Method for Layered Detection of Foundation Pit Bottom Plate Rebound in Thick Soil Layer

Abstract

The present invention discloses a method for layered detection of the rebound of the foundation pit floor in thick soil layers, and the steps are as follows: (1) Loft the rebound points on the foundation pit floor; and vertically drill prefabricated holes; (2) Lower the detection device into the prefabricated holes according to the depth of the prefabricated holes; (3) Fix the vertical rod through the expansion ring; (4) Deflate the expansion ring of the next layer and start detecting the height of the benchmark; (5) If necessary, detect the change in the height of the benchmark at regular intervals; thus, the rebound detection of this layer is completed; (6) Conduct the rebound detection of the next layer; (7) Repeat the above steps (3)-(5) until the rebound detection of the soil of the bottommost layer ends; The advantages of the present invention are: 1. It overcomes the decrease in measurement accuracy caused by the constraint of the soil on other layers on the vertical rod, and can accurately measure the soil rebound of this layer; 2. The vertical rod will maintain a vertical state; 3. The split vertical rod combination structure can adapt to the requirements of different height layers.

Description

Technical Field

[0001] The present invention relates to the field of construction technology, and particularly to a method for detecting the rebound of a foundation pit bottom slab. Background Art

[0002] After the foundation pit is formed, due to the influence of the soil pressure on the side of the foundation pit, a bulge (i.e., rebound) will be formed at the bottom of the foundation pit. The measurement of this bulge has a great impact on building design and construction. The simplest method for measuring the rebound is to bury a measuring vertical pole at the bottom of the foundation pit and judge the rebound amount of the bottom of the foundation pit by observing the height change of the vertical pole. The defects of this method are as follows: 1. It is impossible to detect the rebound amounts of different layers separately, but only to measure the rebound amount of the entire bottom; 2. Since the vertical pole is buried at the bottom of the foundation pit, the extrusion forces of the soil on the side of the vertical pole are different. When the bottom of the foundation pit rebounds, it is possible that the vertical pole is squeezed by the soil and does not rise accordingly, thus affecting the measurement accuracy. 3. It is impossible to ensure the verticality of the vertical pole and the foundation pit, and the operation process disturbs the vertical pole, and these disturbances also affect the measurement accuracy. In addition, Patent Application No. CN2017108398650 discloses a method for detecting the rebound amount of the bottom of a foundation pit. Before the foundation pit is excavated, by drilling holes, burying protection pipes, installing sensing optical cables, filling bentonite in the holes, and connecting the sensing optical cables and the sensing optical cable strain demodulator, a device for detecting the rebound amount of the bottom of the foundation pit is formed. The strain values of the sensing optical cables at each depth measurement point within the depth range of the drilled holes under the bottom surface of the foundation pit are measured. During or after the excavation of the foundation pit, the strain values of the sensing optical cables at each depth measurement point within the depth range of the drilled holes under the bottom surface of the foundation pit are measured several times again; the εj,i~hi relationship curve and the ΔSj,i~hi relationship curve are drawn, so as to obtain the rebound amounts and their distributions of each soil layer and each measurement point under the foundation pit. The present invention can automatically observe the magnitudes and distributions of the rebound amounts of each soil layer under the foundation pit, accurately measure the strain changes of each measurement point, and calculate the rebound amounts of each measurement point. Since this method uses a sensing optical cable for measurement and the sensing optical cable is buried in the soil, the extrusion of the entire sensing optical cable by the soil will cause a part of the sensing optical cable not to rise with the soil, thus affecting the measurement accuracy. Summary of the Invention

[0003] In order to solve the above technical problems, the object of the present invention is to provide a method for detecting the rebound of a foundation pit bottom slab in thick soil layers by layers, and the steps are as follows:

[0004] (1). Loft the rebound points of the foundation pit bottom slab; and vertically drill prefabricated holes;

[0005] (2). Lower the detection device into the prefabricated hole according to the depth of the prefabricated hole. The distance a from the upper end of the expansion ring of the detection layer to the detection layer is 20-30 cm, and pay attention to leaving a space between the lowermost vertical pole and the bottom of the prefabricated hole;

[0006] (3) First, inflate the corresponding expansion ring of the next layer to 0.8-0.9MP, and then inflate the expansion ring of this layer to 0.8-0.9MP. In this way, the pole can be fixed; then set the benchmark for detection above the pole and calibrate the verticality of the benchmark; or detect through the marking points set on the side of the pole of the upper layer;

[0007] (4) Deflate the expansion ring of the next layer until the pole is stable, and then start to check the height of the pole;

[0008] (5) If necessary, retest the height change of the benchmark after a certain period of time; at this point, the rebound test of the layer is completed;

[0009] (6) Perform rebound detection on the next layer:

[0010] First, inflate the expansion rings of the next layer and the next layer to 0.8-0.9MP, then deflate the expansion rings of the inspection layer just inspected, and remove the poles of the inspection layer; then excavate the foundation pit and drain the soil;

[0011] (7) Repeat the above steps (3) to (5) until the soil rebound test of the bottom layer is completed;

[0012] The detection device includes a plurality of vertical poles connected by connecting joints, each vertical pole corresponding to a layer; each vertical pole is provided with an expansion ring, and the expansion ring is connected to the air intake pipe and the exhaust pipe; the inner diameter of the expanded expansion ring clamps the outer diameter of the vertical pole, and the outer diameter of the expansion ring abuts against the inner diameter of the prefabricated hole; at the position of each connecting joint, the lower end of the upper vertical pole and the upper end of the lower vertical pole are fitted with a radial constraint tube, and the inner diameter of the radial constraint tube matches the outer diameter of the vertical pole.

[0013] The vertical rod is modular and includes multiple sections connected by threads.

[0014] A mark is set on the side of the vertical pole, and an observation instrument determines the rebound of the ground of this layer by observing the up and down displacement of the mark.

[0015] The distance between the upper end of the expansion ring and the detection layer is 20-30 cm.

[0016] There is space between the lowest pole and the bottom of the prefabricated hole.

[0017] The advantages of the present invention are as follows: 1. Since different levels correspond to different vertical rods, and the vertical rods are internally connected to the level through expansion rings and are in a suspended state, the vertical rods do not contact other levels, thus overcoming the decrease in measurement accuracy caused by the constraint of the soil of other levels on the vertical rods and enabling accurate measurement of the soil rebound of this level; 2. Exactly because the vertical rods are only restricted by the expansion rings of the measured level and are suspended in the prefabricated holes, affected by gravity, the vertical rods will maintain a vertical state; 3. The split-type vertical rod combination structure can adapt to the requirements of levels with different heights. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic structural diagram of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0019] The following specifically describes the present invention with reference to the drawings. As shown in the figure, the detection device of the present invention includes multiple sections of vertical rods 2 connected by a connection joint 8. Each section of the vertical rod corresponds to a stratification. For example, Figure 1 in the different sub-level surfaces 3 divide the foundation pit bottom soil into several layers; an expansion ring 4 is provided for each section of the vertical rod. The expansion ring 4 is connected to an air inlet pipe 5 and an exhaust pipe 6, and the air inlet pipe is connected to an air pump; the inner diameter of the expanded expansion ring clamps the outer diameter of the vertical rod, and the outer diameter of the expansion ring abuts against the inner diameter of the prefabricated hole 1, thus fixing the vertical rod at a certain level of the foundation pit; at the position of each connection joint 8, the lower end of the upper vertical rod and the upper end of the lower vertical rod are sleeved with a radial restraint tube 7. The inner diameter of the radial restraint tube matches the outer diameter of the vertical rod. In this way, it is ensured that the upper and lower vertical columns are within a cylinder; the connection joint can be a universal joint or a universal shaft connector, and commercially available products can be used.

[0020] To adapt to the requirements of different storey heights, the vertical rod is of a combined type and includes multiple segments connected by threads. For example, Figure 1 the upper section 21 of the vertical rod and the lower section 22 of the vertical rod are connected to the middle section of the vertical rod through threads 23;

[0021] For the convenience of detection, marks are provided on the side of the vertical rod, and the observation instrument determines the rebound of the ground of this level by observing the up and down displacement of the marks.

[0022] The distance a between the upper end of the expansion ring and the detected level is 20 - 30 cm.

[0023] There is a space left between the lowermost vertical rod and the bottom of the prefabricated hole. For example, Figure 1 there is a gap b between the lower end of the lowermost vertical rod and the bottom of the foundation pit to ensure that the vertical rod is in a suspended state.

[0024] The detection method of the present invention is as follows:

[0025] (1). Lofting the rebound points of the foundation pit bottom; and vertically drilling prefabricated holes;

[0026] (2) Lower the detection device into the prefabricated hole according to the depth of the prefabricated hole. The distance a between the upper end of the expansion ring of the detection layer and the detection layer is 20-30cm, and make sure there is space between the lowest pole and the bottom of the prefabricated hole;

[0027] (3) First, inflate the corresponding expansion ring of the next layer to 0.8-0.9MP, and then inflate the expansion ring of this layer to 0.8-0.9MP. In this way, the pole can be fixed; then, a benchmark for detection and benchmark verticality correction can be set above the pole; or detection can be performed through the marking points set on the side of the pole of the previous layer;

[0028] (4) Deflate the expansion ring of the next layer until the pole is stable, and then start to check the height of the pole;

[0029] (5) If necessary, retest the height change of the benchmark after a certain period of time; at this point, the rebound test of the layer is completed;

[0030] (6) Perform rebound detection on the next layer:

[0031] First, inflate the expansion rings of the next layer and the next layer to 0.8-0.9MP, then deflate the expansion rings of the inspection layer just inspected, and remove the poles of the inspection layer; then excavate the foundation pit and drain the soil;

[0032] (7) Repeat the above steps (3) to (5) until the soil rebound test of the bottom layer is completed.

Claims

1. A method for layered detection of the rebound of the foundation pit bottom plate in thick soil layers, characterized in that Here are the steps: (1) Locate the rebound point of the foundation pit bottom plate and drill prefabricated holes vertically; (2) Lower the detection device into the prefabricated hole according to the depth of the prefabricated hole. The distance a between the upper end of the expansion ring of the detection layer and the detection layer is 20-30cm, and make sure there is space between the lowest pole and the bottom of the prefabricated hole; (3) First, inflate the corresponding expansion ring of the next layer to 0.8-0.9MP, and then inflate the expansion ring of this layer to 0.8-0.9MP. In this way, the pole can be fixed; then set the benchmark for detection above the pole and calibrate the verticality of the benchmark; or detect through the marking points set on the side of the pole of the upper layer; (4) Deflate the expansion ring of the next layer until the pole is stable, and then start to check the height of the pole; (5) If necessary, retest the height change of the benchmark after a certain period of time; at this point, the rebound test of the layer is completed; (6) Perform rebound detection on the next layer: First, inflate the expansion rings of the next layer and the next layer to 0.8-0.9MP, then deflate the expansion rings of the inspection layer just inspected, and remove the poles of the inspection layer; then excavate the foundation pit and drain the soil; (7) Repeat the above steps (3) to (5) until the soil rebound test of the bottom layer is completed; The detection device includes a plurality of vertical poles connected by connecting joints, each vertical pole corresponding to a layer; each vertical pole is provided with an expansion ring, and the expansion ring is connected to the air intake pipe and the exhaust pipe; the inner diameter of the expanded expansion ring clamps the outer diameter of the vertical pole, and the outer diameter of the expansion ring abuts against the inner diameter of the prefabricated hole; at the position of each connecting joint, the lower end of the upper vertical pole and the upper end of the lower vertical pole are fitted with a radial constraint tube, and the inner diameter of the radial constraint tube matches the outer diameter of the vertical pole.

2. The method for layered detection of the rebound of the foundation pit bottom slab in a thick soil layer according to claim 1, characterized in that: The vertical rod is modular and includes multiple sections connected by threads.

3. The method for layered detection of the rebound of the foundation pit bottom slab in a thick soil layer according to claim 1, wherein: A mark is set on the side of the vertical pole, and an observation instrument determines the rebound of the ground of this layer by observing the up and down displacement of the mark.

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