Application of German Daldar Hydraulic Rock Splitter in Tunnel Blasting

Application of German Daldar Hydraulic Rock Splitter in Tunnel Blasting

1 Project Overview

Static blasting technology is a new technology for crushing or cutting rock and concrete. Compared with traditional explosive blasting, it has the characteristics of no noise, no vibration, no flying rocks and no pollution of gun smoke. It is mainly used in environmental protection requirements. The high concrete demolition project and the stone block mining field have also been applied in some tunnel excavation constructions in recent years.

The new Ziyang Tunnel on the second line of the Handan Railway passes through the prosperous commercial street, residential area and Provincial Highway 310 in Ziyang County . The tunnel is buried at a depth of 5 to 130m , and there are both Ziyang Tunnels 25 to 31m away from the right side . In order to ensure that residential houses near the tunnel, Provincial Highway 310 and the existing Ziyang Tunnel are not disturbed, static blasting technology has been adopted.

German Darda Splitter

construction process

2 hole body excavation construction method and process

The tunnel is a single-track railway tunnel with a total length of 490m . It is driven through two-way excavation from the import and export, and uses static blasting technology to excavate the cavern. The overall construction method is the hydraulic rock splitting method, the static breaker cracking, and the hydraulic rock splitter trimming and excavation method. The construction technology of the hydraulic rock splitting method and the static cracking agent is mainly introduced as follows.

2.1 Introduction to the Dadar Hydraulic Splitter

The German Darda hydraulic splitter consists of a control valve, a split cylinder and a wedge block. The entire splitter is mainly made of high-quality special aluminum alloy and alloy steel through precision machining, with special high quality seals. Therefore, its light weight, large pressure capacity. At the same time, the reverse wedge has been coated with a special hard alloy after special surface treatment, which has high compressive strength, wear resistance and high temperature resistance.

Germany's Dalda Hydraulic Splitter is the lightest splitter, producing an average splitting force of 9.1 tons per kilogram of weight. It is suitable for quick and easy resolution of medium-strength splitting tasks such as splitting and dismantling of plain concrete and lightweight reinforced concrete.

The strongest splitter in the same weight class of the hydraulic splitter in Dardal, Germany , is used for splitting and demolition of reinforced concrete.

2.2 Hydraulic rock splitting method

Firstly, according to the design requirements, the splitting line of the split rock is determined. According to the degree of rock fracture, the depth of the drill hole and the distance between the holes are determined. The depth of the drill hole must be greater than the maximum value of the middle wedge, and the row holes should be the same. In the plane, avoid canine holes. In this project, the splitter is mainly used for grooving and excavating the outer contour trimming. The depth of the cut boring is 50 to 60cm , and the distance between holes is 10 to 20cm . After the drilling is completed, one or more splitters are inserted into the drilled hole. In the row of holes, the hydraulic power system is started, and the middle wedge is pushed out by the hydraulic force, forcing the pair of opposite wedges clamped on both sides to expand toward the two walls of the rock hole, and the material can be broken within a few seconds. . Subsequently, the middle wedge is retracted, the splitter is pulled out, and the gutter is made as a free surface for the next static blasting.

2.3 Static crusher crushing construction and crushing mechanism

The use of hydraulic rock splitters instead of blasting and conventional crushing methods is mainly due to the fact that it does not generate pressure waves when breaking rocks or concrete, there is no vibration, noise and dust, and it is easy to operate, especially for small crushing volumes and short requirements. The project completed during the time is very suitable. This project uses the German Darda hydraulic rock splitter. The static blasting ( also called static crushing ) of the splitter is an inorganic salt powder containing calcium, aluminum, magnesium, silicon, iron and other elements. The water is transferred into a fluid slurry and directly poured into the borehole. After the hydration reaction, a huge expansion pressure ( up to 30 to 50 MPa) , concrete ( tensile strength of 115 to 310 MPa) or rock ( tensile strength of 410 ~ 1010MPa) Cracked and broken.

2.4 Factors Affecting Inflation Pressure

The static blasting method mainly utilizes the expansion pressure of the static explosive to split the concrete or rock. Therefore, before crushing the design, it is necessary to understand the properties of the breaker and the factors that affect the expansion pressure before the design of the drilling parameters can be performed silently. For crushing construction, the following points must be taken into consideration:

1) Temperature. Because the main component of the crushing agent is CaO , the higher the ambient temperature, the quicker the hydration reaction of the crushing agent and the higher its inflation pressure. According to tests, a certain cracking agent has a swelling pressure of 40 MPa at 20 °C ; at 13 °C , the swelling pressure only reaches 20 MPa . And when the temperature is lower than 15 °C , the expansion pressure is sharply delayed, and the expansion pressure of 30 breakers is rapidly increased.

2) Water-cement ratio. Tests have shown that when the water-cement ratio of the breaker is 20% , the expansion pressure is very high but the fluidity is very poor. When the water-cement ratio is >30% , the expansion pressure drops too much despite the good fluidity. Therefore, considering the reliability of construction, the water-cement ratio should be 25% to 30% . The breakage agent used in Ziyang Tunnel is rod-shaped. It is made of strong paper and made into a cylindrical shape. It is immersed in water for 2 minutes and absorbs about 25% of water . The swelling effect is very good.

3) Aperture. In general, with the increase in pore size, the expansion pressure will also increase because the larger the bore diameter is, the more slurry is loaded into the breaker, so the expansion pressure is also greater. However, when the hole diameter exceeds 60 mm , the dose increases too much. When the working temperature exceeds 30 °C , the hydration and heat release rates are fast and the nozzle hole may occur.

4) Fill density. The filling density of the breaker is related to the water-cement ratio and the hole operation. When the test proved breaker density increased from kg / cm to 1165kg / cm, under the same conditions as the water-cement ratio of 30%, the expansion ratio increased 615% from 015%, and the compressive force is increased from 10MPa to 30MPa, This also proves that the higher the packing density, the better the swelling and crushing effect.

2.5 Drilling and blasting design and construction

The entire construction procedure for the excavation is: determine the excavation step → rock mass survey → static blast design → drilling → select static blasting agent → charge filling → fracture splitting → secondary crushing → cleanup → inspection section.

1) Excavation steps. According to the characteristics of the section of the single-line tunnel excavation, it is divided into four parts for excavation ( see Figure 2) , namely 1 , 2 , 3 , and 4 parts. One excavation is planned ahead and one excavation space is used. With the face of the maneuver as the surface, two vertical excavation holes are made. This will not only save the scaffolding, safe construction, but also improve the construction efficiency. Also use 2 or 3 of the excavation 3 or 4 parts. In the tunnel excavation outside the outline, or because the profile of the curve can not be vertical eye-catching place, then set aside 20 ~ 40cm trimming layer, the use of smooth drilling, accurate trimming. Because of its small size, the trimming layer can be completed in a short period of time using the Dalda rock splitter, achieving time-controlled, ultra-low-excavation control and safe production.

Figure 2 Dalda slot (unit: cm)

2) Rock condition. Most of the new Ziyang tunnels are Grade II and III surrounding rocks, accounting for 85% of the entire tunnel and belong to medium-hard rock. The construction process is mainly used for Grade II and III surrounding rocks, and the static explosion effect is better in the medium hard rock. The tunnel also has Class IV and V surrounding rocks, which are excavated using hydraulic breakers or high-power excavators.

3) Drilling and plugging. Drilling using air-leg pneumatic rock drill, drilling a pore size of <38mm ~ <50mm, a first section perpendicular to the working face and the bore, arranged at Holes tunnel centerline position, a total of five rows of holes 80, the distance between holes 10cm , drilling depth 55cm , the diameter of a vertical hole in the middle of <50mm , as a free surface, the vertical row of holes on both sides of the hole is <42mm , placed Darda rock splitter. After the guttering, the remaining sections are normal static blasting, and the completion of the whole 1 section provides the vertical drilling work surface for the second excavation.

The second vertical drilling arrangement is shown in Figure 3 . According to the technical requirements of K series products, in the medium and hard rock, the best drilling interval is a=15 ~ 36cm . After the test, a=25cm is taken , the drilling is determined as a 25cm * 25cm mesh layout, and 5 rows of drill holes are drilled longitudinally each time. That is, 1125m of footage and 113m of vertical drilling depth . Part 2 uses two-step drilling to excavate. Similarly, parts 3 and 4 are constructed using the above method. In this way, parts 1 , 2 , 3 and 4 can be used for flow operations, effectively using the work surface, which will help speed up the construction progress.

Figure 3 vertical drilling layout (unit: cm)

4) Selection of static explosives. Due to the slow hydration rate of ordinary static explosives, the hydration reaction can take up to about 24 hours , the maximum expansion pressure can be reached, and the tunneling requirements cannot be met. Therefore, the K Series fast static explosives are used in the new Ziyang Tunnel , and the K- series fast static breakers are used in addition to the main body. In addition to the expansion breaker roll, there is also a heat-sensitive static breaker that accelerates the hydration of the static explosive. Its main technical indicators are: maximum expansion pressure 50 ~ 60MPa , hydration reaction time 10 ~ 60min , applicable ambient temperature -16 °C ~ 35 °C , according to different seasons and construction environment temperature selection K2 I ~ K2 IV type static explosive.

5) Borehole bursting sequence. In order to make all kinds of blastholes have more free surface when they burst, so as to improve the bursting effect, there should be a time difference in the bursting sequence of all types of blastholes. For this purpose, arranged on the portion of the borehole crushing procedure 1: Holes → → auxiliary eye surrounding the eye; 2, 3, 4 is broken after the first front → broken back order, or simultaneously charges the range , 5h drug broken.

6) Charge. Charges need to fill the blast holes basically, calculated according to the total length of the holes, and vary with the aperture and hole pitch. The total dosage of the breaker is calculated according to the empirical data of the broken volume multiplied by the unit volume loss broken dose:

Q=Vq

In the formula, Q is the total amount of the breaker (kg); V is the broken volume (m);

q is the unit volume loss crushing dose (kg/m) . q Use according to Table 1.

2.6 Dregs

As a result of the stepped segment excavation, excavation departments smaller space, first, using only two ways of doing + tap of trolleys, slag 1, 2 in the third stack portion reuse excavator ( Placed on the 4th step ) Dregs together.

After the static blasting had taken place, most of the rock had cracked. Then the hydraulic rock breaker used in the excavator was used to secondary crush and decompose the large rock, and then the loader and the transporter used the slag.

1) The operator must wear gloves. After the work is completed, wash hands and hands in time to prevent alkaline irritations.

2) When filling the blast hole, each roll must be compacted, and the hole should be blocked. Before the grouting to the crack occurs, you must not look directly at the hole at a close distance to prevent the occurrence of the spray hole and damage the eyes.

3) The water in the blasthole should be removed before the charge, preventing the water-cement ratio from being too large and the static explosion effect to be reduced.

4) The heat immersion temperature of the heat-sensitive reagent roll should be controlled below 25 °C , and the immersion time should not exceed 2 min to prevent the roll cover from bursting in water. 5) The crushing agent should be used with it. The prepared drug slurry should be loaded into the drill hole as soon as possible and should be used within 10 minutes .

Table 1 Breaker volume per unit volume

Broken Body Category Hard Rocks Hard Rocks Hard Rocks

Aperture /mm

38 to 5038 to 5038 to 50

Unit volume loss crushing dose / (kg/m3)

6 to 1012 to 2218 to 25

4 Conclusion

The static blasting of the new Ziyang tunnel on the second line of the Handan Railway was adopted during the excavation process, which achieved good results. It not only met the tunnel construction period, but also ensured the normal life of the local residents and achieved the operation safety of the National Highway 310 and the existing Ziyang Tunnel. The unanimous approval of the local government, owners, design and supervision units.

However, static blasting also has certain problems. For example, the construction cost is high. Excessive drilling results in slower excavation than traditional blasting. The effect of crushing is greatly affected by temperature, and the cracking time is not suitable. Therefore, this method is only applicable to special construction. It is used in environment and individual restricted projects.

The information in this article comes from the Internet and was reorganized and edited by China Rescue Equipment Network.