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C. Initial dam structure (1) The dam crest width of the initial dam should generally meet the traffic requirements and the operational requirements of the dam crest.
For tailings with waste rock dams, the width of the dam roof should also meet the special requirements for waste rock.
(2) Dam foundation treatment of the initial dam. The initial dam is a hydraulic structure. As the initial dam foundation of the tailings foundation, it must be carefully treated according to the relevant specifications and regulations of the hydraulic structure, and the initial dam should be placed on a stable and reliable basis.
1) Soft soil foundation should be treated according to the weak dam foundation.
2) A foundation composed of grit (egg). Firstly, it should be studied whether there is a concentrated leakage passage and the seepage stability of the basic body. If there is a possibility of concentrated leakage, the passage should be cut off by the intercepting wall; for the foundation that may cause seepage damage, measures to prevent seepage damage should be taken, such as laying reverse Filter layer or excavation.
3) The filter layer of the initial dam should be embedded in a stable and stable formation.
4) The initial dam and bank slope contact area can be properly excavated into a tooth groove, and the filter layer and the inclined wall should be embedded in the tooth gap.
(3) The dam slope of the initial dam. The slope ratio of the dam is related to the structure of the dam body, the nature of the dam material, the quality conditions of the dam foundation, the construction method, the dam height, and the seismic intensity of the area. Generally, it should be determined through stable calculation.
For the static stability calculation of the initial dam, the earth dam is generally carried out by the arc sliding method or the modified arc method; the rockfill dam is calculated according to the folding line method. The dynamic stability calculation is generally calculated by the pseudo-static method, and the selection of its parameters should consider the influence of dynamic load.
On the downstream slope of the initial dam, a ramp with a width of 1 to 2 meters is set every 10 to 15 meters. The downstream dam slope of the earth dam should be set up according to the needs of the dam slope drainage, and the turf should be planted on the slope as a slope protection.
The anti-filter layer in the initial dam is an important part of the dam and is intended to be discussed together in the drainage facility.
(2) Stacking dams in tailings dams are dams that are piled up by tailings themselves, also known as late-stage dams.
A Type of stacking dam and method of dam dam The type of dam is related to the method of dam, which can be summarized as follows:
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The dam-building (including waste rock dam) tailings does not use tailings dams, so there is no dam, which is a special case of tailings.
The stacking dam of the upstream method dam is gradually advanced from the top of the initial dam dam with a certain slope ratio, and the initial dam is equivalent to the drainage rib of the dam. The stacked dam dam has simple process, convenient operation, less capital investment and low operating cost, and is a stacked dam type widely used in China. However, the bottom of the supporting prism is made up of fine tailings, which has poor mechanical properties and is unfavorable for stability. The pile dam has high saturation line and needs to be improved.
The accumulation dam of the middle method dam is as shown in Fig. 5. The axis of the dam is always unchanged at the initial dam axis, and the underflow of the cyclone is increased and the pile slope is continuously moved downstream. The final stacked slope is formed when piled up to the final stack level. The overflow of the cyclone is discharged upstream of the stacking crest line. The accumulation dam improves the basic conditions of the supporting prism of the tailings field. The supporting prism is basically formed by the thick tailings of the underflow of the cyclone, and the immersion line is also reduced, which is beneficial to the stability of the dam, so the production is It is hoped that such a dam can be used, but the construction of the dam with a cyclone brings a lot of troubles to the production, such as the movement and management of the cyclone, the stability of the temporary slope and the dust, which limits its application and its infrastructure. The investment is high, and there are not many practical applications at present.
The stacking dam of the downstream method dam, as shown in Figure 6, begins with the initial dam dam top, and uses the swirler underflow sand (the overflow into the dam) to gradually increase the slope to a certain gradient, first gradually The upstream slope is formed until the final stacking elevation is reached. This kind of stacking dam is built into a stacking dam by using a large number of cyclone underflow sands, which completely improves the basic conditions of the supporting prisms, reduces the saturation line, and has good stability and seismic performance. However, the cyclone stack dam has a large workload, and the balance between the amount of sand sinking in the bottom of the cyclone and the amount of dam work should be considered. There are also problems in the middle reaches of the dam, so there are currently few applications.
Wang set Hubei and Shanxi phosphorus ore tailings field Ekou iron ore tailings field using a second dam downstream HEAP, have been put into operation, will heap dam downstream of the accumulation of experience law.
B The slope of the slope dam of the dam should be preliminarily determined according to the physical and mechanical indexes of the tailings and reference to similar projects. The general value is between 3.0 and 1:5.0, and then the stability calculation is carried out to meet the stability of the slope. The slope required by the minimum safety factor is used as the design slope value. In the proposed slope and stability calculation, the seismic intensity of the area should also be considered for the tailings field in the seismic zone.
In order to facilitate maintenance, the dam slope leaves a ramp at a certain height difference, and its width is determined according to management and traffic conditions.
Dam slopes should be provided with slope protection to prevent rain and dust from flying. Generally, mountain soil can be used to protect slopes, and flowers and small shrubs can be planted on mountain soil. It is forbidden to plant arbor forests, and dam slope drainage and abutment drainage ditch .
C Stabilization of the dam and its calculation The stability of the dam including static stability, dynamic stability and seepage stability should be calculated accordingly.
The purpose of the static stability calculation is to verify the stability and safety of the proposed dam slope. Generally, the arc sliding method or the static finite element method is used for calculation, and the minimum safety factor of the piled slope is required.
The dynamic stability analysis is to verify the stability of the dam slope under dynamic (generally earthquake) conditions and the possibility of vibration liquefaction, the range of liquefaction and the depth of liquefaction. Generally, the finite element analysis method is adopted, and the field test is used for discrimination to verify each other. For general small projects, the quasi-static method can be used for calculation.
The purpose of the seepage stability calculation is to check the stability of the piled dam under seepage conditions, whether there will be seepage damage, and the slope of the seepage and discharge should be controlled to be less than the allowable slope of the tailings.
Stabilization analysis is generally carried out as follows:
(1) Obtain the data and parameters required for stable calculation through engineering geological survey or engineering analogy. And calculate the calculation section.
(2) Perform seepage analysis, determine the wetting line of the stacked dam, and analyze the seepage stability to obtain the section that meets the requirements for seepage stability.
(3) For the accumulation dam without dynamic stability analysis, the slope stability calculation should be carried out, the minimum safety factor of slope stability should be obtained, and the stability of the slope should be judged. If the instability or safety factor does not meet the requirements, the section or Take engineering measures that are conducive to stability, redo the seepage analysis and stability calculation until the minimum safety factor for slope stability is met.
(4) For the tailings field to be analyzed for dynamic stability, static analysis is first performed to determine the static working state. On this basis, dynamic analysis is performed to determine the dynamic stress and stress level, and to determine the liquefaction or not and the range of the liquefaction zone. If necessary, the arc sliding method is used to calculate the slope slip to determine whether the proposed slope is stable. If it is unstable, the slope should be modified or an engineering measure that is beneficial to dynamic stability should be recalculated until the stability requirement is met. [next]
(3) The flood discharge structure of the flood discharge structure is an engineering measure for draining the flood in the tailings mine, and is an important facility to ensure the flood safety of the tailing mine. It is generally composed of an overflow structure and a drain pipe (hole or canal) and its export energy dissipating facilities. .
A tailings flood design standard B Types of drainage structures and their choices The tailings flood control structures are of the following types:
(1) Spillway flood discharge (Fig. 7), generally arranged on the top of the dam abutment or the tailings of the mine, composed of overflow masonry, drainage steep trough and a stilling pool made of masonry or concrete. Discharge of various sizes. However, for tailing mines with rising stacking elevations, they can only be used for flood discharge after the end of the tailings mine or for temporary flood discharge under certain conditions. It is generally used in a tailing mine for dam construction. [next]
(2) chute type flood discharge (Fig. 8), consisting of chute, combined well (absorption well), drain (or tunnel) and outlet stilling tank, suitable for small flow tailings.
(3) Overflow tower type flood discharge (Fig. 9) consists of an overflow tower and a drain pipe (or tunnel) and its outlet energy dissipating facilities, which are suitable for flood discharge of various flows. There are two types of overflow towers, window type and frame type. The former is used for small flow and the latter is used for large flow.
The above various flood discharge structures can be selected according to the maximum discharge flow rate, and the hydraulic calculation can be carried out. If necessary, different types should be selected and determined by economic and technical comparison.
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