Soft foundation sludge in-situ solidification construction method

Abstract

The invention discloses a soft foundation sludge in-situ solidification construction method, which relates to the technical field of soft soil foundation treatment and comprises the steps of site investigation, parameter calculation, construction preparation, in-situ solidification construction and maintenance. According to the method, sludge in each subarea is detected in the site investigation process, parameters comprise the moisture content and sludge components, the sludge components comprise heavy metal or organic pollutants, the curing material formula proportion and the mixing and stirring depth are calculated, layered stirring is conducted during stirring, segmented feeding is conducted during stirring of each layer, and therefore the curing material is obtained. The mixing and stirring depth is regulated and controlled according to the water content of in-situ sludge, the stirring uniformity is improved, the construction quality is improved, the formula proportion of a curing material is regulated and controlled according to the content of pollution components, and the fixing and stability performance is improved; the curing agent and the sludge are fully and uniformly stirred, so that the cured sludge has relatively high strength and stability.

Description

Technical Field

[0001] The invention relates to the technical field of soft soil foundation treatment, and in particular to an in-situ solidification construction method for soft soil foundation sludge. Background Art

[0002] Soft foundation silt refers to geological materials composed of water, fine particles (such as clay, silt and organic matter), which usually has low bearing capacity and high water content. There are many ways to treat silt soft foundation, including chemical reinforcement, composite foundation method, excavation and replacement method, drainage consolidation method, etc. Among them, chemical reinforcement method is widely used due to its good durability, controllable consolidation shape, wide range of application, short construction period and simple construction.

[0003] In coastal areas, the geological conditions of tidal flats are complex and changeable, which poses a huge challenge to the construction of transportation infrastructure, especially the treatment of silt soft foundation for transportation roads. The silt soft matrix has the characteristics of low strength, high compressibility, large natural porosity, complex mineral composition, high natural water content and small permeability coefficient. Therefore, it will lead to low foundation bearing capacity and large uneven settlement, which can easily cause safety problems such as highway collapse, sliding and tilting.

[0004] The Chinese patent with publication number CN108468325A discloses a method for rapid solidification of large-area coastal mud on tidal flats, which specifically includes the following steps: construction zoning; silt excavation and mud drainage; spreading HAS sea mud solidifier; evenly mixing the HAS sea mud solidifier with the sea mud; solidifying the mixed soil to obtain a sea mud consolidation body; backfilling and compacting the sea mud consolidation body in layers and blocks / segments. The beneficial effects of the invention are: the bearing capacity, compaction degree, deflection value, etc. of the foundation after in-situ solidification treatment with the sea mud HAS sea mud solidifier can meet the corresponding standards. After layered backfilling, the uneven settlement is reduced, and the foundation bearing capacity can reach more than 110kPa, which can meet the common foundation requirements such as site leveling foundation, building foundation and road subgrade.

[0005] In the above patent, during the construction process, the mixing depth cannot be regulated according to the moisture content of the in-situ sludge, the mixing uniformity is insufficient, the solidification material formula ratio cannot be regulated according to the content of the pollutant components, and the fixation of heavy metals or organic pollutants is unstable. Summary of the invention

[0006] The purpose of the present invention is to provide a soft base sludge in-situ solidification construction method, which solves the problems that the existing construction method cannot adjust the mixing and stirring depth according to the in-situ sludge moisture content, the stirring uniformity is insufficient, the solidification material formula ratio cannot be adjusted according to the content of pollutants, and the fixation of heavy metals or organic pollutants is unstable.

[0007] The present invention solves the above technical problems through the following technical solutions, and is a soft foundation sludge in-situ solidification construction method, comprising the following steps: Step 1: Site survey: Divide the construction site into zones and test the silt in each zone; Step 2: Parameter calculation: Calculate the solidification material formula ratio and mixing depth through the surveyed sludge parameters; Step 3: Construction preparation: prepare construction machines and fixing materials; Step 4: In-situ solidification construction: The mixing equipment performs preliminary mixing, mixes the solidification material prepared in proportion with the soft base sludge, and mixes and stirs them thoroughly; Step 5: Maintenance: The mixing area is maintained to form a solidified foundation structure, compaction is performed to enhance structural stability, and a protective layer is laid on the surface of the compacted silt layer to prevent the external environment from affecting the solidification effect.

[0008] Preferably, the site survey in step 1 specifically includes the following steps: Step S1, dividing the construction site into different zones; Step S2: Perform sludge detection on each partition, the parameters include water content and sludge composition, and the sludge composition includes heavy metals or organic pollutants.

[0009] Preferably, the parameter calculation in step 2 specifically includes the following steps: Step N1: Obtain the measured total concentration C of heavy metals or organic pollutants t , heavy metal or organic pollutant allowable limit C max ; Step N2: Calculate the dosage control coefficient k, k=C t / C max , if 1≤k<8, α adj =α*(1+lnk), where α is the reference dosage of active mineral additives, α adj is the calculated reference dosage of active mineral additives. If k≥8, α adj =1.5α*k 0.3 , β=0.05:1, β is the added ratio of the coagulant to the total mass of the curing agent.

[0010] Preferably, the parameter calculation in step 2 specifically further includes the following steps: Step V1: Use a microwave moisture meter (accuracy ±2%) or drying method to select 3 measuring points in each 50m×50m grid to obtain the in-situ moisture content value H of the sludge, and query the equipment nameplate to obtain D limit , D limit The maximum permissible stirring depth of the equipment; Step V2: Calculate the theoretical stirring limit depth, D max = (H / C)*D ref , where C is the empirical calibration coefficient, D ref As the reference basic mixing depth, if the calculated D max >D limit , then take D limit .

[0011] Preferably, the construction preparation of step 3 specifically includes the following steps: Step M1, prepare the required mixer, drilling rig and grouting equipment, and control and adjust the mixing depth according to the calculated parameters; Step M2: adjusting the ratio of the fixed material according to the calculated parameters, injecting different types of materials into the powder bin, and stirring them according to a preset ratio on a workbench to form a curing agent.

[0012] Preferably, the in-situ curing construction of step 4 specifically includes the following steps: Step E1, using a stirring device to preliminarily stir the soft base sludge to loosen the sludge for subsequent mixing; Step E2, uniformly add the solidifying material prepared according to the proportion into the mixing zone, and fully stir it with the sludge. Stir it in layers, and add the material in stages when stirring each layer. First, add 50% of the solidifying agent for initial mixing. If a coagulant aid is needed, add it. If not, add the remaining solidifying agent.

[0013] Preferably, the maintenance in step 5 specifically includes the following steps: Step T1, perform maintenance treatment on the area after mixing, and take appropriate measures such as sprinkling water or covering with wet cloth to keep it moist to prevent it from drying out too quickly; Step T2, compaction treatment to improve the density and stability of the solidified structure and enhance the bearing capacity of the foundation; Step T2: laying a geotextile protective layer on the surface of the compacted silt layer to prevent the influence of external environmental factors on the curing effect and ensure stability.

[0014] Preferably, when preparing the curing agent in step M2, fly ash can be added as a filler for cement.

[0015] Compared with the prior art, the beneficial effects of the present invention are: 1. In the present invention, the sludge in each partition is tested during the site survey, and the parameters include moisture content and sludge composition. The sludge composition includes heavy metals or organic pollutants. The solidification material formula ratio and the mixing depth are calculated, and the stirring is carried out in layers, and each layer is stirred in stages. The mixing depth is regulated according to the original sludge moisture content to improve the mixing uniformity and the construction quality. The solidification material formula ratio is regulated according to the content of pollutants to improve the fixing stability performance.

[0016] 2. By adding a curing agent to the soft soil, combined with high-pressure rotary spraying technology and mechanical stirring technology, the curing agent and silt are fully and evenly stirred in the silt soft foundation, so that the solidified silt has higher strength and stability, and the water molecules in the soft soil are fixed in the form of crystal water, reducing the soil moisture content, while enhancing the bonding strength and overall stability of the soil. It not only solves the problem of silt soft foundation treatment, but also has significant advantages such as environmental protection, energy saving, and economy. Through curing treatment, the porosity of the silt is reduced, the permeability coefficient is reduced, and the stability is improved. It can effectively prevent secondary pollution caused by silt infiltration, and at the same time seal heavy metals, with sterilization and deodorization functions. DETAILED DESCRIPTION

[0017] The above and other technical features and advantages of the present invention are described in more detail below in conjunction with embodiments.

[0018] This embodiment provides a technical solution: a soft foundation sludge in-situ solidification construction method, comprising the following steps: Step 1: Site survey: Divide the construction site into zones and test the silt in each zone; Furthermore, the site investigation in step 1 specifically includes the following steps: Step S1, dividing the construction site into different zones; Step S2: Perform sludge detection on each partition, the parameters include water content and sludge composition, and the sludge composition includes heavy metals or organic pollutants.

[0019] Step 2: Parameter calculation: Calculate the solidification material formula ratio and mixing depth through the surveyed sludge parameters; Furthermore, the parameter calculation in step 2 specifically includes the following steps: Step N1: Obtain the measured total concentration C of heavy metals or organic pollutants t , heavy metal or organic pollutant allowable limit C max ; Step N2: Calculate the dosage control coefficient k, k=C t / C max , if 1≤k<8, α adj=α*(1+lnk), where α is the reference dosage of active mineral additives, α adj is the calculated reference dosage of active mineral additives. If k≥8, α adj =1.5α*k 0.3 , β=0.05:1, β is the added ratio of the coagulant to the total mass of the curing agent.

[0020] Through the quantitative relationship between pollution load and material response, precise curing can be achieved, reducing material overconsumption by more than 25% compared with traditional empirical methods.

[0021] Furthermore, the parameter calculation in step 2 specifically includes the following steps: Step V1: Use a microwave moisture meter (accuracy ±2%) or drying method to select 3 measuring points in each 50m×50m grid to obtain the in-situ moisture content value H of the sludge, and query the equipment nameplate to obtain D limit , D limit The maximum permissible stirring depth of the equipment; Step V2: Calculate the theoretical stirring limit depth, D max = (H / C)*D ref , where C is the empirical calibration coefficient, D ref As the reference basic mixing depth, if the calculated D max >D limit , then take D limit .

[0022] It can realize quantitative and adaptive control of mixing depth, and improve work efficiency by 20%~35% compared with the empirical method. Step 3: Construction preparation: prepare construction machines and fixing materials; Furthermore, the construction preparation of step three specifically includes the following steps: Step M1, prepare the required mixer, drilling rig and grouting equipment, and control and adjust the mixing depth according to the calculated parameters; Step M2: adjusting the ratio of the fixed material according to the calculated parameters, injecting different types of materials into the powder bin, and stirring them according to a preset ratio on a workbench to form a curing agent.

[0023] Furthermore, when preparing the curing agent in step M2, fly ash can be added as a filler for cement.

[0024] Step 4: In-situ solidification construction: The mixing equipment performs preliminary mixing, mixes the solidification material prepared in proportion with the soft base sludge, and mixes and stirs them thoroughly; Furthermore, the in-situ curing construction of step 4 specifically includes the following steps: Step E1, using a stirring device to preliminarily stir the soft base sludge to loosen the sludge for subsequent mixing; Step E2, uniformly add the solidifying material prepared according to the proportion into the mixing zone, and fully stir it with the sludge. Stir it in layers, and add the material in stages when stirring each layer. First, add 50% of the solidifying agent for initial mixing. If a coagulant aid is needed, add it. If not, add the remaining solidifying agent.

[0025] Step 5: Maintenance: The mixing area is maintained to form a solidified foundation structure, compacted to enhance structural stability, and a protective layer is laid on the surface of the compacted silt layer to prevent the external environment from affecting the solidification effect; Furthermore, the maintenance of step five specifically includes the following steps: Step T1, perform maintenance treatment on the area after mixing, and take appropriate measures such as sprinkling water or covering with wet cloth to keep it moist to prevent it from drying out too quickly; Step T2, compaction treatment to improve the density and stability of the solidified structure and enhance the bearing capacity of the foundation; Step T2: laying a geotextile protective layer on the surface of the compacted silt layer to prevent the influence of external environmental factors on the curing effect and ensure stability.

[0026] In the present invention, during the site survey, the sludge in each partition is tested, and the parameters include moisture content and sludge composition, and the sludge composition includes heavy metals or organic pollutants. The solidification material formula ratio and the mixing depth are calculated, and the stirring is carried out in layers, and each layer is stirred in stages. The mixing depth is regulated according to the in-situ sludge moisture content to improve the mixing uniformity and the construction quality. The solidification material formula ratio is regulated according to the content of the pollutant components to improve the fixing stability performance; By adding a curing agent to the soft soil, combined with high-pressure rotary spraying technology and mechanical stirring technology, the curing agent and the silt are fully and evenly stirred in the silt soft base, so that the solidified silt has higher strength and stability, and the water molecules in the soft soil are fixed in the form of crystal water, reducing the soil water content, while enhancing the cementing strength and overall stability of the soil body, which not only solves the problem of silt soft base treatment, but also has significant advantages such as environmental protection, energy saving, and economy. Through the curing treatment, the porosity of the silt is reduced, the permeability coefficient is reduced, and the stability is improved, which can effectively prevent secondary pollution caused by silt infiltration, and at the same time seal heavy metals, and has sterilization and deodorization functions; The in-situ solidification technology processes and solidifies the tidal flat geology directly, reducing the processes of earth excavation, transportation and backfilling, thereby significantly reducing construction costs. Compared with the traditional dredging and replacement method, the in-situ solidification technology saves time and labor, and is especially suitable for large-area soft foundation treatment, reducing the overall project cost. The in-situ solidification technology is easy to operate and has a fast construction speed. The carriageway after in-situ solidification has higher bearing capacity and durability, reducing the cost of later maintenance and repair, thereby extending the service life of the road and improving the return on investment.

[0027] The above are only preferred embodiments of the present invention, which are only illustrative and not restrictive. Those skilled in the art understand that many changes, modifications, and even equivalences may be made to the present invention within the spirit and scope defined by the claims, but all of them will fall within the scope of protection of the present invention.

Claims

1. A soft foundation sludge in-situ solidification construction method, characterized in that: The following steps are involved: Step 1: Site survey: Divide the construction site into zones and test the silt in each zone; Step 2: Parameter calculation: Calculate the solidification material formula ratio and mixing depth through the surveyed sludge parameters; Step 3: Construction preparation: prepare construction machines and fixing materials; Step 4: In-situ solidification construction: The mixing equipment performs preliminary mixing, mixes the solidification material prepared in proportion with the soft base sludge, and mixes and stirs them thoroughly; Step 5: Maintenance: The mixing area is maintained to form a solidified foundation structure, compaction is performed to enhance structural stability, and a protective layer is laid on the surface of the compacted silt layer to prevent the external environment from affecting the solidification effect.

2. A soft foundation sludge in-situ solidification construction method as claimed in claim 1, characterized in that: The site investigation in step 1 specifically includes the following steps: Step S1, dividing the construction site into different zones; Step S2: Perform sludge detection on each partition, the parameters include water content and sludge composition, and the sludge composition includes heavy metals or organic pollutants.

3. A soft foundation sludge in-situ solidification construction method as claimed in claim 1, characterized in that: The parameter calculation of step 2 specifically includes the following steps: Step N1: Obtain the measured total concentration C of heavy metals or organic pollutants t , heavy metal or organic pollutant allowable limit C max ; Step N2: Calculate the dosage control coefficient k, k=C t / C max , if 1≤k<8, α adj =α*(1+lnk), where α is the reference dosage of active mineral additives, α adj is the calculated reference dosage of active mineral additives. If k≥8, α adj =1.5α*k 0.3 , β=0.05:1, β is the added ratio of the coagulant to the total mass of the curing agent.

4. A soft foundation sludge in-situ solidification construction method as claimed in claim 1, characterized in that: The parameter calculation of step 2 specifically includes the following steps: Step V1: Use a microwave moisture meter (accuracy ±2%) or drying method to select 3 measuring points in each 50m×50m grid to obtain the in-situ moisture content value H of the sludge, and query the equipment nameplate to obtain D limit , D limit The maximum permissible stirring depth of the equipment; Step V2: Calculate the theoretical stirring limit depth, D max = (H / C)*D ref , where C is the empirical calibration coefficient, D ref As the reference basic mixing depth, if the calculated D max >D limit , then take D limit .

5. A soft foundation sludge in-situ solidification construction method as claimed in claim 1, characterized in that: The construction preparation of step 3 specifically includes the following steps: Step M1, prepare the required mixer, drilling rig and grouting equipment, and control and adjust the mixing depth according to the calculated parameters; Step M2: adjusting the ratio of the fixed material according to the calculated parameters, injecting different types of materials into the powder bin, and stirring them according to a preset ratio on a workbench to form a curing agent.

6. A soft foundation sludge in-situ solidification construction method as claimed in claim 1, characterized in that: The in-situ curing construction of step 4 specifically includes the following steps: Step E1, using a stirring device to preliminarily stir the soft base sludge to loosen the sludge for subsequent mixing; Step E2, uniformly add the solidifying material prepared according to the proportion into the mixing zone, and fully stir it with the sludge. Stir it in layers, and add the material in stages when stirring each layer. First, add 50% of the solidifying agent for initial mixing. If a coagulant aid is needed, add it. If not, add the remaining solidifying agent.

7. A soft foundation sludge in-situ solidification construction method as claimed in claim 1, characterized in that: The maintenance of step 5 specifically includes the following steps: Step T1, perform maintenance treatment on the area after mixing, and take appropriate measures such as sprinkling water or covering with wet cloth to keep it moist to prevent it from drying out too quickly; Step T2, compaction treatment to improve the density and stability of the solidified structure and enhance the bearing capacity of the foundation; Step T2: laying a geotextile protective layer on the surface of the compacted silt layer to prevent the influence of external environmental factors on the curing effect and ensure stability.

8. A soft foundation sludge in-situ solidification construction method as claimed in claim 5, characterized in that: When preparing the curing agent in step M2, fly ash can be added as a filler for cement.