CN110172987B

CN110172987B - Overwater open caisson crossing platform method suitable for deep and thick soft foundation

Info

Publication number: CN110172987B
Application number: CN201910464310.1A
Authority: CN
Inventors: 潘昕; 马晓东; 刘玲晶; 刘润泽; 宋小三; 涂满明; 毛伟琦; 周超舟; 田继开; 陈超凡
Original assignee: China Railway Major Bridge Engineering Group Co Ltd MBEC
Current assignee: China Railway Major Bridge Engineering Group Co Ltd MBEC
Priority date: 2019-05-30
Filing date: 2019-05-30
Publication date: 2021-01-05
Anticipated expiration: 2039-05-30
Also published as: CN110172987A

Abstract

A method for crossing a platform of an overwater open caisson suitable for a deep and thick soft foundation relates to the field of building construction and comprises the following steps: s1: filling gravels in the deep soft foundation surface layer to form a gravel cushion layer, wherein the area of the gravel cushion layer is larger than the area of the bottom surface of the open caisson; s2: sinking the open caisson to a gravel cushion layer; s3: throwing and filling gravels with a certain height at the positions, which are close to the outer wall, on the periphery of the open caisson to form a gravel base layer; s4: digging out the broken stones on the contact surface of the bottom of the open caisson and the broken stone cushion layer, and sinking the open caisson into the deep soft foundation soil layer; s5: and digging soil in the open caisson to make the open caisson sink to a proper position. The invention researches and analyzes the anti-slip stability and the anti-overturning stability of the open caisson in steps, so that the open caisson has the capability of crossing typhoon in each installation step, and the purpose of stably installing the open caisson is achieved.

Description

Overwater open caisson crossing platform method suitable for deep and thick soft foundation

Technical Field

The invention relates to the field of building construction, in particular to a method for crossing a platform of an overwater open caisson suitable for a deep and thick soft foundation.

Background

In the process of land open caisson construction, if a soft soil layer is encountered, the engineering difficulty can be increased rapidly; the soft soil layer has high water content, porosity, compressibility, sensitivity and other indexes, thixotropy and extremely poor engineering property. The open caisson construction is carried out on a soft soil layer, so that the phenomena of over-sinking, inclination, sudden sinking and the like are easy to occur; therefore, people generally adopt a pile foundation method to overcome various problems possibly occurring in the open caisson construction process when meeting soft soil layers during open caisson construction.

The pile foundation method mainly uses cement mixing piles, sand stone piles and other structures to improve the bearing capacity of the foundation, but the method is difficult to adapt to large-area construction.

However, when the open caisson is constructed at the seaside or on the sea surface, because the soft soil layer at the sea bottom is usually deep and the open caisson plane has a large size, the open caisson is easily inclined or deviated due to the influence of typhoon in the construction process by the conventional pile foundation method, and the open caisson is ensured to be capable of crossing typhoon after construction, so that the problems are difficult to solve only by the conventional pile foundation method.

Disclosure of Invention

Aiming at the defects in the prior art, the invention aims to provide the method for crossing the platform of the open caisson on the water, which is suitable for the deep and thick soft foundation.

In order to achieve the purpose, the method for adopting the overwater open caisson ferrying platform suitable for the deep and thick soft foundation comprises the following steps: s1: filling gravels in the deep soft foundation surface layer to form a gravel cushion layer, wherein the area of the gravel cushion layer is larger than the area of the bottom surface of the open caisson; s2: sinking the open caisson to a gravel cushion layer; s3: throwing and filling gravels with a certain height at the positions, which are close to the outer wall, on the periphery of the open caisson to form a gravel base layer; s4: digging out the broken stones on the contact surface of the bottom of the open caisson and the broken stone cushion layer, and sinking the open caisson into the deep soft foundation soil layer; s5: and digging soil in the open caisson to make the open caisson sink to a proper position.

Preferably, the anti-sliding safety coefficient K1 of the open caisson is more than 1.5, and the anti-overturning safety coefficient K2 of the open caisson is more than 1.3; wherein K1 ═ R_{Level of}/F_{Typhoon level}、K2＝M_{Anti-overturning}/M_{Typhoon overturn}，F_{Typhoon level}The horizontal load is generated by the sum of typhoon load, wave force and water flow force on the open caisson; m_{Typhoon overturn}I.e. F_{Typhoon level}The overturning moment is generated to the open caisson; in S2, R_{Level of}Namely the horizontal bearing capacity of the broken stone cushion layer on the open caisson; m_{Anti-overturning}Namely the moment generated by the reaction force of the gravel cushion layer on the open caisson.

Preferably, in S4, R_{Level of}Namely the difference between the lateral pressure of the broken stone base layer in the leeward direction to the open caisson and the lateral pressure of the broken stone base layer in the windward direction to the open caisson; m_{Anti-overturning}Namely the difference of the lateral pressure of the broken stone base layer in the leeward direction to the open caisson and the lateral pressure of the broken stone base layer in the windward direction to the open caisson, which respectively generate the moment difference to the open caisson.

Preferably, R_{Level of}The calculation method of (2) is that the dead weight of the open caisson is multiplied by the friction coefficient of the gravel cushion.

Preferably, after step S5 is completed, earth is continued to be excavated in the open caisson, and the open caisson is lowered to a final bottom elevation.

Preferably, the pressure load F generated by the crushed stone base layer_Self-weightFoundation bearing capacity R smaller than gravel cushion layer_{Crushing stone}And the pressure load generated by the broken stone base layer is less than the bearing capacity R of the deep soft base_{Soft foundation}。

Preferably, the total amount of crushed stones in the crushed stone base layer is substantially equal to the total amount of crushed stones in the crushed stone cushion layer.

Preferably, the open caisson is a cuboid, and the area of the upper surface of the gravel cushion layer is more than five times of the area of the bottom surface of the open caisson.

Preferably, the upper surface of the gravel cushion is substantially flat.

Preferably, the height of the crushed stone base layer is higher as the crushed stone base layer is closer to the outer wall of the open caisson, and the cross section of one side of the crushed stone base layer is in a right-angled trapezoid shape.

The invention has the beneficial effects that:

1. the invention relates to a method for crossing a platform of an overwater caisson, which is characterized in that before the caisson is landed, a broken stone cushion layer is refilled on the surface layer of a deep soft foundation, the area of the broken stone cushion layer is larger than the area of the bottom surface of the caisson, the caisson is arranged above the broken stone cushion layer, the gravity of the caisson passes through the broken stone cushion layer and then acts on the deep soft foundation, the area of the broken stone cushion layer for bearing the gravity is larger and larger from the upper surface to the lower surface of the broken stone cushion layer, the area of the caisson gravity indirectly acting on the deep soft foundation is far larger than the area of the bottom surface of the caisson, and the bearing capacity of the deep; by the above-mentioned meansAfter the open caisson is sunk to the broken stone cushion layer, the broken stone cushion layer provides horizontal bearing capacity R for the open caisson_{Level of}And an anti-overturning moment M_{Anti-overturning}So that the open caisson can be kept stable under the action of typhoon.

2. The method for crossing the platform of the water open caisson comprises the following steps of throwing and filling gravels with a certain height at the positions, close to the outer wall, of the periphery of the open caisson after the open caisson is sunk to a gravel cushion layer to form a gravel base layer; then digging out gravels on the contact surface of the bottom of the open caisson and the gravel cushion layer, wherein the bottom of the edge foot of the open caisson breaks through the gravel cushion layer due to the self gravity of the open caisson and enters a deep soft foundation soil layer; in the process, the anti-slip stability and the anti-overturning stability of the open caisson are researched and analyzed in steps, so that the anti-slip safety coefficient K1 of the open caisson is more than 1.5, and the anti-overturning safety coefficient K2 of the open caisson is more than 1.3; wherein K1 ═ R_{Level of}/F_{Typhoon level}、K2＝M_{Anti-overturning}/M_{Typhoon overturn}The research and analysis enable the open caisson to have the ability of crossing typhoon all the time in the construction process.

3. According to the overwater open caisson crossing platform method, the anti-slip stability and the anti-overturning stability of the open caisson are researched and analyzed in steps, so that the safety and the stability of the open caisson in each stage are guaranteed, the construction is convenient, the open caisson crossing platform method is safe and reliable, and the open caisson crossing platform method has remarkable economical efficiency and applicability.

Drawings

FIG. 1 is a flow chart of an embodiment of the present invention.

Fig. 2 is a schematic diagram of step S2 according to the embodiment of the present invention.

FIG. 3 is a diagram illustrating step S3 according to an embodiment of the present invention.

Fig. 4 is a schematic diagram of step S4 according to the embodiment of the present invention.

Fig. 5 is a schematic diagram of the sinking moment in step S2 according to the embodiment of the present invention.

Fig. 6 is a schematic diagram of the sinking moment in step S4 according to the embodiment of the present invention.

Reference numerals: 1-open caisson, 2-deep soft foundation, 3-gravel base and 4-gravel cushion.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and examples.

As shown in fig. 1, a method for using a water caisson for a deep and thick soft foundation to transition a platform comprises the following steps:

s1: and (3) replacing and filling broken stones on the surface layer of the deep soft foundation 2 to form a broken stone cushion layer 4, wherein the area of the broken stone cushion layer 4 is larger than the area of the bottom surface of the open caisson 1. Preferably, the upper surface of the stone pad 4 is substantially flat.

S2: the open caisson 1 is sunk to the gravel cushion 4.

S3: and throwing and filling gravels with a certain height at the positions, close to the outer wall, of the periphery of the open caisson to form a gravels base layer 3.

S4: and (4) digging out gravels on the contact surface of the bottom of the open caisson 1 and the gravel cushion layer 4, and sinking the open caisson 1 into the deep soft foundation 2.

S5: and (5) digging soil in the open caisson 1, and sinking the open caisson 1 to a proper position.

By the method, the safety and stability of the open caisson at each step end can be ensured, the open caisson cannot incline or deviate due to the influence of typhoon, and the open caisson is convenient to construct, safe and reliable.

As shown in fig. 2, in step S2, after sinking, the caisson 1 is placed above the gravel cushion layer 4, the gravity of the caisson 1 acts on the gravel cushion layer 4 first and then acts on the deep soft foundation 2, the top surface of the gravel cushion layer 4 directly contacts with the bottom surface of the caisson 1 to bear the gravity of the caisson 1, and because the gravel cushion layer 4 has a certain thickness, the area of the gravel cushion layer 4 bearing the gravity of the caisson 1 is gradually increased from the upper surface to the lower surface, and then the area of the caisson 1 gravity indirectly acting on the deep soft foundation 2 is far greater than the bottom area of the caisson 1, thereby greatly improving the bearing capacity of the foundation.

In the step, the anti-sliding safety factor K1 of the open caisson 1 is more than 1.5, which can ensure that the open caisson 1 can not move on the gravel base 4; the anti-overturning safety coefficient K2 of the open caisson 1 is more than 1.3, which can ensure that the open caisson 1 can not incline or collapse;

wherein K1 ═ R_{Level of}/F_{Typhoon level}、K2＝M_{Anti-overturning}/M_{Typhoon overturn}

F_{Typhoon level}The horizontal load generated by the sum of typhoon load, wave force and water flow force on the open caisson 1；R_{Level of}Namely the horizontal bearing capacity of the broken stone cushion layer 4 on the open caisson 1; m_{Typhoon overturn}I.e. F_{Typhoon level}The overturning moment is generated to the open caisson 1; m_{Anti-overturning}I.e. the moment produced by the reaction force of the gravel cushion 4 on the open caisson 1.

Specifically, the typhoon load, the wave force and the water flow force are calculated according to the port engineering load specification by combining the past engineering experience, the local hydrogeology and the meteorological conditions.

Specifically, R_{Level of}The calculation method of (1) is that the dead weight of the open caisson (1) is multiplied by the friction coefficient of the gravel cushion layer (4).

In particular, as shown in figure 5,

and

wherein the content of the first and second substances,

i.e. in the actual process F_{Typhoon level}The overturning moment generated to the open caisson 1,

namely the moment generated by the reaction force of the gravel cushion layer 4 on the open caisson 1 on the open caisson. In this embodiment, M_{Anti-overturning}Is M_{Typhoon overturn}K2 times, and K2 is greater than 1.3, so that the open caisson 1 cannot incline or collapse in the construction process.

Preferably, the open caisson 1 is a cuboid, and the area of the upper surface of the gravel cushion layer 3 is more than five times of the area of the bottom surface of the open caisson 1.

As shown in FIG. 3, in step S3, the pressure load F generated by the stone substrate 3_Self-weightFoundation bearing capacity R smaller than gravel cushion layer 4_{Crushing stone}And the pressure load generated by the gravel base layer 3 is less than the bearing capacity R of the deep soft foundation 2_{Soft foundation}(ii) a The broken stone base layer 3 is prevented from damaging the broken stone cushion layer 4 and the deep soft foundation 2 by self.

Preferably, the total amount of crushed stone of the crushed stone base layer 3 is substantially equal to the total amount of crushed stone of the crushed stone cushion layer 4.

In the embodiment, the height of the crushed stone base layer 3 is higher as the crushed stone base layer is closer to the outer wall of the open caisson 1, and the section of the crushed stone base layer 3 on any side of the open caisson 1 is in a right trapezoid shape.

As shown in fig. 4, in step S4, the caisson 1 mainly depends on its own gravity, and the bottom of the cutting edge of the caisson 1 breaks through the gravel cushion 4 and sinks into the deep soft foundation 2.

In the step, the anti-sliding safety coefficient K1 of the open caisson 1 is more than 1.5, and the anti-overturning safety coefficient K2 of the open caisson is more than 1.3;

wherein K1 ═ R_{Level of}/F_{Typhoon level}、K2＝M_{Anti-overturning}/M_{Typhoon overturn}，

F_{Typhoon level}The horizontal load is generated on the open caisson 1 by the sum of typhoon load, wave force and water flow force; m_{Typhoon overturn}I.e. F_{Typhoon level}The overturning moment is generated to the open caisson 1;

at this time, R is shown in FIG. 6_{Level of}Namely the difference between the lateral pressure of the broken stone basement 3 against the open caisson 1 in the leeward direction and the lateral pressure of the broken stone basement 3 against the open caisson 1 in the windward direction

M_{Anti-overturning}Namely the difference of the lateral pressure of the leeward gravel base layer 3 to the open caisson 1 and the lateral pressure of the windward gravel base layer 3 to the open caisson 1, which are the torque generated by the open caisson 1 respectively, specifically

In particular, the amount of the solvent to be used,

the moment is generated to the open caisson 1 by the lateral pressure of the broken stone base layer 3 acting on the open caisson 1 in the leeward direction,

to welcomeThe moment is generated to the open caisson 1 by the lateral pressure of the wind direction gravel base 3 acting on the open caisson 1. In this embodiment, M_{Anti-overturning}Is M_{Typhoon overturn}K2 times, and K2 is greater than 1.3, so that the open caisson 1 cannot incline or collapse in the construction process.

In step S5, earth is dug in the open caisson 1 to make the open caisson 1 sink slowly, as the sinking depth becomes deeper and deeper, the earth around the open caisson 1 becomes more and more, the extrusion force of the surrounding earth on the open caisson 1 becomes larger and larger, and the stability of the open caisson 1 is gradually enhanced; when the open caisson 1 is sunk to a proper position, the open caisson 1 has no instability risk, and the influence of typhoon on the open caisson 1 is not worried. During the actual installation, after step S5 is completed, earth excavation is continued in the open caisson 1, and the open caisson 1 is lowered to the final bottom elevation. Usually, the open caisson 1 is sunk to the final bottom level, and its bottom surface is located in the pebble bed of the soil layer.

In the present embodiment, the length, width and height dimensions of the open caisson are 55m x 66m x 59 m; the water surface height is changed all the time, the thickness of the deep soft foundation 2 is 41.7m, the thickness of the fine sand layer below the deep soft foundation 2 is 5.1m, and the pebble layer is arranged below the fine sand layer.

According to the method for crossing the platform of the water open caisson, the broken stone cushion layer 4 and the broken stone base layer 3 are utilized to research and analyze the anti-slip stability and the anti-overturning stability of the open caisson 1 in multiple steps, so that the open caisson 1 has the capability of crossing typhoons in each installation step, and the purpose of stably installing the open caisson 1 is achieved.

In step S2, the open caisson 1 is sunk to the gravel cushion 4, and the gravel cushion 4 provides the open caisson 1 with horizontal bearing capacity R_{Level of}And an anti-overturning moment M_{Anti-overturning}。

In step S4, the blade foot of the open caisson 1 breaks through the gravel cushion 4, and the open caisson 1 is laid down into the deep soft foundation 2. At the moment, the broken stone base layer 3 in the leeward direction provides horizontal bearing capacity R for the open caisson 1_{Level of}And an anti-overturning moment M_{Anti-overturning}。

In the two steps, the anti-slip safety coefficient K1 is greater than 1.5, and the open caisson anti-overturning safety coefficient K2 is greater than 1.3, so that the open caisson is prevented from translating or overturning due to typhoon in the open caisson installation process, the open caisson 1 can be kept stable under the action of typhoon, and the stable installation of the open caisson is completed.

The present invention is not limited to the above-described embodiments, and it will be apparent to those skilled in the art that various modifications and improvements can be made without departing from the principle of the present invention, and such modifications and improvements are also considered to be within the scope of the present invention. Those not described in detail in this specification are within the skill of the art.

Claims

1. A method for crossing a platform of an overwater open caisson suitable for deep and thick soft foundations is characterized by comprising the following steps:

s1: filling gravels in the surface layer of the deep soft foundation (2) to form a gravel cushion layer (4), wherein the area of the gravel cushion layer (4) is larger than the area of the bottom surface of the open caisson (1);

s2: sinking the open caisson (1) to a gravel cushion layer (4);

s3: throwing and filling gravels with a certain height at the positions, which are close to the outer wall, on the periphery of the open caisson to form a gravel base (3);

s4: digging out gravels on the contact surface of the bottom of the open caisson (1) and the gravel cushion layer (4) to make the open caisson (1) sink to the deep soft foundation (2);

s5: digging soil in the open caisson (1) to enable the open caisson (1) to sink to a proper position;

the anti-sliding safety coefficient K1 of the open caisson (1) is more than 1.5, and the anti-overturning safety coefficient K2 of the open caisson is more than 1.3;

F_{Typhoon level}The horizontal load is generated on the open caisson (1) by the sum of typhoon load, wave force and water flow force; m_{Typhoon overturn}I.e. F_{Typhoon level}The overturning moment is generated to the open caisson (1);

in S2, R_{Level of}Namely the horizontal bearing capacity R of the broken stone cushion layer (4) to the open caisson (1)_{Level of}The calculation method is that the dead weight of the open caisson (1) is multiplied by the friction coefficient of the gravel cushion (4); m_{Anti-overturning}Namely the reaction force of the gravel cushion (4) acting on the open caisson (1) is opposite to the sinkTorque produced by the well;

in S4, R_{Level of}Namely the difference between the lateral pressure of the leeward gravel base (3) to the open caisson (1) and the lateral pressure of the windward gravel base (3) to the open caisson (1); m_{Anti-overturning}Namely the difference of the lateral pressure of the leeward gravel base layer (3) to the open caisson (1) and the lateral pressure of the windward gravel base layer (3) to the open caisson (1) respectively generated moment to the open caisson (1).

2. The method for the water caisson ferrying platform suitable for the deep and thick soft foundation as claimed in claim 1, wherein: after step S5 is completed, earth is continuously dug in the open caisson (1), and the open caisson (1) is sunk to the final bottom elevation.

3. The method for the water caisson ferrying platform suitable for the deep and thick soft foundation as claimed in claim 1, wherein: pressure load F generated by the gravel base (3)_Self-weightIs less than the foundation bearing capacity R of the gravel cushion layer (4)_{Crushing stone}And the pressure load generated by the gravel base layer (3) is less than the bearing capacity R of the deep soft foundation (2)_{Soft foundation}。

4. The method for the water caisson ferrying platform suitable for the deep and thick soft foundation as claimed in claim 1, wherein: the total amount of the gravels base course (3) is basically equal to that of the gravels cushion layer (4).

5. The method for the water caisson ferrying platform suitable for the deep and thick soft foundation as claimed in claim 1, wherein: the open caisson (1) is a cuboid, and the area of the upper surface of the gravel cushion layer (4) is more than five times of the area of the bottom surface of the open caisson (1).

6. The method for the transition of the water caisson applicable to the deep and thick soft foundation as claimed in any one of claims 1 to 5, wherein: the upper surface of the gravel cushion layer (4) is substantially flat.

7. The method for the transition of the water caisson applicable to the deep and thick soft foundation as claimed in any one of claims 1 to 5, wherein: the height of the broken stone base layer (3) is higher when the broken stone base layer is closer to the outer wall of the open caisson (1), and the section of one side of the broken stone base layer is in a right-angle trapezoid shape.