CN115048611A - Method for calculating embedding depth of deepwater bottom-sealing-free rock-socketed steel sheet pile cofferdam - Google Patents

Method for calculating embedding depth of deepwater bottom-sealing-free rock-socketed steel sheet pile cofferdam Download PDF

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CN115048611A
CN115048611A CN202210526109.3A CN202210526109A CN115048611A CN 115048611 A CN115048611 A CN 115048611A CN 202210526109 A CN202210526109 A CN 202210526109A CN 115048611 A CN115048611 A CN 115048611A
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embedding depth
hard rock
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stress
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杨天伟
王北海
黄宇
王禹
费志高
周杰
朱斌
许涛
陈敏
曾超
易建波
赖炳增
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CCCC First Highway Xiamen Engineering Co Ltd
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Abstract

The invention relates to the field of cofferdam embedding depth calculation methods, in particular to a method for calculating the embedding depth of a deepwater bottom-sealing-free rock-socketed steel sheet pile cofferdam, which comprises the following steps: s1, assumption: critical state of skirt failure, notch hard rock stress equivalent depth of action h e 1m, and the stress is uniformly distributed along the vertical equivalent action depth; the influence of seepage effect on water pressure is not considered; not considering the interaction between the pile, backfill and hard rock; defining each symbol and its corresponding meaning; s2, establishing a critical state balance equation; s3, substituting for calculation, and dividing into two cases, namely that the embedding depth is greater than the notch hard rock stress equivalent action depth and the embedding depth is not greater than the notch hard rock stress equivalent action depthRock stress equivalent depth of action; and S4, combining the two conditions in S3, and comprehensively obtaining a range calculation formula of the embedding depth. The method can quickly provide an embedding depth range with theoretical support, and the embedding depth range is consistent with both an engineering actual empirical value and a three-dimensional finite element simulation result.

Description

Method for calculating embedding depth of deepwater bottom-sealing-free rock-socketed steel sheet pile cofferdam
Technical Field
The invention relates to the field of cofferdam embedding depth calculation methods, in particular to a calculation method of the embedding depth of a deepwater bottom-sealing-free rock-socketed steel sheet pile cofferdam.
Background
The bottom-sealing-free rock-socketed steel sheet pile cofferdam can be used for constructing a low-pile bearing platform in a deep water bridge site area with hard rock as a basic geological condition and provides a dry operation environment for the construction of the bearing platform. For example, the cofferdam construction method is adopted by the second Songhua river super bridge 3, the Guangdong ear guan deep intercity track engineering SZH-5 northeast river main flow super bridge and the like. The process comprises the steps of firstly, slotting on a hard rock foundation by using a machine, and then backfilling clay. Therefore, the steel sheet piles can be inserted and driven by conventional piling equipment, and the backfill soil is synchronously grouted. In order to ensure the sealing property of the bottom of the cofferdam and the stability of the notch of the lead hole, a measure of increasing the length of the steel sheet pile embedded into the rock stratum, namely increasing the embedding depth of the steel sheet pile, is usually adopted according to engineering experience. If the embedding depth is insufficient, the 'skirting damage' of the notch of the lead hole can be caused, the leakage and instability of the foundation pit are further caused, and if the embedding depth is too large, the construction difficulty and the construction cost are increased. Aiming at the problem of how to determine the embedding depth of the rock-socketed steel sheet pile without the sealing bottom, no reference specification or research exists at present, the rock-socketed steel sheet pile without the sealing bottom is generally determined according to engineering experience, no theoretical support exists, and the reliability is poor.
Disclosure of Invention
The invention aims to provide a method for calculating the embedding depth of a deepwater non-sealing bottom embedded rock steel sheet pile cofferdam, aiming at the problem that the embedding depth of a non-sealing bottom embedded rock steel sheet pile in the background technology cannot be calculated.
The technical scheme of the invention is as follows: a method for calculating the embedding depth of a deepwater bottom-sealing-free socketed steel sheet pile cofferdam comprises the following steps:
s1, assume conditions: critical state of skirt failure, notch hard rock stress equivalent depth of action h e 1m, and the stress is uniformly distributed along the vertical equivalent action depth; the influence of seepage effect on water pressure is not considered; not considering the interaction between the pile, backfill and hard rock; each symbol and its corresponding meaning are defined: h is q The embedding depth is the distance between the bottom surface of the steel plate pile and the surface of the foundation pit; h is z The height of the bottom layer support, namely the distance between the bottom layer support and the surface of the foundation pit; h is w The water depth is the distance between the water level line and the surface of the foundation pit; h is e The equivalent acting depth of the notch hard rock stress is obtained; f 1 Is the equivalent resultant force of trapezoidal distributed water load,
Figure BDA0003644534410000021
F 2 the equivalent resultant force of water load distributed in a triangular shape,
Figure BDA0003644534410000022
h 1 is the equivalent resultant force F 1 The distance from the top surface of the trapezoid is,
Figure BDA0003644534410000023
h 2 is the equivalent resultant force F 2 The distance from the surface of the foundation pit,
Figure BDA0003644534410000024
σ e the bearing capacity sigma of the hard rock can be taken in a critical balance state for the equivalent stress of the hard rock c (ii) a Gamma is water volume weight;
s2, establishing a critical state balance equation, taking the steel sheet pile as an investigation object, and taking a moment for the supporting point o to ensure the stability of the steel sheet pile, wherein the method comprises the following steps: the moment generated by the rock mass ultimate stress is more than or equal to the moment of water pressure, namely:
Figure BDA0003644534410000025
s3, substituting calculation, namely h if the embedding depth is greater than the notch hard rock stress equivalent action depth q ＞h e When the average value is 1m, h is taken e Substituting 1m into the equilibrium equation: sigma c ·(h z +0.5)≥F 1 ·h 1 +F 2 ·(h 2 +h z ) And calculating to obtain:
Figure BDA0003644534410000026
if the embedding depth is not more than the stress equivalent action depth of the notch hard rock, namely h q ＜h e When the average value is 1m, h is taken e ＝h q Substituting into the balance equation:
Figure BDA0003644534410000027
namely: (3. sigma.) c -γh w )h q 2 +(6·σ c ·h z -3·γ·h w ·h z )·h q -γ·h z 2 ·(3·h w -h z ) Not less than 0, in the case of deep water hard rock, the following are common: a is 3 sigma c -γh w > 0, axis of symmetry:
Figure BDA0003644534410000028
the discriminant is as follows: Δ ═ 6 σ c ·h z -3·γ·h w ·h z ) 2 +4·(3σ c -γh w )·γ·h z 2 ·(3·h w -h z ) Greater than 0, so the curve opening of the inequality is upward, the embedding depth can only be a positive value, and the solution of the inequality is as follows:
Figure BDA0003644534410000031
s4, determining the range of the embedding depth, and combining the two conditions in S3 to comprehensively obtain the range of the embedding depth as follows:
Figure BDA0003644534410000032
compared with the prior art, the invention has the following beneficial technical effects: the method can quickly provide an embedding depth range with theoretical support, keeps consistent with both an engineering actual experience value and a three-dimensional finite element simulation result, and improves the reliability of embedding depth judgment.
Drawings
Fig. 1 is a simplified diagram of a steel sheet pile;
fig. 2 is a graph of the inequality in S3.
Detailed Description
Example one
As shown in fig. 1-2, the method for calculating the embedding depth of the deepwater bottom-sealing-free socketed steel sheet pile cofferdam provided by the invention comprises the following steps:
s1, assume conditions: critical state of skirt failure, notch hard rock stress equivalent depth of action h e 1m, and the stress is uniformly distributed along the vertical equivalent action depth; the influence of seepage effect on water pressure is not considered; not considering the interaction between the piles, backfill and hard rock; each symbol and its corresponding meaning are defined: h is q The embedding depth is the distance between the bottom surface of the steel plate pile and the surface of the foundation pit; h is a total of z The height of the bottom layer support, namely the distance between the bottom layer support and the surface of the foundation pit; h is w The water depth is the distance between the water level line and the surface of the foundation pit; h is a total of e The equivalent acting depth of the notch hard rock stress is obtained; f 1 Is the equivalent resultant force of trapezoidal distributed water load,
Figure BDA0003644534410000041
F 2 the equivalent resultant force of water load distributed in a triangular shape,
Figure BDA0003644534410000042
h 1 is the equivalent resultant force F 1 The distance between the top surface of the trapezoid and the top surface of the trapezoid,
Figure BDA0003644534410000043
h 2 is the equivalent resultant force F 2 The distance from the surface of the foundation pit,
Figure BDA0003644534410000044
σ e the bearing capacity sigma of the hard rock can be taken in a critical balance state for the equivalent stress of the hard rock c (ii) a Gamma is water volume weight;
s2, establishing a critical state balance equation, taking the steel sheet pile as an investigation object, and taking a moment for the supporting point o to ensure the stability of the steel sheet pile, wherein the method comprises the following steps: the moment generated by the ultimate stress of the rock mass is more than or equal to the moment of water pressure, namely:
Figure BDA0003644534410000045
s3, substituting for calculation, if the embedding depth is greater than the notch hard rock stress equivalent action depth, namely h q ＞h e When the average value is 1m, h is taken e Substituting 1m into the equilibrium equation: sigma c ·(h z +0.5)≥F 1 ·h 1 +F 2 ·(h 2 +h z ) And calculating to obtain:
Figure BDA0003644534410000046
if the embedding depth is not more than the stress equivalent action depth of the notch hard rock, namely h q ＜h e When the average value is 1m, h is taken e ＝h q Substituting into the balance equation:
Figure BDA0003644534410000047
namely: (3. sigma.) c -γh w )h q 2 +(6·σ c ·h z -3·γ·h w ·h z )·h q -γ·h z 2 ·(3·h w -h z ) Not less than 0, in the case of deep water hard rock, the following are common: a is 3 sigma c -γh w > 0, axis of symmetry:
Figure BDA0003644534410000048
the discriminant: Δ ═ 6 σ c ·h z -3·γ·h w ·h z ) 2 +4·(3σ c -γh w )·γ·h z 2 ·(3·h w -h z ) Greater than 0, so the curve opening of the inequality is upward, the embedding depth can only be a positive value, and the solution of the inequality is as follows:
Figure BDA0003644534410000051
s4, determining the range of the embedding depth, and combining the two conditions in S3 to comprehensively obtain the range of the embedding depth as follows:
Figure BDA0003644534410000052
the method can rapidly provide an embedding depth range with theoretical support, keeps consistent with an engineering actual experience value and a three-dimensional finite element simulation result, and improves the reliability of embedding depth judgment.
Example two
The invention provides a method for calculating the embedding depth of a deepwater bottom-sealing-free rock-socketed steel sheet pile cofferdam, which takes a concrete actual project as an example, h w ＝16m，h z ＝3.5m，σ c ＝400KPa，γ＝9.8×10 3 N/m 3 Substituted into h q In the expression:
Figure BDA0003644534410000053
directly calculating to obtain: h is not less than 0.71m q Less than or equal to 2.15m, can quickly obtain the embedding depth range, has theoretical basis and is based on the industryThe determination method of the process experience forms complementation, and the reliability of the judgment of the embedded depth value is improved.
The embodiments of the present invention have been described in detail with reference to the drawings, but the present invention is not limited thereto, and various changes can be made within the knowledge of those skilled in the art without departing from the gist of the present invention.

Claims (1)

1. A method for calculating the embedding depth of a deepwater bottom-sealing-free rock-socketed steel sheet pile cofferdam is characterized by comprising the following steps of:
s1, assumption: critical state of skirt damage, notch hard rock stress equivalent action depth h e 1m, and the stress is uniformly distributed along the vertical equivalent action depth; the influence of seepage effect on water pressure is not considered; not considering the interaction between the pile, backfill and hard rock; each symbol and its corresponding meaning are defined: h is q The embedding depth is the distance between the bottom surface of the steel plate pile and the surface of the foundation pit; h is z The height of the bottom layer support, namely the distance between the bottom layer support and the surface of the foundation pit; h is w The water depth is the distance between the water level line and the surface of the foundation pit; h is e The equivalent acting depth of the notch hard rock stress is obtained; f 1 Is the equivalent resultant force of trapezoidal distributed water load,
Figure FDA0003644534400000011
F 2 the equivalent resultant force of water load distributed in a triangular shape,
Figure FDA0003644534400000012
h 1 is the equivalent resultant force F 1 The distance from the top surface of the trapezoid is,
Figure FDA0003644534400000013
h 2 is the equivalent resultant force F 2 The distance from the surface of the foundation pit,
Figure FDA0003644534400000014
σ e for hard rock equivalent stress, the critical equilibrium state can beTaking the bearing capacity sigma of hard rock c (ii) a Gamma is water volume weight;
s2, establishing a critical state balance equation, taking the steel sheet pile as an investigation object, and taking a moment for the supporting point o to ensure the stability of the steel sheet pile, wherein the method comprises the following steps: the moment generated by the rock mass ultimate stress is more than or equal to the moment of water pressure, namely:
Figure FDA0003644534400000015
s3, substituting for calculation, if the embedding depth is greater than the notch hard rock stress equivalent action depth, namely h q ＞h e When the average value is 1m, h is taken e Substituting 1m into the equilibrium equation: sigma c ·(h z +0.5)≥F 1 ·h 1 +F 2 ·(h 2 +h z ) And calculating to obtain:
Figure FDA0003644534400000016
if the embedding depth is not more than the stress equivalent action depth of the notch hard rock, namely h q ＜h e When the average value is 1m, h is taken e ＝h q Substituting into the balance equation:
Figure FDA0003644534400000017
namely: (3. sigma.) c -γh w )h q 2 +(6·σ c ·h z -3·γ·h w ·h z )·h q -γ·h z 2 ·(3·h w -h z ) Not less than 0, in the case of deep water hard rock, the following are common: a is 3 sigma c -γh w > 0, axis of symmetry:
Figure FDA0003644534400000021
the discriminant: Δ ═ 6 σ c ·h z -3·γ·h w ·h z ) 2 +4·(3σ c -γh w )·γ·h z 2 ·(3·h w -h z ) Greater than 0, so the curve opening of the inequality is upward, the embedding depth can only be a positive value, and the solution of the inequality is as follows:
Figure FDA0003644534400000022
s4, determining the range of the embedding depth, and combining the two conditions in S3 to comprehensively obtain the range of the embedding depth as follows:
Figure FDA0003644534400000023
CN202210526109.3A 2022-05-16 2022-05-16 Method for calculating embedding depth of deepwater bottom-sealing-free rock-socketed steel sheet pile cofferdam Pending CN115048611A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116335216A (en) * 2023-05-31 2023-06-27 中国建筑第六工程局有限公司 Calculation method for rock-socketed depth of open caisson

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116335216A (en) * 2023-05-31 2023-06-27 中国建筑第六工程局有限公司 Calculation method for rock-socketed depth of open caisson
CN116335216B (en) * 2023-05-31 2023-08-01 中国建筑第六工程局有限公司 Calculation method for rock-socketed depth of open caisson

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