# Energy Generation and Attenuation of Blast-Induced Seismic Waves under In Situ Stress Conditions
## 1 Introduction  
In mining and civil industries, more and more underground caverns are being excavated in deep rock masses. It is well known that the rock masses in deep depths are generally subjected to high in situ stress caused by gravity and tectonic movements. For example, the Mponeng gold mine in South Africa has entered a depth of 4350 m [1]. The maximum principal in situ stress at this depth reaches 140 MP [2]. The Bayu tunnel of the Sichuan-Tibet railway in China is excavated with a maximum depth of 2080 m. The measured maximum principal stress approaches 50 MPa [3]. At present, the drilling and blasting method is widely used in deep mining and civil construction for rock fragmentation and removal due to its economy and applicability. During rock blasting, a small fraction of explosive energy is consumed in rock fragmentation and removal. Most of the explosive energy is dissipated in undesired forms, such as seismic waves, air shock waves, noise, light, and heat [4]. In these undesired effects, the seismic waves generated in rock blasting are of greatest concern because they can induce damage and destruction of surrounding structures. In order to prevent structure damage and destruction caused by blasting seismic waves, systematic and intensive studies have been carried out on the generation and propagationof blasting seismic waves. A large number of research achievements have been made in seismic mechanisms, propagation laws, attenuation characteristics, and interactions with structures. It has been confirmed that different types of seismic waves are generated in rock blasting, including compressional P-waves, transverse S-waves, Love waves, and Rayleigh waves [5]. [PERSON] and [PERSON] [6] investigated the energy composition of blasting seismic waves and claimed that most of the energy (about 67%) was carried by Rayleigh waves. The theoretical and experimental studies conducted by many authors have shown that the generation of blasting seismic waves depends mainly on explosive properties, charge weights, charge structures, blasthole geometry, stemming conditions, free surfaces, and delay initiation sequences [7; 8; 9; 10; 11]. The attenuation of blasting seismic waves has also been demonstrated to be complicated, governed not only by site geology, topography, and travel distance but also by rock discontinuities such as faults, voids, and joints [12; 13; 14]. It is generally accepted that the structure responses under blasting seismic waves are dependent upon the vibration PPV and frequency. For dynamic safety assessments of the structures, some thumb-rule formulas were proposed by different authors to predict the PPV and dominant frequency of blasting seismic waves [15; 16]. In recent years, various machine learning methods have been introduced into the prediction, in which more influencing factors are taken into account [17]. It should be noted that in addition to rock blasting, the internal explosions inside underground caverns, such as terrorist attack explosions and fuel tanker explosions, can also produce seismic waves and cause structure damage and destruction [18; 19]. In this regard, [PERSON] and [PERSON] [20], [PERSON] and [PERSON] [21], and [PERSON] et al. [22; 23; 24] systematically studied the rock tunnel responses caused by internal explosions under varied rock types, rock strengths, overburden depths, tunnel shapes, tunnel sizes, lining thicknesses and explosive weights. Their research results provide great insights into the blast-resistant design of subway tunnels. However, these previous studies often focus on blasting in shallow rock masses, in which the effects of in situ stress are smaller or can be ignored. Compared with shallow rock blasting, the generation and propagation of blasting seismic waves in deep or highly stressed rock masses receive much less attention. In this respect, [PERSON] et al. [25] numerically simulated the single-hole blasting under varied hydrostatic and non-hydrostatic in situ stress conditions.