CN-122013759-A - Construction method for reinforcing collapsible loess foundation based on grouting carbonization-compaction cooperation

CN122013759ACN 122013759 ACN122013759 ACN 122013759ACN-122013759-A

Abstract

The invention discloses a construction method for reinforcing a collapsible loess foundation based on grouting carbonization-vibration compaction, which is realized by a stirring grouting-resonance compaction cooperative reinforcing device and comprises the following construction steps of S1, site pretreatment, S2, slurry preparation, S3, paying-off positioning, S4, slurry spraying stirring sinking, S5, stirring and air spraying in a standing mode, S6, vibration-air spraying-lifting, S7, changing the next pile position, and S8, pile hole backfilling. The invention relates to a collapsible loess strengthening construction method with high efficiency, low carbon and low disturbance, which can realize the powerful crushing of loess structure, the high-efficiency mixing and infiltration of the slurry gas and the full excitation of low carbon reaction, and realize the immediate compaction by utilizing vibration, the grouting carbonization-vibration compaction cooperative reinforcement device has the advantages of flexible movement, convenient operation and wide application range, can meet the application requirements of large-scale engineering, and has remarkable advantages in the aspects of realizing resource recycling and carbon emission reduction.

Inventors

LIU HONGSEN
XU WEIDONG
DU BINGJIE
WANG YAOHUI
CAI GUANGHUA
YANG ZHE
WANG ZEXIN
WANG LING
DUAN CHEN
WANG FANGCHAO
DUAN YINGCHAO
Tao Quanlin

Assignees

黄河勘测规划设计研究院有限公司

Dates

Publication Date: 20260512
Application Date: 20260130

Claims (9)

1. The construction method for reinforcing the collapsible loess foundation based on grouting carbonization-compaction is characterized by comprising the following construction steps of: S1, field pretreatment, namely leveling a field, removing sundries such as roots, branches and stones, and determining basic physical and mechanical parameters of a collapsible loess soil layer of the field by combining a reconnaissance result and field complement measurement, so as to determine construction parameters, wherein the basic physical and mechanical parameters comprise soil layer thickness, moisture content, aperture ratio and collapse coefficient, and the construction parameters comprise low-carbon curing slurry doping amount, water slurry ratio and resonance compactness; S2, preparing slurry, namely uniformly mixing microbial bacteria liquid, urea solution, magnesium oxide, carbide slag, slag and additive enzyme according to a designed proportion to prepare low-carbon solidified slurry, and keeping the temperature of the low-carbon solidified slurry at 25-35 ℃ before use; S3, paying off and positioning, namely marking stirring pile positions on a pretreatment field, controlling the center-to-center distance between adjacent stirring pile positions to be 1.5-2.0 times of the radius of effective influence of resonance, then moving a walking chassis of a stirring grouting-resonance compaction cooperative reinforcing device, adjusting the posture of a guide frame of the walking chassis, ensuring that a stirring rod is kept vertical, and aligning the central axis of the stirring rod with the center of the stirring pile positions; S4, spraying, stirring and sinking, namely enabling a stirring rod to rotate clockwise, enabling a spiral drill bit and a fixed blade on the stirring rod to gradually rotate, cutting soil and sinking, and enabling a telescopic blade to be unfolded to the maximum diameter synchronously; S5, stirring and air injection are stopped, namely, after the slurry injection is stopped, the stirring rod continues to rotate clockwise for 1min, then the stirring rod is switched to rotate anticlockwise, the telescopic blades are gradually contracted, and then CO 2 gas is injected into the soil body through the gas pipe and the air injection hole, and the air injection time is controlled within 1 min; S6, vibrating, jetting and lifting, namely starting a vibrator, suspending CO 2 gas injection, enabling a resonance wing and a stratum mixed soil body to generate resonance, keeping vibration for 1-3min, suspending the vibrator, recovering CO 2 gas injection, lifting the vibrator according to a preset speed of 0.4-1.5m/min, and enabling a stirring rod to keep anticlockwise rotating; S7, replacing a next pile position, namely moving the stirring grouting-resonance compaction cooperative reinforcement device to the next stirring pile position, wherein the next stirring pile position is adjacent to or spaced from the previous stirring pile position, and repeating the steps S3-S6 to construct a next pile; And S8, backfilling pile holes, namely, backfilling upper pile holes formed after construction in a layering way by adopting a low-carbon mixture, wherein the thickness of each layer is not more than 40cm, tamping by adopting a small rammer or rolling by adopting a light road roller after backfilling, leveling the surface, and covering and curing for not less than 7 days.
2. The construction method for reinforcing the collapsible loess foundation based on grouting carbonization-compaction is characterized in that the stirring grouting-compaction-cooperation reinforcing device comprises a walking chassis, wherein hydraulic support legs are arranged at the bottom of the walking chassis, and a control box, a slurry tank, a CO 2 gas tank, a winch and a hydraulic rod are arranged above the walking chassis; the side of the guide frame is provided with a lifting frame connected with the winch, the lifting frame is provided with an upper stirring rod supporting frame and a lower vibrator, the vibrator is connected with a resonance column of a hollow structure, a resonance wing is arranged on the outer side of the resonance column, the stirring rod supporting frame is provided with a stirring rod, the stirring rod comprises an outer stirring rod driven by a first motor and an inner stirring rod driven by a second motor, the outer stirring rod and the inner stirring rod are of a hollow structure, the outer stirring rod is sleeved in the resonance column, the inner stirring rod is sleeved in the outer stirring rod, the outer stirring rod and the inner stirring rod are connected through a rotating bearing, a slurry conveying pipe connected with the slurry tank and a pipe connected with the CO 2 gas tank are arranged in the inner stirring rod, the outer stirring rod extends downwards to the outside of the resonance column, the tail end of the outer stirring rod is provided with a blade, the outer stirring rod is connected with a gas conveying pipe connected with the tail end of the gas conveying pipe in a telescopic way, the gas conveying pipe is arranged at the tail end of the gas conveying pipe in a telescopic way, the gas conveying pipe is connected with the tail end of the gas conveying pipe is arranged at the tail end of the gas conveying pipe, the bottom of the inner stirring rod is provided with a spiral drill bit.
3. The construction method for reinforcing the collapsible loess foundation based on grouting carbonization-compaction cooperation according to claim 1, wherein the low-carbon curing slurry in the step S2 is composed of the following raw materials in parts by weight: 10-25 parts of microbial liquid; 5-20 parts of urea; 10-30 parts of magnesium oxide; 20-50 parts of carbide slag; 30-70 parts of slag; Adding 0.1-0.5 part of enzyme; 80-100 parts of water; The microbial bacterial liquid is urease bacteria, is selected from commercial bacillus pasteurizus, has bacterial liquid concentration OD 600 = 0.8-1.2, has effective viable count of more than 10 8 CFU/mL, is light-burned MgO or active MgO, has activity of more than 40 according to an iodine adsorption method, is fine powder of grade S95 or more, is carbonic anhydrase, and is deionized water, distilled water or underground fresh water; The low-carbon cured slurry is required to be stirred continuously in the processes of storage, transportation and spraying, and spraying into the stratum is completed within 6 hours after preparation.
4. The construction method for reinforcing the collapsible loess foundation based on grouting carbonization-compaction is characterized in that the effective radius of influence of the compaction in the step S3 is determined by on-site inching test or numerical simulation, and is the radial distance corresponding to the time when vibration energy or stratum vibration acceleration is attenuated to 15-30% of peak energy.
5. The construction method for reinforcing the collapsible loess foundation based on grouting carbonization-compaction cooperation of claim 1, wherein the rotation speed of the stirring rod in the step S4 is 30-60 rpm, the sinking speed of the stirring rod is 0.8-1.5 m/min, the grouting pressure of the low-carbon cured slurry is 0.5-2.0MPa, and the grouting quantity per unit pile length is determined according to soil parameters and design requirements and is controlled by the sinking speed and the grouting pressure of the stirring rod.
6. The construction method for reinforcing collapsible loess foundation based on grouting carbonization-compaction cooperation according to claim 1, wherein the purity of CO 2 gas in the step S5 is not lower than 60%, the temperature is controlled at 15-30 ℃, and the gas injection pressure of CO 2 is controlled at 0.2-0.4MPa.
7. The construction method for reinforcing the collapsible loess foundation based on grouting carbonization-compaction is characterized in that the vibration frequency of the vibrator in the step S6 is controlled to be 20-40 Hz, the exciting force is adjusted according to the soil property and depth, and the lifting speed of the vibrator is controlled to be 0.5-0.8m/min.
8. The construction method for reinforcing collapsible loess foundation based on grouting carbonization-compaction cooperation according to claim 1, wherein the low-carbon mixture in the step S8 is prepared by stirring and mixing the low-carbon curing slurry prepared in the step S2 with site soil, wherein the mixing amount of the low-carbon curing slurry is 5-15% of the weight of the site soil, or mixing a base slag curing agent with site excavated soil, wherein the mixing amount of the base slag curing agent is 10-25% of the weight of the site soil, the base slag curing agent consists of carbide slag or magnesium oxide and slag, and the mixing amount of the carbide slag or magnesium oxide is 20-30% of the weight of the slag.
9. The construction method for reinforcing collapsible loess foundation based on grouting carbonization-vibration compaction cooperation of claim 1, wherein the collapsible loess foundation has a collapse coefficient of not less than 0.015 before reinforcement and a natural water content of not more than 15%, and the collapse coefficient after reinforcement is reduced to below 0.01.

Description

Construction method for reinforcing collapsible loess foundation based on grouting carbonization-compaction cooperation Technical Field The invention relates to the technical field of foundation treatment, in particular to a construction method for reinforcing a collapsible loess foundation based on grouting carbonization-compaction cooperation. Background Collapsible loess is widely distributed in northwest, north China and yellow river midstream areas of China, has total area exceeding 63 ten thousand square kilometers, and has special engineering properties of large pores, weak cementation and high water sensitivity. The high-strength concrete has low compressibility and high strength in a natural state, but the soluble salts which are glued after meeting water are dissolved and have large collapse coefficients, so that an overhead pore structure is instantaneously disintegrated, sudden local uneven settlement is caused, and fatal threat is formed to settlement-sensitive projects such as railways, subways and large-scale workshops. Therefore, the foundation is subjected to corresponding reinforcement treatment before engineering application so as to meet the requirements of the overlying structure on the bearing capacity and stability of the foundation. The existing treatment methods are divided into two major types of conventional physical methods and chemical reinforcement methods, wherein the former comprises a dynamic compaction method, a filling method, a compaction pile method and the like, and the latter comprises a siliconizing method, an alkali lye method and the like, and have certain defects. The dynamic compaction method has high treatment speed, but has large construction vibration and obvious influence on the surrounding environment. The replacement filling method has the defects of high cost, long period and large soil disturbance, and has limited treatment effect on deep foundations. The compaction pile method provides a high foundation bearing capacity, but is generally expensive to manufacture. The siliconizing method is to inject chemical solvent into stratum to exhaust water and air and to form soil body into one integral structure. The method has more branches, and is typically a pressure double-liquid method, a pressure single-liquid method, a pressure mixed method and an electric siliconizing method. The two-liquid method is different from the single-liquid method in that the chemical solvents are different, wherein the two-liquid method generally adopts two solutions of water glass (sodium silicate) and calcium chloride, and the single-liquid method generally only adopts water glass solution. These solutions react with calcium salt in foundation soil, and can obviously improve foundation strength. The siliconizing method has various kinds and wide application range, and can be flexibly selected according to engineering requirements. However, it should be noted that if the foundation contains organic substances such as asphalt and grease, penetration and contact of the chemical solvents are hindered, and thus the siliconizing method is not suitable for such cases. The alkaline solution method is to make the heated alkaline solution (such as sodium hydroxide solution) automatically flow into the deep layer of the foundation, and react with soil components to generate calcium aluminate complex which is difficult to dissolve in water and has high strength, so that the soil is reinforced, and the alkaline solution method is only applicable to specific soil, and also has risks of groundwater pollution and sudden alkalization. In recent years, emerging low carbon modification technologies have become research hotspots, focusing mainly on MgO carbonization curing technology and Microbial Induced Carbonate Precipitation (MICP) technology. For example, the Chinese patent ZL201210097042.2, ZL201010604013.1, a soil carbonization and solidification method and device, etc. all use active MgO as soil solidifying agent, and carbonize under high concentration CO 2 and high pressure environment, so as to improve soil strength in a short time. Compared with the traditional cement solidified soil, the cement solidified soil has the advantages of high solidification speed, high strength, good environmental benefit and the like. However, CO 2 infiltration and carbonization uniformity are susceptible when treating fine-grained soils with high water content. The MICP technology is used for catalyzing urea to decompose to produce CO 32 -by means of microorganism (such as Bacillus pasteuris or urease), and is combined with Ca 2 + in CaCl 2 to produce calcium carbonate, so that the soil particles are cemented, the mechanical properties of soil body are improved, and the method is mainly used for loose sand, but has limited treatment effect in clay with poor permeability. For example, chinese patent ZL 201811304804.5, a method for reinforcing coarse-grained soil based on microorganism-induced calcium carbona