A drilling pile slurry made of strongly weathered shale material

Abstract

The present application relates to the technical field of underground engineering construction, and specifically refers to a drilling pile mud made of strongly weathered shale material. Seawater and strongly weathered shale are used as raw materials. The strongly weathered shale is light yellow in appearance, has obvious texture, very thin bedding, a Los Angeles abrasion rate of 46.2%-70.0%, a water absorption rate of 13.2%-18.4%, a density of 1.68g / cm^3-1.82g / cm^3, a maximum dry density of 1.92g / cm^3-1.98g / cm^3, an optimum water content of 6.3%-8.9%, a liquid limit of 53.1%-77.3%, a 0.08mm square hole screen residue of 1%-12%, and a CBR of 0.5%. The seawater and strongly weathered shale required by the present application can be obtained locally in the Senegal Fajuni region, and the economic cost is low. No other chemical materials need to be added, and the mud manufactured can be directly discharged into the sea, without causing marine pollution.

Description

Technical Field

[0001] This invention relates to the field of underground engineering construction technology. More specifically, this invention relates to a drilling mud for bored piles made from strongly weathered shale material. Background Technology

[0002] The Fangjuni Bridge in Senegal is located in the Sine-Saloum region of western Senegal, in a coastal environment. The project area is an alluvial plain with relatively flat terrain, sloping slightly from north to south. The lithology consists mainly of Quaternary Holocene and Upper Pleistocene sediments and sandy soils. According to on-site surveys, the north bank of the Salum River is composed of sandy saline soil formed in a coastal environment, while the south bank is composed of sandy soil. Freshwater resources in this area are extremely scarce, and tides are the main hydrogeological factor in the estuary, primarily diurnal tides. This results in high salinity of the water flowing inland from the estuary. Similarly, the salinity of the river tributaries is even higher. In the Sangomar sandbar and Bandiala areas near the ocean, the salinity is 70 g / L; in the Sokone area, it is even higher, reaching 100 g / L, which is 2-3 times the average salinity of the ocean.

[0003] Based on geological and hydrological conditions and geological exploration reports, the construction of the bored pile foundation for the Fangjiuni Bridge requires high-quality mud to act as a protective layer for the bored pile foundation. In particular, the geological conditions of the sandy soil layer and the strong infiltration of groundwater place extremely high demands on the protective layer.

[0004] Expansive clay and fresh water are very common materials, required in large quantities, and are commonly used as drilling mud materials for bored piles. However, the Fangjuni Bridge in Senegal suffers from a lack of fresh water, requiring long-distance purchases of fresh water and imported expansive agents to prepare the drilling mud, resulting in very high costs. Furthermore, the entire country is almost entirely composed of sandy and lateritic soils, making bentonite unavailable. There is an urgent need for a material to solve the construction challenges of bored piles in seawater areas and areas lacking bentonite. Summary of the Invention

[0005] The purpose of this invention is to provide a drilling mud for bored piles made from strongly weathered shale material. The required seawater and strongly weathered shale can be sourced locally in the Fangjuni region of Senegal, resulting in low economic costs. No other chemical materials need to be added, and the mud produced can be directly discharged into the sea without causing marine pollution.

[0006] The technical solution adopted by the present invention to solve this technical problem is: to provide a drilling mud for bored piles made of strongly weathered shale material, characterized in that it comprises: seawater and strongly weathered shale as raw materials;

[0007] The strongly weathered shale has a Los Angeles abrasion rate of 46.2%-70.0%, a water absorption rate of 13.2%-18.4%, and a density of 1.68 g / cm^3-1.82 g / cm^3.

[0008] Preferably, the drilled pile mud made of strongly weathered shale material is characterized by a maximum dry density of 1.92 g / cm³-1.98 g / cm³, an optimum moisture content of 6.3%-8.9%, a liquid limit of 53.1%-77.3%, a sieve residue of 1%-12% on a 0.08 mm square hole sieve, and a CBR of 0.5%.

[0009] Preferably, the drilling mud made from strongly weathered shale material is characterized in that the mud is prepared by mixing raw seawater and strongly weathered shale.

[0010] Preferably, the drill mud made from strongly weathered shale material is characterized in that...

[0011] The strongly weathered shale has a Los Angeles abrasion rate of 58.1%, a water absorption rate of 15.8%, a density of 1.75 g / cm³, a maximum dry density of 1.95 g / cm³, an optimum moisture content of 7.6%, a liquid limit of 65.2%, a residue of 6.5% on a 0.08 mm square mesh sieve, and a CBR of 0.5%.

[0012] Preferably, the drilling mud made from strongly weathered shale material is characterized in that the mud is prepared by mixing strongly weathered shale powder and seawater in a mass ratio of 1:1-5.

[0013] Preferably, the drilling mud made from strongly weathered shale material is characterized in that strongly weathered shale powder and seawater are mixed at a mass ratio of 1:2.42-3.75 to prepare drilling mud for pile foundations.

[0014] Preferably, the drilling mud for bored piles made of strongly weathered shale material is characterized in that strongly weathered shale powder and seawater are mixed at a mass ratio of 1:2.73 to make drilling mud for pile foundations.

[0015] Preferably, the drilling mud made from strongly weathered shale material is characterized in that strongly weathered shale powder and seawater are mixed at a mass ratio of 1:3.75-4.35 to prepare drilling mud for secondary cleaning of pile foundations.

[0016] Preferably, the drilling mud made from strongly weathered shale material is characterized in that strongly weathered shale powder and seawater are mixed at a mass ratio of 1:3.75 to make drilling mud for secondary cleaning of pile foundations.

[0017] Preferably, the drilling mud made from strongly weathered shale material is characterized in that the pH of the strongly weathered shale is 10, and the pH of the mud made from the strongly weathered shale and seawater is 8.

[0018] The present invention has at least the following beneficial effects:

[0019] 1. According to the technical specifications for highway bridge and culvert construction, the mud performance indicators differ for bored piles drilled using different methods. The mud performance can be adjusted based on the mixing ratio of strongly weathered shale and seawater. Test results show that all four drilling methods—forward circulation, reverse circulation, rotary drilling, and impact drilling—meet the requirements. The mud mixing technology of seawater and strongly weathered shale can obtain mud with corresponding performance requirements under various drilling methods. The mixing ratio can be adjusted on-site as needed at different stages of construction. Therefore, this technology has good application potential in areas with freshwater scarcity.

[0020] 2. Strongly weathered shale is combined with seawater to produce mud without the need for any other chemical materials. Both the seawater and the strongly weathered shale are sourced locally, and the mud produced can be directly discharged into the sea, greatly saving freshwater resources, protecting the marine environment, and effectively controlling construction costs.

[0021] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0022] Figure 1 This is a geological exploration columnar section of the Fangjiuni Bridge.

[0023] Figure 2 A graph showing the specific gravity of mud slurry made from seawater-weathered shale powder at different proportions;

[0024] Figure 3 The graph shows the viscosity of mud slurry made from seawater-weathered shale powder at different ratios. Detailed Implementation

[0025] The present invention will now be described in detail and completely with reference to the accompanying drawings. Those skilled in the art will be able to implement the present invention based on these descriptions. Before describing the present invention with reference to the accompanying drawings, it should be particularly noted that the technical solutions and features provided in various parts of the present invention, including the following description, can be combined with each other without conflict.

[0026] Furthermore, the embodiments of the present invention described below are generally only some, not all, of the embodiments of the present invention. Therefore, all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0027] This invention provides a drilling mud for bored piles made from strongly weathered shale material, comprising:

[0028] Using seawater and strongly weathered shale as raw materials;

[0029] The seawater in question originates from the Salum River estuary of the Founti Bridge project in Senegal, which connects to the Atlantic Ocean. It is Atlantic seawater and is representative and universal in nature.

[0030] The test sampling of the strongly weathered shale was conducted on a small hill with a radius of about 1 km. The shale at each sampling location had a similar appearance, but the test data of the shale at each sampling location were different. The CBR value was almost the same. Many places in Senegal are saline-alkali areas, so the pH value of the sampled shale was 10 after being mixed with pure water and the solution was measured.

[0031] The strongly weathered shale exhibits a Los Angeles abrasion rate of 46.2%-70.0%, a water absorption rate of 13.2%-18.4%, a density of 1.68 g / cm³-1.82 g / cm³, a maximum dry density of 1.92 g / cm³-1.98 g / cm³, an optimum moisture content of 6.3%-8.9%, a liquid limit of 53.1%-77.3%, a residue on a 0.08 mm square-hole sieve of 1%-12%, and a CBR of 0.5%.

[0032] like Figure 1 As shown in this embodiment, a preferred implementation is to source seawater and strongly weathered shale locally in Senegal, which saves a lot of economic costs. Based on the geological survey of the Fangjuni Bridge, the soil conditions are complex and there are many interlayers. Therefore, the corresponding drilling method is percussion drilling. The mud used in the construction process needs to be adapted to the soil layer and the drilling method. The mud performance indicators of different drilling methods are different. The mud performance can be adjusted according to the mixing ratio of strongly weathered shale and seawater. The mud can provide a protective effect for the drilled pile foundation.

[0033] The required mud specific gravity for pile foundation drilling is 1.21, and the required mud viscosity is 34s; the required mud specific gravity for secondary cleaning of the pile foundation is 1.10, and the required mud viscosity is 20s. Based on these requirements, experiments are conducted on seawater and strongly weathered shale.

[0034] I. Tests and Comparative Analysis of Strongly Weathered Shale:

[0035] 1. Physical and chemical properties of strongly weathered shale:

[0036] The strongly weathered shale, before crushing, is light yellow in appearance, with obvious texture and very thin bedding. Its Los Angeles abrasion rate is 58.1%. The Los Angeles abrasion rate is a parameter representing the ability of crushed stone ballast to resist the combined effects of impact, abrasion, and edge shear, based on the abrasion index of the Los Angeles abrasion mill. In this embodiment, a higher Los Angeles abrasion rate indicates better rock abrasion resistance.

[0037] The water absorption rate is 15.8%;

[0038] The strongly weathered shale, when crushed, is a light yellow powder with a density of 1.75 g / cm³, a maximum dry density of 1.95 g / cm³, and an optimum moisture content of 7.6%.

[0039] The liquid limit is 65.2%. The liquid limit refers to the water content at the boundary between the plastic and fluid states of cohesive soil, which is the upper limit of the plastic state. In this embodiment, the strongly weathered shale is a high liquid limit clay. High liquid limit clay has poor permeability, high strength when dry and hard, is hard and difficult to excavate, has obvious capillary action, can retain moisture for a long time after absorbing water, and has greater plasticity, weak expansibility and cohesiveness.

[0040] The residue on a 0.08mm square hole sieve is 6.5%. Sieve residue refers to the fineness of powdery materials. It is the mass ratio of the powdery material remaining on the sieve after a certain mass of powdery material is sieved on a standard sieve. The smaller the residue of cement, the finer the cement and the higher its strength.

[0041] The CBR is 0.5%. The CBR, also known as the subgrade fill strength, refers to the ratio of the unit pressure to the standard load pressure when the standard crushed stone is pressed into the same amount of material with a penetration depth of 2.5 mm.

[0042] 2. The Los Angeles abrasion value and water absorption rate of strongly weathered shale, ordinary rock and concrete crushed stone before crushing are compared in Table 1 below:

[0043] Table 1 Comparison of crushed stone tests on strongly weathered shale, ordinary rock, and concrete before crushing.

[0044] Los Angeles wear (%) 58.1 35.2 12.5 Water absorption rate (%) 15.8 3.5 1

[0045] Based on the data in Table 1, it can be concluded that the strongly weathered shale has a certain strength when dry, but due to its high water absorption rate, it is very easy to undergo plastic deformation after being mixed with water.

[0046] 3. The comparison of the liquid limit of crushed strongly weathered shale and ordinary clay used for pulping with CBR is shown in Table 2 below:

[0047] Table 2 Comparison of Crushed Strongly Weathered Shale and Ordinary Clay Used for Pulp Preparation in China

[0048] Liquid limit (%) 65.2 41.6 CBR (%) 0.5 6.8

[0049] Based on the data in Table 2, the crushed strongly weathered shale powder has a high liquid limit and good water retention performance. A low CBR indicates poor load-bearing capacity after soaking in water. The powder softens and becomes sticky when it comes into contact with water, exhibiting strong plasticity and making it easy to operate on-site.

[0050] II. Seawater Test Data

[0051] Table 3 below shows the corresponding tests conducted based on the concrete water usage requirements when seawater from the Senegal project was transported to China in mineral water containers:

[0052] Table 3 Seawater Testing Report

[0053]

[0054]

[0055] In this embodiment, a preferred implementation is: the non-compliance of seawater testing is based on the requirements of concrete construction water standards, which has no impact on the test of seawater and strongly weathered shale mud production technology. Therefore, common seawater is suitable for this test.

[0056] To combat the corrosive properties of seawater and protect the quality of underwater pile foundations when using seawater-based mud, the following measures can be taken:

[0057] a. Strictly control sediment at the bottom of piles;

[0058] b. The diameter of the underwater steel casing is increased by 20cm, therefore the protective layer for the reinforcing steel is increased by 10cm accordingly;

[0059] c. The pile head removed from the top of the pile foundation is expanded to 1.5 meters.

[0060] d. According to European standards, corrosion-resistant cement is used in the concrete for pile foundations.

[0061] III. Water Immersion Test Procedure for Seawater Mixed with Strongly Weathered Shale Soil

[0062] 1. Prepare materials: seawater and strongly weathered shale;

[0063] 2. Required tools: mud testing kit, Marsh funnel viscometer, pH test paper;

[0064] 3. Conduct seawater testing and analyze strongly weathered shale in the laboratory;

[0065] 4. The strongly weathered shale was crushed and ground to obtain a certain amount of powdered solid. Then, the strongly weathered shale powder and seawater were mixed in a ratio of 1:1-5 to prepare trial mud. The specific gravity, viscosity and pH value of the mud were tested at room temperature. The results are shown in Table 4 below.

[0066] Table 4. Tests using strongly weathered shale powder and seawater at different ratios.

[0067] mud specific gravity 1.68 1.34 1.18 1.08 1.05 Martens viscosity (s) 102 48 27 16 9 PH 8 8 8 8 8

[0068] Based on the data obtained in Table 4, a graph showing the mud specific gravity of seawater-weathered shale powder at different proportions is plotted as follows: Figure 2 As shown;

[0069] Based on the data obtained in Table 4, a graph showing the viscosity of mud slurry at different proportions of seawater-strength weathered shale powder is plotted as follows: Figure 3 As shown.

[0070] According to the reference data on mud performance indicators during pile foundation drilling given in the "Technical Specification for Construction of Highway Bridges and Culverts" JTG / T F50-2011, the mud specific gravity for various types of bored pile foundations is generally between 1.1 and 1.4, and the viscosity is between 16 and 35. Figure 2 and Figure 3 The curves of the two graphs show that the mud specific gravity and viscosity simultaneously meet the requirements of the pile foundation drilling process. It can be concluded that the ratio of shale powder to seawater during the pile foundation drilling process is 1:2.42-1:3.75.

[0071] In this embodiment, a preferred implementation scheme is, after... Figure 2 and Figure 3 The two charts confirm that when the ratio of strongly weathered shale powder to seawater is 1:2.73, the mud's specific gravity and viscosity simultaneously meet the requirements for pile foundation drilling in this embodiment. The verification results of the mud preparation based on the shale powder to seawater ratio of 1:2.73 are shown in Table 5 below:

[0072] Table 5 Verification Test of Mud Proportion Required in Pile Foundation Drilling Process

[0073]

[0074] Based on the reference data for mud performance indicators (specific gravity and viscosity) of secondary cleaning mud for pile foundations given in the "Technical Specification for Construction of Highway Bridges and Culverts" JTG / T F50-2011, and the technical requirements of CCTG French General Technical Specifications, Volume 68 - "Construction of Foundations for Civil Engineering Structures", combined with... Figure 2 and Figure 3 The curve relationship between the two charts shows that the ratio of shale powder to seawater during secondary cleaning is 1:3.75-1:4.35.

[0075] In this embodiment, a preferred implementation scheme is, after... Figure 2 and Figure 3 The two charts confirm that when the ratio of strongly weathered shale powder to seawater is 1:3.75, the mud's specific gravity and viscosity simultaneously meet the requirements for secondary hole cleaning of the pile foundation in this embodiment. The verification results of the mud preparation based on the shale powder to seawater ratio of 1:3.75 are shown in Table 6 below:

[0076] Table 6 Verification Test of Mud Proportion Required for Secondary Hole Cleaning

[0077]

[0078]

[0079] According to the "Technical Specification for Construction of Highway Bridges and Culverts" (JTG / T F50-2011), the pH range for mud is 8-11. The pH value of mud obtained from seawater and shale is almost identical. The pH results of this test also meet the requirements. In this embodiment, the above mud mix ratio meets the construction requirements, and the test results were verified by a third-party laboratory in Senegal. The conclusion is that it meets the requirements of European standards and special technical clauses, and can be directly discharged into the sea without causing marine pollution.

[0080] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and embodiments shown and described herein.

Claims

1. A drilling mud for bored piles made from strongly weathered shale material, characterized in that, include: The raw materials are seawater and strongly weathered shale; The strongly weathered shale has a Los Angeles abrasion rate of 46.2%-70.0%, a water absorption rate of 13.2%-18.4%, a density of 1.68 g / cm^3-1.82 g / cm^3, a maximum dry density of 1.92 g / cm^3-1.98 g / cm^3, an optimum moisture content of 6.3%-8.9%, a liquid limit of 53.1%-77.3%, a sieve residue of 1%-12% on a 0.08 mm square hole sieve, and a CBR of 0.5%.

2. The drilling mud for bored piles made from strongly weathered shale material according to claim 1, characterized in that, The mud is prepared by mixing raw seawater and strongly weathered shale.

3. The drilling mud for bored piles made from strongly weathered shale material according to claim 1, characterized in that, The strongly weathered shale has a Los Angeles abrasion rate of 58.1%, a water absorption rate of 15.8%, a density of 1.75 g / cm^3, a maximum dry density of 1.95 g / cm^3, an optimum moisture content of 7.6%, a liquid limit of 65.2%, a residue of 6.5% on a 0.08 mm square hole sieve, and a CBR of 0.5%.

4. The drilling mud for bored piles made from strongly weathered shale material according to claim 2, characterized in that, The mud is prepared by mixing strongly weathered shale powder and seawater in a mass ratio of 1:1-5.

5. The drilling mud for bored piles made from strongly weathered shale material according to claim 4, characterized in that, Strongly weathered shale powder and seawater are mixed at a mass ratio of 1:2.42-3.75 to make drilling mud for pile foundations.

6. The drilling mud for bored piles made from strongly weathered shale material according to claim 5, characterized in that, Strongly weathered shale powder and seawater are mixed at a mass ratio of 1:2.73 to make drilling mud for pile foundations.

7. The drilling mud for bored piles made from strongly weathered shale material according to claim 4, characterized in that, Strongly weathered shale powder and seawater are mixed at a mass ratio of 1:3.75-4.35 to prepare mud for secondary cleaning of pile foundation holes.

8. The drilling mud for bored piles made from strongly weathered shale material according to claim 7, characterized in that, Strongly weathered shale powder and seawater were mixed at a mass ratio of 1:3.75 to prepare mud for secondary cleaning of pile foundation holes.

9. The drilling mud for bored piles made from strongly weathered shale material according to claim 4, characterized in that, The pH of the strongly weathered shale is 10, and the pH of the mud made from the strongly weathered shale and seawater is 8.

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