=d, where , h is the initial depth of foundation pit.

FIG. 3 to FIG. 7 are schematic diagrams showing the principle of measuring the horizontal displacement X and the vertical displacement Y of the foundation pit by the above two measurement methods. In the initial state, the top of the steel wire 1 is fixed at the p point of the fixing plate 5 on the upper edge of the side wall of the foundation pit by the spring 2, and the bottom of the steel wire 1 is fixed at the point o; at this time op=h, h is the initial depth of the foundation pit.

If the angle value θ≠0 and the displacement value d≥0, it is determined that the foundation pit only has a horizontal displacement X, because when the foundation pit only has a horizontal displacement, the upper edge of the sidewall of the foundation pit will drive the springs 2 and 2 through the upper fixing plate 5 as a whole. The wire 1 deflects relative to the vertical direction, the top of the spring 2 moves to point q, and the angle displayed by the inclination sensor 3 is the deflection angle θ. The deflection process of the steel wire 1 may produce a very small stretch, which is negligible (d≥0). As shown in FIG. 3 , since the horizontal displacement is very small compared with the depth h of the foundation pit, the horizontal displacement can be approximately obtained by the arc length formula X=2πh*θ/360°. As shown in FIG. 4 , the horizontal displacement X can also be obtained by the sine formula: X=h*tanθ.

When the foundation pit has vertical displacement (foundation pit settlement), the overall vertical deformation of the steel wire 1 and the spring 2 will be concentrated in the spring 2 part, so the displacement sensor 4 is used to measure the expansion and contraction of the spring 2, and the vertical direction of the foundation pit can be obtained. to displacement. As shown in Figure 5, if the angle value θ=0 and the displacement value d≠0, it is determined that the foundation pit only has vertical displacement, and the vertical displacement Y of the foundation pit can be obtained by measuring the expansion and contraction amount of the spring 2 by the displacement sensor 4, Y=d; d is the measurement value of the displacement sensor 4 .

If the angle value θ≠0 and the displacement value d<0, it is determined that both the horizontal displacement X and the vertical displacement Y have occurred in the foundation pit. As shown in Figure 6, the horizontal displacement X of the foundation pit is obtained by the arc length formula, X=2π(h-d)*θ/360°, and the vertical displacement Y=d, where h is the initial foundation pit depth. As shown in FIG. 7 , the horizontal displacement X can also be obtained by the sine formula: X=(h-d)*tanθ, and the vertical displacement Y=d, where h is the initial foundation pit depth.

Claims (4)

1. A foundation pit deformation measurement device, comprising a steel wire (1), a spring (2), an inclination sensor (3), a displacement sensor (4), an upper fixing plate (5) and a lower fixing plate (6), the upper The fixing plate (5) is fixed at the upper edge of the side wall of the foundation pit and is perpendicular to the side wall of the foundation pit; the bottom end of the steel wire (1) is fixed at the bottom of the foundation pit close to the side wall of the foundation pit, and the lower fixing plate (6) is fixed on the steel wire ( 1) The top is perpendicular to the steel wire (1), one end of the spring (2) and the displacement sensor (4) is connected to the upper surface of the lower fixing plate (6), and the other end of the spring (2) and the displacement sensor (4) is fixed to the upper surface. The lower surface of the plate (5) is connected; the elastic coefficient of the spring (2) is 1-2N/mm; the inclination sensor (3) is fixed on the top of the steel wire (1), placed perpendicular to the steel wire (1), and can be used for The deflection angle of the wire (1) is measured; before the measurement is started, the spring (2) and the wire (1) are pre-tensioned, and the wire (1) and the spring (2) are in a state of vertical tension. 2 . A foundation pit deformation measurement device according to claim 1 , wherein the displacement sensor ( 4 ) comprises a magnetostrictive displacement sensor, a pull rod type linear displacement sensor and a capacitive displacement sensor. 3 . 3. a measuring method of the arbitrary described foundation pit deformation measuring device of claim 1-2, it is characterized in that: real-time monitoring inclination sensor (3) measured angle value θ and displacement sensor (4) measured The displacement value d is determined, and the horizontal displacement X and vertical displacement Y of the foundation pit are determined according to the measured angle value θ and displacement value d. The specific determination method is: If the angle value θ≠0 and the displacement value d≥0, it is determined that the foundation pit only has a horizontal displacement X, X=2πh*θ/360°, where h is the initial foundation pit depth; If the angle value θ=0 and the displacement value d≠0, it is determined that only the vertical displacement Y occurs in the foundation pit, and Y=d; If the angle value θ≠0 and the displacement value d<0, it is determined that the foundation pit has both a horizontal displacement X and a vertical displacement Y, the horizontal displacement X=2π(h-d)*θ/360°, and the vertical displacement Y =d, where h is the initial foundation pit depth. 4. the measuring method of the arbitrary described foundation pit deformation measuring device of claim 1-2, it is characterized in that: real-time monitoring inclination sensor (3) measured angle value θ and displacement sensor (4) measured The displacement value d is determined, and the horizontal displacement X and vertical displacement Y of the foundation pit are determined according to the measured angle value θ and displacement value d. The specific determination method is: If the angle value θ≠0 and the displacement value d≥0, it is determined that the foundation pit only has a horizontal displacement X, X=h*tanθ, where h is the initial depth of the foundation pit; If the angle value θ=0 and the displacement value d≠0, it is determined that only the vertical displacement Y occurs in the foundation pit, and Y=d; If the angle value θ≠0 and the displacement value d<0, it is determined that both the horizontal displacement X and the vertical displacement Y have occurred in the foundation pit, the horizontal displacement X=(h-d)*tanθ, and the vertical displacement Y=d, where , h is the initial depth of foundation pit.

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