CN102829245B - Method for arranging jacking pipe of rectangular open caisson - Google Patents

Abstract

The present invention provides a method for setting pipe jacking force for eccentric jacking of a rectangular caisson, comprising the following steps: (a) obtaining soil parameters and caisson parameters of the area where the working area where the rectangular caisson is applied; (b) Calculate the earth pressure in each direction of the caisson according to the soil parameters and caisson parameters; and (c) calculate the eccentric load of the pipe jacking according to the distribution pattern of the earth pressure and the earth pressure The jacking allowable jacking force, and the jacking force required to advance the jacking pipe is smaller than the allowable jacking force of the eccentric jacking. Because the method of the present invention determines the soil parameters in the working area by geological data and test data, and in combination with the jacking force of the pipeline, obtains the soil pressure acting on each direction of the working well through the earth pressure formula and the earth pressure distribution shape provided. Finally, calculate the allowable jacking force for the eccentric jacking of the pipe jacking of the working well. According to the allowable jacking force, the pipe jacking force of the rectangular caisson as the working well can be safely set.

Description

Setting method of pipe jacking force for eccentric jacking of rectangular caisson

technical field

The present invention relates to the technical field of construction engineering, in particular to a method for setting pipe jacking force for eccentric jacking of rectangular caissons.

Background technique

As a construction method of underground excavation, pipe jacking construction has many advantages, such as small footprint; underground construction does not affect ground activities; when crossing obstacles such as railways, highways, rivers, and buildings, it can reduce the workload of demolition along the line; During the construction process, the existing pipelines and structures will not be damaged, and the normal use will not be affected; the construction will be noiseless and reduce environmental pollution along the line. Therefore, pipe jacking construction technology has been widely used in recent years. The laying of upper and lower sewers, gas, electric power, communication engineering, liquefied petroleum gas, natural gas pipelines and various communication cables such as oil pipes, power cables, broadband networks, optical fiber networks, etc. in municipal engineering have all been constructed using pipe jacking methods.

The pipe jacking well is the starting point of the pipe jacking construction and plays the role of providing recoil reaction force for the pipe jacking. With the increase of jacking distance, pipe diameter, and buried depth in pipe jacking construction, the required jacking force is also increasing. It has risen from hundreds of tons in the past to thousands of tons. ignore. Especially in the case of eccentric jacking of rectangular working wells when double pipes are jacked one after another, the force pattern of the working well changes during eccentric jacking, and its safety issues cannot be ignored. Therefore, the setting of the jacking pipe must be compatible with the allowable jacking force of the working well.

In the calculation of the allowable jacking force under the jacking, the calculation of the soil reaction force based on the earth pressure is the key point. When studying the soil reaction force of rectangular working wells, there are few literatures on the distribution of earth pressure in unilateral eccentric jacking of rectangular working wells.

my country's "Reinforced Concrete Caisson Structural Design Regulations for Water Supply and Drainage Engineering" CECS137:2002 stipulates that in the horizontal direction of a rectangular working well, the soil resistance during unilateral eccentric jacking is triangular, and the resistance at the far end is 0. However, in actual engineering, the remote end is also subjected to earth pressure, and the code does not specify the stress on the front wall of the working well. In the vertical direction, at that time, the earth pressure at the back was 0, and the earth pressure at the top of the working well was 0; but at that time, the code did not specify whether the earth pressure at the top was 0.

When calculating the allowable jacking force, scholars have done a lot of useful research.

Feng Haining et al. (Feng Haining, Gong Xiaonan, Xu Riqing, Discussion on the Calculation of Soil Resistance of the Back Wall of a Caisson, China Municipal Engineering, 2001, 01: 67-69) considered the three-dimensional force of the soil behind the back wall through appropriate assumptions conditions and the size of the passive earth pressure of the soil behind the wall under the action of eccentric loads. At the same time, the caisson is taken as a whole. When calculating the total jacking force, the active earth pressure of the front wall is considered to calculate the maximum jacking force, and the load behind the wall is also considered. The soil adopts the model-shaped sliding surface.

Jiang Yan et al. (Jiang Yan, Ge Chunhui, Analysis of Rectangular Caisson Wall by Pipe Jacking Recoil Force, Special Structures, 2001, 01:1-3) used the principle of jacking force and soil resistance balance to introduce the rectangular caisson Calculation method of internal force of wall during pipe jacking. Gong Ci et al. (Gong Ci, Wei Gang, Xu Riqing, Calculation of Allowable Reaction Force of Rectangular Caisson Working Well in Pipe Jacking Construction, Rock and Soil Mechanics, 2005, 07: 1127-1131) Based on the deformation of the back wall, it is proposed to use the earth pressure related to the displacement to calculate the soil reaction force. Considering the frictional resistance of the bottom and side walls of the caisson, the allowable jacking force is calculated from the overall horizontal force balance of the caisson.

Wei Gang et al. (Wei Gang, Xu Riqing, Gong Ci, Liu Jiawan, Discussion on Calculation Method of Rectangular Caisson Soil Resistance in Pipe Jacking Project, China Municipal Engineering, 2005, 01:50-52) proposed the trapezoidal distribution of back vertical The distribution form of soil resistance, and according to the overall force balance of the caisson, the maximum allowable soil resistance and jacking force calculation formulas of the caisson working well are obtained.

However, these documents, based on central jacking, proposed their respective stress states and calculation methods for the maximum allowable jacking force of the working well, but none of them analyzed the earth pressure distribution and allowable jacking force of the eccentric jacking of the rectangular working well.

Therefore, the industry needs an accurate calculation method for the allowable jacking force for eccentric jacking of rectangular caisson wells, so that the jacking force can be set more safely.

Contents of the invention

Aiming at the deficiency and defects of caisson stress mode in the existing calculation methods and specifications in our country, the present invention provides a method for setting pipe jacking force of rectangular caisson eccentric jacking, which can obtain the eccentric jacking force of rectangular caisson Safely set the pipe jacking force according to the force characteristics.

In order to achieve the above purpose, the present invention provides a method for setting the pipe jacking force of rectangular caisson eccentric jacking, which includes the following steps: (a) Obtain the soil parameters and caisson in the area where the working area where the rectangular caisson is applied parameters; (b) calculate the earth pressure in each direction of the caisson according to the soil parameters and caisson parameters; and (c) calculate the earth pressure according to the distribution pattern of the earth pressure and the earth pressure The allowable jacking force of the eccentric jacking of the jacking pipe, and the jacking force required to advance the jacking tube is smaller than the allowable jacking force of the eccentric jacking.

In some embodiments, step (a) includes collecting existing geological data of the working area to determine the soil parameters of the working area; and determining the caisson parameters according to the construction plan for applying the rectangular caisson.

In some embodiments, the soil parameters include: soil cohesion c, internal friction angle φ, and bulk density γ; the caisson parameters include the buried depth Hs from the bottom of the rectangular caisson to the undisturbed ground , the width B and length L of the working well, the self-weight G of the rectangular caisson and equipment, the distance d from the center of the jacking force to the top of the working well, and the distance l from the resultant force to the nearer end.

In some embodiments, the soil parameters are determined in the following ways: by fully collecting geological data in the work area, analyzing the availability of the data, taking points to classify and analyze the drilling data, and by sampling tests or in-situ tests , to measure the internal friction angle of the soil and cohesion c, and the bulk density γ of the soil is determined by measuring the soil bulk density test with the ring knife method. For layered soil, the corresponding parameters can be calculated equivalently according to the thickness of each layer of soil; and according to the construction design plan, determine The buried depth Hs from the bottom of the rectangular caisson to the original ground, the width B and length L of the working well, the self-weight G of the rectangular caisson and the equipment, the distance d between the center of the jacking force and the top of the working well, and the resultant force To the nearer distance l.

In some embodiments, according to the parameters of the soil mass and the caisson, the earth pressure calculation method considering the displacement is used to determine the front wall earth pressure, the rear wall earth pressure, the side wall friction resistance and the well bottom friction resistance acting on the caisson respectively. .

In some embodiments, the front wall earth pressure is uniform distribution of active earth pressure:

Among them, K _a is the active earth pressure coefficient.

In some embodiments, the left side of the earth pressure distribution on the rear wall is the initial static earth pressure plus a triangular distribution increment, and the right side is the static earth pressure. When the maximum value at the left end reaches the passive earth pressure:

Among them, K ₀ and K _p are static and passive earth pressure coefficients respectively; λ ₁ is the reduction coefficient considering the disturbance caused by caisson construction.

In some embodiments, the sidewall friction resistance:

f _side = 2λ ₂ LHf

Wherein, λ ₂ is the proportional coefficient of frictional resistance; δ is the contact friction angle between the side wall of the caisson and the soil.

In some embodiments, the bottom hole friction is:

f _bottom = λ ₃ Wμ

Among them, _λ3 is the reduction coefficient, W is the self-weight of caisson and equipment minus water buoyancy, and μ is the friction coefficient.

In some embodiments, the allowable maximum jacking force can be calculated with the following formula:

F _max = (F _rear + f _{side wall} + f _bottom - F _front )/k

Among them, k is a safety factor and is 2.0.

Because the method of the present invention determines the soil parameters in the working area by geological data and test data, and in combination with the jacking force of the pipeline, obtains the soil pressure acting on each direction of the working well through the earth pressure formula and the earth pressure distribution shape provided. Finally, calculate the allowable jacking force for the eccentric jacking of the pipe jacking in the working well. According to the allowable jacking force, the pipe jacking force of the rectangular caisson can be safely set as the working well.

Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the subject matter of the invention.

Description of drawings

The above and other features and advantages of the present invention can be more clearly understood through the following detailed description in conjunction with the accompanying drawings, wherein:

Fig. 1 is a flow chart of a method for setting pipe jacking force for eccentric jacking of a rectangular caisson according to an embodiment of the present invention;

Fig. 2 is according to the working well of rectangular caisson according to the embodiment of the present invention wall earth pressure horizontal distribution diagram; And

Fig. 3 is a vertical distribution diagram of earth pressure on front and rear walls of a working well of a rectangular caisson according to an embodiment of the present invention.

Detailed ways

The invention will be described in more detail hereinafter with reference to the accompanying drawings showing embodiments of the invention. However, this invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In these drawings, the size and relative sizes of layers and regions may be exaggerated for clarity.

Referring now to FIG. 1 , a method for setting pipe jacking force for eccentric jacking of a rectangular caisson according to an embodiment of the present invention will be described in detail.

As shown in FIG. 1 , for the calculation method, in step S101 , the soil parameters and caisson parameters of the area where the working area where the rectangular caisson is applied are obtained. Determine soil parameters and caisson parameters according to different working areas of the caisson operation site.

In this embodiment, the existing geological data of the working area where the rectangular caisson is applied are collected to determine the soil parameters of the working area. In addition, the parameters of the caisson are determined according to the construction plan for applying the rectangular caisson.

In this embodiment, the soil parameters include: soil cohesion c, internal friction angle φ, bulk density γ; the caisson parameters include: the caisson parameters include the rectangular caisson bottom to The buried depth Hs of the undisturbed ground, the width B and length L of the working well, the self-weight G of the rectangular caisson and equipment, the distance d from the center of the jacking force to the top of the working well, and the distance l from the resultant force to the nearer end.

Specifically, the soil parameters are determined in the following ways: by fully collecting geological data in the work area, analyzing the availability of the data, taking points to classify and analyze the drilling data, and determining the soil parameters through sampling tests or in-situ tests internal friction angle of soil and cohesion c, and measure the soil bulk density γ by measuring the soil bulk density test with the ring knife method.

In a preferred embodiment, for layered soil, corresponding parameters can be equivalently calculated according to the thickness of each layer of soil.

In addition, according to the construction design plan, it is determined that the caisson parameters include the buried depth Hs from the bottom of the rectangular caisson to the undisturbed ground, the width B and length L of the working well, the self-weight of the rectangular caisson and equipment G. The distance d from the center of the jacking force to the top of the working well, and the distance l from the resultant force to the nearer end.

In step S103, the earth pressure in each direction of the caisson is calculated according to the soil parameters and caisson parameters.

In this embodiment, according to the soil mass and caisson parameters, the earth pressure calculation method considering the displacement is used to determine the front wall earth pressure, rear wall earth pressure, side wall friction resistance and well bottom friction resistance acting on the caisson respectively. .

The calculation of front wall earth pressure, back wall earth pressure, side wall friction and bottom hole friction will be described in detail below.

In the calculation, considering the distribution form in the limit state, the horizontal distribution pattern of the front and rear wall earth pressure is shown in Figure 2, where the front wall earth pressure is the uniform distribution of active earth pressure, and the left side of the rear wall earth pressure is the initial static soil Pressure plus the distribution increment of the triangle, the right side is the static earth pressure, and when the maximum value on the left end reaches the passive earth pressure, it is the limit state. . The vertical distribution of the two is shown in Figure 3, which is a triangular distribution in the vertical direction.

The front wall earth pressure is uniform distribution of active earth pressure:

Among them, K _a is the active earth pressure coefficient.

In the above earth pressure formulas, the left side of the rear wall earth pressure distribution is the initial static earth pressure plus the triangle distribution increment, and the right side is the static earth pressure. When the maximum value at the left end reaches the passive earth pressure, it is the limit state. The formula for calculating the earth pressure on the rear wall is:

Among them, K ₀ and K _p are static and passive earth pressure coefficients respectively; λ ₁ is the reduction coefficient considering the disturbance caused by caisson construction. In a preferred embodiment, λ ₁ is usually taken as 0.8, and it is taken as 1 if foundation pit excavation is adopted.

The side wall friction is:

f _bottom = λ ₃ Wμ

Among them, _λ2 is the proportional coefficient of frictional resistance. In a preferred embodiment, λ ₂ is usually 0.4. In addition, f is the average frictional resistance of the soil to the working well, which can refer to the frictional resistance during the subsidence process.

The well bottom friction is:

f _bottom = λ ₃ Wμ

Among them, _λ3 is the reduction coefficient, which is to consider the disturbance of the soil in the area of the blade foot, which is 0.6. W is the force on the soil at the blade foot plane of the working well, which is equal to the self-weight of the working well and the equipment in the well minus the buoyancy of groundwater, and μ is the friction coefficient. For the coefficient of friction, take 0.25 for cohesive soil and 0.5 for sandy soil. Considering the most unfavorable situation of groundwater, that is, when the buoyancy of water is equal to the self-weight of the caisson, the friction coefficient can be taken as zero.

In step S105, (c) calculate the allowable jacking force of the eccentric jacking of the pipe jacking according to the distribution pattern of the earth pressure and the earth pressure, and make the jacking force required for the advancement of the pipe jacking less than the Allowable jacking force for eccentric jacking.

According to the distribution pattern of the earth pressure and the earth pressure, the allowable jacking force of the eccentric jacking of the working well can be calculated by the following formula:

F _max = (F _rear + f _{side wall} + f _bottom - F _front )/k

Among them, k is the safety factor, which is 2.0. In areas with soft soil, that is, when deformation control is required, the safety factor is 4.0.

After obtaining the allowable jacking force for eccentric jacking, the jacking force required to advance the pipe jacking is smaller than the allowable jacking force for eccentric jacking.

An example of a method for setting pipe jacking force during eccentric jacking of a rectangular caisson according to an embodiment of the present invention will be described in detail below.

Example:

The test site is a pipe jacking project, the depth of the working well is 18.9m, the width is 18.2m, and the center of the pipe jacking is 12.9m from the surface.

In order to optimize the calculation of the maximum jacking force, the force mode shown in Figure 1 is adopted. The specific method and steps are as follows:

1) Measure the average internal friction angle of the excavation through sampling test or in-situ test The average cohesion c=9kPa, the bulk density of soil γ=18kN/m3. According to the construction plan, it is determined that the buried depth from the bottom of the working well to the original ground is Hs=18.9m, the width of the working well is B=18.2, and the length L=11.2m.

Table 1 Soil layer material parameters

2) Substitute the soil mass and working well parameters into each earth pressure formula to determine the earth pressure acting on the working well, take the safety factor of 2.0, and calculate F _max =15615kN.

The present invention has the following advantages:

(1) Since the method of the present invention determines the soil parameters of the working area through geological data and test data, and combines the jacking force of the pipeline, the soil pressure acting on each direction of the working well is obtained through the earth pressure formula and the given earth pressure distribution shape. Finally, calculate the allowable jacking force for the eccentric jacking of the pipe jacking in the working well. According to the allowable jacking force, the pipe jacking force of the rectangular caisson as the working well can be safely set.

(2) The principle of the present invention is simple, has the advantages of high calculation accuracy, can improve economic benefits, and has strong practicability.

Those skilled in the art will appreciate that the present invention may be embodied in many other specific forms without departing from the spirit or scope of the invention. Although embodiments of the present invention have been described, it should be understood that the present invention should not be limited to these embodiments, and that changes and modifications may be made by those skilled in the art within the spirit and scope of the invention as defined by the appended claims.

Claims (2)

1. a jacking forces in pipe-jacking setting method for the eccentric jacking of rectangular open caisson, is characterized in that, comprise the following steps:

A () obtains Soil Parameters and the open caisson parameter of the region, working area of application rectangular open caisson, comprise the existing geologic information of the described working area of collection to determine the Soil Parameters of described working area; According to the arrangement and method for construction of the described rectangular open caisson of application, determine described open caisson parameter;

Described Soil Parameters comprises: the cohesion c of soil property, internalfrictionangleφ and unit weight γ; Described open caisson parameter comprise at the bottom of the open caisson of described rectangular open caisson to original state ground buried depth H, described active well width B, length L, described rectangular open caisson and equipment self-weight G, push up active well apex distance described in power centre distance from d and make a concerted effort to nearer end distance l;

Described Soil Parameters is determined in the following manner: by the geologic information in abundant collection work district, analysis of data can producing level, get and some taxonomic revision and analysis are carried out to borehole data, by sampling test or in-situ test, measure internalfrictionangleφ and the cohesion c of the soil body, and the unit weight γ of the native unit weight test determination soil body is measured by core cutter method etc., wherein for stratified soil, go out relevant parameter according to the thickness Equivalent Calculation that every layer is native; And according to Construction Design Schemes, determine at the bottom of the open caisson of described rectangular open caisson to original state ground buried depth H, described active well width B, length L, described rectangular open caisson and equipment self-weight G, top power centre distance active well apex distance from d, and is made a concerted effort apart from nearer end distance l;

B () goes out the earth pressure in described open caisson all directions according to described Soil Parameters and open caisson calculation of parameter;

Antetheca earth pressure is that active earth pressure is uniformly distributed:

Wherein, K _afor coefficient of active earth pressure;

For rest earth pressure adds leg-of-mutton distribution increment on the left of rear wall geostatic shield, right side is earth pressure at rest, and when left end maximum value reaches passive earth pressure, then rear wall Earth Pressure is:

Wherein, K ₀, K _pbe respectively static, coefficient of passive earth pressure, λ ₁for the reduction coefficient considering that in open caisson construction, disturbance causes;

Side friction power:

F _side=2 λ ₂lHf

Wherein, λ ₂for frictional resistance scaling factor, f is the average friction of the soil body to active well;

Described shaft bottom frictional resistance is:

F _{the end}=λ ₃w μ

Wherein, λ ₃for reduction coefficient, W is that open caisson and equipment self-weight deduct water buoyancy, _μfor the coefficient of friction resistance;

C (), according to the distribution pattern of described earth pressure and described earth pressure, the bias calculating described push pipe allows top power by top, and make described push pipe advance needed for jacking force be less than described bias and allow top power by top,

Allow the following formulae discovery of maximum top power:

F _max=(F _after+ f _sidewall+ f _{the end}-F _before)/k

Wherein, k is safety coefficient, and is 2.0.

2. the setting method of the jacking forces in pipe-jacking of the eccentric jacking of rectangular open caisson according to claim 1, it is characterized in that, according to the described soil body and open caisson parameter, with considering that the Calculating method of earth pressure of displacement determines antetheca earth pressure, rear wall earth pressure, side friction power and the shaft bottom frictional resistance acted on described open caisson respectively.