CN103046583A - Cone penetration test detection method for cement mixing pile with preset guide pipe - Google Patents

Abstract

The invention discloses a cone penetration test detection method for a cement mixing pile with a preset guide pipe. The method includes the steps: firstly, perpendicularly inserting a PVC (polyvinyl chloride) pipe with the bottom closed into the center of the a cement mixing pile within half an hour after cement mixing pile construction, so that a reserved detection hole is formed; and secondly, continuously detecting the pile body strength of the cement mixing pile by means of cone penetration test detection when the cement mixing pile reaches a certain age. The invention further discloses a cement mixing pile body quality evaluation method. The cone penetration test detection method for the cement mixing pile with the preset guide pipe retains the advantages of convenience in implementation, rapidness and low cost, overcomes the defect that a probe is easy to deflect out of the pile so as to be incapable of detecting the pile body completely, and is capable of effectively guaranteeing the angle of the probe.

Description

A Cement Mixing Pile Static Penetration Testing Method with Preset Conduit

technical field

The invention belongs to the technical field of civil engineering, and in particular relates to a static penetration detection method of a cement mixing pile with a preset conduit.

Background technique

Cement mixing pile is a commonly used reinforcement scheme in soft soil foundation treatment engineering, and pile detection is an important quality link. The current specification stipulates that the testing of cement mixing piles is mainly based on the compressive strength test of drilled core samples, and the sampling ratio is 3%-5%. The core-pulling detection method has a long period, low efficiency, and high cost, and cannot achieve the purpose of quickly detecting the quality of the mixing pile.

The static penetration test can obtain continuous strength characteristic information of the test object, and has the advantages of convenient, fast and low cost implementation. The conventional static penetration method is used to detect cement mixing piles, and the probe is easily deflected out of the pile and cannot completely detect the pile body.

Therefore, a new cement mixing pile detection method is needed to solve the above problems.

Contents of the invention

Purpose of the invention: The present invention aims at the defects of the cement mixing pile detection method in the prior art, and provides a static penetrating sounding detection method of the cement mixing pile with a preset conduit.

Technical solution: In order to solve the above-mentioned technical problems, the static penetrating sounding detection method of the cement mixing pile with preset conduits of the present invention adopts the following technical solution:

A static penetration detection method for cement mixing piles with preset conduits, comprising the following steps:

1) Within half an hour after the construction of the cement mixing pile is completed, a PVC pipe with a closed bottom is vertically inserted into the center of the cement mixing pile to form a reserved detection hole;

2) When the cement mixing pile reaches a certain age, the static penetration detection method is used to continuously detect the pile body strength of the cement mixing pile.

Preferably, the diameter of the PVC pipe in step 1) is 40±1mm.

Preferably, in step 2), the specific steps for continuously detecting the pile body strength of the cement mixing pile by using the static penetration detection method are as follows: the probe is aligned with the center of the reserved detection hole, and the probe is fixed on the touch point. On the probe rod, use a static pressure device to press the probe rod into the cement mixing pile along the PVC pipe at a constant speed, and use the probe to detect the resistance of the cone tip and the resistance of the side wall.

Preferably, it also includes a static data collector, and a wire connects the static data collector and the probe. The static probe data acquisition instrument is used to display the cone tip resistance and side wall resistance measured by the probe.

Preferably, the PVC pipe in step 1) has a cone tip resistance of less than 0.5 MPa, and a side wall resistance of less than 5 kPa.

Preferably, the age of the cement mixing pile described in step 2) is 7 days.

Preferably, the speed at which the probe rod is pressed into the cement mixing pile at a constant speed along the PVC pipe is 0.5-1.2m/min.

The invention also discloses a method for evaluating the quality of cement mixing piles, which includes the following steps:

A, in the test pile stage of the cement mixing pile, the cement mixing pile is detected by the static penetration detection method of the cement mixing pile with the preset conduit according to any one of claims 1-6;

b. Establish a corresponding relationship between the test results obtained in step a and the 28-day core sample compressive strength, and evaluate the pile quality of the pile body of the cement mixing pile.

Invention principle: Since the diameter of the probe is slightly larger than the reserved detection hole, the probe can detect the resistance of the cone tip and the resistance of the side wall at the same time, and establish a corresponding relationship with the compressive strength of the core sample at 28 days to evaluate the pile quality of the pile body. Due to the presence of detection channels, the phenomenon of probe 3 offset caused by factors such as uneven pile strength is avoided, and the detection success rate reaches 100%.

Beneficial effects: the static penetrating sounding detection method of cement mixing piles with preset conduits of the present invention not only retains the advantages of convenience, quickness and low cost, but also solves the defect that the probe is easily deflected and the pile cannot be completely detected. Can effectively guarantee the angle of the probe.

Description of drawings

Fig. 1 is a schematic flow chart of the static penetrating sounding detection method of the cement mixing pile with preset conduits of the present invention.

Fig. 2 is a structural schematic diagram of the cement mixing pile with preset conduits of the present invention.

Detailed ways

Below in conjunction with accompanying drawing and specific embodiment, further illustrate the present invention, should be understood that these embodiments are only for illustrating the present invention and are not intended to limit the scope of the present invention, after having read the present invention, those skilled in the art will understand various aspects of the present invention Modifications in equivalent forms all fall within the scope defined by the appended claims of this application.

Please refer to Fig. 1 and shown in Fig. 2, the static penetration detection method of the cement mixing pile with preset conduit of the present invention, comprises the following steps:

1) Within half an hour after the construction of the cement mixing pile 1 is completed, a PVC pipe 2 with a closed bottom is vertically inserted into the center of the cement mixing pile 1 to form a reserved detection hole; the diameter of the PVC pipe 2 is 40±1mm. The resistance of the cone tip of the PVC pipe 2 is less than 0.5 MPa, and the resistance of the side wall is less than 5 kPa.

2) When the cement mixing pile 1 reaches a certain age, the static penetration detection method is used to continuously detect the pile body strength of the cement mixing pile 1, and the age of the cement mixing pile 1 is 7 days. Among them, the specific steps of continuously detecting the pile body strength of the cement mixing pile 1 using the static penetration detection method are as follows: the probe 3 is aligned with the center of the reserved detection hole, the probe 3 is fixed on the penetration rod 4, and the static pressure device is used. 5 Press the probe rod 4 into the cement mixing pile 1 at a constant speed along the PVC pipe 2, use the probe 3 to detect the resistance of the cone tip and the side wall, connect the wire 6 to the probe 3 and the static detection data acquisition instrument 7, and use the static detection data acquisition instrument 7 shows the measured tip resistance and side wall resistance. Wherein, the pressing speed of the probe rod 4 is 0.5-1.2m/min.

Since the diameter of the probe is slightly larger than the reserved detection hole, the probe can detect the resistance of the cone tip and the resistance of the side wall at the same time, and establish a corresponding relationship with the compressive strength of the core sample at 28 days to evaluate the quality of the pile body. Due to the existence of the detection channel, the phenomenon of probe 3 deviation caused by factors such as uneven pile strength is avoided. Within the scope of the test section, 24 piles were randomly selected from 120 piles for detection, and the detection success rate reached 100%.

The static penetrating detection method of the cement mixing pile 1 with preset conduits of the present invention not only retains the advantages of convenience, quickness, and low cost, but also solves the defect that the probe 3 is easily deflected and the pile cannot be completely detected, and can The angle of the probe 3 is effectively guaranteed.

Example 1

Please refer to Fig. 1 and Fig. 2, the static penetrating sounding detection method of the pile quality of the mixing pile with preset conduits of the present invention is to insert a small-diameter PVC pipe 2 in the center of the pile body in a short time after the construction of the cement mixing pile 1 is completed. , wherein the diameter of the PVC pipe 2 is 40±1 mm, forming a reserved detection hole. At the specified age, the conventional static penetrating method is used to continuously detect the strength of the pile body, wherein the specified age of the cement mixing pile in the present invention is 7 days. The method of presetting the conduit is to insert the PVC pipe 2 with a closed bottom vertically into the PVC pipe 2 with the bottom closed within half an hour after the construction of the cement mixing pile 1. The cement soil has not yet solidified and is still in a liquid state in the center of the pile body. The PVC pipe 2 becomes the reserved inspection hole of the cement-soil pile body. The PVC pipe 2 is an industrial product with low material strength and a diameter slightly smaller than the static probe 3 (about 40mm). The length depends on the length of the pile. The length of the PVC pipe 2 is the same as that of the cement mixing pile 1.

During detection, the probe 3 is aligned with the center of the reserved detection hole, and the static pressure device 5 is used to press the probe 3 with the probe 3 into the detection pile at a constant speed along the PVC pipe 2, wherein the pressing speed is 0.5-1.2 m/mim. Since the diameter of the probe 3 is slightly larger than the reserved detection hole, the probe 3 can detect the cone tip resistance and the side wall resistance at the same time. Point resistance and side wall resistance are used to establish a corresponding relationship with the 28-day core sample compressive strength to evaluate the pile quality of the pile body. Due to the existence of detection channels, the phenomenon of probe 3 deviation caused by factors such as uneven pile strength is avoided. Within the scope of the test section, 24 piles were randomly selected for detection out of 120 piles. The detection results of this method are consistent with those of drilling core pulling. The test results are completely consistent, and the detection success rate reaches 100%, which proves that this method is successful.

In the pile test stage of the mixing pile, the cement mixing pile 1 was tested by the static penetration method and the unconfined compressive strength test of the drilled core sample, combined with the static penetration cone tip resistance and the 28d unconfined compressive strength, the establishment Determine the corresponding relationship between the cone resistance and the unconfined compressive strength of different soil layers under the process, and formulate the standard curve. When the piles are successfully tested and constructed in a large area, the cone tip resistance obtained through static penetration testing can be determined according to the standard curve to determine the 28d unconfined compressive strength and evaluate the quality of the piles.

This method has been tried in engineering, and the engineering application effect is good. It solves the problem of the pile deviation of the probe during static penetration detection, and can quickly and conveniently detect the quality of the pile body. The cost is low, and it has a wide application prospect.

Claims (8)

1. A cement mixing pile static penetration detection method with preset conduit, is characterized in that, comprises the following steps: 1) Within half an hour after the construction of the cement mixing pile is completed, a PVC pipe with a closed bottom is vertically inserted into the center of the cement mixing pile to form a reserved detection hole; 2) When the cement mixing pile reaches a certain age, the static penetration detection method is used to continuously detect the pile body strength of the cement mixing pile. 2. The static penetrating sounding detection method for cement mixing piles with preset conduits according to claim 1, wherein the diameter of the PVC pipe in step 1) is 40±1mm. 3. The static penetration detection method of cement mixing piles with preset conduits as claimed in claim 1, characterized in that, in step 2), the static penetration detection method is used to continuously detect the strength of the pile body of the cement mixing pile The specific steps are as follows: Aim the probe at the center of the reserved detection hole, fix the probe on the probe rod, and press the probe rod into the cement along the PVC pipe at a constant speed by using a static pressure device. For the stirring pile, the probe is used to detect the resistance of the cone tip and the resistance of the side wall. 4 . The static penetration detection method of cement mixing piles with preset conduits according to claim 3 , further comprising a static sounding data collector, and a wire is connected to the static sounding data collector and the probe. 5. The static penetrating sounding detection method of cement mixing piles with preset conduits according to claim 1, characterized in that, in step 1), the resistance of the cone tip of the PVC pipe is less than 0.5 MPa, and the resistance of the side wall is less than 5 kPa. 6. The static penetrating sounding detection method for cement mixing piles with preset conduits according to claim 1, characterized in that the age of the cement mixing piles in step 2) is 7 days. 7. The static penetration detection method of cement mixing piles with preset conduits according to claim 3, wherein the penetration speed of the penetration rod is pressed into the cement mixing pile at a constant speed along the PVC pipe. 0.5-1.2m/mim. 8. A quality evaluation method of cement mixing pile, is characterized in that, comprises the following steps: A, in the test pile stage of the cement mixing pile, the cement mixing pile is detected by the static penetration detection method of the cement mixing pile with the preset conduit according to any one of claims 1-7; b. Establish a corresponding relationship between the test results obtained in step a and the 28-day core sample compressive strength, and evaluate the pile quality of the pile body of the cement mixing pile.

Images