WO2022160713A1

WO2022160713A1 - Method for constructing novel starter dam suitable for upstream tailings pond

Info

Publication number: WO2022160713A1
Application number: PCT/CN2021/116002
Authority: WO
Inventors: 许传华; 段蔚平; 毛志远; 邱宇; 杨强胜; 田伟虎; 倪强; 藕明江; 翁金红; 吴光富; 曹金海; 鲁立胜; 汪明海; 林启祥
Original assignee: 中钢集团马鞍山矿山研究总院股份有限公司; 华唯金属矿产资源高效循环利用国家工程研究中心有限公司; 中钢集团马鞍山矿院工程勘察设计有限公司
Priority date: 2021-01-27
Filing date: 2021-09-01
Publication date: 2022-08-04
Also published as: CN112921905B; ZA202204722B; CN112921905A

Abstract

Disclosed is a method for constructing a novel starter dam suitable for an upstream tailings pond, comprising: laying a starter dam body bottom anti-seepage layer; providing a starter dam upstream seepage drainage prism body (1) and a starter dam downstream seepage drainage prism body (1^,) respectively on the upstream and downstream of the starter dam, and laying a starter dam seepage drainage mattress (2) on the starter dam body bottom anti-seepage layer, lower ends of vertical seepage drainage blind ditch pipe (3) being in communication with the starter dam seepage drainage mattress (2); pre-embedding inclined drainage blind ditches at positions where the starter dam contacts mountain bodies, and pre-embedding transverse blind ditches at positions where the starter dam contacts the mountain bodies; and building the starter dam layer by layer from bottom to top, and compacting same in a layered manner, and constructing an anti-seepage protective slope layer (5) on an upstream slope surface of the starter dam. The present invention has advantages of low construction cost, small amount of stones used, and good water-permeable effect. By designing a drainage facility inside a starter earth dam, the earth dam meets the requirement of a water-permeable dam.

Description

A new type of initial dam construction method suitable for upstream tailings pond

technical field

The invention relates to a tailings discharge and stockpiling facility, in particular to an initial dam of a tailings pond, which is especially suitable for the upstream of the proposed tailings pond where there is a lack of stone resources, it is difficult to build a permeable rockfill dam and the traffic is inconvenient The application in the construction of tailings pond can effectively reduce the wetting line of the dam body.

Background technique

The initial dam was built with materials other than tailings, and its main function was to lay the foundation for the subsequent tailings accumulation dam, also known as the foundation dam. According to whether the drainage can be divided into two types: impervious dam and permeable dam.

During the operation of the upstream tailings pond, considering the stability of infiltration in the initial and later stages of the operation of the tailings pond, the initial dam type is usually a permeable rockfill dam. A permeable dam is a dam type that conducts organized drainage in the dam body and allows organized and planned water seepage. Its drainage system differs from the drainage system of an impervious dam in function and role. There is also a drainage system in the impermeable dam, the purpose of which is to discharge the seepage water in the anti-seepage body in an organized manner, protect the anti-seepage body and the initial dam, and prevent seepage deformation. The drainage system of the permeable dam is to remove the seepage water through the dam body in an organized manner, and its main function is to control the position of the infiltration line in the accumulation dam. The main dam type of the permeable dam is to add a reverse filter on the upstream slope of various rockfill dams, or to add drainage facilities in the impervious dam to reduce the infiltration line of the tailings accumulation dam. The permeable dam is the most basic dam type in the initial dam, and it is also an ideal dam type.

The dam type selection of the initial dam should be based on the specific conditions of the body, and implement the principles of adapting measures to local conditions, using local materials, and designing according to materials. Earth-rock dams have the lowest requirements on topographic and geological conditions and the strongest adaptability. If the local stone is not enough to build a permeable rockfill dam, drainage facilities can be added on the basis of the homogeneous dam to achieve permeation.

In the article "Seepage Calculation Analysis of a New Initial Dam Type for Upstream Tailings Ponds" published in the Chinese journal "Science and Technology Wind" in February 2020, a new initial dam type was proposed, which is upstream of conventional rockfill dams. Filling a part of earth-rock mixture in the side zone (about 1/4 of the initial dam height) can not only reduce the tailings "running muddy" in the early stage of operation of the tailings pond, but also ensure the stability of the seepage of the accumulation dam. However, the initial dam is a permeable dam, which requires a lot of rock resources and high construction cost. Moreover, after filling a part of the earth-rock mixture in the upstream side of the conventional rockfill dam, the water permeability is greatly reduced.

According to the site conditions of the tailings pond and the characteristics of the dam-building materials, the invention innovates a design method to make the earth dam meet the requirements of the permeable dam, and design the drainage facilities inside the initial earth dam to make the earth dam meet the requirements of the permeable dam.

SUMMARY OF THE INVENTION

In order to overcome the problems of consuming a large amount of stone resources, high construction cost and poor water permeability of earth-rock dams in the construction of permeable dams in existing tailings ponds, a new method with low construction cost, small amount of stone materials and good water permeability is provided, which is suitable for upstream The new initial dam construction method of the type tailings pond, the designed initial earth dam can meet the water permeability requirements of the permeable dam, and when the site stone is not enough to build the initial rockfill dam and the cost of transporting the stone is high, the method of the invention can be used effectively. Reduce costs, and make the initial earth dam meet the use requirements of permeable dams.

In order to realize the above-mentioned purpose of the present invention, a kind of construction method of the novel initial stage dam suitable for the upstream tailings pond of the present invention adopts the following technical scheme to realize:

The present invention is a construction method of a new type of initial dam suitable for an upstream tailings pond. A shoulder intercepting ditch is arranged on the mountain bodies on both sides of the initial dam, and a dam toe drainage ditch is arranged at the dam foot of the initial dam. The outlet end of the ditch is connected to the drainage ditch at the foot of the dam, and the following technical solutions are adopted:

1) The anti-seepage layer at the bottom of the dam body at the initial stage of laying

The foundation of the initial dam is cleaned, and after the foundation is cleaned, the fine-grained soil layer, the composite geomembrane, the coarse sand layer, the rock layer and the sand and pebble layer are laid from bottom to top to form the anti-seepage layer at the bottom of the initial dam body;

In the fine-grained soil layer, the mass proportion of the 0-0.1mm grain size is ≥95%, the 2-13mm grain size in the coarse sand layer is ≥95%, and the 76-200mm grain size in the boulder layer is ≥95%. %, the mass proportion of the 13-76mm grain size in the sand and pebble layer is ≥95%; among which: the thickness of the fine-grained soil layer is 0.17-0.23m, the thickness of the coarse sand layer is 0.18-0.24m, and the thickness of the rock layer is 1.3 ～1.8m, the thickness of the sand and pebble layer is 0.18～0.25m.

2) Set upstream seepage drainage prisms of the initial dam and downstream seepage prisms of the initial dam respectively on the upstream and downstream of the initial dam, and prevent the bottom of the initial dam body between the upstream seepage drainage prisms of the initial dam and the downstream seepage prisms of the initial dam. The initial dam drainage cushion is laid on the seepage layer, and the upstream seepage drainage prism of the initial dam and the downstream seepage prism of the initial dam are connected with the initial dam drainage cushion; the stones used to build the seepage drainage prism must be good permeable materials , the content of the stone particle size less than 2mm should not be greater than 5%, the maximum diameter of the stone should not exceed 0.5m, the stone should be fresh, hard, weathering and abrasion resistant, no weathered stone should be used, wet compressive strength ≥ 40Mpa, softening coefficient ≥ 0.80; The drainage prism and the drainage mattress are wrapped with double-layer geotextiles.

3) A vertical seepage drainage blind ditch pipe is pre-buried on the initial dam seepage drainage mattress in the initial dam, and the lower end of the vertical seepage drainage blind ditch pipe is communicated with the initial dam seepage drainage mattress; the vertical seepage drainage blind ditch pipe The ditch pipes are made of plastic blind ditch pipes and wrapped with geotextiles, and the vertical seepage drainage blind ditch pipes are symmetrically arranged in the initial dam.

4) Pre-buried oblique drainage blind ditch at the contact part between the initial dam and the mountain, and pre-embedded the horizontal blind ditch in the initial contact part of the dam and the mountain. The upper water inlet of the oblique drainage blind ditch is connected with the horizontal drainage blind ditch The lower water outlet of the ditch is connected to the initial dam drainage pad; the blind ditch is to wrap the rubble with double-layer geotextile, and the rubble should be dense and have good water permeability. The purpose is to increase the contact area between the initial dam and the mountain. The drainage capacity of the dam further reduces the infiltration line of the dam body.

5) Initial dam construction

In the space formed by the upstream seepage drainage prism of the initial dam, the downstream seepage prism of the initial dam and the mountains on both sides of the initial dam, the initial dam is stacked layer by layer from bottom to top, and compacted in layers. After the initial dam upstream seepage drainage prism height, follow the steps below:

Step 1: Use cohesive soil to build and compact the first layer of the initial dam, and construct an anti-seepage slope protection layer on the upstream slope of the first layer of the initial dam;

Step 2: Use cohesive soil to build and compact the second layer of the initial dam on the first layer of the initial dam, and construct an anti-seepage protection slope on the upstream slope of the second layer of the initial dam;

Part 3: Build and compact the third layer of the initial dam with cohesive soil above the second layer of the initial dam, and construct an anti-seepage protection slope on the upstream slope of the third layer of the initial dam;

Steps 4 to n: By analogy, until the stacking reaches the design height.

A geomembrane is laid on the top surface of the initial dam, and a protective layer of crushed stone and dry block stone is laid on the geomembrane. For dry-laid stone specifications, the ratio of long and short sides is not more than 4, the content of less than 20mm is less than 5%, and there is an appropriate gradation.

Further, the anti-seepage slope protection layers are respectively a sand pebble layer, a block stone layer, a sand pebble layer, a coarse sand layer, a composite geomembrane, and a coarse sand layer from the inside to the outside; the composite geomembrane is the middle of the two layers of geotextiles. Sandwich a layer of geomembrane; in the anti-seepage protection layer, the 13-76mm grain size in the sand and pebble layer accounts for ≥95% of the mass, the 76-200mm grain size in the cobblestone layer accounts for ≥95% of the mass, and 2 in the coarse sand layer. The mass ratio of ～13mm grain size is ≥95%; in the anti-seepage protection layer, the thickness of the coarse sand layer is 0.18-0.24m, the thickness of the boulder layer is 1.3-1.8m, and the thickness of the sand and pebble layer is 0.18-0.25m .

Further, in step 5), the stacking height of each layer from bottom to top is 2.2-2.8m, and the thickness of layered compaction is not more than 0.8m. , the number of samples and the technical requirements for porosity determination shall be implemented in accordance with the requirements of the specification, and the porosity of the dam body after compaction shall not be greater than 22%. The precautions and technical requirements for cohesive soil piling must follow the "Technical Specifications for Roller Compacted Earth-rock Dam Construction" DL/5129-2001 and GBJ201-83 "Code for Construction and Acceptance of Earthwork and Blasting Engineering", so that the filling quality can achieve the expected purpose .

Further, the present invention adopts the Bishop method to analyze the stability of the tailings dam; uses the finite element method to analyze the seepage field of the tailings dam, calculates the node water head, and uses the computer to output the water level line.

After adopting the above technical scheme, a construction method of a novel initial dam suitable for an upstream tailings pond of the present invention has the following effects:

(1) When the existing stone materials on the site are insufficient to build a rockfill dam and the cost of transporting the stone materials is too high, this method can significantly reduce the cost;

(2) The seepage drainage facility main body composed of the upstream and downstream seepage drainage prisms and the seepage drainage mattress can realize the seepage drainage of the cohesive soil initial dam;

(3) The infiltration line of the dam body can be further reduced when the infiltration line in the initial dam is relatively high through the pre-buried vertical seepage drainage blind trench pipe in the initial dam;

(4) Pre-buried oblique drainage blind ditch at the initial contact part of the dam and the mountain, and pre-embedded the horizontal blind ditch at the initial contact part of the dam and the mountain, which can increase the drainage effect and further reduce the wetting line of the dam body;

(5) The construction is simple by this method, and the designed drainage facilities mostly use stone, geomembrane and geotextile, and the construction materials are easy to obtain.

Description of drawings

Fig. 1 is a kind of new-type initial stage dam system cross-sectional structural schematic diagram suitable for upstream type tailings pond constructed by the method of the present invention;

FIG. 2 is a schematic diagram of the longitudinal section structure of a new type of initial dam system suitable for upstream tailings ponds constructed by the method of the present invention.

The reference signs are: 1 - upstream seepage drainage prism of the initial dam; 1' - seepage drainage prism downstream of the initial dam; 2 - initial dam seepage drainage cushion; 3 - vertical seepage drainage blind ditch pipe; 4 - dam foot drainage ditch; 5- anti-seepage slope protection layer; 6- late tailings sub-dam; 7- oblique drainage blind ditch; 8- lateral drainage blind ditch; 9- anti-seepage layer at the bottom of the initial dam body.

Detailed ways

The construction method of a novel initial dam suitable for an upstream tailings pond of the present invention will be described in further detail below with reference to the accompanying drawings and embodiments.

The cross-sectional structural schematic diagram of a new type of initial dam system suitable for upstream tailings ponds constructed by the method of the present invention shown in FIG. 1 and combined with FIG. The construction method of the dam is to set the dam abutment intercepting ditch on the mountains on both sides of the initial dam, and set the dam toe drainage ditch 4 at the dam toe of the initial dam, and the outlet end of the shoulder intercepting ditch is communicated with the dam toe drainage ditch 4, And adopt the following technical solutions:

The foundation of the initial dam is cleaned, and after the cleaning is completed, the fine-grained soil layer, the composite geomembrane, the coarse sand layer, the rock layer, and the sand and pebble layer are laid from bottom to top to form the anti-seepage layer 9 at the bottom of the initial dam body; In the fine-grained soil layer, the mass proportion of 0-0.1mm grain size is ≥95%, in the coarse sand layer, the mass proportion of 2-13mm grain size is ≥95%, and the mass proportion of 76-200mm grain size in the boulder layer is ≥95%. In the sand and pebble layer, the mass proportion of the 13-76mm grain size is ≥95%; the thickness of the fine-grained soil layer is 0.2m, the thickness of the coarse sand layer is 0.2m, the thickness of the boulder layer is 1.5m, and the thickness of the sand and pebble layer is 0.2m.

2) On the upstream and downstream of the initial dam, respectively set the upstream seepage drainage prism 1 of the initial dam and the downstream seepage prism 1' of the initial dam, between the upstream seepage prism 1 of the initial dam and the seepage prism 1' downstream of the initial dam The initial dam seepage drainage cushion 2 is laid on the bottom anti-seepage layer 9 of the initial dam body, and the upstream seepage drainage prism 1 of the initial dam and the downstream seepage prism 1' of the initial dam are communicated with the initial dam seepage drainage cushion 2;

3) The vertical seepage drainage blind ditch pipe 3 is pre-buried on the initial dam seepage drainage mattress 2 in the initial dam, and the lower end of the vertical seepage drainage blind ditch pipe 3 is communicated with the initial dam seepage drainage mattress 2;

4) Pre-buried oblique drainage blind ditch 7 at the contact position between the initial dam and the mountain body, pre-embedded lateral blind ditch 8 at the initial contact position of the dam and the mountain body, and the upper water inlet of the oblique drainage blind ditch 7 is communicated with the horizontal drainage blind ditch 8, The lower water outlet of the oblique drainage blind ditch 7 is communicated with the initial dam drainage cushion 2;

5) Initial dam construction

In the space formed by the upstream seepage drainage prism 1 of the initial dam, the downstream seepage prism 1' of the initial dam, and the mountains on both sides of the initial dam, the initial dam is built layer by layer from bottom to top, and the layers are compacted. After compaction to the height of the seepage-draining prism 1 upstream of the initial dam, follow the steps below:

Step 1: Use cohesive soil to build and compact the first layer of the initial dam, and construct the anti-seepage slope protection layer 5 on the upstream slope of the first layer of the initial dam;

Step 2: Use cohesive soil to build and compact the second layer of the initial dam on the first layer of the initial dam, and construct the anti-seepage protection slope layer 5 on the upstream slope of the second layer of the initial dam;

Part 3: Build and compact the third layer of the initial dam with cohesive soil above the second layer of the initial dam, and construct an anti-seepage protection slope layer 5 on the upstream slope of the third layer of the initial dam;

Steps 4 to n: By analogy, until the stacking reaches the design height.

The anti-seepage slope protection layer 5 is, from the inside to the outside, a sand and pebble layer, a block stone layer, a sand and pebble layer, a coarse sand layer, a composite geomembrane, and a coarse sand layer. %, the mass proportion of 76-200mm grain size in the boulder layer is ≥95%, and the mass proportion of 2-13mm grain size in the coarse sand layer is ≥95%; in the anti-seepage slope protection layer 5, the thickness of the coarse sand layer is 0.2m , the thickness of the block stone layer is 1.5m, and the thickness of the sand pebble layer is 0.2m.

The composite geomembrane used in the present invention is a layer of geomembrane sandwiched between two layers of geotextiles, and the specifications of the geotextiles are 300-600 g/m ² ; wherein: the composite geomembrane in step 1) adopts 300 g/m ² geotextiles. 5) The composite geomembrane adopts 600g/m ² non-woven geotextile, and the geomembrane adopts HDPE membrane.

In step 5), the stacking height of each layer from bottom to top is 2.5m, and the thickness of layered compaction does not exceed 0.8m.

After the initial dam is built to the design height, a geomembrane is laid on the top surface of the initial dam, and a protective layer of crushed stone and dry block stone is laid on the geomembrane.

After the initial dam construction is completed and the tailings are discharged to this level, the construction of the sub-dam 6 begins. The construction sequence of the sub-dam 6 is as follows:

The base layer is first leveled, and the fine-grained soil layer, composite geomembrane, and coarse tailings protective layer are constructed from bottom to top on the base layer to form the first-level sub-dam; after the construction of the first-level sub-dam is completed, the tailings are discharged After reaching this level, the second-level sub-dam will be built backward; the construction sequence of the second-level sub-dam is also leveling the base layer→fine-grained soil layer→composite geomembrane→coarse tailings protective layer, and so on. In the fine-grained soil layer, the mass proportion of the 0-0.1mm grain size is ≥95%, and in the coarse sand layer, the mass proportion of the 2-13mm grain size is ≥95%, and the thickness of the fine-grained soil layer is 0.2m; The old tailings pond was excavated and transported, with a thickness of 0.2m; the composite geomembrane is a layer of geomembrane sandwiched between ^two layers of geotextiles.

The invention adopts the Bishop method to analyze the stability of the tailings dam; uses the finite element method to analyze the seepage field of the tailings dam, calculates the node water head, and uses the computer to output the water level line.

Claims

A method for constructing a new type of initial dam suitable for an upstream tailings pond. A dam abutment intercepting ditch is arranged on the mountain bodies on both sides of the initial dam, and a dam toe drainage ditch (4) is arranged at the dam foot of the initial dam. The outlet end of the intercepting ditch is communicated with the drainage ditch (4) at the foot of the dam, and is characterized in that the following technical solutions are also adopted:

1) The anti-seepage layer at the bottom of the dam body at the initial stage of laying

The foundation of the initial dam is cleaned. After the foundation is cleaned, the fine-grained soil layer, the composite geomembrane, the coarse sand layer, the rock layer and the sand and pebble layer are laid from bottom to top to form the anti-seepage layer at the bottom of the initial dam body (9 );

2) Set up seepage drainage prisms (1) upstream of the initial dam and downstream seepage prisms (1') on the upstream and downstream of the initial dam, respectively, and seepage drainage prisms (1) upstream of the initial dam and seepage drainage downstream of the initial dam The initial dam seepage drainage cushion (2) is laid on the anti-seepage layer (9) at the bottom of the initial dam body between the prisms (1'), the seepage drainage prism (1) upstream of the initial dam, and the seepage drainage prism downstream of the initial dam ( 1') is communicated with the initial dam drainage mattress (2);

3) The vertical seepage drainage blind ditch pipe (3) is pre-buried on the initial dam seepage drainage mattress (2) in the initial dam, and the lower end of the vertical seepage drainage blind ditch pipe (3) and the initial dam seepage drainage mattress (2) Connectivity;

4) Pre-buried oblique drainage blind ditch (7) at the initial contact position between the dam and the mountain, pre-embedded lateral blind ditch (8) at the initial contact position between the dam and the mountain, and the upper water inlet of the oblique drainage blind ditch (7) and the horizontal The blind drainage ditch (8) is communicated, and the lower water outlet of the oblique drainage blind ditch (7) is communicated with the initial dam drainage cushion (2);

5) Initial dam construction

In the space formed between the upstream seepage drainage prism (1) of the initial dam, the downstream seepage prism (1') of the initial dam, and the mountains on both sides of the initial dam, the initial dam is built layer by layer from bottom to top, and the layers are layered. Compaction, when compacted to the height of the upstream seepage prism (1) of the initial dam, follow the steps below:

Step 1: Use cohesive soil to build and compact the first layer of the initial dam, and construct an anti-seepage slope protection layer (5) on the upstream slope of the first layer of the initial dam;

Step 2: Use cohesive soil to build and compact the second layer of the initial dam on the first layer of the initial dam, and construct the anti-seepage slope protection layer (5) on the upstream slope of the second layer of the initial dam;

Part 3: Use cohesive soil to build and compact the third layer of the initial dam on the second layer of the initial dam, and construct the anti-seepage slope protection layer (5) on the upstream slope of the third layer of the initial dam;

Steps 4 to n: and so on.
The construction method of a new type of initial dam suitable for an upstream tailings pond according to claim 1, characterized in that: in step 1) the fine-grained soil layer in the fine-grained soil layer accounts for ≥ 95% by mass , the mass proportion of 2-13mm grain size in the coarse sand layer is ≥95%, the mass proportion of 76-200mm grain size in the boulder layer is ≥95%, and the mass proportion of 13-76mm grain size in the sand and pebble layer is ≥95%.
The construction method of a novel initial dam suitable for an upstream tailings pond according to claim 2, characterized in that: the anti-seepage slope protection layer (5) from the inside to the outside is a sand and pebble layer, a block stone layer, and a sand and pebble layer, respectively. layer, coarse sand layer, composite geomembrane, and coarse sand layer; the composite geomembrane is a layer of geomembrane sandwiched between two layers of geotextiles.
The construction method of a new type of initial dam suitable for an upstream tailings pond according to claim 3, characterized in that: in the anti-seepage slope protection layer (5), the mass proportion of 13-76 mm grain size in the sand and pebble layer ≥95%, the mass proportion of 76-200mm in the rock layer is ≥95%, and the mass of 2-13mm in the coarse sand layer is ≥95%.
The construction method of a new type of initial dam suitable for an upstream tailings pond according to claim 4, characterized in that: in step 1), the thickness of the fine-grained soil layer is 0.17-0.23 m, and the thickness of the coarse sand layer is 0.17-0.23 m. It is 0.18-0.24m, the thickness of the rock layer is 1.3-1.8m, and the thickness of the sand and pebble layer is 0.18-0.25m.
A method for constructing a new type of initial dam suitable for an upstream tailings pond according to claim 5, characterized in that: in the anti-seepage slope protection layer (5), the thickness of the coarse sand layer is 0.18-0.24m, the The thickness of the layer is 1.3 to 1.8m, and the thickness of the sand and pebble layer is 0.18 to 0.25m.
The construction method of a novel initial dam suitable for an upstream tailings pond according to claim 1, 2, 3, 4, 5 or 6, characterized in that: in step 5), each layer is stacked from bottom to top The height of the building is 2.2 ~ 2.8m, and the thickness of the layered compaction does not exceed 0.8m.
The construction method of a new type of initial dam suitable for an upstream tailings pond as claimed in claim 7, characterized in that: the stability of the tailings dam is analyzed by the Bishop method; the seepage field of the tailings dam is analyzed by the finite element method. The analysis is carried out, the node water head is calculated, and the water level line is output by the computer.