Shell powder-based environment-friendly wall protection mortar, preparation method and application thereof

Abstract

The application discloses a kind of fruit shell powder-based environment-friendly wall protection mortar and its preparation method and application, belong to the technical field of wall protection mortar.The environment-friendly wall protection mortar is composed of the following mass ratio of raw material components: water, xanthan gum, hydroxypropyl guar gum, fruit shell powder, pre-gelatinized starch, anhydrous sodium carbonate = 1000:1.0~2.0:0.5~1.5:7.5~15:3~9:0.3~0.9;And the total mass of xanthan gum and hydroxypropyl guar gum is not less than 2 ‰ of water, not more than 3.5 ‰ of water.The application recycles waste fruit shell powder as a solid phase film-forming agent, the additives used are green, non-toxic and completely naturally degradable, the prepared mortar is a low solid polymer mortar, has excellent wall protection performance, significantly reduces the filtration loss, ensures that the formula does not contain any non-degradable ingredients, and the solid phase content is less than 1 / 3 of bentonite, has outstanding cost-saving advantages, is suitable for application in bored pile construction, especially suitable for complex stratum environment in coastal areas.

Description

Technical Field

[0001] This invention belongs to the technical field of wall protection mud, and is a low-density, high-performance polymer mud for pile foundation construction. Specifically, it relates to a fruit shell powder-based environmentally friendly wall protection mud, its preparation method, and its application. Background Technology

[0002] In coastal drilling projects, two types of geological formations with poor engineering properties may be distributed within the drilling depth range: highly permeable formations (fine sand, medium sand, gravel) and water-sensitive formations (silty sand, sandy clay, etc.). Highly permeable formations have large pores and strong connectivity, allowing drilling mud to rapidly infiltrate the formation, causing a sudden drop in the mud level within the borehole. This prevents the formation of effective liquid column pressure, leading to problems such as borehole leakage and collapse. Silty soil is prone to expansion when exposed to water, ultimately causing quality problems such as borehole necking and collapse. Currently, commonly used wall-protecting drilling mud often contains recalcitrant polymers such as CMC and PAM. Furthermore, waste bentonite drilling mud has a high water content and strong colloidal properties, making natural settling difficult and resulting in high treatment costs, which does not meet current green construction requirements.

[0003] In near-shore or offshore drilling projects, seawater intrusion is a key factor leading to mud performance degradation and excavation face instability. Existing research generally agrees that the deteriorating effect of seawater on mud is essentially due to the destruction of the mud system's composition, structure, and function by the large amount of electrolytes in seawater (especially high-valence cations such as Ca²⁺ and Mg²⁺). Specifically, after seawater intrudes into bentonite mud, the large amount of high-valence cations in seawater (Ca²⁺, Mg²⁺, etc.)... 2+ Mg 2+ The sodium ions exchange with the Na⁺ on the surface of the bentonite. This compresses the electric double layer on the surface of the clay particles, weakening the electrostatic repulsion between the particles. Due to the weakened repulsion, the clay particles aggregate, resulting in flocculation and sedimentation. With flocculation and sedimentation, the stability of the mud is completely destroyed, leading to segregation and bleeding. Furthermore, the large flocculated particles cannot form a dense mud cake, resulting in reduced filtration performance of the mud. Traditional bentonite, when used to prepare mud in seawater or exposed to seawater intrusion, experiences a sharp deterioration in performance, failing to meet engineering requirements and potentially causing serious accidents such as borehole wall collapse. Therefore, traditional bentonite is not suitable for seawater environments.

[0004] Unlike the "interparticle structural collapse" of ordinary bentonite mud, the deterioration of polymer mud is mainly manifested in the reduction of polymer functionality. The performance of polymer mud mainly depends on the extension, adsorption, and cross-linking of polymer long chains in water. In fresh water, the hydrophilic groups (such as carboxylate groups -COO⁻) on the polymer molecular chains are fully extended due to electrostatic repulsion, forming a strong spatial network structure, which macroscopically manifests as high viscosity. Studies have found that when seawater intrudes, the high concentrations of cations such as Na⁺, Ca²⁺, and Mg²⁺ in the seawater neutralize the negative charges on the polymer molecular chains, shielding them from electrostatic repulsion. This causes the originally extended molecular chains to curl into a tight cluster, drastically reducing its hydrodynamic volume, which macroscopically manifests as a significant decrease in the apparent viscosity, plastic viscosity, and dynamic viscosity of the mud.

[0005] Therefore, developing a new type of wall-protecting mud material that can effectively resist seawater erosion, adapt to complex strata, and simultaneously meet engineering performance and environmental protection requirements has become an urgent need to promote technological progress and sustainable development in related fields. Summary of the Invention

[0006] The purpose of this invention is to provide a fruit shell powder-based environmentally friendly wall-protecting mud, its preparation method, and its application. The prepared wall-protecting mud is a low-solids polymer mud (without bentonite), and the materials used are more environmentally friendly, free of sulfonate copolymers, CMC, and other recalcitrant polymers, and are suitable for use in coastal engineering projects.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows:

[0008] A type of environmentally friendly wall-protecting mud based on fruit shell powder is composed of the following raw material components in the following mass ratio: water, xanthan gum, hydroxypropyl guar gum, fruit shell powder, pregelatinized starch, and anhydrous sodium carbonate = 1000 : 1.0~2.0 : 0.5~1.5 : 7.5~15 : 3~9 : 0.3~0.9; wherein the total mass of xanthan gum and hydroxypropyl guar gum is not less than 2‰ and not more than 3.5‰ of water.

[0009] Xanthan gum and hydroxypropyl guar gum are blended in a specific ratio as a thickener for the mud. The mass fraction of xanthan gum is not less than 1‰ of the water mass to ensure sufficient static shear strength of the mud. Hydroxypropyl guar gum can inhibit clay swelling to a certain extent, increase the apparent viscosity of the mud, and regulate rheology. The mass fraction of the two thickeners after blending is not greater than 3.5‰ of the water mass to avoid excessively high mud viscosity, and the mass fraction after blending is not less than 2‰ of the water mass to ensure good static stability of the mud and prevent mud stratification during static settling.

[0010] Optionally, the xanthan gum has a molecular weight of 200,000 to 600,000.

[0011] Optionally, the viscosity of a 1% aqueous solution of the hydroxypropyl guar gum is in the range of 4000~6000 mPa·s.

[0012] The fruit shell powder is a powder of waste fruit shells, used as a solid film-forming agent for mud, including peanut shell powder, walnut shell powder, etc., or a mixture thereof, using the same particle size or a mixture of different particle sizes.

[0013] Peanut shell powder is highly biodegradable, with its main components being cellulose, hemicellulose, and lignin. It can be completely decomposed by microorganisms into CO2 and water, leaving no toxic residues. It can replace traditional additives such as recalcitrant CMC and lignin sulfonates, reducing water pollution from drilling wastewater. Peanut shells are agricultural waste with a huge annual output, and their cost is only 1 / 3 to 1 / 2 that of traditional chemical additives (such as CMC), combining economic benefits with environmental friendliness. The acidic functional groups (such as carboxyl groups) in peanut shell powder can react with OH⁻ in drilling fluid, moderately lowering the pH of the system.

[0014] Optionally, the particle size range of the nutshell powder is 100 mesh to 300 mesh.

[0015] The pregelatinized starch PGS is used as an environmentally friendly film-forming and filtration-reducing agent for drilling mud. PGS has the characteristics of being swellable in cold water, a molecular structure that can form a three-dimensional network, excellent biodegradability, and cost advantage (cost is only 2 / 5 of CMC). It plays a core role in wall protection drilling mud in terms of efficient filtration reduction, moderate thickening, stabilizing high-permeability formations, and green environmental protection.

[0016] The anhydrous sodium carbonate is used as a dispersant and pH adjuster for the mud. As a dispersant, anhydrous sodium carbonate can promote the dissolution of XG and HPG in water and reduce agglomeration. At the same time, by adjusting the pH of the mud solution, anhydrous sodium carbonate can affect the viscosity and filtration performance of the mud within a small range.

[0017] The nut shell powder-based environmentally friendly wall-protecting mud contains biodegradable plant fiber solid film-forming agents and biopolymer filtration loss reducers, and the mud does not contain recalcitrant synthetic polymers or heavy metal additives.

[0018] A method for preparing the above-mentioned fruit shell powder-based environmentally friendly wall-protecting mud, according to the proportion of raw material components, includes:

[0019] Step 1: Add anhydrous sodium carbonate to the water in the first part and stir until dissolved. Add the mixed xanthan gum and hydroxypropyl guar gum powder and stir to form a homogeneous mixed colloidal solution. Let it stand.

[0020] Step 2: After mixing the fruit shell powder with the pregelatinized starch, add it to the water in the second part. First, stir at the first speed until the pregelatinized starch dissolves, and then stir at the second speed to obtain a slurry. The second speed is greater than the first speed.

[0021] Step 3: Add the remaining water and the slurry obtained in Step 2 to the mixed colloidal solution obtained in Step 1, and stir to obtain the fruit shell powder-based environmentally friendly wall protection mud.

[0022] When peanut shell powder is mixed with pregelatinized starch, the peanut shell powder acts as a dispersant, reducing starch clumping and promoting dissolution. Excessive stirring speed can cause the starch surface to dissolve, forming a chemical film that hinders the dissolution of the internal powder, leading to starch agglomeration. Therefore, slow stirring is necessary initially. After the starch dissolves, some peanut shell powder, being relatively light, will float on the surface; accelerating stirring will help dissolve it.

[0023] More preferably, the first speed is less than 600 r / min, the second speed is 800~1500 r / min, and the stirring time at the second speed is 10~20 min.

[0024] Optionally, the first part of the water accounts for 40% to 60% of the total water consumption, and the second part of the water accounts for 20% to 40% of the total water consumption.

[0025] The above-mentioned environmentally friendly wall-protecting mud based on nutshell powder is used in the construction of bored piles.

[0026] Optionally, the construction may employ rotary drilling rig technology or reverse circulation technology.

[0027] Optionally, the construction environment is a coastal area where highly permeable and water-sensitive formations are distributed within the drilling depth range.

[0028] The beneficial effects of this invention are as follows:

[0029] (1) Xanthan gum and hydroxypropyl guar gum were selected as a thickener for the mud. Hydroxypropyl guar gum (HPG) has good cold water dispersibility, fast dissolution speed, is not easy to agglomerate, and has high salt resistance. It can inhibit clay swelling to a certain extent, increase the apparent viscosity of the mud, and regulate rheology. Xanthan gum has strong thickening and suspension ability, significant pseudoplasticity, and good salt resistance. It has a significant effect on improving the static shear force of the mud. The combination of the two can better regulate the fluidity of the mud, so that the mud has better static shear force and apparent viscosity, improve the static suspension of mud and sand and the sand carrying capacity of the mud, and meet environmental protection requirements. At the same time, it can avoid the problem of mud viscosity rapidly decreasing and affecting the mud wall protection performance caused by the increased salt content of groundwater due to the influence of seawater in coastal projects.

[0030] (2) Fruit shell powder is used as the solid phase film-forming agent of the mud, and pregelatinized starch (PGS) is used as an environmentally friendly film-forming and filtration reduction agent. After the fruit shell powder absorbs water and swells, it forms suspended particles. Its fibrous particles work together with the thickener and filtration reduction agent to form a spatial colloidal network in the mud, effectively "bridging" and blocking the formation leakage channels, reducing the penetration of drilling fluid into the formation. The physical bridging of the fiber structure and the chemical adsorption and hydration of the surface functional groups work together to optimize the quality of the mud cake, reduce filtration loss, and enhance the stability of the well wall. After the pregelatinized starch dissolves in water, it forms a three-dimensional gel network, which plays a "chemical bonding" role. It works synergistically with the fruit shell powder (which plays a "physical bridging" core role in the mud) to further reduce the filtration loss of the mud.

[0031] (3) The mud formula of the present invention realizes the whole-chain environmental protection from raw materials, use to waste treatment. The main components are all degradable, which completely avoids the potential pollution of soil and water environment by traditional bentonite mud or mud containing recalcitrant polymers (such as CMC, PAM), and meets the requirements of green construction and sustainable development.

[0032] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the rheological model of the fruit shell powder-based environmentally friendly wall-protecting mud in Example 1;

[0034] Figure 2 This is a schematic diagram of the strata where the bored pile construction project is located, as shown in the example.

[0035] Figure 3a This is a SEM image of the xanthan gum solution in Example 1 after 24 hours of cold drying;

[0036] Figure 3b This is a SEM image of the hydroxypropyl guar gum solution in Example 1 after 24 hours of cold drying;

[0037] Figure 3c This is a SEM image of the xanthan gum and guar gum mixture solution in Example 1 after 24 hours of cold drying;

[0038] Figure 4 Photograph of the mud from Comparative Example 3 after 24 hours of settling and layering.

[0039] Figure 5a The images show the stratification of mud samples with different seawater intrusion levels after 24 hours in Example 5, corresponding to serial numbers S5-1 to S5-4 from left to right.

[0040] Figure 5bThe images show the stratification of mud samples with different seawater intrusion levels after 24 hours, corresponding to numbers D5-1 to D5-4 from right to left. Detailed Implementation

[0041] The following embodiments are further illustrations of the present invention and serve as explanations of the technical content of the present invention. However, the essence of the present invention is not limited to the embodiments described below.

[0042] The materials used in the examples are from the following sources:

[0043] Xanthan gum, with a content of not less than 99.0%, was purchased from Tianjin Zhonglian Chemical Reagent Co., Ltd.

[0044] Hydroxypropyl guar gum, with a 1% solution viscosity of 5000 mPa·s, was purchased from Hebei Renqiu Pengyu Chemical Co., Ltd.

[0045] The fruit shell powder is made from peanut shell powder, purchased from Lianyungang Surui Agricultural Products Deep Processing Plant.

[0046] Pregelatinized starch, with a pregelatinization degree of 80% or higher, was purchased from Hebei Renqiu Pengyu Chemical Co., Ltd.

[0047] Anhydrous sodium carbonate, analytical grade, purchased from Tianjin Huasheng Chemical Reagent Co., Ltd.

[0048] Bentonite, analytical grade, purchased from Tianjin Zhonglian Chemical Reagent Co., Ltd.

[0049] Sodium carboxymethyl cellulose, chemically pure CP, was purchased from Tianjin Juhengda Chemical Co., Ltd.

[0050] The instruments and models used in the following examples are as follows: AMY-1 three-piece mud set (including standard funnel, hydrometer, and sand content meter), ZNS-2A medium-pressure filtration loss meter (0.7MPa), ZNN-D6B six-speed rotational viscometer, pH test pen (resolution 0.01), magnetic stirrer (speed 0-1500rpm), and balance (accuracy 0.01).

[0051] The rheological parameters of the mud were measured using a six-speed rotational viscometer (model ZNN-D6B). The relationship between the rotational speed (N) of the instrument and the corresponding shear rate (γ) is shown in Table 1.

[0052] Table 1

[0053]

[0054] The specific parameter calculation formulas are as follows:

[0055] Shear stress: Determined by the viscometer scale reading at rotational speed N. The calculation formula is as follows:

[0056]

[0057] Shear rate: calculated from rotational speed N, using the following formula:

[0058]

[0059] Apparent viscosity: Readings at 600 r / min The calculation formula is as follows:

[0060]

[0061] Plastic viscosity: Calculated from the difference between readings at 600 r / min and 300 r / min, using the following formula:

[0062] Dynamic shear force: calculated from the plastic viscosity and the reading at 300 r / min, using the following formula:

[0063] YP

[0064] Static shear force:

[0065] The initial shear force is calculated from the reading at a rotational speed of 3 r / min after resting for 10 seconds, using the following formula: ;

[0066] The final shear force is calculated by reading at a rotation speed of 3 r / min after resting for 10 minutes. The formula is as follows: .

[0067] The filtrate loss of mud is the volume of mud that passes through filter paper within 30 minutes using a medium-pressure filtrate tester ZNS-2A at a working air pressure of 0.70 MPa. The unit is ml / 30min.

[0068] Mud film thickness: refers to the thickness of the solid particle layer wrapped by the chemical film that gradually forms on the filter paper when the mud passes through the filter paper within 30 minutes.

[0069] Funnel viscosity: This refers to the viscosity measured by blocking the outlet of a standard funnel, measuring 500 mL and 200 mL of mud slurry using the matching measuring cup, filtering them through a filter screen, and then pouring them into the standard funnel. Timing begins simultaneously with opening the outlet and stops when the measuring cup is filled with 500 mL of mud slurry. The measured time (in seconds) is the funnel viscosity.

[0070] Example

[0071] The shell powder-based environmentally friendly wall-protecting mud in Examples 1-5 consists of the raw material components listed in Table 2 in grams and 1000 ml of water (fresh water). The abbreviations are as follows: 200-mesh peanut shell powder: 200-mesh PSP; Xanthan gum: XG; Hydroxypropyl guar gum: HPG; Pregelatinized starch: PGS; Soda ash is anhydrous sodium carbonate.

[0072] Table 2

[0073]

[0074] According to the proportions, the preparation methods of each embodiment are as follows:

[0075] Step 1: First, place anhydrous sodium carbonate in 50% water and stir until dissolved; then, thoroughly mix xanthan gum and hydroxypropyl guar gum powder, slowly and evenly sprinkle them into the water, stir for 20-30 minutes, and let stand.

[0076] Step 2: Measure out peanut shell powder and PGS, mix them thoroughly, and then add them to 30% water. First, stir slowly until PGS is fully dissolved at a stirring speed of 300 r / min; then stir quickly at a stirring speed of 1000 r / min to allow some of the unabsorbed peanut shell powder floating on the water surface to absorb water and disperse evenly. Stir for 10-20 minutes.

[0077] Step 3: Add the remaining 20% ​​aqueous solution and the slurry obtained in Step 2 to the mixed colloidal solution obtained in Step 1, and stir for 10-20 minutes to obtain the fruit shell powder-based environmentally friendly wall-protecting slurry. The specific gravity of the slurry in each embodiment is 1.02-1.03, and the pH is 8-10.

[0078] The performance of the fruit shell powder-based environmentally friendly wall protection mud prepared in Examples 1-5 was tested. The test results are shown in Table 3. The static shear force mentioned here refers to the initial shear force.

[0079] Table 3

[0080]

[0081] The shell powder-based environmentally friendly wall-protecting mud obtained in Examples 1-5 meets the following performance requirements: funnel viscosity 18-29s; density 1.02-1.03; static shear force 1-2 Pa; apparent viscosity ≥10 mPa·s; the formed mud film is thin and dense (thickness <1 mm); API filtration loss (0.7MPa pressure difference) 12-18 mL / 30 min; the mud is homogeneous and stable, and there is no stratification after standing for 24 hours.

[0082] Figure 1 The rheological model of the fruit shell powder-based environmentally friendly wall protection mud of Example 1 is shown in the figure. As can be seen from the figure, the rheological behavior conforms to the power law model and has good suspension and sand carrying capacity.

[0083] Figure 2 In this example, the environmentally friendly wall-protecting mud based on nutshell powder is applied to the construction of bored piles. The geological conditions of the project site are as follows: it is a coastal area, and the strata include medium sand, silty sand, silty clay, and sandy clay. The environmentally friendly wall-protecting mud based on nutshell powder used in this example, in addition to meeting the basic performance requirements of the specifications, has lower filtration loss, a certain degree of inhibition, and higher environmental friendliness. It can reduce the hydration and expansion of clay minerals, avoid leakage from infiltrated strata, thereby reducing the number of borehole collapses and improving the efficiency of pile formation.

[0084] refer to Figure 3a , Figure 3b and Figure 3c From a microscopic perspective, xanthan gum possesses a rigid double-helix structure, making it resistant to destruction by cations in seawater and preventing significant shrinkage, thus exhibiting high salt resistance. Based on SEM microscopic characterization, hydroxypropyl guar gum displays a flexible, flat, lamellar molecular chain morphology, forming a dense, stacked structure through the overlapping and entanglement of molecular chains. Compared to the typical porous three-dimensional network structure of xanthan gum, this dense stacked structure significantly enhances the adsorption and coating capacity for solid particles, thereby constructing a denser, low-permeability mud film during filtration. Hydroxypropyl guar gum is a green thickener and filtration reducer, with superior salt resistance compared to virgin guar gum powder. However, after seawater intrusion, the molecular chains may still shift from an extended, coiled conformation to a compact one, resulting in a reduction in hydrodynamic volume and viscosity. Hydroxypropyl guar gum, when combined with xanthan gum, is mainly used in mud to improve apparent viscosity and filtration properties, while xanthan gum is mainly used to provide mud viscosity and static shear force, thereby mitigating the impact of a sharp drop in viscosity caused by high-valence cations.

[0085] Simultaneously, using coconut shell powder instead of bentonite as a component of the mud film can avoid the phenomenon of bentonite particles flocculating due to seawater ions compressing the electric double layer and undergoing ion exchange. Replacing bentonite with coconut shell powder, along with pregelatinized starch, further reduces filtration loss, preventing rapid deterioration of mud performance, mud failure, and pile hole wall collapse.

[0086] Comparative Example 1

[0087] The wall-protecting slurry of each experimental group in Comparative Example 1 was composed of the raw material components in grams as described in Table 4 and 1000 ml of water, with the rest being the same as in the Example.

[0088] Table 4

[0089]

[0090] Performance tests were conducted on the wall-protecting mud of each experimental group in Comparative Example 1. The test results are shown in Table 5. The static shear force mentioned here refers to the initial shear force.

[0091] Table 5

[0092]

[0093] Excessive viscosity modifier content leads to excessively high mud viscosity, which will increase mud flow resistance, raise pump pressure during pumping (potentially exceeding the equipment's rated pressure), slow down circulation speed, increase drill bit resistance during drilling, slow down drilling speed, and affect pile quality.

[0094] Comparative Example 2

[0095] The wall-protecting slurry of each experimental group in Comparative Example 2 consisted of the raw material components in grams as described in Table 6 and 1000 mL of water, with the rest being the same as in the Example.

[0096] Table 6

[0097]

[0098] Performance tests were conducted on the wall-protecting mud of each experimental group in Comparative Example 2. The test results are shown in Table 7. The static shear force mentioned here refers to the initial shear force.

[0099] Table 7

[0100]

[0101] In Comparative Example 2-1, although the mud viscosity was high, the absence of peanut shell powder as a solid film-forming agent prevented the formation of a mud film, resulting in complete water loss. In Comparative Examples 2-2 to 2-7, the addition of peanut shell powder enabled the formation of a mud film, and the filtration loss decreased with increasing peanut shell powder content; however, the filtration loss remained high due to the lack of a film-forming and filtration-reducing agent—PGS. In formations with high clay content, high filtration loss can cause clay mineral hydration and expansion, leading to borehole collapse and pile failure. In high-permeability formations, high filtration loss can hinder the effective exertion of liquid column pressure, thus affecting the mud's performance and reducing pile formation efficiency.

[0102] Comparative Example 3

[0103] The wall-protecting slurry of each experimental group in Comparative Example 3 consisted of the raw material components in grams as described in Table 8 and 1000 mL of water, with the rest being the same as in the Example.

[0104] Table 8

[0105]

[0106] Performance tests were conducted on the wall-protecting mud of each experimental group in Comparative Example 3. The test results are shown in Table 9. The static shear force mentioned here refers to the initial shear force.

[0107] Table 9

[0108]

[0109] Among them, as the dosage of the film-forming filtration loss reducer PGS increases, the filtration loss of the mud continuously decreases. However, when the xanthan gum (XG) dosage is less than 1‰ of the water mass, even if the funnel viscosity meets the requirements, insufficient static shear force leads to obvious stratification of the mud during settling. Figure 4 This will lead to inconsistent mud properties, a significant decrease in wall protection ability, and problems such as hole collapse, diameter reduction, and poor hole cleaning ability.

[0110] Comparative Example 4

[0111] The wall-protecting slurry of each experimental group in Comparative Example 4 consisted of the raw material components in grams as described in Table 10 and 1000 mL of water, with the rest being the same as in the Example.

[0112] Table 10

[0113]

[0114] Performance tests were conducted on the wall-protecting mud of each experimental group in Example 4. The test results are shown in Table 11. The static shear force mentioned here refers to the initial shear force.

[0115] Table 11

[0116]

[0117] When the hydroxypropyl guar gum (HPG) content is insufficient, or the total mass fraction of XG and HPG after blending is low, the apparent viscosity of the mud is too low, and the mud fluidity and static stability are insufficient. This will lead to insufficient flow and sand-carrying capacity, drilling cuttings settling to the bottom, difficulty in cleaning the hole, mud stratification, poor stability, and difficulty in guaranteeing performance, which will directly lead to many problems such as hole formation, hole cleaning, grouting, and pile quality.

[0118] Referring to the artificial seawater formulation in ASTM D1141-98 (2003) "Standard Practice for the Preparation of Substitute Ocean Water", artificial seawater was prepared by adding NaCl (24.53 g / L), CaCl2 (1.16 g / L), MgCl2·6H2O (11.10 g / L), KCl (0.695 g / L), and ultrapure water (1L), and adjusting the pH to 8.0. The wall-protecting mud composed of the components of Example 5 was used, but the water (pure fresh water) was replaced with mixed water prepared in different proportions of artificial seawater and fresh water. For example, 1L of water with 50% seawater intrusion was prepared by mixing 500ml of artificial seawater and 500ml of fresh water, resulting in mud samples with different seawater intrusion levels. The mud in Comparative Example 5 was a bentonite mud, composed of 60g of bentonite, 1g of CMC, and 1L of water at a certain seawater intrusion level. Preparation method: Add 60g of bentonite to 1L of water with a certain seawater intrusion degree, stir at 1000rpm for 30min, let stand for 24h until completely hydrated, then add 1g of CMC, stir at 1000rpm for 20min, and let stand for later use. The serial numbers of different samples and their corresponding seawater intrusion degrees are shown in Table 12. Seawater intrusion degree: seawater / water (%).

[0119] Table 12

[0120]

[0121] The performance test results of mud samples with different seawater intrusion levels in the examples and comparative examples are shown in Table 13. Photos of the stratification of mud samples with different seawater intrusion levels in Example 5 and Comparative Example 5 after 24 hours are shown below. Figure 5a and Figure 5b As shown.

[0122] Table 13

[0123]

[0124] Comparative Examples D5-1 to D5-4 show that when the seawater intrusion is 0%, the bentonite mud has good viscosity and filtration performance. As the seawater intrusion increases, the mud viscosity decreases by 28.4%, 35.1%, and 36.5%, respectively, and the filtration performance also deteriorates, with the filtration loss increasing by 25%, 58%, and 75%, respectively. After standing for 24 hours, the mud separates into layers, its performance fails, and it can no longer play a role in maintaining the stability of the borehole wall.

[0125] In Examples S5-1 to S5-4, as the seawater intrusion increased, the static shear strength and apparent viscosity of the mud decreased. However, due to the increased salt content, the solution thickened, and the funnel viscosity increased slightly, without the sharp decrease in viscosity caused by the influence of cations in the seawater. Furthermore, the filtration loss of the mud decreased with increasing seawater intrusion, indicating that seawater intrusion is beneficial to the filtration loss reduction performance of the mud described in this study. After 24 hours of settling, no stratification occurred in the mud, indicating that the mud in these examples has good salt tolerance and stability.

[0126] The above embodiments are only used to further illustrate the present invention of a fruit shell powder-based environmentally friendly wall protection mud, its preparation method and application. However, the present invention is not limited to the embodiments. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. The application of a fruit shell powder-based environmentally friendly wall-protecting mud in bored pile construction, characterized in that, The environmentally friendly wall-protecting mud based on fruit shell powder is composed of the following raw material components in the following mass ratio: water, xanthan gum, hydroxypropyl guar gum, fruit shell powder, pregelatinized starch, anhydrous sodium carbonate = 1000 : 1.0~2.0 : 0.5~1.5 : 7.5~15 : 3~9 : 0.3~0.9; wherein the total mass of xanthan gum and hydroxypropyl guar gum is not less than 2‰ and not more than 3.5‰ of water; the particle size of the fruit shell powder is 100 mesh to 300 mesh; the construction environment is a coastal area, and the drilling depth range contains highly permeable strata and water-sensitive strata.

2. The application of the fruit shell powder-based environmentally friendly wall-protecting mud according to claim 1 in the construction of bored piles, characterized in that: The xanthan gum has a molecular weight of 200,000 to 600,000.

3. The application of the fruit shell powder-based environmentally friendly wall-protecting mud according to claim 1 in the construction of bored piles, characterized in that: The viscosity range of the 1% aqueous solution of the hydroxypropyl guar gum is 4000~6000 mPa·s.

4. The application of the fruit shell powder-based environmentally friendly wall-protecting mud according to claim 1 in the construction of bored piles, characterized in that: The shell powder includes at least one of peanut shell powder and walnut shell powder.

5. The application of the fruit shell powder-based environmentally friendly wall-protecting mud according to claim 1 in the construction of bored piles, characterized in that, The preparation method of the fruit shell powder-based environmentally friendly wall-protecting mud includes, according to the proportion of raw material components: Step 1: Add anhydrous sodium carbonate to the water in the first part and stir until dissolved. Add the mixed xanthan gum and hydroxypropyl guar gum powder and stir to form a homogeneous mixed colloidal solution. Let it stand. Step 2: After mixing the fruit shell powder with the pregelatinized starch, add it to the water in the second part. First, stir at the first speed until the pregelatinized starch dissolves, and then stir at the second speed to obtain a slurry. The second speed is greater than the first speed. Step 3: Add the remaining water and the slurry obtained in Step 2 to the mixed colloidal solution obtained in Step 1, and stir to obtain the fruit shell powder-based environmentally friendly wall protection mud.

6. The application of the fruit shell powder-based environmentally friendly wall-protecting mud according to claim 5 in the construction of bored piles, characterized in that: The first part of the water accounts for 40% to 60% of the total water consumption, and the second part of the water accounts for 20% to 40% of the total water consumption.

7. The application of the fruit shell powder-based environmentally friendly wall-protecting mud according to claim 1 in the construction of bored piles, characterized in that: The construction process employs rotary drilling rig technology or reverse circulation technology.

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