Additive and method for improving one-time drilling qualified rate under gobi desertification geological condition

Abstract

The invention relates to the technical field of engineering construction, in particular to an additive and method for improving the one-time drilling qualified rate under the gobi desertification geological condition, raw materials of the additive are composed of lime, cement and water, and the total weight of the lime and the cement accounts for 15-40% of the total weight of the raw materials. The method comprises the steps that the pile position and the target pore-forming pile diameter are determined firstly, and then the admixture is injected into the position of the target pore-forming pile diameter; and after the admixture permeates and consolidates the sand layer, drilling is carried out. According to the method, the additive is poured into the pile hole in the drilling process, so that the stability of the pile hole is higher, and the pile forming quality defect caused by hole wall collapse is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of engineering construction, and particularly relates to an admixture and method for improving the qualified rate of one-time drilling under gobi desertification geological conditions. Background Technique

[0002] The pile foundation is one of the main foundation reinforcement projects to increase the overall stability of the foundation and improve the bearing capacity of the foundation. According to the construction method of the pile, it can be divided into displacement piles, partially displacement piles and non-displacement piles. Among them, the bored cast-in-place pile in the non-displacement piles is widely used due to its high bearing capacity, no soil displacement, no seismic damage during construction, low noise and being suitable for use in areas with dense urban buildings.

[0003] When the bored cast-in-place pile is applied to the desert gobi beach, due to the harsh construction environment, most of the project site areas are soft soil, the topsoil is mostly sandy soil, the physical and mechanical properties of the soil are poor, and the distribution is uneven. Therefore, when the bored cast-in-place pile is constructed on this type of soil, problems such as hole wall collapse and necking often occur, resulting in pile quality defects and seriously affecting the bearing capacity of the foundation.

[0004] Chinese Patent Application CN109987898A discloses a cement stabilized macadam mixture and its preparation process, which relates to the technical field of subgrade materials and solves the problem that the overall flexural tensile strength of the cement stabilized macadam is poor during use and dry shrinkage cracks are easily generated, resulting in overall damage to the road. A cement stabilized macadam mixture includes the following components in parts by weight: 4-5 parts of portland cement; 30-45 parts of new aggregate; 20-25 parts of recycled aggregate; 28-36 parts of stone chips; 4-8 parts of polypropylene fiber; 10-12 parts of wollastonite powder; 0.3-0.5 part of aluminum titanate; 5-10 parts of expansive agent; 4-8 parts of water. The cement stabilized macadam in this invention has good flexural tensile strength, is not easy to generate dry shrinkage cracks, and has high overall quality, keeping the road in good stability and not being easily damaged. However, the mixture has complex components and is not suitable for drilling under gobi desertification geological conditions.

[0005] Chinese Patent Application 202110197247.7 discloses a construction method for a water-injected rotary drilled cast-in-place pile, including the following steps: pre-construction preparation, site leveling, measurement positioning, drilling, hole formation detection, hoisting the steel reinforcement cage, embedding the screw rod, and concrete pouring. The construction method of the present invention is applicable to the construction of cast-in-place piles in desert areas. Its principle is to use water injection to consolidate the sand layer for the special geological structure of desertification to solve the problems of frequent hole collapse and too thick sediment in the construction of gravel layer pile foundations in desert areas and improve the pile foundation construction efficiency.

[0006] The prior art has conducted certain explorations on the methods of bored cast-in-place piles. Under conventional geological conditions, the commonly used construction methods for bored cast-in-place piles include dry-boring cast-in-place pile construction, slurry-supported bored cast-in-place pile construction, and steel sleeve static-pressure slurry-supported bored cast-in-place pile construction. Although these methods are technically feasible, considering the conditions in the gobi desert geological environment, there are drawbacks such as scarce water resources that are difficult to meet the construction needs, excessive construction costs, and complex processes that seriously affect the contract construction period. They cannot meet the requirements of the project contract construction period and cost control. Therefore, it is necessary to find a construction method suitable for drilling operations under gobi desert geological conditions. Summary of the Invention

[0007] The object of the present invention is to propose a method for improving the one-time drilling qualification rate under gobi desertified geological conditions, aiming to solve the technical problem that the pile hole stability of the existing bored cast-in-place piles is poor, and the hole wall is prone to collapse, resulting in quality defects of the formed piles.

[0008] To achieve the above object, the present invention proposes an admixture for improving the one-time drilling qualification rate under gobi desertified geological conditions. The raw materials of the admixture are composed of lime, cement, and water, and the total weight of lime and cement accounts for 15-40% of the total weight of the raw materials.

[0009] Preferably, the total weight of lime and cement accounts for 20-25% of the total weight of the raw materials.

[0010] Preferably, the mass ratio of lime to cement is 1:1-3.

[0011] Preferably, the mass ratio of lime to cement is 1:3 or 1:2 or 1:1.

[0012] The second object of the present invention is to provide a method for improving the one-time drilling qualification rate under gobi desertified geological conditions, including the following steps:

[0013] (1) Determine the pile position and the target hole diameter of the formed hole, and then inject the above-mentioned admixture at the position of the target hole diameter of the formed hole;

[0014] (2) After the admixture penetrates and consolidates the sand layer, carry out drilling.

[0015] Preferably, the diameter of the admixture injection in step (1) is larger than the target hole diameter of the formed hole.

[0016] Preferably, the diameter of the admixture injection in step (1) is 1.2-1.3 times the target hole diameter of the formed hole.

[0017] Preferably, the consolidation time in step (2) is 5-15 minutes, and 2.5-3.5 L of the admixture can penetrate and consolidate a sand layer with a depth of 2-3 m.

[0018] Preferably, the aperture of the drilling hole in step (2) is 25 - 30 cm. With one addition of the admixture, the depth that can be drilled is 1.5 - 2.5 m.

[0019] Preferably, when the depth of the drilling hole is greater than 2 m, the admixture is added multiple times. The operation of adding the admixture multiple times is as follows: after the first drilling is carried out, the drill rig is withdrawn and the hole is cleared, then the admixture is added again, and steps (1) and (2) are repeated until the hole depth meets the requirements.

[0020] The third object of the present invention is to provide an application of an admixture in drilling under target geological conditions.

[0021] Preferably, the target geology is one or more of gobi desertification geological regions, aeolian sand soil layers regions, silt geological regions, silty clay geological regions, and silty sand soil layers regions.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) By pouring the admixture into the pile hole during the drilling process, the present invention makes the pile hole more stable, thus avoiding the occurrence of hole wall collapse and causing defects in the pile forming quality.

[0024] (2) By adding the admixture during the drilling process to improve the soil stability, the one - time hole forming qualification rate reaches more than 95%, and the cost can be significantly saved.

[0025] (3) After determining the pile position and the required pile hole diameter to be formed in the present invention, the additive needs to be added within a range that is 1.2 - 1.3 times the diameter of the formed hole. The principle is to enhance the stability of the hole wall after hole formation through the admixture. The range of adding the additive needs to be slightly larger than the target hole formation diameter range to achieve the effect of consolidating the hole wall.

[0026] (4) The actual application scenario of the present invention is the pile hole formation of photovoltaic projects in desert or desertified gobi regions, which is characterized by a small pile diameter (25 - 30 cm), a short pile length (generally 1.6 - 2.5 m, and individual special - purpose piles will be extended to 5 - 6 m), and a very large quantity (for a 1 MW photovoltaic installed capacity, the corresponding number of piles is about 900).

[0027] (5) When forming a pile foundation with a relatively deep pile length in the present invention, the admixture needs to be added in batches. Taking the longest 6 - m pile on the site as an example, the implementation process is "adding - forming a 2 - m hole - withdrawing the drill rig and clearing the hole - adding for the second time - forming a 2 - m hole (total depth 4 m) - withdrawing the drill rig and clearing the hole - adding for the third time - forming a 2 - m hole (total depth 6 m)". Detailed implementation manners

[0028] The present invention will be further elaborated in detail below in conjunction with specific embodiments. The following embodiments are not used to limit the present invention, but only to illustrate the present invention. Unless otherwise specified, the experimental methods used in the following embodiments are those without specific conditions, which are usually carried out under conventional conditions. The materials, reagents, etc. used in the following embodiments can be obtained from commercial channels unless otherwise specified.

[0029] In the southern part of Xinjiang Uygur Autonomous Region, the geological type is desert and gobi beach, the construction environment is harsh, the soil in the project area is soft, the topsoil is mostly sandy soil, the physical and mechanical properties of the soil are poor, and the distribution is uneven; according to the exploration results, the main strata of the proposed project site are aeolian sand, silt, silty clay, silty sand, and cobblestone from top to bottom in turn.

[0030] Example 1

[0031] An admixture for improving the qualified rate of one-time drilling under gobi desertification geological conditions, the raw materials of the admixture are composed of lime, cement and water, and the total weight of lime and cement accounts for 20% of the total weight of the raw materials.

[0032] The mass ratio of the lime, cement and water is 1:3.

[0033] A gobi desertification geological drilling method, the specific steps are as follows:

[0034] (1) Determine the pile position and the target hole-forming pile diameter, and then inject 2L of the admixture at the position of the target hole-forming pile diameter. The diameter of the admixture is 1.2 times larger than the target hole-forming pile diameter;

[0035] (2) After the admixture penetrates and consolidates the sand layer (7 minutes), use a spiral drill bit to drill in the area of the target hole-forming pile diameter;

[0036] (3) Drill to the preset depth of 2m, stop drilling, and extract the spiral drill bit.

[0037] Example 2

[0038] An admixture for improving the qualified rate of one-time drilling under gobi desertification geological conditions, the raw materials of the admixture are composed of lime, cement and water, and the total weight of lime and cement accounts for 25% of the total weight of the raw materials.

[0039] The mass ratio of the lime, cement and water is 1:2.

[0040] A gobi desertification geological drilling method, the specific steps are as follows:

[0041] (1) Determine the pile position and the target hole-forming pile diameter, and then inject 2L of the admixture at the position of the target hole-forming pile diameter. The diameter of the admixture is 1.2 times larger than the target hole-forming pile diameter;

[0042] (2) After the admixture penetrates and consolidates the sand layer (10 min), use a spiral drill bit to drill a hole in the target hole diameter area;

[0043] (3) Drill to the preset depth of 2 m, stop drilling, and extract the spiral drill bit.

[0044] Example 3

[0045] An admixture for improving the one-time drilling qualification rate under gobi desertification geological conditions, the raw materials of the admixture are composed of lime, cement and water, and the total weight of lime and cement accounts for 40% of the total weight of the raw materials.

[0046] The mass ratio of the lime, cement and water is 1:1.

[0047] A gobi desertification geological drilling method, the specific steps are as follows:

[0048] (1) Determine the pile position and the target hole diameter, and then inject 2 L of the admixture at the target hole diameter position. The diameter of the admixture is 1.2 times larger than the target hole diameter;

[0049] (2) After the admixture penetrates and consolidates the sand layer (15 min), use a spiral drill bit to drill a hole in the target hole diameter area;

[0050] (3) Drill to the preset depth of 2 m, stop drilling, and extract the spiral drill bit.

[0051] Example 4

[0052] An admixture for improving the one-time drilling qualification rate under gobi desertification geological conditions, the raw materials of the admixture are composed of lime, cement and water, and the total weight of lime and cement accounts for 15% of the total weight of the raw materials.

[0053] The mass ratio of the lime, cement and water is 1:3.

[0054] A gobi desertification geological drilling method, the specific steps are as follows:

[0055] (1) Determine the pile position and the target hole diameter, and then inject 2 L of the admixture at the target hole diameter position. The diameter of the admixture is 1.3 times larger than the target hole diameter;

[0056] (2) After the admixture penetrates and consolidates the sand layer (5 min), use a spiral drill bit to drill a hole in the target hole diameter area;

[0057] (3) Drill to the preset depth of 2 m, stop drilling, and extract the spiral drill bit to clean the hole;

[0058] (4) Then add 2L of admixture into the drilled hole. After the admixture penetrates and consolidates the sand layer (5 minutes), continue drilling with a spiral drill bit until the drilling depth reaches 4m, stop drilling, and extract the spiral drill bit to clean the hole;

[0059] (5) Add another 2L of admixture into the drilled hole. After the admixture penetrates and consolidates the sand layer (5 minutes), continue drilling with a spiral drill bit until the drilling depth reaches 6m, stop drilling, and extract the spiral drill bit to clean the hole.

[0060] Comparative Examples 1 - 9

[0061] The differences between Comparative Examples 1 - 9 and Example 1 are only that the raw material ratios of the admixture are different, as shown in Table 1 specifically. Whether it meets the requirements, the situations where the optimized and stable soil structure is not satisfied are: hole collapse and excessive bottom sediment in the hole.

[0062] Table 1 Statistical Table of Admixture Mix Ratio Tests

[0063]

[0064] Comparative Example 10

[0065] The difference between this comparative example and Example 1 is only that the admixture is different. The admixture in this comparative example is only water. By injecting water to infiltrate the soil, the stability of the soil layer is improved, and 3 pile holes are infiltrated with water per 1m. 3 Water infiltrates 3 pile holes.

[0066] Comparative Example 11

[0067] The difference between this comparative example and Example 1 is that no admixture is added, and a spiral drill bit is directly used to drill in the target area.

[0068] Comparative Example 12

[0069] The difference between this comparative example and Example 1 is only that no admixture is added. A steel pipe mold is used for hole formation and fixation, and the steel mold sleeve is pressed into the soil layer to be drilled to stabilize the structure of the position to be drilled. The economy, operability of this scheme are not ideal, and the feasibility is poor.

[0070] Effect Test

[0071] Using the drilling methods of Examples 1 - 3 and Comparative Examples 1 - 11, drilling tests are respectively carried out on the same construction site with the same number, the same operating machinery (XRHS1096 CD SQ WA NA), and the same operating personnel. The same construction site is located in the southern part of Xinjiang Uygur Autonomous Region, with a geological type of desert gobi beach, a harsh construction environment, soft soil quality in the project area, sandy soil in the surface soil, poor physical and mechanical properties of the soil, and uneven distribution; according to the exploration results, the main strata of the proposed project site are aeolian sand, silt, silty clay, fine sand, and cobblestone from top to bottom in sequence.

[0072] The test results are shown in Table 2.

[0073] Table 2 Test Results

[0074] Group Number of drill holes First-pass yield Example 1 100 98％ Example 2 100 96％ Example 3 100 95％ Comparative Example 1 100 66％ Comparative Example 2 100 75％ Comparative Example 3 100 81％ Comparative Example 4 100 85％ Comparative Example 5 100 75％ Comparative Example 6 100 67％ Comparative Example 7 100 70％ Comparative Example 8 100 63％ Comparative Example 9 100 65％ Comparative Example 10 100 35％ Comparative Example 11 100 5％

[0075] The economic benefit analysis of drilling was carried out using the drilling methods of Example 1 and Comparative Examples 10 - 11, and the results are shown in Table 3.

[0076] Table 3 Results of Economic Benefit Analysis

[0077]

[0078] Note: 1. According to the actual site conditions, water costs 60 yuan for 20 m 3 ; lime costs 60 yuan for 50 kg; cement costs 400 yuan for 1000 kg. Then, water costs 0.003 yuan per kilogram, lime costs 1.2 yuan per kilogram, and cement costs 0.4 yuan per kilogram.

[0079] 2. Using the infiltration method, 1 m 3 of water infiltrates 3 pile holes, so each hole requires materials (water cost) of 1 yuan.

[0080] 3. Using a mixture of lime, cement, and water, each pile hole requires 1.2 kg of lime, 3.6 kg of cement, and 7.2 kg of water, which cost 1.44 yuan, 1.44 yuan, and 0.0216 yuan respectively, with a total of 2.9016 yuan.

[0081] The above are only optional embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structural transformation made using the content of the specification of the present invention under the inventive concept of the present invention, or any direct / indirect application in other related technical fields, is included within the patent protection scope of the present invention.

Claims

1. An admixture for improving the qualified rate of one-time drilling under the geological conditions of desertification in the Gobi, characterized in that, The raw materials of the admixture are composed of lime, cement and water, and the total weight of lime and cement accounts for 15-40% of the total weight of the raw materials.

2. The admixture according to claim 1, wherein The total weight of the lime and cement accounts for 20-25% of the total weight of the raw materials.

3. The admixture according to claim 1, characterized in that, The mass ratio of the lime to the cement is 1:1-3.

4. The admixture according to claim 1, characterized in that, The mass ratio of the lime to the cement is 1:3 or 1:2 or 1:

1.

5. A method for improving the qualified rate of one-time drilling under the geological conditions of desertification in the Gobi, characterized in that, It includes the following steps: (1) Determine the pile position and the target bored pile diameter, and then pour the admixture described in any one of claims 1-4 at the target bored pile diameter position; (2) After the admixture penetrates and consolidates the sand layer, carry out drilling.

6. The method according to claim 5, characterized in that, In step (1), the diameter of the poured admixture is larger than the target bored pile diameter.

7. The method according to claim 5, wherein In step (1), the diameter of the poured admixture is 1.2-1.3 times the target bored pile diameter.

8. The method according to claim 5, characterized in that, In step (2), the consolidation time is 5-15 min, and the dosage of the admixture used for penetrating and consolidating the sand layer with a depth of 2-3 m is 2.5-3.5 L.

9. The method according to claim 5, characterized in that In step (2), the diameter of the drilled hole is 25-30 cm. By pouring the admixture once, the depth that can be drilled is 1.5-2.5 m; and / or, when the drilling depth is greater than 2 m, the admixture is poured multiple times. The operation of pouring the admixture multiple times is that after the first drilling is carried out, the drill is withdrawn and the hole is cleaned, and then the admixture is poured again, repeating steps (1) and (2) until the hole depth meets the requirements.

10. The application of the admixture described in any one of claims 1-4 in drilling under target geological conditions; the target geology is one or more of the gobi desertification geological area, aeolian sand soil layer area, silt geological area, silty clay geological area and silty sand soil layer area; and / or, the application of the admixture in the bored pile formation of photovoltaic projects in desert or desertified gobi areas.

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