Basic knowledge of hydrogeology in deposits (basic consolidation)

Since the mine (or pit) is an independent production unit, the water that flows into the well from the whole well is also called the mine (pit).

Along the length of the trend, because the range of the mine field is too large, the mining fashion needs to be divided into smaller units according to the inclination angle and technical conditions of the ore body (layer) for sequential mining.

For inclined ore bodies (layers), the slopes are divided into a number of strips parallel to the strike at a certain elevation, which is called a stage. The upper boundary is the stage return airway, the horizontal plane is called the return air level; the lower boundary is the stage transport flat roadway, and its horizontal plane is called the transport level.

b. Ways to open the mining bed

The construction of open-pit mining and open-pit mines When the deposit is buried near the surface, the cover layer is thin, or the shallow ore body from the shallow to the deep deposit is mined, it should be exploited in an open-air manner, that is, directly from the ground to a deep area. Open-air channel, the way to form a mining surface for mining ore.

Open pit mining schematic section

1-step; 2-step slope; 3-drain, 4-mineral; 5-step slope

The composition of the underground mining and mining system uses underground mining to mine deposits buried deep underground, which is the use of suitable types of underground roadways and different mining methods to extract ore from the ground.

Comprehensive schematic diagram of underground mining mine shaft

1- vertical well; 2-inclined well; 3-flat raft; 4-deep vertical well; 5-slip well; 6-stone gate; 7-mine gate; 8-mine silo; 9-up mountain road; 10-down mountain road; Well; 12-rock formation alley; 13-mineral alley

c. Steps to open the mining bed

open up. It is the first step of mining. It is designed to dig a series of pioneering roadways from the ground to the ore body to establish engineering systems for transportation, ventilation, drainage and water supply.

Appropriate. In the stage or panel that has been developed, it is further cut into a mining area or a mining wall to prepare for mining; at the same time, it is used for pedestrians, transportation and ventilation.

Picking up. It is a production process that extracts a large amount of ore from the mining area or the mining room where the mining is completed. d. Mining methods

The supporting mining method is divided into natural and artificial: natural support method (mine method): the method of retaining the safe pillar (permanent and temporary) to maintain the stability of the surrounding rock, suitable for the stable mining area of ​​the surrounding rock;

Artificial support mining method: It is to control the area by artificial support and protect the safe production of the mining area.

Caving mining method: It is used in the mining area where there is no town, surface water or strong aquifer above the goaf. It is to fill the goaf with the rock falling from the roof and control the displacement of the surrounding rock to ensure safe production. The caving method is the most commonly used mining method, but it also poses the greatest threat to the filling of the deposit.

Filling mining method: Mining is carried out without substantially changing the overlying stratum, but the cost is high, and it is mostly used in the case of towns, roads, surface waters and strong aquifers on the roof and floor. two

Analysis of water filling factors in mineral deposits

1, the basic concept

Filling the deposit: water present in the deposit and surrounding rock in a natural state;

Water in the pit: the water flowing through the wells during mining;

Mine water inrush: Instantaneous flooding of water beyond the normal drainage capacity of the mine. Water filling intensity, water inrush intensity and water inrush intensity: the amount of water filled with water, water and water.

The reason why there are water inflows in mine shafts is caused by various water sources entering the wells through various channels. The amount of water influx is mainly controlled by the specific conditions of deposits and mining.

Therefore, the water-filled water source and channel are necessary conditions for the formation of mine water.

In addition to the factors affecting the strength of the water inrush, the comprehensive effect of the three is called the water filling condition of the deposit.

Schematic diagram of water filling analysis of mineral deposits

The reason why there are water inflows in mine shafts is caused by various water sources entering the wells through various channels. The amount of water influx is mainly controlled by the specific conditions of deposits and mining. Therefore, the water-filled water source and channel are the necessary conditions for the formation of mine water gushing, and the factors affecting the water inrush strength, the comprehensive effect of the three is called the water filling condition of the deposit.

2, water-filled water source

a. Atmospheric precipitation is the main source of water-filled deposits, and its charge (swell) water characteristics are closely related to precipitation, topography, lithology and structure. The mine water inrush dynamics are consistent with the local precipitation dynamics, with obvious seasonal and multi-year periodic changes. The maximum value of water in one year is in the snowmelt and rainy seasons, and the minimum is in the dry season; the maximum water inflow in the mine appears in the wet year and the dry year is the smallest, and the water inrush accident occurs in the flood season of the wet year.

Curve of mine water inflow with precipitation (Jingxi Wangping Village Mine)

1-Precipitation; 2: Mine water inflow

Most deposits increase the amount of water inflow from the mine with the depth of mining, and the peak of the high water inflow is prolonged. The amount of water influx in the mine is also closely related to the nature of precipitation, strength, continuous time and infiltration conditions. Usually, continuous rain reduction for a long time is beneficial to infiltration. Mines with good catchment conditions, bare water-filled layers, and large surface permeability have large water inflows, and vice versa. Typical types: deposits located above the local erosion datum, mines without surface water distribution, watersheds and deposits in the groundwater level variator, deposits with shallow buried water-filled aquifers.

b. Mineral deposits with surface water as the main water source

Such deposits are found near or below the surface waters of rivers, lakes and oceans in mountain valleys and plains. The water filling characteristics mainly depend on the way the surface water is replenished. According to the way and strength of surface water entering the well, it can be divided into four situations:

It is not replenished by surface water: there is a thick and reliable water-repellent layer at the top of the ore body, and there is no water connection between the ore body and the surface water;

It is a weak supply of surface water: there is a weak aquifer at the top of the ore body, and a small amount of surface water can be supplied to the well through it;

It is the surface water infiltration or replenishment: the dredging funnel is bounded by surface water, and the surface water passes through the infiltration channel, which can enter the well more;

Schematic diagram of boundary conditions transformation in Enkou mining area

1-T1s+P2d lower stacking Daye Formation; 2-P2l upper stack Longtan Formation aquifuge; 3-P1m+P1q4 Lower Erdu Maokou Formation and Qixia Formation karst aquifer; 4-P1q3 Lower Erodiqixia Formation Lizitang Segmental aquifer; 5-I, II, III, level of drainage.

c. The law of water inrush in surface water-filled deposits:

The water inrush in the mine changes seasonally with the abundance of surface water, and its water inrush intensity is related to the type, nature and scale of surface water. A deposit that is recharged by a river with a large change in seasonal flow. Its water inrush intensity also changes seasonally. When there is a replenishment of a large water body in a perennial state, it can cause a large amount of water in the stable water supply and it is difficult to drain. When there is a surface water supply with a large catchment area, the amount of water inflow is large and the decay process is long.

The water inrush intensity of the mine is also related to the distance between the well and the surface water body, lithology and structural conditions. In general, the smaller the spacing, the greater the water surge strength. The stronger the permeability of the rock formation, the greater the water inrush intensity. When a thick and complete aquifer is distributed between them, the water inrush is minimal or has no effect. In the meantime, the formation is more severely damaged by the structure, and the intensity of the water in the roadway is also greater.

Schematic diagram of the distance between the drainage tunnel and the river

1-aqueous layer; 2-water-blocking layer; 3-mineral layer; 4-drainage tunnel; 5-water drain line

d. Impact of mining methods

According to the hydrogeological conditions of the deposit, the correct mining method is adopted. If the deposit of the near-surface water body is mined, the water inrush intensity will increase, and the production will not be too much affected. If the method is improper, the caving crack can be connected or collapsed with the surface water body. Water inrush and sediment collapse.

e. Mineral deposits with groundwater as the main source of water

The aquifer that can cause water in the wells is called the water-filled layer of the deposit. Some aquifers, although close to the mine, do not belong to the water-filled layer of the deposit, except that water cannot enter the well during natural and mining. However, when mining destroys its water-blocking conditions, it can also be converted into a water-filled layer. When groundwater becomes the main source of gushing water, there are the following rules.

The water inrush intensity of the mine is related to the porosity of the aquifer and its water richness. Generally, the water-filling strength of the fissure water is small, the pore water is the largest, and the karst water is the largest; the water in the well-prone area is large, and the water in the weak water-bearing area is small; when the ore body and the surrounding rock contain saturated water, the sand can be caused. Crush. The water inrush intensity of the mine is related to the thickness and distribution area of ​​the water-filled layer. If the water-filled layer is thick and the distribution area is large, the amount of water in the mine is also large; otherwise, it is small. The intensity of water inrush in mines and its changes are related to the composition of aquifer water. When the influx of water is mainly used for storage, it is revealed that the initial water inflow is large and easy to burst, and then gradually decreases, and it is easy to drain; when the water is mainly supplied, the amount of water inflow increases from small to large, and then tends to be relative. Stable, not easy to drain.

f. Mineral deposits with Laoshui as the main water source

Laoshui refers to the accumulated water in abandoned mine pits and submerged production wells. It is a common water-filling source for shallow mining in mining areas.

Its water gushing characteristics:

The water in the old air is generally fierce; the acidity is large, and it contains harmful gas and carries rock, which is destructive; the old water can also become a channel for other water sources to flow into the pit; the old water is too long and the distribution range is unclear. The investigation is difficult. The water inrush (gushing water) of a single mine is mainly based on a certain kind of water source, and multiple water sources are comprehensively replenished. In the actual work, not only to find the main water source, but also to analyze the pre-harvest (natural) water source and post-harvest (artificial) water source, in order to propose accurate water prevention measures.

3, water filling channel

Although there is water in the ore body and around it, only through some kind of passage. They can enter the wells to form water or water. Gushing channels can be divided into two categories: pores in the stratum, fault zones, etc., which are naturally formed channels; and artificial gushing channels caused by unreasonable exploration and exploitation.

a. natural passage

The fissures of the rock strata and the joint-type fissures in the deposits in the hard rock strata of the fault zone are more developed and connected to each other to form a fissure water channel. Fractured aquifers, due to uneven development of fractures, are uneven in water, mostly weak aquifers. Their permeability is weak and the amount of water in the mine is small. In the history of mining at home and abroad, the water guide channel formed by small and medium-sized fault zones is the most common cause of water inrush. According to the exploration and mining data, the fault zones can be divided into two types, namely the water-blocking fault zone and the water-permeable fault zone.

The karst channel karst space is extremely heterogeneous and can range from small dissolved pores to huge caves. They can communicate with each other, serve as a conduit for communicating various water sources, and can also form isolated water-filled pipes. Many metal and non-metal mining areas in China suffer from it. The key to understanding this channel is whether it can accurately grasp the karst development law and the characteristics of karst water in the mining area; large, medium and small karst channels: the water inrush channel formed by small karst and dissolution gap, although it can increase the amount of water in the mine. However, it is still small; the water inrush from the large and medium karst (karst caves and pipelines) and the dissolution fault zone will greatly increase the amount of water in the mine, which is more likely to cause water inrush disasters.

Karst separation and "skylight"

Karst separation: refers to the soil layer covering the water-filled (or air) space. The external force (pumping, water release, heavy rain) acts instantaneously. The karst space gap existing in the first place provides for the containment and transport of the fallen material. The necessary space conditions, which are the result of karst dynamic geological processes, are different from those generated in non-soluble rocks. Karst sulcus is a serious hydrogeological engineering geological problem of karst water-filled deposits. It not only causes sudden mine collapse, but also destroys various facilities on the ground, leading to river water interruption and water resources destruction.

China's karst sedimentation occurs in the southern cave-filled water deposit, and the northern cavernous water-filled deposit accounts for only 1.8%. “Skylight” refers to the unconsolidated and semi-cemented stratum between the karst water-filled aquifer and the overlying alluvial layer, which is thinned or even disappeared due to sedimentary phase transition or valley incision, resulting in water-filled aquifer and overlying Quaternary water. The direct contact of the layers forms a water-conducting "sunroof". In the natural state, the "skylight" is the groundwater discharge channel of the water-filled aquifer and is also a favorable part of the karst compartment. Once the "skylights form a septum, the replenishment pattern is immediately evolved from infiltration replenishment to concentrated infiltration replenishment.

Pore ​​channel pore channel, mainly refers to pore diving between loose layer particles. It can be encountered when mining sand deposits and mining deep bedrock deposits overlying loose layers. The former is mostly uniform water, only in large grain areas and mines with abundant water sources can cause water inrush; the latter mostly cause damage during the construction period. Such channels can transport water from the aquifer into the well and can also serve as a conduit for communicating surface water.

b. Artificial channel

When the mining area forms a large area of ​​goaf, the original stress balance is destroyed. Under the action of concentrated stress, the roof of the goaf ruptures and falls, and irregular falls occur above the goaf. The belt, the water-conducting fracture zone and the weakly moving overall belt, and the formation of depression on the ground.

The above-mentioned zoning law is relatively complete in the mining area where the rock layer is gently inclined, and is related to the caving mining method. The rip belt and the water guiding crevice belt are collectively referred to as the rip belt. When the crack zone reaches the overlying surface water source, it will cause water inrush. Therefore, the maximum height of the belt and the water-conducting fracture zone is an important basis for ensuring safe mining depth or mining ceiling when mining in strong aquifers or surface water.

When the goaf is located above the high-pressure water-rich karst aquifer, the karst water will break into the pit of the weak layer of the aquifer in the goaf under the action of the mine pressure and the water pressure head of the floor. . Therefore, the weak section of the aquifer can be regarded as an alternative to other water conduits.

Poorly closed or unclosed boreholes can be used as a direct channel to communicate the influx of water sources into the pits if they are improperly disposed of the various completed boreholes. There are records of borehole water inrush at home and abroad, so it is required that each hole has been completed. The drill holes are strictly sealed to stop the water. The first is to protect the ore body from oxidative damage; the second is to prevent direct infiltration of large groundwater or other water sources.

The suddenness, complexity and disaster of the water guiding channel in the process of water filling are its important significance. The three are interdependent and are the most complete embodiment in the mining of large water deposits. The main water inrush passages of China's large water deposits are different. The north is dominated by water in the stratum, while the south is dominated by ground depression, which are all related to faults.

Therefore, the fracture karst depression and the water inrush channel of the floor are the research priorities.

4, the water filling strength of the deposit

In the investigation stage before mining, it is inaccurate to measure the strength of the water filling of the deposit, and indirectly use the value of the spring and well water output in the mining area; the more accurate is the value of the mine water inflow when the mine is mined or The water influx is determined by comparing the amount of water in the similar mine that has been mined. Analysis of the mining data shows that the amount of water inflow in the mine is related to the nature and characteristics of the water-filled water source and channel, as well as the following main influencing factors.

a. Boundary conditions of the deposit

The boundary conditions between the deposit and the aquifer will play a major role in controlling the amount of water in the future.

Lateral boundary of the deposit: When there is a strong permeable boundary between the deposit and the directly water-filled aquifer system, the groundwater or surface water of the system will flow into the mine quickly and in large quantities during mining. The longer the boundary with sufficient water supply, the more water and the more stable the water. If the ore body or the direct water-filled layer is closed by the water-blocking boundary, the mine water inflow will be small or become smaller or even dry. If the original non-water-filled layer or new water source enters the mine due to mining, a new water-filling system will be formed, the mine water inflow will increase, and the original boundary will be transformed into a new boundary condition. For the first exploration, the boundary conditions of the karst groundwater system were not ascertained. The water level of the pumping test was reduced by 1.695 m, the unit water inflow was 125.5 m3/hm, and the permeability coefficient was 100 m/d. Calculated by the infinite boundary, the water inflow at the -100 m level was 160,000 m3. /d, is an open large water mining area.

Hydrogeological sketch of Yangzhuang Iron Mine, Yanxing

The top and bottom boundaries of the deposit: the separation and permeable conditions of the deposit and its top and bottom, also control the water inrush intensity of the mine. Therefore, if they can maintain their water-proof performance or weaken their penetration strength, the purpose of maintaining or reducing the amount of water in the mine can be achieved. There are four cases of top and bottom section boundaries:

The direct top floor is a reliable water-repellent layer, and there is basically no external water supply;

The bottom plate is separated by water. The ore body and the direct water-filled layer can only obtain strong or weak atmospheric precipitation or surface water supply;

The top plate is separated from water, and only the weakly permeable bottom plate is used to generate over-flow or directly obtain strong replenishment;

Both the top and bottom plates are constructed of strong or weak permeable water. If the lithology of the aquifer is dense, the water-blocking ability is strong. If the thickness is large and stable and the integrity is good, the water inflow and the amplitude of the mine are small; the tensile strength is reduced in thinning, missing or broken. On the lot, the amount of water inflow will increase.

b. Geological structural conditions

The type, scale and distribution of geological structures play a restrictive role in the formation of total influx of mines. If the deposit is located in a fold or fault structure, it will have a greater impact on the spatial distribution of the deposit and the aquifer, and the conditions of the groundwater discharge, and the water-filling strength will be affected. The deposits in the same type of structure vary with the size of the structure and the location of the mine. c. Conditions for recharge of water-filled rock formations

FIG fill condition may represent upper field of North CARBONIFEROUS Permian coal, water filling level and where the contact layer is exposed to a water source. They have a great impact on the strength of mine water inrush.

The higher the degree of exposure of the water-filled layer and the ore body, the stronger the water permeability of the cap layer, and the more contact area with the recharge water body, the greater the water inrush intensity of the mine.

Mine under condition A: It is in the front of the mountain where there is no replenishment. The direct roof is a strong water-filled layer, but the upper layer is a clay layer, and the recharge is obtained at a. The amount of water inflow is generally 50-200m3/h. At the beginning of mining, the amount of water is large, but the attenuation is fast and easy to drain. Mine under B condition: distributed in the plain area, the water-free layer of the bedrock is in direct contact with the overlying gravel layer and is recharged at b. The amount of water in the mine is often stable at 500-1000 m3/h, which is not easy to drain.

Mine under C condition: for lake underwater mining, deposit and water-filled layer directly exposed at the bottom of the lake, c is threatened by surface water all year round, easy to cause large and stable water inrush, easy to flood and difficult to recover. In mining, it is necessary to keep a safe mine, but also strictly strengthen the roof management to avoid causing the lake water to enter the well. Mine under D condition: the water-filled layer directly exposes the surface, and only accepts atmospheric precipitation and infiltration (replenishment at d). The amount of water in the mine is generally small, and the dynamics vary with the seasons and are easy to drain. Mines under E conditions: distributed under the seasonal rivers, the river water flow changes seasonally, and the mine water receives river water supply at e, which also changes seasonally. The amount of water inflow varies between medium and small, and a few mining areas can cause water inrush during the wet season. Such deposits should be mined from the far river to the near river and left in the pillars, while the rivers should be mined in the dry season. three

Deposit hydrogeological type

Long-term exploration and mining practices show that deposits with similar hydrogeological conditions have basically the same water-filling conditions and close mine water inflow and post-harvest major hydrogeological engineering geological problems. With the accumulation of data and experience, the internal relationship between the internal and external environment and the water-filling conditions and the water-filling intensity of the deposit is gradually revealed, which lays a foundation for theoretical classification. The classification should not only summarize the water-filling conditions of complex and variable deposits in China, but also identify many types of basic hydrogeological features. At the same time, the boundaries between different types are clear and easy to grasp and apply. In 1993, the Institute of Hydrogeology and Engineering Geology proposed the "Types of Hydrogeological Exploration of China's Karst Water-filled Deposits", which further divided the karst water-filled deposits into three sub-categories: water-filling, water-filling, and water-filling. 991-10-01 The State Bureau of Technical Supervision issued new national standards on the basis of the "Hydrological and Geological Exploration Types of Karst Water-filled Deposits" and the "Specifications for Exploration of Hydrogeological Engineering Geology in Mining Areas" issued by the Ministry of Geology and Mineral Resources in 1982. "Code for Hydrogeological Engineering Geological Exploration in Mining Areas" (GB12719-91).

The program is as follows:

1. Classes and sub-categories Firstly, the water-filled deposits are divided into three categories according to the characteristics of the water storage space of the main water-filled layer of the deposit:

The first category: a deposit dominated by pore aquifers, referred to as pore-filled deposits.

The second category: a deposit dominated by a fractured aquifer, referred to as a fractured water-filled deposit.

The third category: a deposit dominated by karst aquifers, referred to as karst water-filled deposits. The karst water-filled deposits can be divided into three sub-categories according to the karst form:

The first type is a karst water-filled deposit dominated by dissolution fissures.

The second category is a karst water-filled deposit dominated by karst caves.

The third category is a karst water-filled deposit dominated by the dark river. 2, different water filling methods and types

According to the spatial relationship between the ore body (or layer, the same below) and the main water-filled aquifer, the above-mentioned various types of water-filled deposits are divided into: directly filled water deposits, which refer to the main water-filled layer of the deposit (including the fall zone and the bottom plate damage). Thickness), direct contact with the ore body, groundwater directly into the pit; roof indirect water-filled deposit, which means that the main water-filled layer is located above the mining zone, and there is a water-separated layer or a weak aquifer between the ore layer, and the groundwater is broken by the structure. The belt and the weak aquifer enter the pit;

The indirect water-filled deposit of the bottom plate means that the main water-filled layer is located below the ore layer, and there is a water-blocking layer or a weakly permeable layer between the ore-bearing layer, and the pressurized water passes through the weak section of the bottom plate, the structural fracture zone, the weakly permeable layer or the karst fall of the water-conducting layer. The column enters the pit. If the relationship between the ore body and the local erosion datum is considered comprehensively, the recharge conditions of the groundwater, the close relationship between the surface water and the main aquifer, the water-rich and water-conducting of the main aquifer and the structural fracture zone, and the Quaternary coverage The situation and the complexity of the hydrogeological boundaries, etc., can be divided into three types:

Type 1: A deposit with a simple hydrogeological condition. The main ore body is located on the local erosion reference surface, and the terrain is favorable for natural drainage, or the main ore body is below the reference surface, but there is no surface water body nearby. The main water-filled layer and structural fracture zone of the deposit are weak to medium-rich, the groundwater recharge conditions are poor, little or no Quaternary coverage, and the hydrogeological boundary is simple.

Type 2: a deposit with a medium hydrogeological condition. The main ore body is located above the local erosion reference surface, the terrain has natural drainage conditions, the main water-filled aquifer and the structural fracture zone are medium to strong, and the groundwater recharge conditions are good; or the main ore body is below the local erosion reference surface, but the nearby surface Water does not constitute the main water-filling factor of the deposit. The main water-filled aquifer, the structural fracture zone is rich in water, the groundwater recharge conditions are poor, the Quaternary coverage area is small and thin, and the drainage drainage may produce a small amount of collapse, and the hydrogeological boundary is complicated. . The third type: a deposit with complex hydrogeological conditions. The main ore body is located below the local erosion reference surface. The main water-filled aquifer is rich in water, good recharge conditions, high water pressure, tectonic fracture zone development, strong water conductivity and strong aquifer or surface water body in communication area. The system has large thickness and wide distribution, and the drainage and drainage have the possibility of large area collapse and settlement, and the hydrogeological boundary is complicated.

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