CN108507526A - A kind of foundation pit deformation measuring device and its measurement method - Google Patents

Abstract

A foundation pit deformation measuring device and its measuring method, the measuring device includes a steel wire, a spring, an inclination sensor, a displacement sensor, an upper fixing plate and a lower fixing plate, the upper fixing plate is fixed on 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 on 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 is 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 is 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 angle of the steel wire ; Before the measurement starts, the spring and the steel wire are pre-tensioned, and the steel wire and the spring are in a vertically stretched state. The device can replace existing measuring methods such as a total station, saving labor costs.

Description

A 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 foundation pit deformation in real time, belonging to the field of foundation pit deformation measurement.

Background technique

With the continuous advancement of the urbanization process, the space utilization rate of modern cities is getting higher and higher, and the 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 excavation of underground deep foundation pits is necessary for the utilization of a large number of underground spaces such as underground parking lots, underground shopping malls and underground tunnels.

After the excavation of the foundation pit, the horizontal supporting force of the soil is reduced, and the precipitation caused by the excavation of the foundation pit causes the groundwater level to drop and the water level outside the pit is 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 subsidence, lateral deformation, inclination, displacement and even cracking of surrounding important buildings and ground, which will affect important buildings and personnel and construction safety; in addition, considering the existing foundation pit support design methods and geological conditions, the support The protection scheme cannot fully guarantee the absolute safety of the foundation pit engineering. Therefore, monitoring foundation pit construction is very necessary for the safety of surrounding important buildings and personnel as well as foundation pit engineering itself.

At present, most of the methods used in foundation pit monitoring are total station coordinate change method. 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 reflective 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 subsequent deformation monitoring data processing after difference and balance. 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 measuring station is not required to coincide with the previous one, but the three-dimensional measuring station of this measurement must be measured by using the differential datum point coordinate. Afterwards, measure and calculate the coordinate value of each monitoring point of 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 three-dimensional direction is converted into the horizontal displacement value and the vertical settlement value in the normal direction of the edge of the foundation pit.

Foundation pit monitoring has high requirements for data accuracy and monitoring frequency. Although the coordinate change method of the total station is simple to operate, it requires staff to observe one or several cycles a day because of the manual operation. The workload is very large 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 index. In modern urban construction, these shortcomings have brought hidden dangers to 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 an urgent technical problem to be solved by those skilled in the art.

Contents of the invention

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

The present invention realizes its object of the invention and at first provides a kind of foundation pit deformation measuring device, comprises steel wire, spring, inclination sensor, displacement sensor, upper fixing plate and lower fixing plate, and described upper fixing plate is fixed on the upper edge of foundation pit side wall And perpendicular to the side wall of the foundation pit, the bottom end of the steel wire is fixed on 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 is 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 the measurement starts, pre-tighten the spring and steel wire, and make the steel wire and spring in a vertical tension state.

Further, the displacement sensor of the present invention includes a magnetostrictive displacement sensor, a 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. Tie rod type linear displacement sensor, small size, easy installation, diverse output signals, high precision, fast response. The capacitive linear displacement sensor has the advantages of simple structure, high temperature resistance, radiation resistance, high resolution, good dynamic response characteristics and low cost. Through experiments, the above three kinds of displacement sensors are used in this measuring device to measure the vertical displacement with accurate measurement results, convenient installation and strong adaptability.

The invention realizes the purpose of the invention and also provides two methods for measuring the deformation of the foundation pit using the above-mentioned foundation pit deformation measuring device, one of which 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 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=2π(h-d)*θ/360°, and the vertical displacement Y =d, where h is the initial foundation pit depth.

Another method is: 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 displacement of the foundation pit according to the measured angle value θ and displacement value d Displacement Y, 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 foundation pit depth.

Principle of the present invention is:

If the angle value θ≠0 and the displacement value d≥0, it is judged that only horizontal displacement X occurs in the foundation pit, because when only horizontal displacement occurs in the foundation pit, the upper edge of the side wall of the foundation pit will drive the spring and steel wire through the upper fixing plate to generate a whole deflection, and the bottom end of the steel wire is fixed, so the steel wire will deflect relative to the vertical direction, and the angle displayed by the inclination sensor is the rotation angle θ. The wire deflection process may produce very small stretches, which can be ignored (d≥0). Since the horizontal displacement is very small compared with the depth h of the foundation pit, the horizontal displacement X can be approximated by the arc length formula X=2πh*θ/360°, and the horizontal displacement X can also be approximated by the sine formula, X=h *tan theta.

When the vertical displacement of the foundation pit occurs (the foundation pit settlement), the deformation of the steel wire and the spring as a whole in the vertical direction 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 through the displacement sensor. If the angle value θ=0 and the displacement value d≠0, it is determined that only the vertical displacement of the foundation pit occurs, and the vertical displacement Y of the foundation pit can be obtained by measuring the expansion and contraction of the spring through 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°, and can also be approximated by the sine formula, X=h*tanθ vertical displacement Y=d, where h is Initial 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 terms of horizontal displacement is about 2.5mm. The early warning value required for detection of a 15-meter foundation pit in the project is 3mm. Therefore, this measuring device fully meets the requirements for foundation pit measurement. The measurement accuracy of the vertical displacement depends on the displacement sensor, which can be selected according to the 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 stations, which greatly reduces the work intensity of the staff, saves labor costs, high detection accuracy, and low cost; the data can be directly displayed to the detection personnel through the measurement of the inclination sensor. There are no professional requirements for testing personnel; and it can be developed to form remote automatic monitoring without the need for staff to go to the site for monitoring.

2. By cooperating with the inclination sensor and the displacement sensor, 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 spring with an elastic coefficient of 1-2N/mm can ensure that the spring and the steel wire can be fully preloaded in the initial state. When the upper edge of the side wall of the foundation pit produces a horizontal displacement, the steel wire and the spring will tilt as a whole, so that the inclination sensor can be used to measure The angle is obtained to calculate the horizontal displacement at the upper edge of the side wall of the foundation pit; it can also ensure that when the vertical displacement of the foundation pit occurs (the foundation pit settlement), the deformation of the steel wire and the spring as a whole in the vertical direction will be concentrated in the spring part, which can be obtained through the 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 the embodiment of the present invention.

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

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

Fig. 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 the 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 sine formula according to the embodiment of the present invention.

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

Detailed ways

Example

Fig. 1 and Fig. 2 show, a kind of foundation pit deformation measurement device, comprise steel wire (1), spring (2), inclination sensor (3), displacement sensor (4), upper fixed plate (5) and lower fixed plate ( 6), the upper fixing plate (5) is fixed on 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 on the bottom of the foundation pit near the side wall of the foundation pit, and the lower fixing plate ( 6) Fixed on the top of the steel wire (1) and 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), the spring (2) and the displacement sensor (4) The other end of the upper fixed plate (5) is connected with the lower surface; 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), perpendicular to the steel wire ( 1) Placement, which can be used to measure the deflection angle of the steel wire (1); before the measurement starts, pre-tighten the spring (2) and the steel wire (1), and make the steel wire (1) and the spring (2) in a vertical tension state .

The displacement sensor (4) in this example includes a magnetostrictive displacement sensor, a pull rod type linear displacement sensor and a capacitive displacement sensor.

The size of the spring 2 in this example is: outer diameter 8mm, length 30mm, spring wire thick 1mm.

A kind of measuring method of the above-mentioned foundation pit deformation measuring device is: real-time monitoring angle value θ measured by the inclination sensor 3 and displacement value d measured by the 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, and 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 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=2π(h-d)*θ/360°, and the vertical displacement Y =d, where h is the initial foundation pit depth.

Another measurement method of the above-mentioned foundation pit deformation measuring device is: real-time monitoring of the angle value θ measured by the inclination sensor 3 and the displacement value d measured by the 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, and 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 foundation pit depth.

Fig. 3 to Fig. 7 are schematic diagrams of 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 point p of the fixed plate 5 on the upper edge of the side wall of the foundation pit through the spring 2, and the bottom of the steel wire 1 is fixed at point o; at this time op=h, where h is the initial depth of the foundation pit.

If the angle value θ≠0 and the displacement value d≥0, it is judged that only horizontal displacement X occurs in the foundation pit, because when only horizontal displacement occurs in the foundation pit, the upper edge of the side wall of the foundation pit will drive the spring 2 and The steel 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 Figure 3, since the horizontal displacement is very small compared with the depth h of the foundation pit, the horizontal displacement can be approximated by the arc length formula X=2πh*θ/360°. As shown in Figure 4, the horizontal displacement X can also be obtained by the sine formula: X=h*tanθ.

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

Claims (4)

1. a foundation pit deformation measuring device, comprising steel wire (1), spring (2), inclination sensor (3), displacement sensor (4), upper fixed plate (5) and lower fixed plate (6), described upper The fixing plate (5) is fixed on 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 on the bottom of the foundation pit near 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 (3) is 1-2N/mm; the inclination sensor (3) is fixed on the top of the steel bar (1), placed perpendicular to the steel wire (1), and can be used for The deflection angle of the steel wire (1) is measured; before the measurement starts, the spring (2) and the steel wire (1) are preloaded, and the steel wire (1) and the spring (2) are in a vertically stretched state. 2. A foundation pit deformation measuring device according to claim 1, characterized in that: the displacement sensor (4) includes a magnetostrictive displacement sensor, a pull rod type linear displacement sensor and a capacitive displacement sensor. 3. A measuring method of the arbitrary described foundation pit deformation measurement system of claim 1-2, characterized in that: the measured angle value θ and the measured angle value θ of the inclination sensor (3) and the measured value of the displacement sensor (4) are monitored in real time The displacement 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 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=2π(h-d)*θ/360°, and the vertical displacement Y =d, where h is the initial foundation pit depth. 4. A measuring method of the arbitrary described foundation pit deformation measurement system of claim 1-2, characterized in that: the measured angle value θ and the measured angle value θ of the inclination sensor (3) and the measured value of the displacement sensor (4) are monitored in real time The displacement 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=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 foundation pit depth.