In Situ Needle Penetration Test and Its Application in a Sericite Schist Railway Tunnel, Southwest of China

The sericite schist is a typical metamorphic soft rock. Large deformation of surrounding rock often occurs in the construction of a tunnel in this stratum. Due to the broken rock mass structure and poor mechanical strength in Baishitou tunnel project of Dalin line of Southwest railway, it is impossible to prepare standard samples for a traditional rock mechanical test. Therefore, we chose penetrometer (SH-70) for an in situ test. Firstly, we monitored the deformation of typical sections and analyzed the characteristics of large deformation of soft rock in the tunnel. Secondly, we tested the needle penetration index of fresh excavation face and side wall. Then, we estimated some mechanical parameters of sericite schist by a needle penetrometer and Hoek-brown criterion and discussed the acquisition of mechanical parameters of soft rock. The results show the following: (1) the characteristics of extrusion rock tunnel are summarized as large deformation, fast deformation rate, and obvious construction disturbance. (2) The reference value of penetration index of sericite schist (the vertical joint direction) is 3.90~7.77 N/mm, and the parallel joint direction is 1.27~2.99 N/mm. (3) The uniaxial compressive strength estimated by a penetrometer is 0.78~8.53 MPa, and the strength of the surrounding rock is negatively correlated with the amount of deformation. Therefore, it can be considered that the insufficient strength of surrounding rock is the fundamental reason for large deformation. (4) The reference value of cohesion of sericite schist estimated by a penetrometer is 0.203 MPa, and the reference value of internal friction angle is 18.224°. Compared with the common estimation methods, the penetrometer is more convenient and economical, which can provide a new idea for obtaining the mechanical parameters of sericite schist soft rock tunnel.

JOINT DIRECTION AND PROXIMITY CLASSIFICATION OF OVERLAPPING SOUNDEVENTS FROM BINAURAL AUDIO

Sound source proximity and distance estimation are of great interest in many practical applications, since they provide significant information for acoustic scene analysis. As both tasks share complementary qualities, ensuring efficient interaction between these two is crucial for a complete picture of an aural environment. In this paper, we aim to investigate several ways of performing joint proximity and direction estimation from binaural recordings, both defined as coarse classification problems based on Deep Neural Networks (DNNs). Considering the limitations of binaural audio, we propose two methods of splitting the sphere into angular areas in order to obtain a set of directional classes. For each method we study different model types to acquire information about the direction-of-arrival (DoA). Finally, we propose various ways of combining the proximity and direction estimation problems into a joint task providing temporal information about the onsets and offsets of the appearing sources. Experiments are performed for a synthetic reverberant binaural dataset consisting of up to two overlapping sound events.

Numerical investigation of the influence of discontinuity orientations on fault permeability evolution and slip displacement

A pre-existing plane of weakness along the fault is comprised of a particular pattern of joints dipping at different orientations. The fault stress state, partially defined by the orientation of fault, determines the potential of slip failure and hence the evolution of fault permeability. Here the influence of fault orientation on permeability evolution was investigated by direct fluid injection inside fault with three different sets of fault orientations (45°, 60° and 110°), through the coupled hydromechanical (H-M) model TOUGHREACT-FLAC3D. The influence of joints pattern on slip tendency and magnitude of potential induced seismicity was also evaluated by comparing the resulted slip distance and timing. The simulation results revealed that decreasing the dip angle of the fault increases the corresponding slip tendency in the normal fault circumstance. Also, with changing joints dip angle associated with the fault, the tendency of the fault slip changes concurrently with the permeability evolution in a noticeable manner. Permeability enhancement after the onset of fault slip was observed with the three sets of fault angles, while the condition of 60° dipping angle resulted in highest enhancement. Joints pattern with a dip angle of 145° (very high dip) and 30° (very low dip) did not trigger a shear slip with seismic permeability enhancement. However, high dip and intermediate dip angles (135°, 50° and 70°) yielded high permeability in varying orders of magnitude. The large stress excitation and increasing permeability during shear deformation was noticeably high in intermediate joint dip angles but decreases as the angle increases. Article highlights The magnitude of injection-induced permeability enhancement is largely influenced by the fault and joint spatial orientations. With a slight change in the joint direction, there is an increasing possibility for fault to approach a different critical state of failure. Stress elevation at the point of failure is controlled by the orientations of fault/joint planes with respect to the direction of maximum principal stress.

A Novel Unitary ESPRIT Algorithm for Monostatic FDA-MIMO Radar

A novel unitary estimation of signal parameters via rotational invariance techniques (ESPRIT) algorithm, for the joint direction of arrival (DOA) and range estimation in a monostatic multiple-input multiple-output (MIMO) radar with a frequency diverse array (FDA), is proposed. Firstly, by utilizing the property of Centro-Hermitian of the received data, the extended real-valued data is constructed to improve estimation accuracy and reduce computational complexity via unitary transformation. Then, to avoid the coupling between the angle and range in the transmitting array steering vector, the DOA is estimated by using the rotation invariance of the receiving subarrays. Thereafter, an automatic pairing method is applied to estimate the range of the target. Since phase ambiguity is caused by the phase periodicity of the transmitting array steering vector, a removal method of phase ambiguity is proposed. Finally, the expression of Cramér–Rao Bound (CRB) is derived and the computational complexity of the proposed algorithm is compared with the ESPRIT algorithm. The effectiveness of the proposed algorithm is verified by simulation results.

Joint 2-D angles and time delay estimation of coherent wideband signals

Joint direction of arrival (DOA) and time delay (TD) estimation of wideband signals such as WIFI and mobile communication signals has to face the challenges aroused by multipath effect in indoor environments. New methods that can deal with coherent wideband signals with high estimation accuracy are necessary. To achieve localization when signals are coherent, this paper proposes a new joint estimation method which fully utilizes the subcarriers of wideband signals. This method could greatly extend the array aperture and accomplish the joint estimation through UCA-ESPRIT and one-dimensional (1-D) search. Simulation experiments are conducted to show the validity and efficiency of this method.

Joint DOD and DOA Estimation Using Reduced-Capon Method in Bistatic MIMO Array

In order to resolve the problem of joint direction of departure (DOD) and direction of arrival (DOA) estimation in bistatic MIMO array, a dimensional reduced-Capon method based on Taylor series expansion and signal subspace is proposed in this paper. Firstly, the Taylor series expansion of the steering vector is used to reduce the two-dimensional (2D) spectrum peak searching of Capon method to one-dimensional searching. Then, the DOD estimator can be achieved via Lagrange multiplier by one-dimension search. Finally, the steering vector of DOA corresponding to the DOD estimator is achieved and the DOA can be estimated. Hence, the estimated DOD and DOA are obtained automatically paired. And also, the proposed method can avoid the high computational complexity of MIMO Capon method. Simulation results are presented to illustrate the effectiveness of the proposed method.

Joint DOA and Frequency Estimation for Linear Array with Compressed Sensing PARAFAC Framework

In this paper, a joint direction of arrival (DOA) and frequency estimation algorithm of narrow-band signals is proposed via compressed sensing (CS) parallel factor (PARAFAC) framework. The proposed algorithm constructs the data model into a PARAFAC model, and compresses it to a smaller one. Then trilinear alternating least-squares (TALS) algorithm is exploited to estimate the compressed parameter matrices, and finally the joint DOA and frequency estimation is obtained via the spatial sparsity and the frequency sparsity. Due to compression, the proposed algorithm has lower computational complexity than the conventional PARAFAC algorithm, and saves more memory capacity for practical application. The DOA and frequency estimation performance of the proposed algorithm is very close to that of the conventional PARAFAC algorithm, and better than those of the estimation of signal parameters via rotational invariance techniques (ESPRIT) algorithm and the propagator method (PM). Furthermore, the proposed algorithm can achieve automatically paired DOA and frequency estimation. Besides, it is applicable for nonuniform linear arrays. Effectiveness of the proposed algorithm is assessed by simulations.