Introduction
Slope instability leading to landslides and collapses is an extremely serious natural disaster. According to the literature, the United States suffers annual economic losses of over 1 billion US dollars due to landslides. The Vajont landslide in Italy in 1963 and the Nagano landslide in Japan in 1985 have both caused massive destruction. China is also one of the countries prone to landslide disasters. In many fields such as road construction, shipping, water conservancy, and open-pit mining, the stability of slopes is of crucial importance. The normal operation of these industries depends on stable slope conditions, and any slope instability may trigger serious accidents and impede industry development.
Given the continuous changes in the natural environment and climate, it is of great significance to attach full importance to slope maintenance to ensure slope stability and prevent the occurrence of geological disasters. Slope maintenance can not only protect people’s lives and property and avoid huge economic losses but also serve as a necessary prerequisite for the sustainable development of various industries. Only by effectively carrying out slope maintenance can we effectively reduce the negative impacts of disasters such as landslides and collapses and maintain the stable development of the social economy.
In the field of slope protection, design units, and construction enterprises use various means to implement anchoring support for the easily sliding parts of slopes to address this difficult problem. Among them, self-drilling anchor bolt support is highly favored and praised by construction personnel due to its remarkable advantages.
This article takes the basic forms and causes of slope failure and the characteristics of self-drilling anchor bolts as the starting point to conduct an in-depth analysis of the principles followed when self-drilling anchor bolts are applied to slope supporting. First, let’s understand the basic forms and causes of slope failure.
Basic Forms and Causes of Slope Failure
Basic Forms of Slope Failure
The basic forms of slope failure mainly include three types: collapse, landslide, and toppling failure.
- Collapse: It refers to the geological phenomenon in which the rock and soil mass on the upper part of the slope suddenly detaches from the parent body under the action of gravity, falls, rolls, and accumulates at the foot of the slope. Usually, it occurs suddenly and at a high speed.
- Landslide: It means that the soil or rock mass on the slope, under the influence of factors such as river erosion, groundwater activity, rainwater soaking, earthquakes, and artificial slope cutting, slides down the slope integrally or dispersedly along a certain weak surface or weak zone under the action of gravity.
- Toppling Failure: It includes two forms: collapse and dislocation. Collapse is the phenomenon of the instability and falling of the slope rock and soil mass. Dislocation is the overall downward displacement of the rock mass along a nearly vertical fracture surface, with the vertical displacement greater than the horizontal displacement.
Causes of Slope Failure
The causes of slope failure can be analyzed from two aspects: internal factors and external factors.
A. Internal Factors
- Stratum and Lithology: The stratum characteristics and lithology determine the basic strength of the slope. If the lithology is weak (such as clay and strongly weathered rock), its deformation resistance is poor, which is likely to lead to failure.
- Geological Structure: Geological structures such as faults and joints can weaken the integrity of the rock mass, form stress-concentrated areas or sliding surfaces, and reduce the stability of the slope.
- Rock (Soil) Mass Structure: The structural form of the rock and soil mass (such as layered and fragmented structures) affects its stress characteristics. When the structure is loose or fragmented, it is more likely to become unstable.
- Effect of Water: The seepage of groundwater softens the rock and soil mass, or the surface water scours the foot of the slope, which can reduce the strength of the rock and soil mass and increase the sliding force.
B. External Factors
- Slope Shape Modification: Artificial slope excavation changes the original slope gradient and height, destroys the natural balance, and may lead to instability.
- Meteorological Changes: Heavy rain and long-term rainfall increase the water content of the rock and soil mass, increase its unit weight, and soften the structure. Freeze-thaw cycles can also damage the structure of the rock and soil mass.
- Engineering Load: Loads on the top of the slope, such as building loads, increase the pressure on the slope. When the pressure exceeds its bearing capacity, failure will occur.
- Human Factors: Unreasonable engineering activities (such as over-mining and random drainage) destroy the original stable conditions of the slope and increase the risk of instability.
The causes of slope failure are complex and diverse, covering many factors. In this context, it is extremely important to select an appropriate support method to ensure slope stability. Then, as one of the many slope-supporting methods, Can Self-Drilling Hollow Anchor Bars Achieve the Ideal Supporting Effect? Next, I will answer this question by elaborating on the characteristics of the self-drilling anchor bolt and its application in slope support.
Introduction to Self-drilling Anchor Bolts
Self-drilling anchor bolts are similar in appearance to ordinary hollow anchor bars, but they are essentially different in functional attributes and application scopes – not all hollow anchor bars can be defined as self-drilling anchor bolts. As an integrated support component, the self-drilling hollow anchor bar consists of core components such as the self-drilling hollow anchor bar, drill bit, coupler, nut, plate, and centralizer.
With the “drilling, grouting, and anchoring” trinity of functional characteristics, self-drilling anchor bolts can efficiently deal with complex geological conditions such as fractured surrounding rocks, sandy soils, and strongly weathered rock layers. In projects such as tunnel excavation and slope supporting, for easily collapsed strata where conventional methods have difficulty in forming holes, it can directly drill holes and complete grouting and anchoring, avoiding the risk of hole collapse, significantly improving the strength and stability of the rock and soil mass structure, and strengthening the safety guarantee for engineering construction.
Application Principles of self-drilling anchor bolts in slope supporting
Introduction to slope supporting
Slope supporting refers to a series of engineering measures of retaining, reinforcing, and protecting slopes to ensure the safety of slopes and their surrounding environments. The core purpose is to improve slope stability and prevent the risk of failure such as collapse and landslide.
Application Principles of self-drilling anchor bolts in slope supporting
In slope protection, the application of self-drilling anchor bolts goes through the following two processes:
- Integrated Drilling and Grouting Process: According to the precise angle determined by the engineering design, the self-drilling hollow anchor bar slowly drills into the slope that needs to be supported. The front end of the self-drilling hollow anchor bar is equipped with a specially made high-strength drill bit. During the drilling process, this drill bit fully exerts its powerful rock-breaking ability, continuously crushing the rock and soil mass, enabling the anchor bar to penetrate deeper into the complex rock and soil mass that is broken, loose, and highly prone to hole collapse.
- At the same time, during the drilling process, the grouting machine is activated for the first grouting through the hollow channel inside the anchor bar. The water-cement ratio of the grout for this grouting is strictly controlled at approximately 1:1. The prepared grout is evenly diffused radially from the inside to the outside through the pre-set grout outlet holes of the drill bit. While providing certain auxiliary support for the drilling process, it preliminarily fills some of the voids in the rock and soil mass.
- Secondary pressurized grouting method: When the self-drilling hollow anchor bar is drilled to the designed depth, the second grouting is carried out immediately. At this time, the water-cement ratio of the grout is adjusted to approximately 0.45 – 0.6:1. The grout is injected into the rock and soil mass again through the grouting machine, the hollow channel of the anchor bar, and the grout outlet holes of the drill bit. Compared with the first grouting, due to the change in the water-cement ratio, the consistency of the grout in the second grouting is more appropriate. It can penetrate more fully into the fine cracks of the rock and soil mass, further strengthening the structure of the rock and soil mass, greatly enhancing its overall density and deformation resistance, thus better playing the supporting role of the self-drilling hollow anchor bar for the slope.
- Anchor Body Construction: After grouting is completed, install the plate and nut close to the rock mass surface. The plate serves as a force-transmitting medium to expand the contact area between the anchor bar and the rock mass. The nut applies prestress by tightening so that the self-drilling anchor bar, plate, and rock and soil mass work together to form a stable anchor body. When the rock and soil mass of the slope deforms under the action of external forces, the force exerted by the rock and soil mass on the plate and nut will be quickly transmitted to the anchor body. At this time, relying on the strong friction between the solidified grout and the rock and soil mass, the anchor body generates a reverse anchoring force. This anchoring force opposes the deformation trend of the rock and soil mass, effectively suppressing the displacement of the rock and soil mass, preventing the slope from sliding, and ultimately achieving the enhanced protection of slope stability.
The self-drilling anchor bolts, from the integrated drilling and grouting process to the construction of the anchor body, have closely linked processes, and all play a significant role in providing a solid guarantee for slope support. It effectively proves that self-drilling anchor bolts can achieve the ideal support effect in slope supporting and are an effective support method worthy of wide promotion and application in the field of slope engineering.
Conclusion
Geological disasters such as landslides and collapses caused by slope instability pose a major threat to the global social economy and engineering safety. Historical cases in the United States, Italy, Japan, and the frequent occurrence of landslide disasters in China highlight the urgency and necessity of slope maintenance.
Can self-drilling anchor bolts achieve the ideal support effect? The answer is yes. As an integrated support technology, self-drilling anchor bolts, with their “drilling – grouting – anchoring” trinity of functional characteristics, can provide efficient solutions for slope protection under complex geological conditions. If you are facing slope-supporting problems, Sinorock can provide reliable support. Sinorock’s self-drilling anchor bolt products, relying on advanced technology and strict processes, are of reliable quality and can effectively help solve various slope-supporting problems and ensure the safety and stability of engineering projects.
