A dynamic correction method for controlling the penetration of hammer during hammer pile construction

Abstract

The present invention aims to provide a dynamic correction formula for controlling the penetration of hammer piles during construction, which can be dynamically corrected according to the deviation of the actual pile length during construction, and changes the penetration constant value control method commonly used in current engineering practice into a dynamic correction method. The correction method of the present invention includes the following steps: Step A, obtaining the characteristic value of the designed single pile bearing capacity, the unit of which is kN; Step B, obtaining the characteristic value of the calculated single pile bearing capacity, the unit of which is kN, and the value is calculated based on the actual pile length and the soil layer parameters provided in the geological survey report; Step C, according to the design drawings, obtaining the penetration control index of each of the last three arrays, the unit of which is mm / array; Step D, according to the above three values, the corrected penetration control index of each of the last three arrays is obtained by the following formula, the unit of which is mm / array, and the formula is, The present invention is applied to the technical field of pipe pile construction.

Description

Technical Field

[0001] The present invention is applied to the technical field of pipe pile construction, and particularly relates to a dynamic correction method for controlling the penetration of hammers during hammer pile construction. Background Art

[0002] Pile foundations effectively solve and prevent the problem and risk of uneven settlement of buildings and the resulting collapse of buildings by transferring the load of the upper buildings to the underground bearing layer. Therefore, they are widely used in civil engineering. In engineering applications, piles are mainly divided into cast-in-place concrete piles and precast pipe piles. The construction methods of precast pipe piles are divided into static pressure method and hammer method.

[0003] The hammering method is to drive the pile into the ground by hammering with external force. When driving in harder soil layers, whether the hammering standard is met is generally determined by the requirements. The penetration (penetration refers to the depth of the pile into the soil after being hammered) is measured every 10 hits (1 round) before the hammering, and the penetration of each round is required not to exceed the set limit (generally 20mm, the limit is related to factors such as pile length, geological conditions, hammer type and weight, and design bearing capacity). If the actual hammering penetration is too large, it will not meet the load requirements and cause safety hazards. If it is too small, it may cause the pipe pile to be over-driven and the pile body to be damaged. Therefore, it is very important to select an appropriate hammering penetration control value based on the pile length.

[0004] The Chinese patent with publication number CN113638414A discloses a method for automatically identifying and hammering pipe piles in pile foundation construction. It automatically collects relevant data on piling to ensure data accuracy and reduce the situation where pipe piles are under-driven or over-driven due to manual measurement errors. In the process of collecting data, no manual intervention is required, which can effectively reduce manpower expenditure. It can provide real-time feedback to construction personnel on the last three arrays and the footage of each array ΔH, and independently judge whether the current pile driving operation meets the hammering standard and send a hammering completion instruction to remind the operator to hammer. However, this patent only solves the problem of automatic recording and compliance judgment of penetration, but does not solve the problem of whether the final penetration control value determined by the design when hammering is stopped is reasonable and how to adjust it under special circumstances.

[0005] In the practice of hammer pile withdrawal, for safety reasons, designers are accustomed to using the dual control method of penetration and pile length (pile tip elevation) to determine the withdrawal standard, resulting in the following two typical scenarios that have long troubled all responsible parties: First, in long pile projects, the penetration control value is often set too strictly (for example, the specification requires that the penetration of each array of 10 hits should not be less than 20mm, but in engineering practice it is often controlled at 20mm / array or 30mm / array), resulting in the pile length exceeding the estimated pile length, but the measured penetration still cannot reach the design control value, commonly known as "the hammer cannot be withdrawn". In order to reach the design control value, the pile length is often too long or the pile body is damaged; second, in some short pile projects with better soil quality, the actual penetration is less than the design control value, but the pile length is still less than the estimated pile length, commonly known as "it cannot be driven down", so the penetration control value is blindly adjusted to a small value or even the penetration is close to zero, resulting in large-scale pile body damage.

[0006] Therefore, it is necessary to provide a dynamic correction method for controlling the penetration depth during hammer pile construction, which can be used to perform dynamic correction according to the deviation of the actual pile length during construction, and transform the penetration depth constant control method commonly used in current engineering practice into a dynamic correction method. Summary of the invention

[0007] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a dynamic correction method for controlling the penetration depth of hammer during hammer pile construction, which can be dynamically corrected according to the deviation of the actual pile length during construction, thereby transforming the penetration depth constant value control method commonly used in current engineering practice into a dynamic correction method.

[0008] The technical solution adopted by the present invention is: the correction method comprises the following steps:

[0009] Step A: Obtain the characteristic value of the designed single pile bearing capacity , its unit is kN;

[0010] Step B: Obtain the characteristic value of the bearing capacity of a single pile , whose unit is kN, and the value is calculated based on the actual pile length and soil parameters provided in the geological survey report;

[0011] Step C: Obtain the final penetration control value required by the design according to the design drawings , the unit is mm / array;

[0012] Step D, based on the above three values, calculate the corrected final penetration control value by the following formula: , its unit is mm / array,

[0013] The formula is,

[0014] The basic idea of ​​the above dynamic correction method for penetration is: according to the statistical results of static load tests in this area for many years, the measured value of the vertical compressive ultimate bearing capacity of a single prestressed pipe pile is generally 0.9 to 2.5 times the calculated value, and a few short piles are close to 4 times, with an average value of about 1.5 times; based on this phenomenon, the final penetration control value required by the design can be As a base number, dynamic corrections are made during construction based on the deviation of the actual pile length (reflected in the formula as the deviation in the calculated bearing capacity), thus transforming the constant-value control method of penetration rate commonly used in current engineering practice into a dynamic correction method.

[0015] One area of ​​application is that this method is suitable for situations where the "hammer cannot be put away".

[0016] Assuming the pile diameter is 600mm, the bearing layer at the pile end is designed to be strongly weathered granite, and the characteristic value of the bearing capacity of a single pile is designed to be The final penetration control value required by the design is 2800kN. 20mm / array;

[0017] During construction, although the pile length has reached the expected pile length, the measured penetration is 50mm / row, which fails to reach the final penetration control value required by the design. At this time, an attempt is made to continue injection;

[0018] When the pile length is increased by 0.5m, the characteristic value of the single pile bearing capacity is calculated. The corresponding increase is estimated according to the formula. The result is that the corrected final penetration control value is 22.5mm / array. However, the actual penetration is 40mm / array, which fails to reach the corrected final penetration control value. At this time, the injection is continued;

[0019] When the pile length is increased by 0.5m, the final penetration control value after correction is estimated according to the formula to be 25.2mm / row. At this time, the measured penetration is 35mm / row, which still does not meet the requirements. At this time, the injection is continued;

[0020] When the pile length is increased by another 1m, that is, a total of 2m, it is estimated according to the formula that the corrected final penetration control value is 31.3mm / array. At this time, the measured penetration is 30mm / array, which meets the corrected final penetration control value and the hammer can be stopped.

[0021] One area of ​​application is that this method is suitable for situations where the opponent cannot be defeated.

[0022] Assuming the pile diameter is 600mm, the bearing layer at the pile end is designed to be strongly weathered granite, and the characteristic value of the bearing capacity of a single pile is designed to be The load is 2800 kN, the estimated pile length is 10 m, and the final penetration control value required by the design is Not less than 20mm / array;

[0023] During construction, when the pile length is 6m, the measured penetration has reached 20mm / pile. At this time, the characteristic value of bearing capacity is calculated is 1895 kN, that is =0.68 According to the formula, the final penetration control value after correction should be 6.2mm / array. The measured penetration does not reach the final penetration control value after correction, so the hammer cannot be withdrawn yet and the hammer should be continued.

[0024] When the pile length is increased to 7m, it is calculated =0.76 , and then estimated according to the formula, the result is that the corrected final penetration control value should be 8.7mm / array. At this time, the measured penetration is 15mm / array, and the hammer cannot be withdrawn, so try to continue the injection;

[0025] When the pile length is increased to 8m, it is calculated =0.84 , and then estimated according to the formula. The result is that the corrected final penetration control value should be 11.8mm / array. At this time, the measured penetration is 8mm / array, which is less than the corrected final penetration control value, meets the requirements, and the hammer can be stopped.

[0026] A preferred solution is when >1.5 However, when the measured penetration rate still does not meet the calculation result of the correction method, it is advisable to adopt verification measures such as pile tip elevation control, additional investigation and on-site static load test.

[0027] A preferred solution is that when the measured penetration is less than 5 mm / array, <0.65 It is advisable to use a higher specification pile hammer, reduce the design single pile bearing capacity, and perform on-site static load test verification measures. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is the formula diagram of the present invention. DETAILED DESCRIPTION

[0029] Embodiment 1, the present invention comprises the following steps:

[0030] Step A: Obtain the characteristic value of the designed single pile bearing capacity , its unit is kN;

[0031] Step B: Obtain the characteristic value of the bearing capacity of a single pile , whose unit is kN, and the value is calculated based on the actual pile length and soil parameters provided in the geological survey report;

[0032] Step C: Obtain the final penetration control value required by the design according to the design drawings , the unit is mm / array;

[0033] Step D, based on the above three values, calculate the corrected final penetration control value by the following formula: , its unit is mm / array,

[0034] The formula is,

[0035] In this embodiment, this method is applicable to the scenario of "unable to collect the hammer".

[0036] Assuming the pile diameter is 600mm, the bearing layer at the pile end is designed to be strongly weathered granite, and the characteristic value of the bearing capacity of a single pile is designed to be The final penetration control value required by the design is 2800kN. 20mm / array;

[0037] During construction, although the pile length has reached the expected pile length, the measured penetration is 50mm / row, which fails to reach the final penetration control value required by the design. At this time, an attempt is made to continue injection;

[0038] When the pile length is increased by 0.5m, the characteristic value of the single pile bearing capacity is calculated. The corresponding increase is estimated according to the formula. The result is that the corrected final penetration control value is 22.5mm / array. However, the actual penetration is 40mm / array, which fails to reach the corrected final penetration control value. At this time, the injection is continued;

[0039] When the pile length is increased by 0.5m, the final penetration control value after correction is estimated according to the formula to be 25.2mm / row. At this time, the measured penetration is 35mm / row, which still does not meet the requirements. At this time, the injection is continued;

[0040] When the pile length is increased by another 1m, that is, a total of 2m, it is estimated according to the formula that the corrected final penetration control value is 31.3mm / array. At this time, the measured penetration is 30mm / array, which meets the corrected final penetration control value and the hammer can be stopped.

[0041] From the above formula analysis, it can be seen that as the depth into the bearing layer increases, the actual pile length exceeds the expected pile length, and the calculation of the characteristic value of the single pile bearing capacity is It will also exceed the characteristic value of the designed single pile bearing capacity The more piles there are, the larger the penetration control value will be. This practice is called the "pile length for penetration" mode.

[0042] Embodiment 2: This method is applicable to the situation where the fight cannot be continued.

[0043] Assuming the pile diameter is 600mm, the bearing layer at the pile end is designed to be strongly weathered granite, and the characteristic value of the bearing capacity of a single pile is designed to be The load is 2800 kN, the estimated pile length is 10 m, and the final penetration control value required by the design is Not less than 20mm / array;

[0044] During construction, when the pile length is 6m, the measured penetration has reached 20mm / pile. At this time, the characteristic value of bearing capacity is calculated is 1895 kN, that is =0.68 According to the formula, the final penetration control value after correction should be 6.2mm / array. The measured penetration does not reach the final penetration control value after correction, so the hammer cannot be withdrawn yet and the hammer should be continued.

[0045] When the pile length is increased to 7m, it is calculated =0.76 , and then estimated according to the formula, the result is that the corrected final penetration control value should be 8.7mm / array. At this time, the measured penetration is 15mm / array, and the hammer cannot be withdrawn, so try to continue the injection;

[0046] When the pile length is increased to 8m, it is calculated =0.84 , and then estimated according to the formula. The result is that the corrected final penetration control value should be 11.8mm / array. At this time, the measured penetration is 8mm / array, which is less than the corrected final penetration control value, meets the requirements, and the hammer can be stopped.

[0047] The above approach is called the "penetration depth for pile length" model.

[0048] In this embodiment, in order to avoid excessive injection to damage the pile body or joints, the measured penetration rate should not be less than 5 mm / row.

[0049] In the implementation of the present invention, when >1.5 However, when the measured penetration rate still does not meet the calculation result of the correction method, it is advisable to adopt verification measures such as pile tip elevation control, additional investigation and on-site static load test.

[0050] In the implementation of the formula of the present invention, when the measured penetration is less than 5 mm / array, but <0.65 It is advisable to use a higher specification pile hammer, reduce the design single pile bearing capacity, and perform on-site static load test verification measures.

Claims

1. A dynamic correction method for controlling the penetration of hammer during hammer pile construction, characterized in that: The correction method includes the following steps: Step A: Obtain the characteristic value of the designed single pile bearing capacity , its unit is kN; Step B: Obtain the characteristic value of the bearing capacity of a single pile , whose unit is kN, and the value is calculated based on the actual pile length and soil parameters provided in the geological survey report; Step C: Obtain the final penetration control value required by the design according to the design drawings , the unit is mm / array; Step D, based on the above three values, calculate the corrected final penetration control value by the following formula: , the unit is mm / array; The formula is, .

2. A dynamic correction method for controlling hammer penetration during hammer pile construction according to claim 1, characterized in that: This method is suitable for the situation where the hammer cannot be collected: Assuming the pile diameter is 600mm, the bearing layer at the pile end is designed to be strongly weathered granite, and the characteristic value of the bearing capacity of a single pile is designed to be The final penetration control value required by the design is 2800kN. 20mm / array; During construction, although the pile length has reached the expected pile length, the measured penetration is 50mm / row, which fails to reach the final penetration control value of 20mm / row required by the design. At this time, an attempt is made to continue injection; When the pile length is increased by 0.5m, the characteristic value of the single pile bearing capacity is calculated. The corresponding increase is estimated according to the formula. The result is that the corrected final penetration control value is 22.5mm / array. However, the actual penetration is 40mm / array at this time. The actual penetration fails to reach the corrected final penetration control value. At this time, continue to inject; When the pile length is increased by 0.5m, the final penetration control value after correction is estimated according to the formula to be 25.2mm / row. At this time, the measured penetration is 35mm / row, which still does not meet the requirements. At this time, the injection is continued; When the pile length is increased by 1m, that is, a total of 2m, it is estimated according to the formula that the corrected final penetration control value is 31.3mm / array. At this time, the measured penetration is 30mm / array. The measured penetration meets the corrected final penetration control value, and the hammer can be stopped.

3. A dynamic correction method for controlling hammer penetration during hammer pile construction according to claim 1, characterized in that: This method is suitable for the situation where you can't fight anymore: Assuming the pile diameter is 600mm, the bearing layer at the pile end is designed to be strongly weathered granite, and the characteristic value of the bearing capacity of a single pile is designed to be The load is 2800 kN, the estimated pile length is 10 m, and the final penetration control value required by the design is Not less than 20mm / array; During construction, when the pile length is 6m, the measured penetration has reached 20mm / pile. At this time, the characteristic value of bearing capacity is calculated is 1895 kN, that is =0.68 According to the formula, the final penetration control value after correction should be 6.2mm / array. The measured penetration does not reach the final penetration control value after correction, so the hammer cannot be withdrawn yet and the hammer should be continued. When the pile length is increased to 7m, it is calculated =0.76 , and then estimated according to the formula, the result is that the corrected final penetration control value should be 8.7mm / array. At this time, the measured penetration is 15mm / array, and the hammer cannot be withdrawn, so try to continue the injection; When the pile length is increased to 8m, it is calculated =0.84 , and then estimated according to the formula. The result is that the corrected final penetration control value should be 11.8mm / array. At this time, the measured penetration is 8mm / array, which is less than the corrected final penetration control value, meets the requirements, and the hammer can be stopped.

4. A dynamic correction method for controlling hammer penetration during hammer pile construction according to claim 1, characterized in that: when >1.5 However, when the measured penetration rate still does not meet the calculation result of the correction method, it is advisable to adopt verification measures such as pile tip elevation control, additional investigation and on-site static load test.

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