Keywords

1 Introduction

Ship lift and lock are two main types of navigation structures (Niu et al. 2007), among which ship lift has the advantages of small water consumption, fast operation speed and less technical restrictions on lifting height (Hu et al. 2016). It is especially suitable for navigation of high dams and has been widely used in navigation of mountainous rivers in central and western China in recent years.

The docking between the ship chamber and the upper/lower approach is an important link in the whole process of ship lift operation (Hu et al. 2016). The hydro-junction operation such as flood discharge and powerplant generation can easily lead to large fluctuations of the water surface near the head and chamber of the ship lift. If the water level changes too fast during chamber docking, the chamber cannot be docked (Zhang Yong 2016). If the water level of the channel changes too much during chamber docking, the ship may hit bottom or the water level in the ship chamber exceeds the total height of the ship chamber structure and water overflow (Shang et al. 2020).

To deal with the problems of steep rise and fall of river water level in mountainous areas of central and western China and fluctuation of water level of hub operation, China invented a unique launching type vertical lifting ship lift with wire rope winch (Wang et al. 2013). The ship chamber of launching ship lift directly enters the water. If the ship chamber is large in scale, launching ship lift requires a large motor to enhance power (Li et al. 2016). At the same time, it will also face mechanical equipment processing manufacturing and layout problems.

China has conducted theoretical study and engineering practice on building up an auxiliary lock to cope with unsteady flow changes during ship lift docking, in addition to adopting the type of launching ship lift and warning measures of unsteady flow at the hydro-junction. The measures of setting auxiliary locks to block unsteady flow from downstream to ship chamber were proposed for the first time in the study on the influence of unsteady flow generated by the operation of TGP project on the docking operation of ship lift (Qi et al.2013), but they were not put into practical application. Also on the Yangtze River, the Xiangjiaba ship lift installs an auxiliary lock downstream of the ship lift to isolate the water level of the ship chamber from that of the downstream, avoiding the influence of water level changes, which is a first-time engineering approach for solving the problem (Hao et al. 2020; Mei et al. 2020).

In the navigation facilities to be built in Baise junction on the Youjiang River, the ship lift adopts the fully balanced steel wire rope winch lift. The Baise ship lift exit is 0.5 km below the Dongsun Power Station dam (Preliminary Design of Navigation Facilities Of Baise Water Conservancy Project in Guangxi (2021)). The Dongsun Power Station’s discharge operation causes a huge variation and high frequency in the downstream water level of the Baise ship lift. An auxiliary lock is also set downstream of the ship lift to tackle the problem of water level variation downstream of the ship lift. The Baise ship lift auxiliary lock consists of a transition and berthing section that can accommodate two lines of vessels berthing inside the lock chamber, hence increasing the ship lift’s traffic capacity., but the lock chamber area is increased to 2.39 times that of Xiangjiaba auxiliary lock chamber. Bearing the two-way hydraulic head, the extreme lift height of the Baise auxiliary lock is 5.64 m. The Xiangjiaba auxiliary lock’s simple water filling/emptying (F/E) system under the gate cannot be employed. To increase water filling/emptying efficiency, minimize the transit time of ships through the ship lift as much as feasible, and maintain the safety of vessels berthing in the lock chamber, a reasonable water F/E system and gate operation mode must be determined.

2 Project Overview

The main buildings of navigation facilities of Baise Hydro Project Navigation include a saving-water lock, intermediate channel, navigable aqueduct, vertical ship lift, and so on. The design of the ship type is 2 × 500 ton fleet and 1000 ton single vessel.

The Baise ship lift auxiliary lock has a total length of 228 m, a progressive section length of 90 m, and an orifice width that gradually changes from 12.0 m to 34.0 m (Fig. 1).The straight part is 138 m long, and the lock’s sill elevation is 109.7 m. The auxiliary lock’s effective scale is 120 m × 34 m × 4.7 m (length, width, and sill depth). For ordinary operation, the lower head of the auxiliary lock uses a vertical lift gate for water retention.

This paper proposes a F/E system combining gate and grid energy dissipation type, and establishes a physical model of Baise auxiliary lock (scale 1:30) to evaluate the berthing condition of vessels in auxiliary lock and hydraulic characteristics of F/E system, then recommends the vertical gate operation mode of the auxiliary lock, which can provide a technical basis for design.

Fig. 1.
figure 1

Baise Ship lift and its auxiliary lock.

Full size image

3 Water Filling/Emptying System Selection and Arrangment

3.1 Water Filling/Emptying System Selection

The filling/emptying systems can be divided into two main types. One is the filling and emptying”through the heads”, and the other is the “through longitudinal culverts” system (PIANC report N 106 (2009)). According to Chinese Design Code for Filling and Emptying System of Shiplocks (JTJ 306-2001, China), the formula \({\text{m = T/}}\sqrt {\text{H}}\) can be used to select hydraulic system for inland navigation locks. In which, H(m) is the lift height of lock and T(min) the time to fill the chamber. According to the fluctuation frequency of downstream water level and traffic capacity of Baise ship lift, the design water filling/emptying time T is no more than 3.5 min when H = 1.5 m under normal condition, and T is no more than 5.0 min when H = 3.0 m under design condition for Baise ship lift auxiliary. Substitute the water filling time and lift height of Baise ship lift into the formula, \({\text{m = }}\left( {{3}{\text{.5}}\sim{5}{\text{.0}}} \right){/}\sqrt {1.5\sim3.0} = 2.86\sim2.89\). According to the Chinese specification requirements,if 2.5 < m < 3.5, the two types of water filling and emptying system can be selected.Considering the few days of extreme working condition of Baise ship lift every year, the normal lock lift is only 1.5 m, it is proposed to adopt “through the heads” system for downstream auxiliary lock.

3.2 Water Filling/Emptying System Layout

The Baise ship lift’s auxiliary lock uses a through-the-head technology that combines a flat vertical gate with grid energy dissipation to ensure that the water energy is effectively dissipated and the water transit time is shortened once the ship enters the chamber. The grid energy dissipation chamber has a vertical gate at the bottom. Water flow energy dissipates as water through the grid energy dissipation when the vertical gate is lifted and the bottom of the vertical gate does not exceed the sill level, ensuring uniform flow and proper energy while entering the chamber. When the water level difference between upstream and downstream reaches a specific point, lift the vertical gate, and the water flow through the vertical gate and grid energy dissipation chamber significantly increases, reducing the time it takes for the water to fill and empty. This plan can not only adapt to the operation of a low lift height lock, but also the vertical gate of the lock is involved in water filling/emptying, eliminating the need for another culvert valve, allowing the project to save work while boosting the lock’s water filling/emptying efficiency (Figs 2 and 3).

Fig. 2.
figure 2

The vertical gate is lifted to the sill and water go through the grid energy dissipation chamber.

Full size image
Fig. 3.
figure 3

The vertical gate is lifted above the sill level and water go through the grid energy dissipation chamber and under the gate.

Full size image

Two water inlets share one grid energy dissipation chamber, for a total of four grid energy dissipation chambers with a total volume of 196 m3. The outlet grid is located at the top of the grid energy dissipation chamber; the length of the grid is 4.4 m and the width is 0.3 m; each grid energy dissipation chamber has 8 outlet grids, totaling 32 grids with a 42.24 m2 area.

Two water inlets share one grid energy dissipation chamber, a total of four grid energy dissipation chambers, size of 7.0 m × 5.0 m × 1.4 m (length × width × height), total volume of 196 m3. The top of the grid energy dissipation chamber is provided with the outlet grid, the length of the grid is 4.4 m, the width is 0.3 m, each grid energy dissipation chamber is provided with 8 outlet grids, a total of 32 grids and area of 42.24 m2 (Fig. 4).

Fig. 4.
figure 4

Baise lock gate slot and its water F/E system.

Full size image

The Baise ship lift auxiliary lock hydraulic physical model was created using the gravity similarity criterion and a length scale of L = 30. Auxiliary lock, water F/E system (containing vertical gate and grid energy dissipation chambers), and upper/lower approach are all included in the hydraulic model. The berthing conditions of the ship in the lock and the hydraulic characteristics of the water filling/emptying system are investigated using the physical model, the rationality of the water filling/emptying system design is confirmed, and the operation mode of the vertical gate of the auxiliary lock is recommended.

4 Berthing Conditions of Vessels in Lock Chamber

To evaluate the berthing circumstances of vessels in lock chamber, the Baise auxiliary lock chamber physical model and three-dimensional mathematical model are constructed. Because 2 × 500T fleets are uncommon in the Youjiang River, this paper focuses on the berthing conditions of 1000T vessels. The length, width, and full load draft of the 1000T vessels are 67.5 m × 10.8 m × 2.9 m, and its displacement is equivalent to the European CEMT-IV.

4.1 3D Mathematical Model Evaluation

The flow state when water fills the chamber and the mooring conditions of vessels in the chamber are computed first, using a three-dimensional mathematical model. The river’s water level is 1.50 m higher than the auxiliary chamber (typical encountered), and the vertical gate bottom raises to sill elevation (109.7 m) at a speed of 2 m/min, according to the calculations.

Figure 5 depicts the typical flow pattern in the gate chamber while the auxiliary chamber is filled with water. The water flow in the chamber is rather stable during the auxiliary gate chamber filling process, as shown in the figure, and the water flow velocity in the inlet behind the gate exceeds 4m/s during the vertical gate raising procedure.

Fig. 5.
figure 5

Flow profile at the vertical gate in the chamber during water filling

Full size image

The maximum longitudinal water surface slope and mooring force on the vessel when water filling the chamber calculated by the three-dimensional mathematical model are shown in Fig. 6. It can be seen from the figure that in normal conditions, when the vertical gate bottom is lifted to 109.7 m at a rate of 2 m/m, the maximum longitudinal water surface slope is 2.28‰. According to European Longitudinal force criteria for CEMT-IV class, the longitudinal water gradient of lock is required to be no more than 1.1‰ when locks filling through lock head (PIANC report N 106(2009)). So the lifting speed of the flat gate needs to be reduced to ensure the safety of ship berthing.

Fig. 6.
figure 6

Longitudinal water surface slope and mooring force on the vessel in the chamber.

Full size image

4.2 Physical Model Evaluation

When the downstream river water level is higher than the lock chamber, the berthing circumstances of vessels in the lock chamber are termed extreme (H = 5.64 m), design (H = 3.00 m), and normal (H = 1.50 m) in physical model evaluation. The test vessels were of the 1000T class and carried a heavy load (67.5 m × 10.8 m × 2.9 m). For the test, the vessels were lined up in a single row in the calm part of the auxiliary lock. The vertical gate lifts at a rate of 2 m/min and 1 m/min, respectively. The lifting elevation of the vertical gate bottom in the physical model test at extreme and design conditions is the sill elevation (109.7 m) and 1m above the sill (110.7 m). The vertical gate is continuously elevating above the water in normal condition.

The maximum value of mooring force under the conditions of extreme head, design head and common head with different gate lifting speed and mode is shown in Table 1 and Table 2. Typical curves of mooring force of 1,000T vessel are shown in Fig. 7.

As shown in Table 1, the maximum longitudinal mooring force of a 1000T single vessel berthing in the upper lock is 70.93 kN, 47.14 kN, and 25.85 kN, respectively, when the vertical gate lifts to the sill elevation of 109.7 m at the speed of V = 2 m/min under three working conditions of extreme condition, design condition, and normal condition. Except for the normal condition, the mooring force values mentioned above are significantly higher than the standard requirements. The lifting speed of the vertical gate is too fast, given that the maximum longitudinal mooring force of the vessel in the chamber is mostly affected by the flow rate rise of ∆Q/∆T at the beginning stage of gate lifting (Huang et al. 2016), which leads to a large flow rate increase at the initial stage of water filling in the auxiliary chamber. Therefore, the lifting speed of the vertical gate shall be reduced.

The gate lifting speed is lowered to V = 1 m/min in extreme condition, and the increasing rate of beginning water flow is reduced when the vertical gate is raised to 109.7 m (i.e. sill elevation). A designed 1000T vessel’s maximum longitudinal mooring forces are also reduced to 31.80 kN, which meets the China code’s standards. If the vertical gate is lifted to 110.7 m (i.e., 1m higher than the sill elevation) at a speed of V = 1 m/min in order to improve the water traffic efficiency, not only does the energy dissipation grid chamber pass the flow, but additional flow flows beneath the vertical gate, increasing the maximum longitudinal mooring force of the specified 1000T single vessel moored in the chamber to 41.65 kN, which exceeds the code’s standards. Therefore, it is recommended that the vertical gate be lifted to 109.7 m at a speed V = 1 m/min in extreme condition.

Under design condition, when the vertical gate lifts to 110.7 m at the speed V = 1 m/min, the maximum longitudinal and transverse mooring forces of the designed 1000T single vessel moored in the chamber are 24.54 kN and 8.73 kN respectively, which meet the requirements of the code. Therefore, in the design condition, it is recommended that the vertical gate be opened to 110.7 m at the speed V = 1m/min.

When the vertical gate lifts to 110.7 m at a speed V = 1 m/min under normal condition, the maximum longitudinal and transverse mooring forces of the designed 1000T single vessel mooring chamber are 14.39 kN and 3.57 kN, respectively. When the vertical gate is lifted above the water continuously, the maximum longitudinal and transverse mooring forces of the designed 1000T single vessel berthed in the chamber are 15.53 kN and 3.38 kN respectively. As the water level difference between upstream and downstream is small, the lifting speed of gate is slow. When the gate is lift to the sill evevation, the water level of upstream and downstream is basically flat, so the increase of ship mooring force when the gate is continuously lifted is small. The mooring forces under the two operation modes of the vertical gate both meet the requirements of the code. Considering the operation efficiency of the lock, it is recommended to lift the gate continuously above the water at a speed of V = 1 m/min in normal condition.

Table 1. Maximum mooring forces for 1000T vessels in lock chamber (energy dissipation way:Grid).
Full size table
Table 2. Maximum mooring forces for 1000T vessels in lock chamber (energy dissipation way:Grid+gate).
Full size table
Fig. 7.
figure 7

Mooring force curves of 1000t vessel berthing in upper chamber. (H = 3.00 m, lift the vertical gate to 110.7 m at a speed V = 1 m/min)

Full size image

5 Hydraulic Characteristics of Auxiliary Chamber

The physical model of the auxiliary lock of Baise ship lift adopts the recommended water filling and emptying system and gate operation mode. The measured hydraulic characteristic values of the water filling and emptying process are shown in Table 3, and the curves of the water filling flow process in typical working conditions are shown in Fig. 8 and Fig. 9.

As can be seen from Table 3, when the vertical gate is lifted at a speed of 1 m/min to 109.7 m at extreme condition, the water filling time of the chamber is 513 s, the maximum flow rate is 161.28 m3/s, and the maximum water surface rising speed Umax of the chamber is 1.22 m/min.

When design condition, the vertical gate is lifted at the speed of 1 m/min to 110.7 m, the water filling time of the chamber is 239 s, which can meet the requirements of the design locking time T (not more than 5 min). The maximum flow rate is 162.41 m3/s, and the maximum water surface rising speed Umax of the chamber is 1.20 m/min, which can meet the requirements of the specification.

By comparing the filling flow curves in the chamber under different conditions (Fig. 8 and Fig. 9), it can be seen that when the height of the gate stop elevation is 109.7 m, water only enters the lock through the grid energy dissipation chamber, and the flow curve shows a peak.When the height of the gate stop position is 110.7 m, the water flow first dissipates through the grid energy dissipation chamber, then the water flow enters the lock through the bottom of the gate and grid energy dissipation chamber as the height of the gate bottom exceeds 109.7 m, so there are two peaks in the curve of the flow rate.

When the vertical gate is continuously lifted at the speed of 1m/min at normal condition, the water filling time of chamber is 214 s, which basically meets the requirement that the design water filling/emptying time (no more than 3.5 min). The maximum water filling flow rate and the water surface rising speed of chamber are greatly dropped compared with the extreme and design conditions.

In extreme conditions, if the vertical gate is lifted at a speed of 1m/min and the gate stops at 109.7 m, the emptying time of the lock is 438 s, the maximum flow rate is 167.71 m3/s, and the maximum water surface falling speed of chamber is 1.33 m/min.

When the design and normal conditions, the characteristic values of emptying time, maximum emptying flow rate and water surface falling speed of the chamber are greatly reduced compared with the extreme condition, which can meet the specification and design requirements.

Therefore, the recommended gate operation mode can meet the water filling/emptying time requirements of the lock, and the water filling and emptying system layout is reasonable.

Table 3. Hydraulic Characteristics of Filling and Emptying System in Chamber.
Full size table
Fig. 8.
figure 8

Hydraulic characteristic curves of auxiliary chamber (H = 5.64 m, lift the gate to 109.7 m at a speed V = 1 m/min).

Full size image
Fig. 9.
figure 9

Hydraulic characteristic curves of auxiliary chamber (H = 3.00 m, lift the gate to 110.7 m at a speed V = 1 m/min).

Full size image

6 Conclusions

  1. (1)

    The Baise ship lift’s auxiliary lock uses an F/E system that combines gate + grid energy dissipation to satisfy the needs of rapid filling and emptying of the auxiliary chamber under various fluctuations in downstream water level. The hydraulic system is well-designed, and the use of an auxiliary lock to deal with changes in downstream water level is feasible.

  2. (2)

    The recommended operation of the auxiliary lock gate under various lift heights is proposed based on model testing. The mooring force of the planned 1000T single vessel may meet the criteria of Chinese standard when the gate is operated as recommended.

  3. (3)

    The physical model test measured the design condition (H = 3.00 m), the water filling time of the lock chamber is 239 s, and the maximum water filling flow is 162.41 m3/s under the recommended lock gate operation mode. The water filling time of the lock chamber is 214 s at normal condition (H = 1.50 m), and the maximum water filling flow is 85.57 m3/s. The water filling/emptying system structure is suitable, and the recommended gate operation mode can meet the lock’s water filling/emptying time requirements.