1、附录外文资料及翻译 Straight to the source of seepage Jim Swaisgood, Jerry Montgomery and Val Kofoed report on the investigative work undertaken to discover the source of seepage at River Reservoir dam in the US. Water seeping through an earthen embankment suggests a number of possible circumstances, and none
2、 of them are good. At best, the reservoir owner is losing a valuable commodity. The worst case scenario is that the seepage may be the precursor of dam failure. The first step in addressing a problem with seepage is as obvious as it is difficult: pinpointing its source. In the past, procedures for d
3、etermining the exact location and nature of seepage points have been both costly and time consuming. Of course, when dam failure is imminent, there is much more than money and time at stake； the efficiency and speed with which engineers can locate the source of seepage may make the difference betwee
4、n a timely fix and catastrophe. River Reservoir dam is an arched earthen structure on the headwaters of the Little Colorado River. It is located about 24km southwest of Eagar, Arizona, US, and is owned and operated by Round Valley Water Users Association (RVWUA). Based on very limited engineering, t
5、he dam was constructed by settlers in 1896 of local materials and without a clay core. Due to recurring sloughing problems, the dam received significant modifications on at least four separate occasions. The embankment consists of clayey soils within a rockfill shell, measuring 335m long with a maxi
6、mum height of approximately 21.3m and is founded upon basalt bedrock. In 1996 additional riprap was installed to reduce the original slope of the upstream and downstream faces. A review of the early inspection reports revealed that the left abutment drain was constructed using tabular rocks to creat
7、e a box-shaped opening over the rock foundation. However, the contacts between these rocks were neither sealed nor grouted. There has been much speculation regarding the original purpose of this drain. Most investigators believe that it was constructed to carry away water that emerges from a perenni
8、al spring rumored to exist within the left abutment； it may also have been intended to function as a temporary outlet to the reservoir. In late March 2004 an unusual amount of water was observed to be seeping from the left-abutment weir box. This seepage contained significantly higher than normal si
9、lt content. The path of the seepage was thought to be related to the supposed spring, its associated clay pipe, and the stone-box drainage system. Investigators feared the possibility of imminent dam failure. Emergency personnel were mobilised to the site to monitor and address the situation. RVWUA
10、immediately contacted the State of Arizona, which agreed to fund the investigation and subsequent remediation work. RVWUA also enlisted the services of Turner Collie & Braden (TCB), an AECOM company, which contacted Willowstick Technologies (Willowstick). Working together, TCB and Willowstick were a
11、ble to assist RVWUA in investigating and resolving the rapidly deteriorating situation. Aquatrack technology The manner in which the investigative work was done can only be fully appreciated when understanding how WillowsticksAquaTrack technology works. AquaTrack uses a low voltage, low amperage, au
12、dio-frequency electrical current to energise the groundwater or seepage in question. Electrodes are placed strategically in wells, springs or surface water so as to induce electricity to flow through the groundwater system of interest. Because groundwater is a conductor, the electrical current will
13、follow the path of the groundwater between the electrodes. As it flows through the groundwater the current creates a magnetic field. This magnetic field can be identified and surveyed from the surface using a highly sensitive and specially tuned magnetic receiver. The magnetic receiver measures the
14、specific magnetic field, filters out interference, and amplifies the signal. Repeated measurements are recorded over time to ensure consistent results. The equipment used to measure the magnetic field includes three sensors oriented in orthogonal directions, a data logger used to collect, filter and process the sensor data, a Global
