CN107476156B

CN107476156B - Optimization design method of soft foundation pile bearing reinforced embankment

Info

Publication number: CN107476156B
Application number: CN201710707358.1A
Authority: CN
Inventors: 张惠明; 黄少杰; 赵敏
Original assignee: Guangdong Shewei Technology Co ltd
Current assignee: Guangdong Shewei Technology Co ltd
Priority date: 2017-08-17
Filing date: 2017-08-17
Publication date: 2020-04-21
Anticipated expiration: 2037-08-17
Also published as: CN107476156A

Abstract

The invention discloses an optimization design method of a soft foundation pile bearing reinforced embankment, which inputs basic parameters according to the existing specifications, preliminarily selects related information of a soft foundation pile, determines the maximum allowable clear space between piles, analyzes and selects proper pile space and pile cap size to minimize the construction cost by combining the bearing capacity of a single pile, and performs selective purchasing and engineering design of the soft foundation pile according to the finally determined parameters, thereby saving the engineering expenditure.

Description

Optimization design method of soft foundation pile bearing reinforced embankment

Technical Field

The invention relates to the technical field of civil engineering, in particular to an optimal design method of a soft foundation pile supported reinforced embankment.

Background

The existing soft foundation pile bearing reinforced embankment design calculation theory can reliably solve the overall stability problem and the settlement problem of the soft foundation embankment, but is conservative and has larger optimization space. For example, can the bearing capacity of the foundation pile be improved on the premise of meeting the performance requirements of the pile-supported reinforced embankment? Can more economical pile forms and pile caps be used when the embankment is not loaded much? How much the pile spacing or net spacing has excavation potential, whether it can be further increased under the action of the reinforcement mat?

Disclosure of Invention

Based on the above, there is a need to provide an optimal design method for a soft foundation pile bearing reinforced embankment, so as to improve the utilization rate of the load borne by soil between piles, further expand the pile spacing, and achieve the purpose of optimal design.

In order to achieve the above object, the present invention adopts the following technical solutions.

An optimal design method of a soft foundation pile bearing reinforced embankment comprises the following steps:

inputting the thickness of the filling soil and the thickness of a pavement structure layer according to the road planning requirement;

preliminarily selecting the thickness, the pile type, the diameter of a pile body and the size of a pile cap of the reinforcement cushion layer;

determining the weight of the reinforced cushion layer, the cohesive force of the filled soil and the friction angle of the pavement structure layer according to the materials of the reinforced cushion layer, the filled soil and the pavement structure layer;

determining road surface load according to road planning requirements, and calculating the maximum inter-pile clear space and pile cap size;

determining the deformation modulus of the reinforced cushion layer and the filling soil and the tensile modulus of the geogrid according to the materials of the reinforced cushion layer and the filling soil;

checking corresponding standard data, inputting the weight of the steel bar, the pile cap reinforcement ratio and the reinforcement composite coefficient, calculating reinforcement tension according to the reinforcement composite coefficient, and further determining the type and parameters of the reinforcement body;

inputting soil layer information provided by a geological survey report, wherein the soil layer information comprises a soil layer name, a side resistance characteristic value, an end resistance characteristic value and a soil layer thickness, and calculating a pile length and a single-pile bearing capacity characteristic value of a selected pile type;

checking whether the characteristic value of the bearing capacity of the single pile meets the design requirement, and if not, adjusting the diameter of the pile body or the length of the pile until the characteristic value meets the design requirement;

and selecting the soft foundation pile according to the determined pile type, pile length, pile body diameter, single pile bearing capacity, maximum inter-pile clear space and reinforcement tension force, and carrying out construction design on the soft foundation pile.

The optimal design method of the soft foundation pile bearing reinforced embankment selects proper design parameters on the premise of meeting technical requirements, so that the construction cost is the lowest, the pile bearing capacity is the most saved, the proper pile spacing and the proper pile cap size are analyzed and selected, the construction cost is the lowest, and the construction expenditure is saved.

Drawings

Fig. 1 is a schematic flow chart of the method for optimally designing the soft foundation pile bearing reinforced embankment according to the present invention.

Detailed Description

The prior research results are relatively consistent in the view that the transfer of the embankment load to the pile cap follows the soil arch effect. The formation principle of the soil arch effect is as follows: the soil arching effect is generated by local differential deformation. When soil particles between piles sink, the soil particles on the edge of the pile cap sink less, and the latter has a supporting and resisting effect on the former; due to the overlapping and supporting and blocking effects of soil particles, the range of the less-sinking soil body on the top of the pile cap gradually extends towards the space between the piles; when the height is increased to a certain height, a soil arch is formed when the less-sinking soil body between the adjacent pile caps is folded; the fill load above this height is transferred to the pile cap through this arch. On the same plane, the settlement outside the soil arch is similar to that of the pile cap, while the settlement inside the soil arch is larger; when the soil body reaches the soil arch top plane, the soil body presents equal settlement, so the soil arch top plane is also called as an equal settlement plane.

According to the soil arch effect principle, when the filling height of the embankment is greater than the equal sinking surface height, the settlement of the roadbed surface is consistent no matter in the range of the pile cap or the range of soil among piles, and differential settlement is not generated due to the difference of the soil among the piles. Thus, designs often require fill heights greater than full soil arch heights, even if full soil arching does not actually occur.

There are several calculation theories for the complete soil arch, such as BS8006 regulation in england, Nordic handbook, japan rules, germany DBGEO regulation, etc. which use different soil arch theories.

The existing design method has obvious problems:

1. the assumption of complete soil arching does not conform to the actual situation;

2. the calculation result of the reinforcement tension force is seriously inconsistent with the actual situation;

3. by adopting an empirical test method, an ideal design scheme is not easy to obtain.

The skilled person needs to optimize the design of the existing design method. On the premise of meeting the technical requirements, proper design parameters are selected, so that the construction cost is saved to the minimum. For the pile bearing reinforced embankment, the maximum allowable clear distance between piles is determined, and the proper pile distance and the size of a pile cap are analyzed and selected to minimize the construction cost by combining the bearing capacity of a single pile, so that the design process is optimized.

The optimal design method of the soft foundation pile bearing reinforced embankment is divided into 4 blocks which are respectively 'basic parameters', 'soil layer information and single pile bearing capacity', 'calculation results' and 'design selection parameters'.

Based on the existing data of engineering, such as: drilling reports, embankment planning conditions and the like are input into corresponding basic parameters and soil layer information and single-pile bearing capacity modules according to prompts, so that calculation results can be displayed in the calculation result modules, and the optimal pile type, pile diameter, pile length, pile spacing, pile cap size, reinforcement type and technical index, and cushion type and thickness parameters of the project can be obtained in the design selection parameter modules, as shown in figure 1, and the modules and the execution process thereof are respectively described below.

One, basic parameter

Step 1: and inputting the thickness of the filling soil and the thickness of the pavement structure layer according to the road planning requirement.

Step 2: and (5) initially determining the thickness of the reinforced cushion layer.

And step 3: and (5) initially determining the diameter of the pile body and the size of the pile cap.

And 4, step 4: and determining the gravity, the cohesion and the friction angle of the reinforced cushion layer, the filling and the road surface structure layer according to the materials of the reinforced cushion layer, the filling and the road surface structure layer.

And 5: and determining the road surface load according to the road planning requirement.

Step 6: according to the selected material, checking the corresponding specification data, and determining the deformation modulus of the cushion layer and the filling and the tensile modulus of the grid.

And 7: and determining the comprehensive unit price of the pile, the concrete and the reinforcing steel bar according to the market condition at that time.

And 8: checking corresponding standard data, and inputting the steel weight, pile cap reinforcement ratio and reinforced composite coefficient.

Soil layer information and single pile bearing capacity

And step 9: according to the land survey, soil layer information is input, wherein the soil layer information comprises soil layer names, side resistance characteristic values, end resistance characteristic values and soil layer thicknesses. And calculating to obtain the pile length and the single pile bearing capacity characteristic value of the selected pile type.

Step 10: and checking whether the characteristic value of the bearing capacity of the single pile meets the design requirement. When the pile length does not meet the requirement, the diameter or the pile length of the pile body is adjusted.

Thirdly, calculating the result

Step 11: and after the steps are completed, checking whether the calculation output result meets the standard requirement.

Fourthly, selecting parameters for design

Step 12: when the calculation results all meet the standard requirements, the optimal selection values of the design can be obtained, wherein the optimal selection values comprise pile diameter, pile spacing, pile cap size, geogrid tensile resistance, reinforced cushion layer thickness and filling thickness.

The above-mentioned embodiments only express the embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims

1. An optimal design method of a soft foundation pile bearing reinforced embankment is characterized by comprising the following steps:

checking whether the characteristic value of the bearing capacity of the single pile meets the design requirement, and if not, adjusting the pile type, the diameter of the pile body or the length of the pile until the characteristic value meets the design requirement;

and selecting the soft foundation pile according to the determined pile type, pile length, pile body diameter, single pile bearing capacity, maximum inter-pile clear space, reinforcement tension force, pile cap size, geogrid tensile resistance, reinforcement cushion layer thickness and filling thickness, and carrying out construction design on the soft foundation pile.