Vertical jet grouting technology has been successfully used for reinforcement, seepage prevention and water stop under various formation conditions (such as clay, sand, silt, sand mixed with pebbles, moraine soil, loess, humus soil and peat soil, etc.). ) and show its advantages. Under some conditions, vertical drilling is impossible or inappropriate, but high-pressure jet grouting is needed, so people naturally think of horizontal or inclined drilling. Japan and Italy are the first countries to research and develop horizontal jet grouting technology. 1983, the horizontal jet grouting technology was first applied to the tunnel advance support by Italian RODIO company. The United States began to use this technology in the 1980s, and 1987 was first applied in South America.
The application of jet grouting in horizontal drilling is closely related to the development of tunnel construction technology. The construction of underground structures in weak strata with thin overburden faces serious problems such as unstable strata, easy collapse and ground subsidence. The successful development of high-pressure jet grouting makes the engineering and technical circles think of using it to improve the stability of tunnel surrounding rock. Jet grouting around the tunnel by vertical drilling from the ground has some shortcomings, such as too deep drilling depth, difficult to ensure drilling accuracy, and overlapping between consolidated bodies. In addition, controlled by the bond strength and shear strength between consolidated bodies, the reinforcement range is relatively large.
Accordingly, people naturally think of using horizontal drilling to realize the problem of jet grouting.
Several generations of jet grouting method in Japan
2. 1 CCP-H construction method
This method was developed on the basis of single-pipe jet grouting in Japan in the early 1980 s and is specially used for horizontal drilling. It is to set an expansion drill at the back end of grouting pipe to strengthen the damage to the soil. When drilling, the expansion bit retracts into the groove of the drill pipe, and when it retreats, it is automatically opened by resistance and begins to rotate and spray. Before rotary spraying, mix the soil layer to ensure and enlarge the diameter of the horizontal rotary spraying cylinder. In order to accelerate the consolidation of mud and soil particles, an appropriate amount of accelerator and hardener are added to the mud. The First Engineering Bureau of Japan Railway Corporation has carried out the test and construction by this method.
2.2 RJFP construction method
With the continuous development of jet grouting technology, Japan put forward the RJFP construction method [1] (Figure 1). In this method, steel bars or steel pipes can be inserted into the solidified body formed by rotary spraying on the outer edge of tunnel arch, so that the solidified arch shed has both lateral compression resistance and longitudinal bending resistance. They have successfully built dozens of tunnels in this way. This method generally only strengthens the arch of the tunnel, so that the jet grouting piles overlap each other to form an arch shed. The drilling length is 13m, the jet grouting length is 1 1m, and each arch shed overlaps 1m.. The jet pressure used in these tunnels is about 40MPa, the diameter of the consolidated body is 60 ~ 70 cm, and the uniaxial compressive strength of the rotary jet consolidated body is 3.5～8.0 MPa.
2.3 MJS construction method
MJS construction method is the abbreviation of "omni-directional high-pressure jet technology". The biggest feature of this method is that it has a sludge discharge mechanism. This is developed to solve the problem that the excess slurry gushes out of the orifice and pollutes the working environment by the general rotary jet grouting method. With the increase of the depth of rotary jet grouting hole, the difficulty of grouting increases, and the effect of spraying and mixing decreases. Set the MJS device on the monitor. The device is a mud discharge suction port installed behind the nozzle, through which mud can be sucked, and the mud discharge amount and the pressure on the foundation can be adjusted to make full use of the injection pressure. The device can be used not only for deep vertical jet grouting, but also for horizontal and inclined directions. Because the drill pipe is also equipped with seven pipes, it is also called the seven-pipe rotary jet method.
This advantage is that it does not pollute the site and maintains a good construction environment, but the equipment is too complicated, takes up a lot of space and is not convenient to carry.
3 Current situation of horizontal jet grouting method in Europe and America
Italy is a mountainous country, its tunnel and underground engineering construction technology is relatively developed, and the development and application of horizontal jet grouting technology is in a leading position in Europe. 1992 At the international conference on tunnel and underground engineering held in Slovenia, the representatives of this country systematically summarized the tunnel surrounding rock reinforcement methods in this country and all over the world, and listed high-pressure jet grouting method, static grouting method, freezing method and mechanical pre-cutting groove as the basic methods for tunnel surrounding rock reinforcement [2]. The most typical method is to overlap horizontal drilling holes and jet grouting piles along the outer edge of the arch to form an arch shed, and excavate the upper section under its protection. In the step method construction, in order to improve the strength of the arch foot stratum, oblique holes are drilled on both sides of the tunnel, and jet grouting piles are connected into the wall. Fig. 2 shows a two-lane highway tunnel with a cross-sectional area of 120m2, a jet grouting column length of 13m, a center distance of 50cm, a jet grouting column diameter of 60cm, and an overlap of 3 m between adjacent jet grouting sections.
According to the engineering practice in Italy, the quality of horizontal jet grouting pile is good in sandy soil and medium-fine sand stratum, and the average compressive strength of consolidated body reaches 18~ 19MPa, which is close to C20 grade concrete. Under the protection of jet grouting arch shed formed by overlapping horizontal jet grouting columns, the stress measurement of arch ribs set during excavation shows that the stress is very small, which shows that the jet grouting arch shed has good rigidity and can bear the pressure of the mountain.
The tunnel of Bonn Metro 1 Bid Section in Germany passes through loose unconsolidated Rhine gravel and uneven mud and sand layer, with an average permeability of 8mm/s and an average buried depth of 3.5m, and a sewage pipe passes through the top. In order to control land subsidence and ensure the safety of sewage pipes, jet grouting combined with NATM (Figure 3) was adopted, and good results were achieved [3]. The jet grouting pile is 12m long, 60cm in diameter, 47cm in center distance, 3m overlapping, and inclined outward 10. When the jet grouting pressure is greater than 40MPa, the ground uplift has reached 965438±0mm, and it has been reduced to 8mm after taking measures such as depressurization and drilling pressure relief holes. The problem of ground heave caused by high-pressure jet grouting has attracted the attention of engineering circles.
In the early 1980s, jet grouting technology was first applied in the United States and achieved success. It is widely used in the United States because of its low price and universal application to various soils. Large-scale horizontal jet grouting was used in the tunnel construction to the east of Washington Metro Naval Factory, which made EPB shield pass under the sewer of brick and plain concrete structure with the diameter of 18ft(5486.4mm) built a hundred years ago.
In the construction of Zurich subway, Switzerland adopted the horizontal jet grouting technology as the advanced support for the first time [4]. There is a loose and broken moraine belt between St Antoniuskirch station and Stadehofen station. Although the overburden is the thinnest in the whole project, it cannot be excavated because of the railway line above. The most serious landslide accident occurred when the mechanical excavation of the interval tunnel encountered the loose and broken moraine layer. Finally, it was changed to horizontal jet grouting to pre-support the stratum and passed through the loose fracture zone smoothly. Before excavation, 23 horizontal jet grouting piles with a length of 16m and a diameter of 70cm were set at the arch of the tunnel to form a supporting arch. Borehole diameter 10cm, jet grouting pressure 40 ~ 80 MPa. After the shotcrete arch shed is completed and the consolidated body is fully consolidated, the step method is adopted for construction. The footage of the upper step is 1m, and it takes 7 days to complete the excavation of a shotcrete section. Two adjacent jet grouting sections overlap by 2m. The length of the jet grouting pile is 16m, which is the longest data record found so far.
4 the present situation of horizontal jet grouting method in China
4. 1 Research Work of Railway Research Institute
In order to promote the development of jet grouting technology, the Railway Research Institute conducted a horizontal jet grouting test in the light loam stratum near Wulanhaote, Inner Mongolia on 1987. The test results show that under the pressure of 20MPa, the diameter of the column can reach 58cm, the strength of the consolidated body is 2.8MPa, the thickness of the arch shed is 20~25cm, and there are no cavities and broken columns. Grout is injected into some soft soil and soil joints under the action of high-pressure jet, which, like tree roots, has strengthened the soil to a certain extent and achieved initial results.
4.2 Research work of Shijiazhuang Railway Institute
Since 1994, Shijiazhuang Railway Institute has started the research on horizontal jet grouting machine and horizontal jet grouting technology. Four horizontal and inclined jet grouting tests and a series of tests were carried out in thick sandy clay layer and loose fine sand layer, and a lot of research results were obtained. We also jointly designed and manufactured the TGD-50 horizontal drilling rotary jet machine with Xuzhou Construction Machinery Factory, as shown in Figure 4. This machine can be used for drilling and jet grouting with vertical dip angle 15. It can be used not only for the advanced support of tunnels, but also for the reinforcement of subgrade and slope, and as a soil anchor for foundation pit walls. In199865438+February and199965438+1October, the advance support was carried out in the aeolian sand stratum at the entrance of Shahalamo tunnel and the shallow-buried eccentric section of Songjiaping tunnel, which was successful in one fell swoop. The test results of deformation and pressure after excavation show that. The reinforcement effect is good, which initially shows the superiority of this construction method. The successful application of horizontal jet grouting reinforcement technology fills the gap in China.
5 Research trend of horizontal jet grouting machinery
The main machines of horizontal jet grouting technology are horizontal jet grouting machine and high pressure grouting pump.
5. 1 horizontal rotary jet
Generally, foreign horizontal jet grouting machines install the drilling and spraying mechanism on a multifunctional drilling rig, which can drill both horizontal and vertical holes. This multifunctional drilling rig can carry out various operations and is very popular with users. At present, the general development trend of various drilling rigs has the following characteristics.
5. 1. 1 Pay attention to one machine for multiple purposes.
Adopt building block combination design, pay attention to one machine with multiple functions. According to the needs of different projects and different operations, components can be easily replaced to form models with different construction methods. The drilling rigs SM-405, SM-400 and SM- 103 of Italian company can be used for horizontal jet grouting, especially the SM- 103 micro-hydraulic drilling rig can work in closed and narrow places (Figure 5), and the maximum construction depth of jet grouting can reach 9m. Ingersoll rand's GH, KG, KR, KS and other series can be equipped with rotary jet drilling rigs. Figure 6 shows our KR803-02 geotechnical drilling rig. L6 and PG 125 horizontal jet grouting pile machines produced by Casalandi Company in Italy are mainly used for tunnel construction. Fig. 7 shows the pre-support operation of PG 125 horizontal drilling rig in the tunnel.
5. 1.2 adopts full hydraulic transmission and centralized control.
In order to meet the requirements of large torque and long stroke feed, the variable motor configuration scheme is adopted in the structural design, and the adjustment of constant power and constant torque is realized. Manipulation and control are concentrated in the control room, and small drilling rigs generally have a movable console outside the machine. Most of the hydraulic system is controlled by pilot proportional valve, which ensures the accuracy and sensitivity of control. At the same time, the control system is provided with a display device and an instrument monitoring device. For example, the control room of BG30 drilling rig of Baoe Company is equipped with a continuous depth recording device, and the C48 model of geotechnical company is equipped with a concrete pressure sensor; GH series of Ingersoll Rand Company is equipped with a depth and precision tester, which can read the depth and verticality of drilling holes at any time.
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