CN102493430A - Method for prevention and emergency treatment of soil geological hazards - Google Patents

Abstract

The invention relates to a method for preventing and emergency treating soil geological hazards, belonging to the technical field of geological hazards treatment. The method firstly adds fluorinating agent, lime, cement and fly ash to the soil, and mixes each component with the soil in proportion, or dissolves the above-mentioned components in water, and pours the water solution into the soil in proportion, Or pressure injection into the damaged soil in the form of solution or suspension; react for 10 hours to 24 hours. The invention can be applied to the emergency treatment, preventive treatment and permanent restoration treatment of extensive soil slopes and roadbed foundations, as well as embankments, dams, ditches and weir pond soils. It can be applied to emergency reinforcement and stabilization of earth embankment hillsides and dams on the edge of collapse, repairing the soil foundation of roads, railways, airports, and building structures, and can also be used for emergency or permanent prevention and treatment/repair of soil foundations caused by changes in environmental factors Damage to infrastructure by ettringite or similar minerals.

Description

A Method for Preventing and Emergency Handling of Soil Geological Hazards

technical field

The invention relates to a method for preventing and emergency treating soil geological hazards, belonging to the technical field of geological hazards treatment.

Background technique

Expansive soil and soft soil are widely distributed in more than 40 countries in the world. Expansive soil and soft soil exist in every province, city, and autonomous region in my country. In our country, the building area caused by damage to the expansive soil foundation reaches more than 10 million square meters every year, and the degree of damage to highways and railways is particularly serious. Due to the destructive effect of expansive soil on the natural environment, society and infrastructure (such as landslides, mud flows, cracking, uplift or subsidence of the road surface, the displacement and fracture of the foundation of the building due to the seasonal expansion and contraction of the expansive soil, which in turn causes the building Cracks on the wall, etc.) have repetitive and long-term potential hazards. According to incomplete statistics, the economic loss caused by expansive soil in China alone reaches 15 billion U.S. dollars every year. Therefore, controlling the hazards of expansive soils to ensure engineering safety and quality has been perplexing the engineering community and is a major technical problem recognized worldwide. Common geological hazards include: a. The collapse and collapse of embankments and earth dams due to the erosion of water flow; b. Landslides after heavy rain and earthquakes; c. Damage to roads, railways, airports and soil foundations under buildings.

Expansive soils and soft soils often cause the above-mentioned geological hazards. When expansive soil absorbs water, it expands in volume and becomes less dense, and when it loses water, it becomes dry, shrinks, and hardens. This feature makes the zone/soil rich in expansive soil and soft soil a place that is prone to geological disasters. Infrastructure facilities often suffer from cracking, subsidence, collapse and other damages due to their existence. There are expansive soils and soft soils in every province, city, and autonomous region in my country. When the flood season comes every year, disasters or damages caused by soil loss of mountains or road foundations often occur, which brings huge losses to the local life and property safety and economy. Loss. Another common hazard is soft soils missed during exploration, whose poor bearing capacity often leads to localized damage. It is very important and urgent to solve the world-recognized major technical problem of treating expansive soil/soft soil to accelerate the construction of modern infrastructure in my country and protect people's lives and property as well as national property.

The following three methods are usually used for expansive soil subgrade treatment: (1) modifying soil; (2) controlling humidity; (3) replacing soil. In general, physical and chemical modification of the soil is necessary to meet engineering needs. The vast majority of human buildings and civil structures are built on soil. However, the soil itself is not necessarily a good building material, because the soil itself does not have high tensile and compressive strength, and the volume stability of the soil itself is also poor, so changes in the environment, including various natural disasters , causing damage to the soil. Physical modification is mainly to improve the mechanical properties of soil by increasing the density of soil; chemical modification is to add modified materials to soil to change the structure, physical and chemical properties of soil particles through chemical reactions. Using lime, cement or other solidification materials to achieve the modification of expansive soil through physical and chemical interaction with expansive soil, so as to achieve the purpose of enhancing the strength of expansive soil and reducing the volume instability of water swelling. At present, the method of using lime to solidify and stabilize expansive soil is more common and popular in construction practice. However, there are also difficulties when using lime to treat expansive soil. Greater swell when not in use. In this case, the current practice in foreign countries (such as the United States) is to prohibit the use of lime to stabilize sulphate-rich soils. In addition, lime is easy to lose when the soil is soaked in water, and the effect is not easy to last. Because it is impossible to fully understand and grasp all the characteristics of relevant soils in engineering practice, geological hazards still occur continuously. Other chemical modification methods are not suitable for emergency treatment of geological hazards. Moisture control methods, including pre-wetting the soil and attempting to control and stabilize the soil moisture content, or, attempting to block soil particles from contact with surrounding moisture to reduce soil swelling, such as the use of polymeric stabilizers. Polymer stabilizers need to be mixed with the soil; acid stabilizers have no long-term stabilizing effect. Lime is relatively effective when used with finely ground blast furnace slag, but the reaction time required is too long to be suitable for emergency treatment. Soil replacement is a relatively simple and effective method in expansive soil subgrade construction. Soil replacement is to dig out the original expansive soil and fill it with gravel soil or other non-expansive soil. The depth of soil replacement needs to be determined according to the physical and chemical characteristics of the original expansive soil and the local climate characteristics.

Another common example is water facilities that are in a state of disrepair. When the soil in embankments, dams, ditches, and weir ponds is washed by long-term water, soaked and swallowed by insects and ants, the density will decrease, and some of the cementing agents, such as calcium sulfate, will also will be lost. When heavy rains and floods come, collapses can happen. The commonly used method is to add soil reinforcement. However, the disadvantage of adding soil reinforcement is that it costs a lot, the construction period is long, it is not suitable for emergency situations, and the construction safety cannot be guaranteed. Similarly, methods such as grouting when repairing the foundation are relatively expensive.

When the foundation of a building is built on expansive soil/soft soil, if the groundwater level changes, the soil bearing capacity will decrease, or the natural environmental conditions will cause the formation of highly expansive ettringite in the soil, which may cause the foundation to move and tilt. In turn, it will cause the building to tilt, damage the wall of the building, and in severe cases, the house will be unusable. At present, the commonly used treatment method is to repair the foundation foundation by grouting and other methods.

Contents of the invention

The purpose of this invention is to propose a method for preventing and emergency treatment of soil geological hazards, using inorganic chemical reactions, using minerals with abundant reserves or inorganic compounds produced by simple processes, to quickly stabilize and strengthen the foundation soil, and make the foundation Or the foundation is restored to its original position to prevent the building from tilting or the continued development of structural cracks; or prevention and emergency treatment to prevent the loss of surface soil (including mountains) and protect the safety of people's lives and property.

The method for the prevention and emergency treatment of soil hazards proposed by the present invention, for stabilizing and strengthening foundation soil treatment, its process comprises the following steps:

(1) add fluorinating agent, lime, cement and fly ash in soil, wherein add each component and account for the weight percentage of soil is:

(2) Mix the above-mentioned components with the soil in proportion, or dissolve the above-mentioned components in water in proportion, and pour them into the soil with aqueous solution or suspension;

(3) React for 10 hours to 24 hours.

The method for the prevention and emergency treatment of soil geological hazards proposed by the present invention is for the emergency treatment of geotechnical structures such as embankments, dams, ditches, weir ponds and soil slopes, or for the crisis of once or regenerated soil loss geological disasters Emergency treatment, the process includes the following steps:

(1) add fluorinating agent, lime, cement and fly ash in soil, wherein add each component and account for the weight percentage of soil is:

(2) Pressure injection of the above-mentioned components into the damaged soil in the form of solution or suspension;

(3) React for 10 hours to 24 hours.

In the above two methods, the added fluorinating agent can be any of the following three forms:

a: sodium fluoride

b: Potassium fluoride

c: a mixture of sodium fluoride or potassium fluoride and calcium fluoride, the weight percentage of mixing is: (sodium fluoride or potassium fluoride): calcium fluoride = 70%: 30%.

A method for preventing and emergency treatment of soil geological hazards proposed by the present invention, mixing, infiltrating or injecting fluorine-containing compound additives that can provide free fluorine ions, rapidly improving the strength of clay soil or expansive soil, so as to eliminate the occurrence of expansive soil water swelling. Fluoride ions with a controlled concentration are small in size, so they can migrate quickly and react quickly with related components in the soil, so that the soil can improve its bearing capacity and volume stability. In this process, there is very little reliance on large mechanical equipment. Therefore, the present invention can be applied to emergency treatment, preventive treatment and permanent restoration treatment of extensive soil hillsides and roadbed foundations, as well as embankments, dams, ditches and weir pond soils. It can be applied to emergency reinforcement and stabilization of earth embankment hillsides and dams on the edge of collapse, repairing the soil foundation of roads, railways, airports, and building structures, and can also be used for emergency or permanent prevention and treatment/repair of soil foundations caused by changes in environmental factors Damage to infrastructure by ettringite or similar minerals.

Detailed ways

The method for the prevention and emergency treatment of soil hazards proposed by the present invention, for stabilizing and strengthening foundation soil treatment, its process comprises the following steps:

(1) add fluorinating agent, lime, cement and fly ash in soil, wherein add each component and account for the weight percentage of soil is:

(2) Mix the above-mentioned components with the soil in proportion, or dissolve the above-mentioned components in water in proportion, and pour them into the soil with aqueous solution or suspension;

(3) React for 10 hours to 24 hours.

The method for the prevention and emergency treatment of soil geological hazards proposed by the present invention is for the emergency treatment of geotechnical structures such as embankments, dams, ditches, weir ponds and soil slopes, or for the crisis of once or regenerated soil loss geological disasters Emergency treatment, the process includes the following steps:

(1) add fluorinating agent, lime, cement and fly ash in soil, wherein add each component and account for the weight percentage of soil is:

(2) Pressure injection of the above-mentioned components into the damaged soil in the form of solution or suspension;

(3) React for 10 hours to 24 hours.

In the above two methods, the added fluorinating agent can be any of the following three forms:

a: sodium fluoride

b: Potassium fluoride

c: a mixture of sodium fluoride or potassium fluoride and calcium fluoride, the weight percentage of mixing is: (sodium fluoride or potassium fluoride): calcium fluoride = 70%: 30%.

The method for the prevention and emergency treatment of soil geological hazards proposed by the present invention is to remove the ettringite generated in expansive soil due to changes in the environment (such as moisture content) by introducing a compound additive that can release fluoride ions, such as sodium fluoride or similar minerals to reduce swelling or damage in sulphate-rich soils. The method of the present invention can be applied to prevent or emergency repair or refurbish the surface cracking, uplift or damage caused by damage to foundations such as roads, airport runways, buildings, etc., and the base or sub-base of similar buildings due to the formation of ettringite or similar minerals The situation where the foundation is partially lifted and damaged due to generation. The method of the invention is also suitable for repairing the foundations of existing buildings which have been damaged. For soil layers stabilized with lime or without lime, it is possible to prevent, reduce or eliminate potential or existing damage or destruction caused by expansion by introducing a set amount of compound additives that release fluoride ions.

The method of the invention has strong universal applicability, even if the soil types are different, the method of the invention can also be used. The present invention adds specific materials to the soil, and the adding method can be to release fluoride ions into the soil through solid compounds or compound solutions to generate chemical reactions, thereby achieving the purpose of strengthening the soil. The fluorinating agent in the method of the present invention includes a fluorine-containing inorganic compound or a mixture of a fluorine-containing inorganic compound and other commonly used soil stabilizers. Commonly used soil stabilizers include lime, fly ash, cement, etc.

Examples of the method of the present invention are described below.

Embodiment one

In the process of road construction, a section of soft soil needs to be mixed, plasticized and strengthened. After testing, the plasticity index of soil is 18, and the content of silt and clay is 20%, and sulfate content is 0.1%, can handle with one of following several methods of the present invention:

1. Mix sodium fluoride directly with the soil, and the dosage of sodium fluoride is 0.5% of the soil weight. After mixing with water, carry out layer-by-layer compaction, and the thickness of each layer can reach 15 cm. After 12 hours, the next step of construction can be carried out.

2. Mixed use of fluorine-containing compounds and lime. Among fluorides, the mass ratio of sodium fluoride to calcium fluoride is: sodium fluoride: calcium fluoride = 4:1, and the amount of lime is 5% of the weight of the soil. The dosage of fluorine compound additive is 0.5% of soil weight. After mixing with water, carry out layer-by-layer compaction, and the thickness of each layer can reach 15 cm. After 24 hours, the next step of construction can be carried out.

3. Potassium fluoride additive and cement are mixed, the amount of cement is 10% of the weight of the soil, and the amount of potassium fluoride is 0.5% of the weight of the soil. After mixing with water, carry out layer-by-layer compaction, and the thickness of each layer can reach 15 cm. After 24 hours, the next step of construction can be carried out.

Embodiment two

During the construction of the earth dam, a section of soft soil needs to be mixed to reduce plastic and strengthen. After testing, the plastic index of the soil is 18, while the content of silt and clay is 29%, and the sulfate content is 0.08%, which can be processed with one of the following methods of the present invention:

1. Mix sodium fluoride directly with the soil, and the dosage is 0.7% of the soil weight. After mixing with water, it is compacted in layers, and the thickness of each layer can reach 15 to 45 cm. After 12 hours, the next step of construction can be carried out.

2. Sodium fluoride and lime are mixed, the consumption of lime is 6% of the weight of the soil, and the consumption of sodium fluoride is 0.6% of the weight of the soil. After mixing with water, it is compacted in layers, and the thickness of each layer can reach 15 to 45 cm. After 24 hours, the next step of construction can be carried out.

3. Potassium fluoride and cement are mixed, the amount of cement is 10% of the weight of the soil, and the amount of potassium fluoride is 1.0% of the weight of the soil. After mixing with water, it is compacted in layers, and the thickness of each layer can reach 15 to 45 cm. After 24 hours, the next step of construction can be carried out.

4. Mixed use of fluorine-containing compound additives and fly ash. Among the fluorine-containing compounds, the mass ratio of potassium fluoride to calcium fluoride is: potassium fluoride: calcium fluoride = 6:1, and the amount of fly ash is the soil weight 20%, and the dosage of fluorine compound additive is 0.5% of the soil weight. After mixing with water, it is compacted in layers, and the thickness of each layer can reach 15 to 45 cm. After 12 hours, the next step of construction can be carried out. Embodiment Three

In the process of repairing the foundation of the house, a section of expansive soil under the foundation needs to be stabilized and strengthened. After testing, the plasticity index of soil is 25, and the content of silt and clay is 20%, and sulfate content is 0.06%, can handle with one of following method of the present invention:

1. Drill a single hole or multiple holes, inject saturated sodium fluoride solution directly into the expansive soil in stages, and the total amount of fluoride is 1% of the estimated weight of the expansive soil. After each injection of fluorine-containing compound (0.3%), the hole is sealed, and the degree of downward settlement of the house is observed. Every two weeks until settlement stabilizes or 1.0% is used.

2. Drill a single hole or a multi-hole, inject sodium fluoride additive and lime saturated solution directly into the expansive soil in stages, the sodium fluoride is 1% of the weight of the expansive soil, and the amount of lime is 10% of the weight of the expansive soil. Each time, inject fluoride (0.3%) to seal the holes, and then inject lime solution (3%) after one week to observe the degree of house sinking. Cycle every two weeks until sedimentation stabilizes or 1.0% fluoride and 10% lime are achieved.

Embodiment Four

When stabilizing a mountain with cracks and danger of landslides, it is necessary to stabilize and strengthen the soft soil or expansive soil in the mountain. After testing, the plastic index of the soil is 15, and the content of silt and clay is 30%, and the sulfate content is 0.01%, which can be processed with one of the following methods of the present invention:

1. Carefully observe the cracking of the mountain, and record the position and depth of each crack. Select a crack with a depth greater than 30cm and inject a saturated solution of potassium fluoride additive until the solution overflows from the crack. Stop the perfusion and continuously observe the movement of the mountain. Grouting was repeated two weeks later until the movement of the mountain stabilized or stopped.

2. Carefully observe the cracking of the mountain, and record the position and depth of each crack. Select cracks with a depth greater than 30cm and inject sodium fluoride and lime saturated solution in stages. Inject a saturated solution of sodium fluoride additive until the solution overflows from the crack. A week later, inject a saturated solution of sodium fluoride and lime until the solution overflows from the crack. Stop the perfusion and continuously observe the movement of the mountain. Start the grouting process again a week later until the movement of the mountain stabilizes or stops.

Embodiment five

Pavement swelling or subsidence caused by expansive soil and other factors will not only bring driving discomfort, but also threaten driving safety. At present, there is no better way to deal with it, only to smooth the bulging road surface, but this will reduce the service life of the road surface. In this case, one of the following methods of the present invention can be used for processing:

1. Drill holes in the bulging part of the road surface with a diameter of 1 cm and a distance of about 1 meter. Boreholes are drilled through soft or expansive soils, or at least to a depth of two meters. Inject sodium fluoride saturated solution up to road level. Cover the borehole with an iron plate or other bearings and resume traffic. The change in pavement height was measured after one week. If there is little change, remove the iron plate and continue to inject the saturated sodium fluoride solution.

2. Drill holes in the bulging part of the road surface with a diameter of 1 cm and a distance of about 1 meter. Boreholes are drilled through soft or expansive soils, or at least to a depth of two meters. Inject a saturated mixed solution of fluorochemical additives and lime up to the pavement level. Among the fluorides, the mass ratio of potassium fluoride to calcium fluoride is: potassium fluoride: calcium fluoride = 8:1. Cover the borehole with an iron plate or other load-bearing objects and resume traffic. The change in pavement height was measured after one week. If there is little change, remove the iron plate and continue to inject the mixed solution of fluorine compound additive and lime.

Claims (3)

1. the method for prevention and emergency processing soil geology harm is characterized in that this method may further comprise the steps:

(1-1) in soil, add fluorization agent, lime, cement and flyash, the percentage by weight that wherein adds each ingredients constitute soil is:

(1-2) with above-mentioned each component in proportion with soil mix mutually, perhaps that above-mentioned each component is soluble in water, pour in the soil in proportion with the aqueous solution;

(1-3) reaction is 10 hours～24 hours.

2. the method for prevention and emergency processing soil geology harm is characterized in that this method may further comprise the steps:

(2-1) in soil, add fluorization agent, lime, cement and flyash, the percentage by weight that wherein adds each ingredients constitute soil is:

(2-2) above-mentioned each component is injected the impaired soil body with solution or form of suspension pressure;

(2-3) reaction is 10 hours～24 hours.

3. according to claim 1 or claim 2 method is characterized in that wherein said fluorization agent is any in following three kinds of forms:

A: sodium fluoride

B: potassium fluoride

C: the mixture of sodium fluoride or potassium fluoride and calcirm-fluoride, the percentage by weight of mixing is: (sodium fluoride or potassium fluoride): calcirm-fluoride=70%: 30%.